Want to see the inside of a Fotek SSR

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Want to see the inside of a Fotek SSR

Postby Aleman » Fri Jan 29, 2016 12:33



So reasonably well designed, but only half the specs . . .Good reason for using a 40A and hope it had a 20A TRIAC . . .Think I need to have a look at taking one apart :D

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Re: Want to see the inside of a Fotek SSR

Postby Dave1970 » Fri Jan 29, 2016 13:04

All a bit beyond me, but I understood enough to be glad I went for a 40A in my RIMS controller though

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Re: Want to see the inside of a Fotek SSR

Postby Springer » Fri Jan 29, 2016 13:23

Beyond me as well, but nice to hear someone who knows his electronics and 40 amp for me next time, just to make sure. :)
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Re: Want to see the inside of a Fotek SSR

Postby Hairybiker » Fri Jan 29, 2016 15:46

Until we know a 40A one has a better triac in it, it is still up for debate. I don't have any to take apart so will be interested in what Aleman finds out.

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Re: Want to see the inside of a Fotek SSR

Postby Graham_W » Fri Jan 29, 2016 16:57

The triac being underrated does not give confidence in these Chinese clones. It is not even clear if it is zero crossing, but as the driver chip seems to have six pins it is likely to be an MOC3063 which is zero crossing. Some of these Chinese SSRs that people have bought are not zero crossing. One in particular, that was very popular among home brewers had its internal circuit diagram published on the ebay sellers page and that certainly was not zero crossing.

It is probably safer, for those with the skills, to build their own. One snubberless triac of a rating of choice, one MOC3063 and three resistors and the job is done. Won't match Chinese prices, but is still quite inexpensive and at least you know what you have got. The most expensive bit is the heatsink, but you can buy that from China with relative security.

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Re: Want to see the inside of a Fotek SSR

Postby AltonAnt » Sat Jan 30, 2016 09:47

Honestly. What do people expect for £2? ;)
I went for the 40A too just in case which has been fine.
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Re: Want to see the inside of a Fotek SSR

Postby Graham_W » Sun Jan 31, 2016 00:02

AltonAnt wrote:Honestly. What do people expect for £2? ;)

I would suspect that they would expect the rating of the triac to exceed the rating published on the label, which it clearly does not. If it does not do what it says on the tin, then it is fraudulent and possibly dangerous, apart from the disappointment and frustration involved by people trying to use them at their rated value, only to find that they fail at an unacceptable frequency.

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Re: Want to see the inside of a Fotek SSR

Postby AltonAnt » Sun Jan 31, 2016 09:52

A quality solid state relay rated for 25a would cost £40+ so if you use one that costs £2 are you seriously expecting the same quality. If something appears to good to be true then it most likely is.
I work on the premise that they are likely to fail but if they last a year then it would take 20 years of failures to match the high price item. Buy cheap, buy twice etc.
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Re: Want to see the inside of a Fotek SSR

Postby Springer » Sun Jan 31, 2016 10:44

I can see the different points of view and I know where my next one will come from.............................China of course :D
Still a great video

S
P.S. might get a few spares at the price. :)

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Re: Want to see the inside of a Fotek SSR

Postby cyclops » Sun Jan 31, 2016 11:08

I have a few of these, around 6 on my system although mine at the 40A version. Never had 1 fail yet but then again it is only driving around 10amp.

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Re: Want to see the inside of a Fotek SSR

Postby Graham_W » Sun Jan 31, 2016 14:05

AltonAnt wrote:A quality solid state relay rated for 25a would cost £40+ so if you use one that costs £2 are you seriously expecting the same quality. If something appears to good to be true then it most likely is.
I work on the premise that they are likely to fail but if they last a year then it would take 20 years of failures to match the high price item. Buy cheap, buy twice etc.

£40+ is hell of a lot of money, a bit of a rip-off really, when one considers that there is less than a fivers' worth of electronic components in them. An MOC3063 costs 33 pence. A 25A snubberless, insulated-tab triac costs £1.89, up to four resistors and a capacitor will cost another few pence. These are at R.S. one-off, single unit prices, and RS are not the cheapest place to buy components by a long way. Surface mount components would be somewhat cheaper. It has a minimal PCB, which does not even need to be double sided.

There is, of course, the case that it is in, but this is just a couple of plastic mouldings and an aluminium plate. I suspect that these are available from a third party somewhere for peanuts and that the SSR manufacturer doesn't need to make it himself or invest in mouldings. If a Chinese back-room cowboy can get the cases, they must be available somewhere. There are several indications in that video that those units are not professionally built in quantity; the use of through-hole components for one; the lousy PCB layout and the lack of a lacquer or conformal coating to prevent any moisture from breaching the isolation clearances being another two.

The author of the video made a good point about the isolation clearances. I don't have access to the European Low-Voltage Directive now that I am retired, and I doubt if those clearances would meet the C.E. specification, but it is difficult to tell from the video what those clearances are. The lack of a lacquer for moisture protection would be another point against it.

I can see the attractions of cheapo Chinese stuff, when compared to rip-off-Britain prices, but I am not sure that I would trust the stuff where safety and reliability are involved.

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Re: Want to see the inside of a Fotek SSR

Postby roscoe » Sun Jan 31, 2016 23:33

.... could n't believe the fotek deal, I got them,

THEY ALL FAILED

and unlike most relays they FAILED ON.

I opened mine up, utter dinky-toy clone crap

can't win them all....
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Re: Want to see the inside of a Fotek SSR

Postby Hairybiker » Mon Feb 01, 2016 12:43

Most relays I have used have failed on as well. The contacts weld together. When I used to work in the capacitor manufacturing sector (early 80's), one of the jobs was "un-welding" the relay contacts in the test bench. 30+A relays were used and they used to weld together regularly.
With SSR's the path gets "burned in", making it always on.
I have a couple of those "remote control" mains sockets that both have relays that have welded in the on position. The led claims it is off but the device is ON.

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