Do you think it’s a counterfeit?
I have a counterfeit FOTEK which was supposed to be an original…
http://www.ebay.com/itm/322484008013
It’s going to cost 83USD for the SSR and that’s without the shipping, which is going to be somewhere around 60USD to Cyprus + import duties…
Too much… Any other alternatives?
I’ll looking to run a 23A Heatbed setup.
550W @24V
Maybe a different solution than using an SSR?
For DC-to-DC I think you should look into a Mosfet to control the bed versus an SSR. DC-to-DC SSR have a bad failure mode, tending to stick latched which would be a bad time. The AC SSR failure mode tends not to be fail closed circuit, so much better.
And I couldn’t agree more with +Peter van der Walt. For high power beds you should look into Mains power, then a DC-to-AC SSR for switching.
@Eclsnowman , any suggestions on which Mosfet would be suitable?
@raykholo , you still have those remote mosfet boards available? They aren’t on the website.
I have some, sure. Limit is only a few amps DC though before they get really hot.
@raykholo what mosfet do i need to run the BigBed from
A safe, super cheap and super reliable way to drive a high power bed is to use … an old-school solenoid-based relay instead of a solid state one.
They only require a much slower switching rate: say, a few seconds are more than OK though (make sure to disable PWM in your firmware! Marlin has all what it needs). Slow changing heated beds need no fast control. Relays are certainly less sexy, but they are easy and efficient, and they work as well with DC loads. Oh, and you also hear them work 
Nb: I used to buy Fotek SSRs on ebay, but nowadays the market is crippled with fake ones (it is easy to tell when they do not trigger at the claimed 3.2V ipo 5V, but in your case of a 5V-rated trigger, who knows…).
Oh I have my Remix running that. It’s fun! I use a SQM120N04 - rated for 120amps and low RDSon value. It still gets hot. Frankly you need it on a 10x10cm PCB with a heat sink and a fan mount for ideal performance.
@Jeremie_Francois , I just tested the FOTEK SSR with the 3V input and it triggered just fine… It may be a legit one after all?..
With the money saved on cheap/foreign SSRs, why not invest in a thermal fuse for the bed? Probably still money ahead, but a little extra peace of mind.
@Panayiotis_Savva “working ones” may still be fakes though as shown below. Ugly fake ones will probably try to reduce cost on the MOSFET and Triac (trigger level, internal resistance). They could perhaps both be measured after buying, but I still would not trust them too much! Checking how hot it becomes during use is a must though!
Even if you do 10s cycles on a reputable mechanical relay, you can quickly exceed the cycle rating on the contacts. A 100,000 cycle rating means you exceed rated cycle life in less than 280 hours of operation.
@Panayiotis_Savva It’s not a fake Fotek but a genuine Mager. Normally they sell between 20 and 30 $ per piece (I don’t know who tries to charge you 83 USD). Take notice that the voltage drop over the power connections is around 1.5V. So if you switch 23A the ssr dissipates 35 Watts!! It needs to be cooled. (Aliexpresss dd220d40 gives you an example for a radiator).
The 1.5V drop comes from the power components used. For AC thyristors or triacs are http://used.They have a drop of about 1.2V. To switch DC mosfets or GTOs are used. And they have the 1.5V voltage drop as I mentioned earlier.
Hope this was helpfull.
@Ben_Verdel , the FOTEK of obviously not a Mager. I was asking if this Mager was a good alternative to a suspected fake FOTEK 
The 83 USD is for another brand from digikey.
@Jeff_DeMaagd sure, there are trade-offs. Relays are not sexy, but they work and they are super cheap, that is all I wanted to say
They switch slowly and they are less durable. But you can find cheap, 40A, genuine ones as low as 2€ at mouser. At this price, you can change them cheaply if/when they start failing…
In reality, I always was amazed that the wiper relays of old cars still work after 30+ years: the claimed cycle rating is probably a warranty more than an indication of (half-)life. As for me, the little 5V ebay relay I added to my main printer in october 2012 never failed so far, but I may be lucky.
Finally, (cheap) SSR mostly die by melting, which could be riskier than how a relay fails (they do not heat when running – though I did not look for any data to justify this feeling when they are at the end of their life: bad contacts also often heat).
I’ve ordered SQM120N04, I’ll give that a try if i get an SSR meltdown…
@raykholo thanks for the advice.
Btw, did you get the mini c3d batch yet? When will they be available?
following on what Eric Lien’s note: I bought an SSR and it advertised having a zero-crossing feature - it only changed state when the voltage hit 0. Apparently this was to limit noise and spikes. So running PWM faster than 120hz on AC would have been useless, and utterly useless for DC.
@Panayiotis_Savva you need a pcb to put the mosfet on.
Mini batch is 1-2 weeks out.
So I wired the the Fotek SSR up to the heatbed…
+24v to the SSR +(2) terminal.
-24v to the heated bed negative.
SSR -(1) terminal to the heated bed positive terminal.
It switched on just fine.
When it reached target temperature the SSR light went off and the world seemed perfect…
Then i noticed that the bed temperature kept climbing and climbing… Slowly but surely just kept going up and up…
I measured the voltage on the heatbed connections to find that 1.3V from the SSR/Power supply were still being leaked…
How is it even possible for a 24V bed to get so hot from 1.3V?
I guess the SSR is bad…