Solid State vs Electro Mechanical Relays

[@webslinger2011]

Good thing my creality 3d printer now uses mosfets for heating the bed instead of an SSR. Seen some posts with that thing staying closed overheating the bed on older models.

[@gregferguson7737]

Seems to be a reasonably common problem. A number of people have done the conversions

[@brianwood5220]

Well explained Paul. Love the sound of the water trickling in the background.

[@TheTubejunky]

That's awesome to know that the EMR switches at zero volts. Thanks for describing the cons of this relay as well.

[@acestudioscouk-Ace-G0ACE]

Another video helping me on my learning curve. Thanks!

[@OsoPolarClone]

Please explain isolated bias supply. Thanks

[@benhetland576]

3:35 I may have got this wrong, but isn't the "magnetic breakdown" primarily something associated with the coils in an AC circuit, not the switching itself? If so, that issue (and ems) comes mostly with the relay coil, not the SSR's triac. Instead the abrupt change in current/voltage when switching on or off at non-zero causes high frequency EM radiation, aka electrical noise. The latter applies to both relays and SSRs though, but the triac helps eliminate the switch OFF noise for an SSR, which is not so easily done with a relay. Some SSRs also have zero-crossing detection so that they switch ON only at (or immediately after) a zero point as well.

[@gregferguson7737]

"Fail closed"...erk...yeah that gives pause

[@stevetobias4890]

Great video Paul, thank you

[@georgechambers3197]

I've used both and I'm with you the mechanical relays are preferable. Thanks for the video!

[@Hugatry]

Well done with the comparison. I would add leakage current to the disadvantages: SSR often have leakage current in range of couple of milliamps. It's not much, but can cause mysterious behavior with small loads.

[@michaelpadovani9566]

see a lot of those style SSR on air conditioning units

[@warrenscorner]

I used solid state relays in my electrical designs that required heating elements such as in a hot stamp machine. Whenever troubleshooting a machine I looked at all of the mechanical relays first. Most of them have clear plastic covers so it’s very easy to single out the one that had a burned cover.

[@baldrickdaisy8982]

Very informative. Thanks mate 👌

[@tommays56]

We use them and they suck unless you have space for a BIG HEAT SINK

[@fertilizerspike]

Higher resistance isn't necessarily a disadvantage

[@RogerCillion]

What about time comparing those two ? There seems to be bit lag of the actual switch. Sometimes this timing is critical. Which one to use then ?

[@waynegram8907]

You didn't talk much about why they need an isolated bias supply voltage? When the solid state fail is closed this can cause damage to the circuit because it's a short 120vac short ?

[@keithking1985]

why does it only switch at the zero crossing?? anyone?

[@loucinci3922]

Interesting. Thanks for sharing.

[@boots7859]

Additionally, if you need responsiveness, SSR's are going to be worse as they wait for zero point crossing.

[@englishrupe01]

Great video, thanks Paul! Failing ON is a huge downside it would seem to me.

[@learnelectronics]

It is

[@benhetland576]

Downside or upside depending on the application, I'd say. For instance in my case it is used to switch on a heating system for a water pipeline during winter, and if it fails ON at least I still avoid the water freezing :-) Now the challenge is just to assure that this will always be the failure mode when/if it happens...

[@madcockney]

It should be noted that you can buy NO (normally open) in both types and they are the ones that usually fail in the open fail safe way. With mechanical ones besides being used to switch high currents they were often used so that the control side is low voltage with the output contactor side being high voltage and the electronic SS versions can be used the same way with the relevant type. Electro mechanical ones are usually not as efficient as electronic, could cause issues to very sensitive equipment , more likely to fail, though at one time was the preferred type in industry (UK) as if it failed you picked up a replacement at the local electrical factors. However if mounted on a circuit board or similar the electronic SS version is usually the preferred method. One of the things that noticed over the years is that some circuit designers pushed SS relays to their limits and this was less common with electro mechanical types.

[@JasonLeaman]

Good video sir !

[@ep_dimi]

I like your channel, and the simplicity to your videos. It would be nice to see an implementation of a hybrid relay next time. Thank you

[@tonyguerich9854]

I'll be darned if the preroll ad wasn't from Phelps County Mo where I went to college. Cool. Watched the whole thing.Hope it helps your numbers Paul.

[@TheTubejunky]

That's probably just google + youtube giving you ads based on your personal information they have gathered over the years.

[@pulesjet]

You need two SSR and other circuits to toggle them.

[@gerufish]

GREAT video as always. I've only used mechanical relays. I'll have to try solid state sometime.

[@opalprestonshirley1700]

Well explained. I'd forgotten about solid-state relays. Hope everything is going well with your mm. ATB!

[@Elfnetdesigns]

Another HUGE CON with these is that there are a fair amount of counterfeits out there that claim to be X Amps but are really Y Amps IE: The cheap FOTEK 25 Amp actually has a 12 amp TRIAC in it. This is VERY dangerous because someone not in the know will install it and it may switch the load a few times before it goes bang and up in smoke which can (depending on it's installed location) start a fire. You KNOW you found a legit SSR because the price will reflect it.

[@spacewolfjr]

Great video! I have a little Raspberry Pi project planned where I'm going to be selecting speakers "A pair" and/or "B pair" using some EMR relays (one of those cheap but plentiful 4 relay boards), I've made sure the board has the appropriate flyback diode and resistor to avoid damage via a current rush. I hope the EMR doesn't provide too much noise (besides the initial switch).

[@weerobot]

Cool...

[@boots7859]

Cost?

[@henricoderre]

In your schematic of the EMR example, the relay contact switch will be in its NC position when the electromagnet is deenergized and the circuit is ON. Applying a small voltage will energize the electromagnet and draw the contact switch towards the NO position when the circuit is OFF. So, your diagram is of a NC EMR. Are these devices also available as NO EMRs? In which case the relay contact switch will be in its NO position when the electromagnet is deenergized and the circuit is OFF, and applying a small voltage will energize the electromagnet and draw the contact switch towards the NC position when the circuit is ON. You make no mention of this.

[@blic-sx9ix]

On double throw EMRs you have your choice. If you want signal voltage to close the circuit hook your load to the NO terminal. If you want signal voltage to open the circuit hook your load to the NC terminal. Most industrial socketed units are double throw. The little circuit board mount "bricks" can be NO only or double throw (NO and NC).

[@henricoderre]

@@blic-sx9ix Thanks for the info blic.

[@bblod4896]

Cool

[@kingblondie7075]

So fail closed is when Luke shoots the blast door controls and the door closes and fail open is when he hits the controls with his light sabre and the door opens. Makes sense now.

[@stephenwong9723]

And Solid State Relays do not have NC contact.

[@paulp2089]

If you get a chance then visit a telephone exchange museum and check out what used to be done with electro mechanical relays. The 50s/60s 'Step-by-step' and 'Rotary' automatic exchanges were high maintenance, hot and VERY LOUD .... but also very hard to kill. I worked in one that had been in operation for well over 25 years and had been offline for less than 20 minutes. The replacement computerized exchanges crashed at the drop of a pair of pliers :-)). Make sure you visit the museum, not just Google it. Google wont give a true indication of physical size of the switching units. 50 volt lead/acid batteries that took up half a building floor, multi-phase rectifiers, 5000 amp circuit breakers. Aahhh those were the days ! Hhhhmmm probably explains my reduced hearing and tinnitus too. Huh, life is a ^&%$#.

[@XPFTP]

RF? antenna switch box . noise on RF if at all ? 100 watts RF. maybe a tunner also . tho would need like 10 of them lol LDG does it . why cant we.

[@frankowalker4662]

There are only 2 terminals, does that mean you can't have it switch 2 things at once? (one off, the other on?)

[@learnelectronics]

Correct

[@bluegizmo1983]

Uh, Duh! Solid States are ones that don't have any rivers, lakes, or other nature bodies splitting the state in two! 🤣