Build a Dim Bulb tester to protect equipment under test

[@zulumax1]

I have 3 bulbs on mine. I like the clear bulbs, easier to see the filaments glowing. Same kind of bulb holders screwed on a piece of scrap wood. Bulbs are 60, 40, and a 17 watt. I do have a 200 watt if I need more umph. The 200 watt is 1.73 amps, the 60 watt draws 470 mA.

[@FindLiberty]

PERFECT - very nice.

[@goodun2974]

The dim-bulb tester I use at work is mounted on top of a Variac that also also has voltage and current meters and a bypass switch for the series-wired bulb. It has been using the same 150 W clear glass bulb for the better part of 15 years.

[@cotto887]

The 200 watt bulb drews 1.66 amps

[@cotto887]

The 60watt bulb draws 0.500 amps

[@zulumax1]

@@cotto887 thereabouts, it draws 467 mA which is very close. 308 mA on the 40, and 68 mA on the 7.5 watt (which is drawing 8.5 watts)

[@unclefrogy743]

thanks again for a good video. you put it at an angle because you are funky and demystify repair work It does not have to be all pristine it has to work . your bench looks cleaner then mine.

[@goodun2974]

"Your bench looks cleaner than mine". That's a frightening statement!

[@FindLiberty]

@@goodun2974 Mine is three to four layers deep with no flat surfaces visible...

[@12voltvids]

@@FindLiberty A clean bench is a sign of nothing being accomplished.

[@JaypiTechPHOfficial]

This is very effective especially if you need to adjust bias using this dim bulb tester.

[@groovejet33]

I really enjoy these electronic "Teach In" content, . Always interesting to a hobbiest like myself. Thanks Dave Am i correct in semising that most Old school repair guys make some kind of protection device/Transformer set up, to pprotect them, when they touch theat lLive CRT? ha ha ha

[@wayneo7307]

Thanks , For The Video . Looks like A Fun Project and Useful tool.

[@alvinpillay9995]

What? Just yesterday I was looking for a schematic to build one. Thanks for the video.

[@ElectoneGuy]

An edison bulb socket to two-prong adapter works great. Just plug it into one of the slots on the receptacle and done.

[@FindLiberty]

EXACTLY, just screw in the desired wattage bulb. Add a bypass switch for built-in full power. (a quad outlet arrangement could also eliminate the need for any switch, but that's not as slick looking. As a kid, I also used a screw-in push button "fuse shaped" circuit breaker (that was a popular upgrade in the years before circuit breakers).

[@goodun2974]

Yes, this can be done, but it only works if you wire the two halves of the dual socket together *in series*; the stock configuration of the dual socket is of course PARALLEL-wired.

[@razpones]

I just built a dim bulb tester based on this video, many thanks 12voltvids for the tutorial, it will be put to good use. Cheers!

[@Dicofol1]

I don't understand the working principle of this tool. Why would the bulb get brighter if there is a short? Isn't the bulb acting as a resistor, so it should prevent the equipment from starting if the Wattage of the bulb is too high, correct?

[@Poppinwheeeeellllllieeeeez]

Excellent video. Simple and straightforward instruction.

[@stphinkle]

Is that bypass switch in the correct position or the correct type? It is interesting that it is in PARALLEL with the lamp. It would seem like that circuit creates two paths when closed, as some of the electricity will still flow through the lamp at a reduced voltage while others at full voltage, essentially creating a circuit in which two different voltages are connected in parallel but in phase with each other. I wondered if the correct circuit is to use a 3-way (single pole, double throw) switch on the hot side which one output goes to the bulb and the other switch output goes direct to the outlet. This way you are switching the actual path rather than paralleling a reduced voltage path with a full voltage path. Unless there is something I am not getting here. Might be interesting to see if you are indeed getting full voltage across the outlet with the switch closed.

[@cajuncoinhunter]

Current takes the LEAST path of resistance , The light bulb is a resistor in a way , current will flow thru the switched direct wire more easier ..

[@12voltvids]

The switch literally short circuits the lamp effectively taking it out of the circuit.

[@zulumax1]

@@12voltvids The resistance of the switch would be so unmeasurably low that there would be no current running through the light bulb, at least nothing worth mentioning. However, in theory, what he says is a logical assumption. I had a bond and ground meter at my old job that would send high current through a ground jumper and measure the small voltage across it to calculate micro ohms. I wonder what the resistance of a house wall switch is? I don't think my ESR meter will go that low, as it may be less than 0.001 ohms. Ya, ya, 99.999% goes through the switch, but once my mind goes into thinking about ohms law, I can't shut my mind off.

[@cajuncoinhunter]

Plug that unit into a isolation transformer and have the peace of mind for no shock ...

[@12voltvids]

It is plugged into isolation transformer. Everything I am working on is. After all I am not a "Dim Bulb" and judging from a few of the comments I would have to say a few viewers are.

[@StuffnSuch]

I was literally just about to look up how to make one. Sweet!

[@billsutherland9193]

I was tempted to make one like this but I'm concerned about not having a switch to turn the unit off quickly in case of a short!

[@12voltvids]

The thing is that is the point. If there is a short the light will glow bright and limit the current so no damage. Won't even blow the fuse. That is why these are an important troubleshooting tool, a must have.

[@billsutherland9193]

@@12voltvids makes sense, thanks!

[@conwaynoel3715]

What happens if you forget to change the switch ? Just plug the DUT out and plug it into the mains ! No messing no chance of a mistake ?

[@12voltvids]

Perhaps YOU would forget the position of the switch but I wouldn't.

[@michaeltempsch5282]

If the switch is in the closed position as you plug in, it's the same as plugging the device you're testing directly to mains (or isolation transformer), so no protection from the bulb's current limiting (as the bulb is bypassed with the switch closed).

[@12voltvids]

@@michaeltempsch5282 the switch won't be in the closed position.

[@marka1986]

You can write full power and limited on the switch plate if you like.

[@zulumax1]

@@michaeltempsch5282 In which case I hope your wiring of the dim bulb device can handle the brunt of the full 15 or 20 amps of the breaker. At least put a 2 amp fuse inline if you use a bypass switch to be safe. Cut off the cord of an old Christmas light cord with a built in fuse in the plug.

[@zx8401ztv]

As govenments ban everything usefull , future bulbs for testing radios will be resistance and thermisters to try to create a similar effect. The visual feedback is always nice :-D

[@12voltvids]

Incandescent readilly available here. Specialty lamps. Loophole. A they had to do is call them a specialty bulb.

[@FindLiberty]

Kids need to be careful to not get Salmonella poisoning from their Grandparent's original Easy-Bake (toy oven) that required a hot 100 lamp to cook properly.

[@stphinkle]

There are exceptions to the incandescent lamp phase out. Most rough service bulbs are not banned. Stage lighting is another one that is not banned. There are also certain incandescent made for industrial equipment and other very specialized applications that are not banned as well.

[@12voltvids]

@@stphinkle Only general purpose lamps are banned.Heat lamps, plant lamps, speciality lamps such as for picture frames, rough service ect are still available.

[@zulumax1]

Oven bulb 40 watt clear still available, also used in lava lamps for heating the action.

[@frankowalker4662]

Incandescent bulbs are only available on ebay in the UK. With the state of some of my deliveries, I don't think they would survive shipping.

[@goodun2974]

I bet you could find incandescent bulbs at a flea market or bric a brac store.....

[@DGTelevsionNetwork]

I believe pet stores still sell incandescent bulbs across the pond. They're meant for reptiles, usually pretty high wattage rating though.

[@FindLiberty]

When I lasted "vacationed" in the UK ~30 years ago, I brought back an assortment of standard clear 250 volt lamps for this exact purpose.

[@cajuncoinhunter]

Regular light bulbs at the dollar stores are plentiful in my area .. I have plenty 100 watt bulbs just for this reason..

[@goodun2974]

@@DGTelevsionNetwork , infrared heat lamps used as food warmers in restaurants would also work. Similar bulbs are also used in some bathroom ceiling fixtures to help dry you off when you get out of the shower, typically in cooler climates anyway. Years ago, one of my Floridian cousins was visiting us up here in New England, and after using the guest bathroom, she asked my mom, "Aunt Cindy, why do you have red lights in your bathroom?" 😀

[@theotherchannel2279]

The problem is here in the UK you cannot get old bulbs now, they are all LED bulbs!

[@FindLiberty]

Nice. I use mine with a 15 watt bulb to set an external trim pot that adjusts Idle Current for my modified "200" Watt -sub-woofer- Plate amps. The large heatsink fins run just slightly warm with no audio input. See zulumax comment!

[@Dutch-linux]

Dave a question .. here in the netherlands we can no longer buy regular bulbs only LED and that wont work for a dimbulb tester is there a alternative to make a dimbulb tester ? as i like to make one but I do not know what I can use as alternative to a regular bulb thanks

[@12voltvids]

Can you not buy speciality bulbs? We have tons of them here. Sold as garage door opener

[@Dutch-linux]

@@12voltvids all is LED here so no .. unless i would order it from the us or uotside europe but we have 240 volts so that is another draw back cant just order from the us .... or could put 2 of the 120 in series

[@Dutch-linux]

or would a hallogen bulb work ? we can get those still

[@geirendre]

You should also be able to substitute the bulb with a (big watt) resistor. Given the formula: R=V^2/P so (240*240)/50 = 1152 Ohms would equal a 50W bulb. And then put a voltmeter across the resistor to monitor the voltagedrop over it. The bulb is a much better solution, but if you can't get any...

[@frankowalker4662]

@@geirendre The problem of using a resistor is the build up of heat. You would need a realy good , (and big), heatsink.

[@michaelblack5011]

nice build

[@johnboudreau842]

Dig the home made wire strippers. LOL

[@goodun2974]

Plastic lamp sockets are barely suitable for LED bulbs, but definitely inappropriate for use with a hot-running incandescent bulb. Use a ceramic socket, fer chrissakes. (BTW, even LED bulbs will usually benefit from the use of a ceramic socket because the ceramic will conduct heat away from the electronics in the base of the bulb far better than a plastic socket will, and thereby extend the life of the LED bulb). If the main reason for using a ceramic socket is so that you can cut the base of it with a Dremel tool, then maybe you should be using a larger enclosure. I have the bulb socket wired to the output of my Variac and mounted on top of the Variac housing, with a bypass switch. Far more convenient this way, especially because the Variac has a voltmeter and ammeter built-in.

[@eDoc2020]

You definitely don't want to see my dim bulb tester where I have the bulbs held in with hot glue.

[@12voltvids]

This is't plastic. It is a composite type material. Ceramic sockets are not readilly available here anymore. This is all they have.

[@goodun2974]

@@eDoc2020 , years ago, a friend of mine replaced the speakers in the top dashboard of his Saab 900 (originally a pair of upwards facing 4" philips woofers and dome tweeters) with better quality drivers, hot-glued in place. He did this in the fall; next summer, when the sun hit the dashboard, the speakers fell off their mounting plates and down inside the dash!

[@goodun2974]

@@12voltvids I just took a quick look online and it appears that ceramic sockets and incandescent bulbs are still widely available. Granted, I have not had to buy a ceramic lamp socket in years because I often find them for free at the swap-shop area of our local transfer station (ie, the "dump").

[@zulumax1]

I have never run my dim bulb tester long enough to put out enough heat to be a concern. I have thought about building a cage around the light bulbs however, in case something knocks over and breaks a bulb.That would make for an interesting day!

[@markc871]

I want some Five Guys now

[@12voltvids]

Haven't been there is awhile. Now I remember why I stopped going. I had to take a double take when I handed a 20 and the guy said it was more than that!

[@markc871]

@@12voltvids you’ll spit your chips if you see Australian prices.

[@12voltvids]

@@markc871 I have a brother in-law that lives down there. I know how much stuff costs there. But here where I am if you don't have a couple million you ain't buying a house. Housing costs here are on another planet

[@markc871]

@@12voltvids catching up here