This is really neat. It's a mass produced module for use in fridges and freezers that controls the duration of the start winding current when the compressor starts.
Traditionally the same task would have been done by a current operated switch that would close with the high initial current of the stationary motor and then drop out once the motor was running and the current dropped, but this method achieves the same results in a cheap, simple way with no moving parts.
Here's how it works. It goes in series with the start winding of the motor, which is usually only energised briefly at startup. When power is applied the device appears as a low resistance allowing current to flow through the start winding. The current causes the PTC element to heat up and its resistance rises, which means it dissipates more power, gets hotter and this behaviour results in a sudden increase in resistance until the only current that is passing is the amount required to maintain it at its holding temperature.
When the power to the motor goes off the PTC cools down and returns to its low resistance state.
The thermal effect means that the PTC module will take about a minute to recover to its starting resistance, but in a fridge or freezer the time between compressor cycles is long enough to allow a full reset.
The trip time will depend on the modules initial resistance, starting temperature and the load current passing through it. With a 100W lamp on 240V the current was low enough to take about 90 seconds to final reach its trigger temperature. With very low currents the unit might never trip. This opens up the interesting possibility of wiring one in series with a light fitting so it could only be used with low power lamps.
There are probably many other uses where a suitable load could be protected from long run times or overload. That could be to protect a high power solenoid or other coil, or to protect a motor from a stalled condition.
Best thing is that because they are a mass produced item they are very cheap on eBay in a range of different start resistances. Common resistance values seem to be 4.7, 12, 15, 22 and 33 ohm. I'd guess lower resistances are for higher power loads. There are also a few case styles and pin numbers. I'd recommend the 2 or 3 pin units for ease of connection. Note that an unused pin will probably be connected to the other on the same side and should be covered if not used.
https://www.ebay.com/sch/i.html?_from=R40&_trksid=p2334524.m570.l1313.TR0.TRC0.A0.H0.Xptc+start+relay.TRS2&_nkw=ptc+start+relay&_sacat=0&LH_TitleDesc=0&_sop=15&_osacat=0&_odkw=ptc+start+relay+3&LH_BIN=1
Also keep in mind that these should be regarded with the same mild suspicion applied to all cheap eBay components.
If you enjoy these videos you can help support the channel with a dollar for coffee, cookies and random gadgets for disassembly at:-
http://www.bigclive.com/coffee.htm
This also keeps the channel independent of YouTube's advertising algorithms allowing it to be a bit more dangerous and naughty.
Traditionally the same task would have been done by a current operated switch that would close with the high initial current of the stationary motor and then drop out once the motor was running and the current dropped, but this method achieves the same results in a cheap, simple way with no moving parts.
Here's how it works. It goes in series with the start winding of the motor, which is usually only energised briefly at startup. When power is applied the device appears as a low resistance allowing current to flow through the start winding. The current causes the PTC element to heat up and its resistance rises, which means it dissipates more power, gets hotter and this behaviour results in a sudden increase in resistance until the only current that is passing is the amount required to maintain it at its holding temperature.
When the power to the motor goes off the PTC cools down and returns to its low resistance state.
The thermal effect means that the PTC module will take about a minute to recover to its starting resistance, but in a fridge or freezer the time between compressor cycles is long enough to allow a full reset.
The trip time will depend on the modules initial resistance, starting temperature and the load current passing through it. With a 100W lamp on 240V the current was low enough to take about 90 seconds to final reach its trigger temperature. With very low currents the unit might never trip. This opens up the interesting possibility of wiring one in series with a light fitting so it could only be used with low power lamps.
There are probably many other uses where a suitable load could be protected from long run times or overload. That could be to protect a high power solenoid or other coil, or to protect a motor from a stalled condition.
Best thing is that because they are a mass produced item they are very cheap on eBay in a range of different start resistances. Common resistance values seem to be 4.7, 12, 15, 22 and 33 ohm. I'd guess lower resistances are for higher power loads. There are also a few case styles and pin numbers. I'd recommend the 2 or 3 pin units for ease of connection. Note that an unused pin will probably be connected to the other on the same side and should be covered if not used.
https://www.ebay.com/sch/i.html?_from=R40&_trksid=p2334524.m570.l1313.TR0.TRC0.A0.H0.Xptc+start+relay.TRS2&_nkw=ptc+start+relay&_sacat=0&LH_TitleDesc=0&_sop=15&_osacat=0&_odkw=ptc+start+relay+3&LH_BIN=1
Also keep in mind that these should be regarded with the same mild suspicion applied to all cheap eBay components.
If you enjoy these videos you can help support the channel with a dollar for coffee, cookies and random gadgets for disassembly at:-
http://www.bigclive.com/coffee.htm
This also keeps the channel independent of YouTube's advertising algorithms allowing it to be a bit more dangerous and naughty.
Technology Connections video sent me to this video in 2023. 👍
I've got an old small freezer that uses a relais instead of a PTC. Its running quite nicely on mains but if i try to run it on a battery powered inverter the relais flickers like crazy. I guess the inverter isnt strong enough altough its ratet 600 w nominal and 1200 w peak.
Is there any possibility to change the relais to one of those cheap ebay modules to make it run?
So if you have a motor that had its centrifugal start switch burn out, i wonder if one will hold up to shutting the start winding off after motor start..? Ive got an old motor that relies on a potential current relay which is basicallt the same thing except its more like a solenoid that has to stay in a certain position so the contacts will lift when the current shoots up….
I love this channel.
I have never been a fan of PTC start winding control. I prefer either centrifugal internal in split phase motors which is common on air compressors, bench grinders and traditional central ac or electromagnetic potential relay to control the start winding common in US refrigerators
This terminals are designed to mate with the standard three pin, hermetic sealed, feed through normally seen on small refrigeration compressors. Pre PTC days the compressor used a current relay wired with the operating coil in series with the run winding. On start up the high current draw would close the contacts on the current relay and feed power to the start windings. When the current in the run windings dropped the relay would drop off and the start winding would be disconnected. All the ones I ever came across were manufactured but a company called Klixon. The only time I ever saw a failed one was from where the start winding had failed so the current relay had stayed on and got black and crispy. Compressor checks were always pretty straight forward, the run winding is normal about twice the resistance of the start winding. Repairing it after was a job is hand over to the Refrigeration Engineer; I didn't work on enough refrigeration kit to justify the expense of more tools (and refrigeration tools are pretty costly)
so from what I've gathered, this lesson is not about the light cause that was used in place of a refrigerator compressor which would have regulated the current being that as the inside of the black mystery box gets hot then …..
My fridge has a 10uF AC start cap in it and the compressor has a thermal cutout device on it. A fridge compressor under load (high head pressure) cam draw more than 15 amps on startup on a 120 VAC supply. This depends on the size of your fridge of course. A window or RV rooftop AC unit can draw nearly 30 amps (on 120 VAC line) under load at startup and you homes central AC unit outside can draw over 100 amps on a 240 VAC line under load at startup.
The #1 failure in home AC units is a capacitor on the air handler / fan or compressor. next would be the units contactor relay an / or 24VAC transformer
Had to replace entire a/c unit on my house about a year ago. Frequent Power Loss is my power supplier. When installing the condenser/compressor (the outside unit) I spent $20 on a delay switch. When power loss occurs the switch cuts the power for 5 min. We have a real problem with the power blinking out for a few seconds then popping back on and blowing again, which obviously isn't so good for things like motors. When we get these cycles often u can hear the neighbors a/c units just humming away until it overheats and resets. I'll deal w not having a/c for 5 min rather than setting the fans and compressor to the broil position. Also if ur having ur unit worked on it pays to buy an extra capacitor. Caps don't like hot climates very much and are basically a consumable item. Having the right one on hand can save u hours or days of discomfort and a hefty bill from a repair company.
Clive, if there's time, could you look at a few ebay soft start modules? I'm hoping to find out , one what's in the devil's and two, if they'd work on much lower current
I must have replaced 500 of these in my career.
For most modern refrigerators that use the type of motor that is designed for it needs 2 more spade connectors for a run capacitor. To increase the efficiency by about 2/5's lower amps. They will run for a while but will over amp the run windings in the compressor.
Available now is the capacitor start(never a bad thing) capacitor run unit that comes with a 12 mfd cap. which is the most common. But you can attach the original cap. if it is of a different value. The motor is designed to run with that particular mfd cap for maximum efficiency, and they only very rarely fail. Like almost never.
'Supco' brand components and it's called a 4-n1 start relay. Very useful. Definitely NOT the '3-n-1' which doesn't have the crucial run cap. connections available. I have replaced many compressors that were ruined by this misapplication.
I would like to see a video on the electronic type of relay- for instance Whirlpool brand part number w10189190. It has an interesting little board and stuff in there and B.C. could go to town on it.👍
I think the security tags when you steal from from stores would be nice quick vid.
Half the fun is getting stuff apart!
It has been said that incandescent lamps do not appreciably strobe. Well, they do strobe enough to cause a 100 (or 120) Hz hum when operating an exciter bulb in a film projector, even with fairly good rectification and filtering. The LED and laser based red exciter assemblies that were introduced in the mid-noughties (accompanied by cyan dye in the soundtrack instead of black) did improve the hum problem because they actually had regulation. Although, digitalization was dawning already in 2004 when the first producers started making their prints with the cyan dye. And it was gaining good speed already in 2010. My theory is that although it was said the extra black dye used in the soundtracks would release toxic products into the atmosphere when burned, the truth behind all this was that the red light/cyan dye technology had to be sold somewhere in a rush, AND because the change would cost up to 10k EUR per machine, there would be cinemas that would not be able to swallow the pill. Truly, many went out of business because the distributors would no longer supply prints to cinemas without the new red exciters. A friend of mine got a few more prints when he lied to the distributors about the status of his cinema, and he would just ramp the volume up a few notches (although there would be a lot more noise). Once all distributors started requiring a certificate of the red exciter installation from a licensed contractor, no more luck. 2006 was the last year before an oncoming municipal merger, and our municipality would no longer grant support for the cinema. So out of business he went. And, to be frank (which I am not) I think all this was done to kill off "a few" booths so they wouldn't be queued for digitalization. There really was no true need to get rid of a potentially toxic component that had been used for decades, just to get by a few years. There would still be more cinemas that could not afford to digitalize. Now it is about ten years from the last foreign movie that was distributed here on film, and a wee bit less from the last domestic one.
Are there not delays calibrated into the grid? Ive seen the power go out, transformers exploding ive seen with my own eyes more than once. It seems to take a full second maybe to reset. Would that be enough?
9$ for me and it fixed my wine fridge 10/10 saved it from the endless trash heap at the dump.
If Clive made a clip about the Second Law of thermodynamics i'd definitely be interested in watching and possibly learn a lot more about it than i did in school! B.T.W Clive ever considered a career in teaching? Then again in a way through Youtube.