Defrost control timer. More complex than you might think

If you've ever heard a loud click at a random time from your fridge or freezer, it's most likely the defrost timer initiating a cycle.
You'd think it might be something simple like a continuous timer that switches from running to defrosting for a specific amount of time each day, but it's much more clever than that. It only accumulates time between defrosts based on the total amount of compressor run time, and will terminate the defrost and switch back to chilling as soon as the maximum defrost temperature is reached.
The gear mechanism itself is very clever. It uses a special type of gear wheel that increments the next gear in single steps per revolution to allow a long time interval, and uses a similar gear to turn the switch cam in decisive steps to allow the contacts to change state twice in a very short rotation angle.
The contacts are moved by two spiral cams that gradually reset them for most of the revolution, but then have a sudden snap action at the end.
If you enjoy these videos you can help support the channel with a dollar for coffee, cookies and random gadgets for disassembly at:-
www.bigclive.com/coffee.htm
This also keeps the channel independent of KZbin's advertising algorithms allowing it to be a bit more dangerous and naughty.

[@Nono-hk3is]

The apparent contradiction between wanting to call devices like this both *complex* and *simple* has something to do with it being the result of a deep understanding of multiple problems/requirements, in this case the need to be both cheap and effective. I think *clever* is the right word for it.

[@ThePlacehole]

A tedious person might argue that "complex" really means "composed of many parts." Therefore, a design with surprisingly few parts should be called "simple," no matter how convoluted or hard to follow it is.

[@cheeseschrist2303]

@@ThePlacehole Or simply complex?

[@Nerd3927]

@@cheeseschrist2303 It is a simple device doing a complex task. Try explaining the function in detail on a birthday party. Don't be surprised if you find your self gagged in the backyard shed before you are done :-)

[@kimvibk9242]

Ingenious?

[@GFlCh]

@@ThePlacehole - I think Clive sums it up nicely at the end when at 15:13 he says "it's all very simple and all very clever but sophisticated too."

[@evensgrey]

"A design is perfect not when there is nothing left to add, but when there is nothing left to take away."

[@happyundertaker6255]

And getting there is much harder than just adding stuff to get the thing working properly.

[@millomweb]

I can't agree to that at all - standing in the queue at the chippy.

[@justtime6736]

Absolutely.

[@eDoc2020]

I've been working an repairing an antique TV from 1949 and it was having problems syncing onto signals. Eventually I disconnected one particular capacitor and it suddenly had rock solid sync. Who would've thought?

[@evensgrey]

@@eDoc2020 That a 72 year old capacitor would be leaky? Probably anyone who's restored vintage electronics before. Capacitors are really obnoxious things as they age. Most of the dielectrics we've tried break down badly over time. (Ceramic disc capacitors seem to be extremely stable, but they are also usually extremely small value. While the stability is nice, most people would probably conclude than a single 47 microF capacitor that might fail in a decade or five is worth the savings over replacing it with a FIELD of 100 nF ceramic disc capacitors.)

[@8Jory]

I've lost track of how many of these things I've replaced over my time as an appliance repair man. Getting stuck just before kicking on the defrost was the most common failure I remember. They could be manually turned to defrost, and they would start turning around again, only to get stuck just before defrost again...

[@throttlebottle5906]

not as common as burnt contacts heating the metal so hot it melts the plastic cam lobes or the arms lose spring tension, then the compressor starts being cycled on /off wildly as the plastic melts or the contacts make and break poorly, burning more. I have seen them fill the inside of fridge with smoke, after they melted the timer case, plus fridge above and insulation! in more than one case the people called the fire department

[@DavePetrillo]

9:08 "It's not exciting" ... i have never been more excited

[@millomweb]

Surely it'd be a lot simpler and cheaper to run with a quartz crystal oscillator firing once every 3 hours !

[@DavidGauthiersquidpride2014]

This also goes for the Ice Maker, don't put your hand in there to clear a wayward ice cube. The ice maker gets VERY hot during the defrost cycle and will leave you with 1st-degree burns. Fortunately, there was ice nearby...hehe

[@psirvent8]

I did touch the hot coils of two ice makers that I was fixing and oddly enough they were nowhere near hot enough to cause any burn. The ice cubes on the other end were melting just enough for them to fall into the receiving bin inside the machine as it should happen. (The faults on both machines were the same: Corrosion from electrolysis on the water level sensors by the way, nothing to do with the refrigeration part of things).

[@ShinyPeeko]

Just a heads up. Don't put ice on a burn, only running cold clean water. Ice can actually keep burning burns

[@boyd19043]

Funny thing about getting Bruns with out knowing it gets hot. I was clearing a jam in a toner printer burned the living fuck out of my finger tips. I felt like Will Smith in MIB when he gets his finger prints erased.

[@Francois_Dupont]

i remember touching the tubing behind a fridge when i was a boy and it burned my hand.

[@wickett7078]

In industrial refrigeration we run a defrost regulator around 75 psi, which is about 45 to 50 degrees saturation temp for ammonia(R717)

[@baconcatbug]

"Orange is closer to Brown" *Technology Connections Flashbacks Intensify*

[@ozzymandius666]

Mad scientists are trying to invent a brown light bulb as we speak!

[@Peter_Yachymczyk]

@@ozzymandius666 As long as it does not make brown notes also!

[@gustavrsh]

Was looking for this comment

[@TheStanHill]

The theme of this video and the title are very Technology Connections as well.

[@flaplaya]

I absolutely love this man's accent and fluent terminology in these reverse engineering videos. Not seen a mistake yet. Top notch content 👌

[@johnpossum556]

He made mistakes. He forgot to specify which motors turn off. This defrost timer motor never turns off. All it does is run constantly so that, depending on the model, every 4/6/10/12 hours it cycles the defrost system to turn on & it turns the compressor off while the defrost cycle happens. In models with ice makers this unit is usually built in to the end of them. I know this because I went to school for residential refrigeration & furnace repair. I think he made more mistakes but I just woke up and don't feel like going through it all now. Even if the circuit is wrong he got the general gist of what it does correctly.

[@kain0m]

@@johnpossum556 he specifically, at multiple points in the video, adressed that THIS defrost motor ONLY runs when the compressor runs. And that there is the other model with the different schematic, with the comment "never the twain shal mix" at 1:05, and that "the connection of the motor is different". As AvE once said, "if you assume, you make an ass out of u and me". You assumed you know better without listening to (or watching) the video. Clive even explained the exact function of the circuit in great detail, beyond any shadow of a doubt that knows how it works. Just try substituting model A for model B in his schematic and you will be surprised to find that it completely changes the way the defrost motor works.

[@millomweb]

So you missed the fact he got the pen tops mixed up and referred to the thermostat 'calling for heat' (10:08) when it's running refrigeration equipment !

[@KirstyTube]

Just wait for the pink calculator! 🤪 Loves BigClive 😂

[@donmoore7785]

I tripped across this item when my fridge malfunctioned some years ago. I recall marveling at the design. I then remembered what was required before these were invented - my mom used to go through the routine of defrosting our fridge and a separate commercial freezer once a year. It was quite a process - packing all the contents into boxes for hours, and waiting for ice to melt. This is a VERY useful item indeed!

[@LiLi-or2gm]

You're a rather busy guy. All hail us aspies! My laundry units do this too. The timer motor on the washer is attached to a multi-track cam wheel that activates several contacts to change the motor speed and the solenoids that control water (hot and cold) valves, and transmission action between wishy-washy and spin.

[@jothain]

They must be bit older units as logic boards seem to be cheaper to manufacture for that usage. Though I suppose it's somewhat nice to be able to replace parts fairly easily.

[@Lucien86]

Old fashioned mechanical automatic washing machines - the control drum, now there is a complex machine.

[@eDoc2020]

My old dishwasher also does this, and even has a similar setup during a heating phase where the motor is put in series with the heating element and then shorted until temperature is reached.

[@dcallan812]

WOW I would never have thought so much effort went into the defrost cycle.

[@sootikins]

You should see how complicated defrost control strategies get when dealing with industrial scale ammonia refrigeration systems.

[@dcallan812]

@@sootikins I guess more complicated. I have see a few documentrys of ice rink refrigerant leaks killing people

[@sootikins]

@@dcallan812 Yep, ammonia is very efficient, well understood but deadly if it gets out of control. If you're interested, here's a report on a real world case of a botched defrost. 32 hospitalized... kzbin.info/www/bejne/lZrGl2BrqtSNmMU

[@dcallan812]

@@sootikins Cheers for the link just abut to watch it. 👍👍

[@newoldbrain]

Interesting, relaxing, soothing and you always learn something. I especially love how Big Clive ends his videos: no faffing around, no reminders to like or subscribe - they just stop when the topic is done.

[@abraham4124]

High-frequency push-through word of the week: “complex”. Nice job!

[@Peter_Yachymczyk]

Good better then the other word which you can probably guess!

[@abraham4124]

@@Peter_Yachymczyk ha?

[@elijahwatson8119]

I am a huge fan of seemingly simple devices with interesting engineering. I feel like we miss out on that in a lot of devices nowadays. If you gave an engineer the task of building a defrost timer nowadays, it would be a simple microcontroller and a relay. Boring! If you ever get the chance, take apart a basic refrigerator ice maker. They incorporate many of the design ideas from this timer. A valve to let the the tray fill up with water, a little heater to help the cubes release, and a motor that drives gears to activate the relay, heater, and little fingers that push out the cubes. Beautifully simple. I can't speak to more expensive refrigerators' ice cube makers being as simple. I've wasted many of kilowatts having the freezer door open watching the gear slowly move while it does its thing to make ice. Maybe I'm just easily amused.

[@RambozoClown]

My freezer is too old for this. The timer is just a wheel with a hamster in a parka.

[@webchimp]

The timer on mine is if I can't open the top drawer anymore.

[@izzystuart7798]

I have an old freezer from the early 2000's will it have one of these?

[@NOWThatsRichy]

@@webchimp Yes or when you find there is more ice than food inside!

[@eDoc2020]

@@izzystuart7798 If it's self defrosting (excessive ice doesn't build up on the shelves or walls) and has a mechanical knob to adjust the temperature rather than a digital control, it almost certainly has something like this.

[@franceslarina5508]

Luxury! Mine starts opening the door slightly when the ice grows too thick, thus allowing the ice cream to melt which makes me swear and chip the ice off.

[@bradpayn1839]

Hi Clive ... Afew finer points on the electricals. 1. heating stops when the defrost termination switch senses the temp of the evap coil above 6 degrees c, even though the now seemingly reverse current is flowing through the timer, to advance out of defrost mode. This path only carries the mentioned 1.5 whatts, which is too small to operate both the heater and the compressor, 2. motors that run on single phase ac electicity always run the same way no matter which way they are connected to the A and N .This one is called a shaded pole motor and rotation is fixed at factory, by a copper insert in the magnetic flux path. However a smart elecky can reverse some of the bigger single phase motors. 3. I preferr the option of the timer motor running during defrost. this type of timer was set to an average time greater than what is expected, by a minuite or two, and thus act as a backup to terminating the defrost. This was always a good safety feature,as a shorted terminator could melt the feezer compartment into a plastic blob. 5. An extra to this, is that the air circulation fan inside the freezer, is connected electrically, so as to shut down during the defrost, and also wait for the compressor to operate after, this removes the heat from the defrost event, before air circulation restarts. so as heat is not injected into the freezer, propper. This is aprox a two minites delay. Thanks for allowing my input. Brad

[@mikeselectricstuff]

Isn't the 1-tooth gear also about getting a high reduction ratio with fewer gears

[@MrMistery101]

I'd be more tempted to call it a cam at that point, as it turns continuous rotation into interrupted actuation, even if not entirely linear.

[@AAAyyyGGG]

I think Clive missed explaining that bit; can't be any other reason for it...

[@bigclivedotcom]

I think the first one is, but the second one it ensure a rapid switch transition to restart the compressor when the motor starts running again.

[@nrdesign1991]

It kinda is a Geneva gear mechanism

[@millomweb]

1 tooth gears driving 10 teeth gears are used in mechanical counters. You get the rotation ratio reduction but the speed remains the same - so that 59999 changes to 60000 at the same speed as 0 changes to 1.

[@BjornV78]

2:19 When you rotate the shaft of these micromotors, they work like a generator and they can generate a few 100V due the gear ratio. You can use these for making a handpowered Megger.

[@jtveg]

Some cheap fridges don't even have a defrost heater and simply use the defrost timer contacts as a 10 hours ON 20 minutes OFF on the compressor, while the power to the defrost motor never gets disconnected. Thanks for sharing. 😉👌🏼

[@piconano]

That gearbox is very clever. Never saw one before. Thanks for sharing.

[@channelsixtysix066]

Not everything needs to be electronic. This mechanical device works just fine for the application. I was surprised you didn't warn all and sundry about the dangers of mains electricity, then proceed to take the mech apart, whilst it was still plugged in. Thanks again, Clive. 👍

[@straightpipediesel]

Actually they do have to be electronic. These are obsolete: modern fridges use adaptive defrost based on a microcontroller measuring things like door opening cycles, evap temp, compressor and fan runtimes (which are now decoupled). The cause is strict energy efficiency requirements by both the EU (Ecodesign) and the US (Energy Star, California Title 20).

[@channelsixtysix066]

@@straightpipediesel Yep, fair point. I forgot about modern fridges and more precise control requirements.

[@johnpossum556]

It's even more clever than that because if that unit just turned on the electrical defrost heaters you can end up with meat that has rings of rot throughout it. To avoid this cutout limit switches are clipped onto the evap coils. Usually their temp cutout is near the melting point of water and this cuts out the heat before it rots any food. But it was true that this is the basic "brain box" of most older defrost models.

[@zh84]

All those cogwheels made me think of the Antikythera Device. I'd like to have seen an ancient Greek Megacliveos taking that apart and explaining how it works!

[@BruceGinkel]

Me: How does this work Greek Megacliveos Greek Megacliveos: Τι στο διάολο είπες απλώς για μένα, σκατά; Θα ξέρετε ότι αποφοίτησα στην κορυφή της τάξης μου στις ναυτικές σφραγίδες και έχω εμπλακεί σε πολλές μυστικές επιδρομές στην Αλ-Κουάιντα και έχω πάνω από 300 επιβεβαιωμένους σκοτωμένους.

[@zh84]

@@BruceGinkel Νόμιζα ότι μιλούσαμε για περίπλοκους μηχανισμούς ρολογιού;

[@aaaaaaaaaaaaaaaaaaaaaaaaaab]

@@BruceGinkel is this the navy seals copypasta?

[@kornaros96]

Σκαστε ρε μαλακες να ακούσουμε το Μεγαλομπαλταδακη...

[@bobwatkins1271]

It's the kind of design you'd get marked down for in college but rewarded for in industry.

[@Stuartrusty]

Indeed a very clever and well thought out design. It helps me to remember that within my lifetime we have gone from electro mechanical control logic, to valve/transistor logic to full microcontrollers. Kudos to all those mechanical engineers of yesteryear who designed these kind of automation and control devices. At one time, most automated control systems were electromechanical logic.

[@Acamperfull]

Thanks Clive, how minimalistic and clever! Now I also realized how the minute hand on a railway stations clock can move so fast every minute.

[@bigclivedotcom]

They're often stepped by a magnetic impulse motor. You may notice that the second hand pauses at the top briefly until the minute hand steps.

[@yodaco]

I've seen loads of different defrost timer systems. Some are vastly different

[@throttlebottle5906]

not many if any are wired that way here, they generally run the timer motor from case thermostat to neutral, so it runs as long as thermostat is closed. then the defrost thermostat only opens the heating element circuit on temp rise of evap. coil. the timer continues forward regardless and kills defrost heating at XX minutes time and goes back to cooling cycle. if the heater fails to work, it will ice the coil and quit cooling the fridge side, while the freezer side turns into an iceberg :)

[@securityrobot]

Fascinating stuff and so clever by design, to think a similar device such as this in my Fridge which has been going for years without the need for maintenance or has degraded through wear and tear.

[@BensWorkshop]

Thanks for that Clive. Very clever stuff.

[@Jamie_Pritchard]

New subscriber here, and though I haven't a clue about electronics or engineering of any kind I really enjoy both the way you present these videos and your personality.

[@CutiePie4325]

the tiny window is so cute. why don’t they just make parts like this clear, though? is it that much more expensive?

[@johnsona6428]

It limits you material selection quite a bit. Unless it's really necessary no one will sign off on making it clear. No doubt the engineer would have probably loved to do it.

[@mattostrokol]

One of the whirlpool defrost timers is clear.

[@mattostrokol]

Part # W10822278 I think

[@McTroyd]

@@mattostrokol All the way clear? The one I most recently swapped had a clear dome over the motor, but the cogs were still in opaque white plastic like Clive had.

[@mattostrokol]

@@McTroyd just the clear dome, but it still makes it easier to see the motor running.

[@Peter_S_]

That's a rather ingenious mechanical state machine. Very cool!

[@johnpossum556]

But he forgot to mention the timing and the thermal limit cutout switches that make it possible to defrost the freezer coils w/o inducing so much heat inside the freezer box that it forms rings of rot into the meat. In general I think his wording could have been a little more precise in this video.

[@Lucien86]

@@johnpossum556 Touching the machine shakes the timer and probably helps push it over.

[@Lucien86]

These timers actually remind me of an Internet Protocol state machine we worked on as a project at university. A tiny program but almost insanely complex.

[@greenaum]

Clever! I understand it now, thanks as ever to Clive's diagrammatic narration, and his narrative diagrams! You should move up into stop-frame animation, Clive, you could do that with a few separate drawings, or even go Ivor The Engine style and just cut bits of paper out and slide them around.

[@stridermt2k]

THANK YOU CLIVE!!! This is the kind of stuff I will take apart just for the fun and watching is fun too! :D Cogwell's Cogs!

[@dashcamandy2242]

Are they really better than Spacely Sprockets, though?

[@Peter_Yachymczyk]

@@dashcamandy2242 Worse but cheaper to purchase in bulk!

[@mikemike7001]

Wonder if the same function is performed by electronics in some fridges. My fridge has at least two rather complex circuit boards, one actually called a motherboard. Both of the circuit boards have - of course - failed and needed to be replaced. Nothing as obvious as a burnt component or a bulging capacitor. Perhaps the electromechanical timer shown in the video is a better approach. The effort put into the design of these things is phenomenal. Doubt if the code in my fridge's motherboard is as carefully optimized. "Cool" stuff.

[@TheSoundmanPete]

The timer is a "known" set time... compressor run time. It defrosts whether the box needs it or not. The new defrost systems are "smart". They monitor compressor run time but they also monitor how much time it takes for the defrost thermostat to open. They monitor the defrost thermostat action. Based on the time.... the board will shorten the defrost time as well as extend time between defrost cycles. This smart defrost method saves energy by only activating the defrost cycle when needed.

[@mikemike7001]

@@TheSoundmanPete Thanks. That makes sense. Electronics do make for smarter appliances. I just wish they were more reliable. Every time one of my appliances fails, I need to replace an expensive circuit board, sometimes two.

[@heyarno]

This explains why my old freezer frustrates me so much. I tried to avoid the automatic defrost and cleared it out, pulled the plug and defrosted it before I suspected it would do it again. Then I switched it back on and loaded it with fresh food. Which spoiled a week later, when it went to automatic defrost again. Since then I made it a non food fridge for rechargeable batteries, disinfectant, chemlights, epoxy, uv curing resin, thermal glue and so on.

[@objection_your_honor]

My old fridge was an old POS and its defrost cycle was controlled by the micro-controller like the rest of the fridge. Ended up buying a new Frigidaire fridge, which broke after two month! We make everything out of shit now. Bravo humanity.

[@brianleeper5737]

Supco makes a universal electronic replacement for defrost timers. It's adjustable for both defrost time and frequency. I bought one for my old fridge and set it to the minimum defrost time (10 minutes) and the maximum defrost inverval (12 hours). I figure it probably saved me a bit of electricity.

[@Peter_Yachymczyk]

Yep the newer frost free refrigerators actually use more power then the older ones! Electricity suppliers in the USA want you to get modern "energy efficient" models those are the exact opposite the new stuff is junk with electronic controls for everything and they use more energy because they run more to meet the set point as the box is not insulated as good thus using more energy the supplies main intention as they sell more electricity and the new crap fails in a year LG = Like Garbage Samsung = SamSucks

[@LeithJones]

The whole time I was thinking if the motor switches out when the switch makes, how does it proceed, and the neutral path through the compressor blew my mind.

[@CM-kl9qh]

See my comment @ about the same time as this comment. Good catch! I hope Big Clive responds.

[@BradTech.]

I wish we could bump this channel up to modern 2160p

[@jkbrown5496]

Similar with the standard "old" icemaker control module. Just the rotating wheel with contacts underneath the connect copper traces that stops then gets that kick back to the normal contacts with the thermostat closing to indicate the ice is ready for harvesting. I've opened two of the defrost timers for the US market. One like the one in this video had a capacitor to drop the voltage for the clock and the other used a resistor. The clocks actually being 12v.

[@cheechmarin4812]

Love it!! Thats genuinely interesting af!!

[@hadireg]

Pretty cool system, good timer for other uses

[@dobythedog]

A good while back, a certain company had problems where the timer was failing on defrost and the fridge freezers went up in flames. A programme of replacing them with solid state timers with no moving parts (except for relays, of course) was put in place.

[@ch2o2]

..the day on which you put an end to the multiplex flickering mode on your "HOPI" will be like Christmas for many of us, I guess :) (kidding - I still love your highly informative and also personable clips, dear Clive)

[@gyrgrls]

They don't use those mechanical defrost timers anymore in production. Most any fridge less than 10 years old uses a control board which takes care of the defrost cycle, the box temp (thermistors are used), among other things. Everything is governed by a microcontroller these days. You would be hard pressed to find mechanical timers and cold controls on newer machines. About the only mechanical switches are the door switch for the light and the defrost termination thermostat.

[@straightpipediesel]

In fact, LG even had a VW Dieselgate-style scandal where they rigged the software to detect the Energy Star test cycle and suppress defrost.

[@Robothut]

Back in the day when a fridge would last 30 or more years these mechanical timers were common. These days I have not found a fridge that uses the mechanical defrost timer. All the units seem to be fully digital control and fail with in 6 years. That way you either pay to fix it to get 6 more years "if your lucky" or buy a new fridge.

[@BersekViking]

I'm sure there is a digital counter in there that causes it to stop working as soon as the warranty expires.

[@PaulSteMarie]

I wouldn't say complex quite as much as subtle. It's a very simple circuit and only has six pieces to it, but using the defroster and the defroster thermostat as a voltage divider, and then connecting the neutral of the motor through the compressor, that all was quite clever. My water heater at the house back in Ohio was even more annoyingly clever. It had a side exhaust, that was fan driven, and when the thermostat turned on, the only thing the thermostat actually controlled was the fan. Once the fan started pumping enough air out the side exhaust, a vacuum switch would close and start the gas. A very elegant safety measure.

[@williefleete]

They are also in dehumidifiers. They act as a fail safe if the humidity control sticks on (or if you modify it to act as an aircon). It shuts off the compressor leaving the condenser fan running while the evaporator defrosts

[@rmd2387]

KZbin’s algorithm is odd. Wondered why I hadn’t seen any videos from you in a while and it was a solid typical KZbin moment. Apparently if I watch three videos related to one another in a row, I get 70 videos similar to those three for the next four weeks.

[@McTroyd]

I had to replace this in our drink fridge. Whirlpool uses a variant where the motor is discreet parts, under a clear plastic dome. Unfortunately the cogs are in the same opaque white plastic, but it was fun watching the motor whirr. Kinda wish it had some kind of over-temperature bypass, re-engaging the compressor. Never fun finding a warm fridge.

[@johnpossum556]

Most of them only stay off for 20 minutes so the water has time to melt & flow out of the freezer. So, in a sense, they do have it. It just might not be as fast as you think it should be. But because there are plastic panels over the cooling coils you never see the frost & ice in a modern refrigerator. The panels help the heat be isolated to just the frost & ice and so they don't ruin your food. I have seen large meat roasts which had rings of green spoilage within them when the limit cutout switch failed to do its job repeatedly.

[@McTroyd]

@@johnpossum556 Good to know. In this case though, it had clearly been off (or in defrost?) for a while longer. The fridge was warm, and the freezer was about room temperature (with frozen items thawing). We've had this particular fridge for the better part of a decade, and that's only happened a couple times, but it's still aggravating when it does.

[@motioncompensation1544]

Why oh why is this fun to watch? I’m watching and I don’t know why!

[@Boraxo]

Some of the systems I worked on used a air switch to detect reduced air flow across the coil to initiate defrost.

[@kiranshashiny]

I have an old fridge and the timer is somewhat similar, and there are times when I don't need the freezer compartment freezing. So I unhooked( or unscrewed) the sensor wire from the timer and just it hang outside. Why is the freezer aluminium still showing signs of freezing. I think the temperature may be too cold. So I wrapped the thin piece of wire with styrofoam, so that it will not show the fridge is too cold ( wire = I think its the temperature sensor with some gas inside. ) Yet the freezer aluminium compartment gets cold ? So here are my two questions : 1. How can I turn on and off the freezer compartment with the timer ? 2. How to lower the temperature even further ? what material can I use. I used a plastic straw around the wire - still no good. Appreciate responses from readers. BTW; Clive : I like your videos and your practical ways of hacking things - they are just like how I do it. I remove few screws and this thing is not opening and then I pry it - until I look underneath and there are more screws to be removed ! Argh. I enjoy your videos. Very educational and your explanation is just right.

[@andrewtitcombe8378]

As a fridge commercial fridge engineer, For many years now we use electronic defrost temperature controllers. However years ago we had mechanical defrost clocks that had a pins set every six hours that would trigger a similar mechanism. And defrost termination was via a solenoid pulled in from the neutral side defrost termination stat. I often wondered why they decided to design it using neutral side switching. As this was hard to diagnose an issue using a volt meter unless you knew it was neutral switched. This must be a design based on this principle for commercial refrigeration. With the added safety improvement that the clock still rotated while on defrost and so was also able to set an arm time that would push the same defrost release as the solenoid. So not only did it terminate on temperature but also time , which ever happened first

[@eDoc2020]

Clive used to work on those freezers as an industrial electrician and I believe I remember him saying they triggered the defrosters based on time of day rather than time since last defrost so that multiple units wouldn't come on at the same time and overload the electrical supply.

[@ironfrog3192]

Very interesting as usual

[@thegamefanaticshow]

7:16 Oh dear. The things Clive will do to electronics.

[@felixcat4346]

The one I had in my house in Mexico worked using a pic micro controller and a mechanical thermal cut-out that told the micro the temperature in the freezer reached 70 degrees and then stopped the defrost heating element and restarted the whole 24 hour cycle. It was a re branded GE unit called appropriately a MABE.

[@johnpossum556]

You sure it was 70 degrees? All of those cut outs I have seen are around the freezing point of water. They don't need to get any hotter than to melt the water so that it drains away from the evaporative cooling coils into the drain pan at the bottom of the refrigerator. There would be no reason to heat the water to 70 degrees whenit will flow just fine at 33 degrees F.

[@eDoc2020]

@@johnpossum556 The sensor would need to wait for a temperature a fair bit above the melting point in order to ensure the entire evaporator was hot enough to melt, though 70F still seems too high. Maybe the 70 degree cutout was just a safety limit switch and the actual control was done digitally. Or maybe it was actually a 7.0 degree C cutout.

[@johnpossum556]

@@eDoc2020 fuck, I lost my message. Maybe I'll get to remaking it later.

[@publicmail2]

Adaptive Defrost measures how long it takes to melt ice off evap based on temp and then either shortens or lengthens next defrost interval. Also, measure door opening and compressor runtime and can enter vacation mode if door not opened. Mine averages 60 hrs or 2.5 days.

[@o2wow]

Very interesting. Ice makers have a similar control to heat the tray allowing the discharge of frozen cubes, cycling the part that removes lose cubes and then turning on the water to refill the ice mold.

[@ib9rt]

A tiny detail, since you said it more than once, but the thermostat in the freezer doesn't call for "heat", it calls for "cold" :-)

[@Rich-on6fe]

Our 10 year old Beko fridge freezer went wrong and is now in a state of working ok with a lashed-on Arduino thermostat, but still with this persistent weird warming up period that happens occasionally. I bypassed the main controller board and I'm now commanding the compressor myself, but there seems to be some other layer of defrosting control buried within the bowels of the fridge where I haven't found it yet. Still active, it causes the whole thing to warm up when it should be cooling down. But happily it no longer freezes our cucumbers.

[@Brian-cr6rb]

Typically, as I am in the appliance repair business, ,the most common problem I run into is a failure of the defrost thermistor. The defrost timer keeps ticking, so the compressor resumes normal operations. But you wind up with freezer burn and soft ice cream, and sometimes find your freezer warm. It's so alarming! But a couple wire nuts and a 17 dollar part will fix the fridge in 10 minutes.

[@jacquesb5248]

very informative

[@darylcheshire1618]

Reminds me about the washing machine we had when I was a kid, the dial could be set to a position and then it would rotate taking an hour to go 360 degrees. My father took it out, it had a bunch of wires connected to various solenoids. The solenoids would go “klunk” with a loud noise and the TV would jump and the lights would flicker.

[@zlatkojurkovac6981]

Nice! Thanks!

[@davey6024]

Triple pole fako?! Wow that thing looks nuts!

[@mrrkrr]

9:05 I know you said "small cog wheels" but that's not what I heard ... 😂

[@RS-Amsterdam]

A dirty mind is a joy forever ;-)

[@Fingers896]

I visualised a Cannon.

[@garbo8962]

Had one of the first energy saving house refrigetators that were made by Amana back in early 70's. Had to replace the defrost timer 3 times in the 17 years that I owned the piece of crap. Also had to replace defrost timer once. Found out that they saved energy by installing an undersized compressor. While me and the Mrs worled all day and doors were not opened for over 11 hours ice cream was so soft during summer. Had to run the central air conditioner to prevent this.

[@jimsvideos7201]

...and on the other end of the spectrum is the fridge I saw at the big box store with a great big touchscreen and a plaintive digital cry for a software update.

[@jothain]

Just couple of months ago we replaced big steel clock faced defrost timer at my working place. Big metal one that had been running from was it late 70's. They don't make stuff like that anymore. I was bit disappointed to notice that electrician had thrown it in trash. I would've wanted to open it and see how gearing were done, especially from bushing/bearing side that it was able to run for so long.

[@shaunsiz.itsbetterbytube2858]

When indulging in a relaxing herbaceous tea. The small sharpie dot on the lower gear transforms into a wee little insect running around in circles. Very hypnotic. Still fridge related off for some munchies

[@siberx4]

This is a clever little cost-engineered widget, but I'm amazed that in this day and age it's not cheaper to delegate a task like this to a tiny few-cents microcontroller plus a relay.

[@sir_maxi630]

Are you teacher by any chance sir Much respect Very interesting content 👌

[@JessicaFEREM]

I like your wago makeshift quicktest

[@D6isD6]

Scrolling past I'd misread that as "Bifrost control timer" and wondered when Heimdallr had called for a repair.

[@CM-kl9qh]

I’d never heard of Heimdallr before. I learned something new! Thank you! Is your profile image based on mythology as well?

[@CM-kl9qh]

I’d never heard of Heimdallr before. I learned something new! Thank you! Is your profile image based on mythology as well?

[@eDoc2020]

I had a fridge with the 'A' type timer (keeps running while defrosting) which I had unplugged for whatever reason. When I plugged it back in the compressor wouldn't turn back on even though I knew it was warm enough. I unplugged it and put my multimeter across the plug and the resistance redings seemed normal. There was low resistance when I set the thermostat to cold and infinite (or light bulb resistance if the door was open) when I set the thermostat to off. For the longest time I was stumped, but then I figured out it was just unplugged during the defrost cycle. I turned the override and then it immediately turned back on.

[@AttilaAsztalos]

This suggests that when defrosting ends and the timer motor restarts, as soon as it clicks back to "normal service" it stops again (because the defrost stat is likely still open) - then it starts again once the (still running) compressor cools things down enough for the defrost stat to close again.

[@eDoc2020]

I didn't think of that, but I suppose you're right.

[@phils4634]

Amazingly complex for a "consumable" item! Must be cheaper to build these than even a basic electronic version, and I'm wondering whether I can find another application . . . .

[@arialarms7994]

very cool!

[@wtmayhew]

What is amazing is that these defrost timers haven’t changed much in the last 45 years, and they are still present in refrigerators for sale today here in the US. There is some very cool mechanical engineering going on here. I am very impressed with the interaction with the compressor contactor and the defrost heater that allows the timer to dynamically adjust the heat dwell time so it is just enough to clear the evaporator but not let the freezer compartment warm enough to spoil the food. You could throw PIC, thermistor and a relay or two at the problem, but the mechanical solution is elegant - no need. Bonus points: reverse engineer a mechanical timer from a Hobart/Kitchen Aid dishwasher. They’re a work of art. Almost all top loader washing machines use the same electronics board no matter the manufacturer. There is usually service booklet stowed inside the washer. Some neat tricks that can be done in service mode as described in the booklet.

[@krashd]

Love it when Clive gets out his doodle.

[@AlecKristi]

Curious to know how the circuit operates for the other version of the timer...

[@williamsquires3070]

This is one of those products designed to do a lot with very little. And then there are products designed to do very little with a lot (lot of parts, lot of cost, lot of frustration to repair, etc...) 🤣

[@Bobby11]

I would love to see you take apart components at both ends of the scale. parts designed cheaply and to break and the equivalent part designed to last be be reliable.

[@TinkerbatTech]

Cool! I've been thinking about hacking my fridge with a relay to disable the defrost cycle if the fridge is running from the battery system. It's about 400W, IIRC, and I'd rather not burn battery juice heating, then cooling the refer again. Figure skipping a defrost cycle (or two..) while on emergency power wouldn't hurt anything, and save some juice. (Could even rig it to force a defrost cycle when switched back to line, but doubt it'd be needed.) I see by what you're showing that it's not just open the heater circuit. There's more to it than that. (I have to get the schematic for the refer first, of course.) Also need to time the average defrost cycle, might be so short that it's not an issue. (Hey, when I'm not blowing up batteries, I'm trying to cut my usage as much as possible. At some point, if it's a multi-day outage, have to run the genny to top it off. So the longer I can 'coast' the better. And it's cheaper and easier to stuff the batts from the utility...) Anyway, enjoyable and informative vid! Take care! Thanks, Stu.

[@davidareader]

Quite. If it's as Clive has shown, opening the defrost stat will mean that the defrost cycle is almost immediately terminated .. I suppose the question thien is "how long is almost immediately". It might be simpler instead to use a relay to take the defrost switch out of circuit, so it's only ever running the compressor . and operate that when on battery? that will also mean that the time to next defrost is extended by the time on battery, rather than the defrost cycle being skipped.

[@AndrewGillard]

That's interesting... 🤔 I'm never in the position of running freezers from batteries, but we're on Octopus Energy's "Agile" time-of-use tariff where the unit cost varies every ½-hour based on wholesale costs¹, with day-ahead rates being published around 4pm (UK time) each day. So it'd be nice to prevent the defrost heaters in our two frost-free freezers running during the most expensive times of day. I don't think they use a lot of energy compared to the rest of the house, but it'd still help to run them overnight at 0~10p/kWh instead of late-afternoon at 25~35p/kWh! In one of the freezers I have a temperature sensor reporting readings to InfluxDB² so I know that the defrost heater only runs once a day, so I'd only need to find a single ½-hour period of cheap electricity per day. I've also considered building battery packs to run e.g. PCs from batteries during peak hours, recharging them during the cheapest times (maybe even using "PicoPSU"-style PSUs to run the PCs direct from the battery's DC, instead of wasting a load of energy converting to 240V AC just to convert right back to ≤12V DC 🙄), but return on investment isn't great for that, I don't think. The side-effect of having longer-lasting UPSs would be nice, though. Incidentally, time-of-use tariffs (and the sustainable, lower-carbon electric grid that they encourage) are a great reason for network-connected appliances - washing machines, tumble dryers, dishwashers, central heating, water heaters, air conditioning, electric vehicles, fridges and freezers (as per the above), etc. I don't know whether existing IoT appliances offer this functionality, but they _could_ be scheduled to run whenever electricity is cheapest/greenest, pulling data from your energy supplier's API, and could even communicate with other appliances throughout the country to spread demand. Even better for appliances doing tasks that can be paused if electricity is briefly more expensive or there's a sudden high demand on the grid. Think about it: you often don't care _exactly when_ your laundry is cleaned or your dishes are washed, as long as it's done before you get up in the morning or whatever. So tell the appliance "clean my clothes by 7am, costing the least money and CO2 emissions possible". There are some promising possibilities - although the current situation leaves a lot to be desired (security; privacy; vendors shutting down online services, effectively bricking hardware; devices breaking during Internet connection outages; ...). There's a reason I self-host much of my "smart home" infrastructure... ¹ It's worth noting that Agile is capped at £0.35/kWh - including 5% VAT - so we'll never see completely ridiculous rates like many Texans did during the storms in February when the wholesale rate apparently jumped from $30~$40/MWh to its cap of $9000/MWh for several days! Note: that's _per-MWh_ rather than _per-kWh_. I don't know how Texan supplier(s) convert that to rates charged to consumers. It's probably higher than just "÷ 1000" ($0.03~$0.04/kWh, jumping to $9/kWh), but even $9/kWh is very painful and would mean $200/day [£145, €167] for this house - and it'd be so much worse if we relied on electric heating! 😬 (Texas Feb 2021 storm info is all from this excellent _Practical Engineering_ video that I highly recommend to anyone interested in the *technical side* of what happened to the Texas electric grid to cause the outages: kzbin.info/www/bejne/ZmnQqIt_eL5ngK8 ) ² If anyone's interested: ESPHome on a Wemos D1 Mini outside the freezer with DHT22 and DS18B20 sensors connected via FFC to minimise door seal gaps; sends data to Home Assistant and then to InfluxDB, using Grafana for graphs.

[@TinkerbatTech]

@@AndrewGillard Good point. Something like that is starting up around here soon as well. (Thankfully, got my mom on a solar system that currently covers all her usage annually. I can't do that, redwood trees everywhere here!) If it's anything like the ratios you are talking, I could shift to total battery during the greedy times, and recharge at the off-peak. Even Li-Ion cells are good for 1000's of shallow cycles. All my lights, fans, computer/modem/routers and such are on a UPS tied into the scooter batteries. The refer/freezer will be on a switched inverter. (Still building the setup) By the way, a really easy and cheap way to get your PCs and such on batteries is to pick up a quality used UPS on Ebay or such, sold cheaply when the batteries failed. (And usually shipped without them, which is great for waste and shipping costs!) I used a small APC UPS as a power source for over a year, hooked up to 6 golf cart batts. Charged via small inverter generator in the afternoon-evening, ran things the rest of the time. Now using a larger unit, sine wave 800W/1000VA industrial style unit. (Minute-man brand, designed to use with as many external batts as you want to hook up, as long as you charge externally as well.) About $75 US. It's hard to find a 36V based UPS, but that is what the scooter packs (10S Li-Ion) are putting out. The cost of the batteries and the quality made it worth the 36V hassles. Power is more than dicey up here with the trees, fires, winds and such. Can drop from a short glitch to several days. Many times most of a day or more. Now I can keep running just fine, and hook up the generator if things stay out for more than 24 hours, run the charger (42V/30A Cisco surplus supplies. Two for like $45 or so the pair. Into an intelligent buck-style P/S, that can output 50A max, current and voltage adjustable/limited. Works a treat.) Once I get the rest of the battery bank finished, without any more explosions, please, I could run the whole (very energy frugal 900Sqft house) place for a few days on battery alone if I use tablets and laptops instead of the 'big' computer setup. And that would be with freezer and refer. (Microwave as well would run on the 3000W inverter for the big loads, but only running on demand. The UPS covers the critical loads.) Definitely consider 'retired' UPSes as an option, all different sizes and types out there, usually very cheaply. The little APC I used for over a year was a little Back-ups model, modified to bring out the battery leads to a couple of big brass bolts on the side. It ran a load of between 40W to 300W, 24/7 for over a year. (Hillslide tore the power away from my house, took awhile to get support back under the house and a new power feed.) After I de-commissioned the unit, I took it apart and studied it for stress points, capacitors, browned circuit board and so on. It was still perfect. No signs of stress. This was the Back-Ups 600, IIRC, and was one of the low-frequency transformer-based units. Still a low end model. So best of luck with your setup. Sounds like you've got a ton of monitoring already, that'll help. Keep your loads as tight as possible. (Note that in my battery-explode video, there was a Mini-split cassette in the shot. Heat pumps are very rare in the US for some reason, but I put one in here. Love it to death. The rest of the world definitely knows the way to do things. Even my small (1800W) inverter generator can run the mini-split, _and_ put quite a bit of juice back in the batteries at the same time, as long as I don't crank the nutz out of the thermostat. Only pulls what it needs... Nice widget! Take care, stay safe! (No drywall screws thru lithium batteries..:) Stu the batty.

[@jock-of-ages73]

The thermostat for my old heating system had a mercury tilt switch in it!! I still have the little ampule of mercury.

[@millomweb]

My new dehumidifier has a defrost function that doesn't appear to have any idea at all. Having found it frosted up, I used a timer to turn it off for an hour or two to defrost itself. And, when it's not been running for 5 hours and then times on, it's gone into defrost mode 5 minutes later !

[@nixonnelson5181]

I had one of these, never found out how the motor works it was very different from the normal dc motors i disassembled , this timer motor is the one thing that is replaced annually and one odd type of relay, for our fridge.

[@soupflood]

This timer is part of an analogic computer: it requires all components to work in order for the fridge to start (unless the thermostat is always on,in which case the user can tell the compressor is only turning off when defrosting)

[@lawrenceharris7717]

I had the fridge fail when the defrost temperature sensor failed. It was an old fridge and I had already replaced the timer once so I nearly junked it and bought a new fridge. I figured it wouldn't hurt to disassemble it and see how it worked. I found a little metal button sensor snugged into the coils that seemed it could be the culprit, so a couple of bucks at the repair store and 10 years later it's still working. But yes, the failure mode was the timer just stopped waiting for the sensor to say the freezer had warmed enough and never restarted.

[@tubastuff]

Last year, I discovered what happens when one of these gizmos fails in the "defrost" position. Water on the floor; soft ice cream and melted ice cubes. Darned nearly drove me nuts running it down. I first suspected the compressor start relay, nope. No refrigerant leaks. Finally discovered this thing hidden behind a dress panel behind the interior light. Short-term solution was to rotate the timer to "refrigerate"; order a new unit and install it a week later. FWIW, compressor start relay is one of those PTC cheapies as well...

[@Alacritous]

You should make yourself a foot pedal power switch so you can turn a device on and off while your hands are busy holding stuff in front of the Camera. I have a set of lights over my work bench set up with a foot switch so that I can turn extra lights on when I'm working on something and I realize that I need more light to see what I'm doing.

[@eDoc2020]

Even without the camera it would be useful if you need to hold probes or something in place during powerup. If it's a momentary switch it could also be useful as a dead man's switch when working on potentially dangerous devices. Just be sure you use a properly rated double pole switch if working with mains.

[@Thingsthatgopew22]

Is that motor one of those that give you one hell of a zing if you hold the leads and twist the motor shaft? If so, make a projekt with it as a wind powered generator, lighting some LEDs.

[@bigclivedotcom]

Yes, the synchronous motors do pack a punch.

[@carldawson5069]

In the seventies i repaired refrigerators. The defrost timers are very reliable. But if you hear a growling noise, consider getting a spare. In a few years the gears may bind and the poor motor will stop and you don't notice until the first day stores close. You can manually switch it into defrost, the cooling might not restart. * suggestion, my Chinese is horrible, but i still enjoy Chinese to 'Engrish' translations. Could we have a send in your/everyone 'wurst' translations video post?

[@ozzymandius666]

What an odd little device. I could see it being re-purposed, but for what, I have no idea....it essentially turns device A off and B on for a set amount of time, then turns A on and B off again. Maybe to turn lights off and a sprinkler on in a hydroponics system, or, here in North America, to stop something from blowing a breaker if the sum of the power consumption of both devices exceeds 1800W...? Pretty neat, at any rate.

[@jameswest848]

Clever, but if the defrost heater fails it will get stuck in the defrost cycle until the whole fridge warms up. It could do with a timeout function.

[@jamesplotkin4674]

It is clever, as you don't want to engage defrost if the compressor hasn't been running. You'll get a warm freezer and spoilt, formerly frozen yogurt.

[@kompaac]

Any chance of getting an introduction to what is this device meant to do? Never heard of anything like a defrost timer.

[@MadElectroScientist]

Hoping this comment helps someone in the conundrum I found myself-- had a dorm style refrigerator (with defrost cycle, most new cheap ones don't have this feature anymore) the timer went bad (gears gum up/bearing surfaces resist so motor fails to turn) fridge gets stuck in a either mode-- the replacement for my particular refrigerator was a more exotic model because of the smaller size (defrost time was significantly less like 10 min); OEM replacement was like $50 at the time, the generic solid state timers I tried were both crap they would get stuck in an oscillation where you could hear the relay rapidly cycle for several seconds when switching mode?? Not sure what caused that, maybe a voltage drop? Either way it didn't want to impose that kind of stress on the compressor so abandoned those as an option, so as a last stride effort I bought a cheap standard mechanical timer opened it up to inspect the guts and compare it side by side with the original, all the construction was identical, gearing, cam lobes, I couldn't wrap my head around what would cause the defrost cycle to be longer or shorter but I eventually figured it out, know how it's done? The length of the arm past the contactor! It rides on the contour of the cam for a longer amount of time! Elegence in simplicity! I snipped off ~⅛ of the metal edge on a 30 min timer and saved myself $40 😅

[@MadElectroScientist]

I composed this comment before I was able to watch the video, I see now this defrost timer has some different operational principals; the style I countered had constant gearing; the cam the contactors ride on was always moving, it did not index like this, much smaller motor and far simpler contactor setup.