loading

Not too long ago we had a serious warranty issue with some of the controllers we manufacture. The controllers were passing test and would initially work for our customers, but would eventually fail. And this failures occurred after a long run of controllers that did not fail, so I knew that something changed. We have used FOTEK SSRs in our controllers from day one and they have turned out to be very reliable. One change we made is we switched from buying directly from a Chinese supplier to buying through USA based suppliers selling on Amazon.com. I had been watching prices for a while and my cost through Amazon.com dropped to close to what I was paying for parts direct from China.

Suspecting that the SSRs I bought through Amazon.com was the problem, I broke apart a 25 Amp rated part and a 40 Amp rated part and what I found surprised me. I expected junk but both SSRs were built very well, but they were both built with under-rated TRIAC's. For reference, the TRIAC is the part that actually switches current on and off inside your SSR.

The 25 Amp SSR was manufactured with a BTA12-400C TRIAC. I did a quick online search and discovered that the part is rated at a continuous load of 12 Amps and a non-repetitive load of 126 Amps. In other words, the TRIAC used in the 25 Amp SSR is only rated for 12 Amps! Here's my BTA12-400C Google search

The 40 Amp SSR was manufactured with a BTA20-600C TRIAC. I did a quick online search and discovered that the part is rated at a continuous load of 20 Amps and a non-repetitive load of 200 Amps. In other words, the TRIAC used in the 40 Amp SSR is only rated for 20 Amps! Here's my BTA20-600C Google search

I did a third search on FOTEK SSR counterfeit and discovered This Article as well as hundreds of forum conversations claiming counterfeit. And even though some of the counterfeit claims are likely failures caused by improper installation, apparently counterfeit SSRs are quite a problem! My next question was - are there even legitimate FOTEK SSRs out there? Yes there are and here is their Web Site. And BTW, I'm not just picking on FOTEK or Amazon.com. If you decide to buy any brand SSR from any online supplier including Amazon, eBay or "Joe's SSR Shop" not licensed to sell the product you are basically making a "shot in the dark" purchase.

I mentioned earlier that even the counterfeit SSRs were built well. All of the soldering was high quality and the TRIAC was properly mounted to the back plate with plenty of thermal grease. I suspect that these counterfeits are nothing more than lower current models re-labeled as higher current models. If this weren't so I believe the counterfeits I disassembled would be poorly built. There is a huge financial motivation to do this. Lower current models cost less than higher current models and any re-labeled product would result in instant extra profit!!!!

After this discovery I immediately went back to buying directly from my Chinese supplier and except for an occasional controller, the failures have disappeared. I have not broken apart one of the SSRs that work, but based on the difference in performance it's obvious that there is a internal difference in these parts.


Step 1: What If You Are Already Using a FOTEK SSR or Are Designing Your Own Controller?

If you have been using your SSR with no issues for a while then most likely you have a good one. FOTEK is a well known name in China and a good product and your SSR should continue working for a long time.

What should you do if you are designing your own controller?

Should you buy something other than FOTEK? I'd say not necessarily because FOTEK SSRs are a great value compared to anything you can buy from a USA name brand supplier. For example, a 25 Amp rated Crydom SSR will easily cost you $40 or more, while a 25 Amp rated FOTEK SSR will cost you less than $10 through eBay or Amazon. The best solution is to 'assume' that the part you buy has been re-labeled and buy a SSR with higher current rating than you need. Buy a 40 Amp SSR to control a 20 Amp load, etc. The cost is not much higher and you still purchase a quality part for far less than a SSR you would buy from a USA name brand supplier.

Or you could just buy a name brand like Crydom, but with counterfeits so common these days how do you know if your eBay sourced Crydom SSR is real or counterfeit? You don't!

The best solution if you are buying one that has to work is to "bite the bullet" and buy your SSR from a licensed distributor like digikey.com. A Quick Digikey Search for Crydom 25A SSRs returns a selection in the $41.00 and up range.

Tom - www.kegkits.com

<p>For what it's worth, I did a similar teardown of a failed fake SSR60-DA on my awful neglected pretend blog:</p><p><a href="http://epicbeardquest.blogspot.com/2014/10/how-to-destroy-fake-fotek-ssr.html" rel="nofollow">http://epicbeardquest.blogspot.com/2014/10/how-to-...</a></p><p><br></p><p>I agree that it's relatively simple and inexpensive to design your own SSR's from triacs or SCR's; however, there are a number of appnotes relevant to addressing component selection and protection that are perhaps better than blindly grabbing a schematic from GIS. </p><p>Use and protection of triacs:</p><p><a href="http://www.littelfuse.com/~/media/electronics/application_notes/switching_thyristors/littelfuse_thyristor_miscellaneous_design_tips_and_facts_application_note.pdf.pdf" rel="nofollow">http://www.littelfuse.com/~/media/electronics/appl...</a></p><p><a href="http://educypedia.karadimov.info/library/6785.pdf" rel="nofollow">http://educypedia.karadimov.info/library/6785.pdf</a></p><p><a href="http://www.datasheetcatalog.com/datasheets_pdf/A/N/4/3/AN437.shtml" rel="nofollow">http://www.datasheetcatalog.com/datasheets_pdf/A/N...</a></p><p></p><p><a href="http://www.onsemi.com/pub_link/Collateral/AN1048-D.PDF" rel="nofollow">http://www.onsemi.com/pub_link/Collateral/AN1048-D...</a></p><p>Using &amp; snubbing optotriacs:</p><p><a href="https://www.fairchildsemi.com/application-notes/AN/AN-3003.pdf" rel="nofollow">https://www.fairchildsemi.com/application-notes/AN...</a></p><p><a href="https://www.fairchildsemi.com/application-notes/AN/AN-3004.pdf" rel="nofollow">https://www.fairchildsemi.com/application-notes/AN...</a></p><p>Direct gate drive circuits:</p><p><a href="http://www.st.com/web/en/resource/technical/document/application_note/CD00266635.pdf" rel="nofollow">http://www.st.com/web/en/resource/technical/docume...</a></p><p><br></p><p>Lastly, if you do decide to roll your own, be aware that there are counterfeit triacs on ebay too, and they'll give you just as much trouble, if not more. </p>
<p>Thanks for the great references. Based on what I read, if I do design my own SSR it will be with one of the snubberless TRIACs rated for at least twice the line voltage I'm switching. One of my motivations for &quot;rolling my own&quot; is I can build the SSR directly onto the heatsinks I'm using, eliminating one thermal resistance layer.</p><p>In the mean time I did find one brand that performs as advertised. They are PQLYT SSR - I order them directly from China.</p>
<p>Thanks for the heads-up I have bought some of these relays, but I think building my own would assure me of the desired rating. <a href="http://www.theprojectasylum.com/electronicsprojects/triacssrelay/triacssrelaycircuitdrawings.html" rel="nofollow">Here</a> is one example.</p>
<p>Just beware that the example you provided is designed around a 16 Amp TRIAC attached to a very thin aluminum housing. The amount of current that project will be able to switch will be limited to the watts dissipated by the TRIAC - about 1.5 watts per Amp and the ability of the housing to radiate that heat away. Assuming the SSR itself does not fail, all the components inside will be cooking at whatever temperature the housing settles to.</p><p>My &quot;best guess&quot; is this one is good for up to 5 Amps based on the housing. A larger housing is better, a finned heat sink is even better and a fan cooled finned heat sink is best - all depends on how much heat you generate!</p>
Thanks for finding this. I was building an automation setup and was thinking of using the foteks. On my budget, I'll buy the higher rated ones. Thanks again
<p>You'll note from the article that I am not against FOTEK SSRs. I believe that the counterfeiters have taken advantage of and are profiting from their popularity. One point I made is even the counterfeit SSRs were well built. And based on what I found I would not have a problem using them if I had to, I would just use a higher current SSR than my project called for. But fortunately I can buy direct from China and I've never had a problem with the SSRs I've bought direct.</p>

About This Instructable

9,777views

6favorites

License:

More by Tom Hargrave:Sturdy Bench Seat without cutting a Single Board Build Rustic Planter Boxes from Recycled Fencing Make Keurig Ramen Noodles 
Add instructable to: