Replace the relay in a STC1000

I was dumb and burned out the heat-side relay in an STC1000 (plugged a heat stick right into it). I was bored so I desoldered it from the board and was wondering if I could run some wires out of the board to drive an external mechanical relay or SSR. Seems that's all the board is doing right? Does anyone know the control voltage&amps the STC1000 is providing on the board to drive its relays? What relay should I buy to replace the one I torched?

I understand that I could probably just buy a new STC1000 since they are so cheap, but now I just want to see if I can do it.

Yeah you can do that,, it uses 12v dc to control the relay coils.

And as long as the STC can deliver the needed current to drive the SSR/relay/contacter. Those micro relays the STC has only pull a few mA.

Sounds like a great Frankenstein project!

So I hooked it up and I get 12 v DC across 2 contacts. I'm pretty ignorant when it comes to picking electrical equipment; what should I search for on amazon to come up with the right relay? I've used and SSR in another project, but at the urging of "the internet" I put a fan in that box. I'd like to use a relay that won't require a fan if that's possible.

Can you post a picture of the markings of the relay that was originally used? If only the relay was damaged (no burnt traces on the pcb) then you can probably solder in the same relay right to the circuit board if we can figure out the part number.

In the STC-100+ thread there's a picture showing the STC-1000 guts.



Info on those two HF32F0G relays can be found here.

Finding replacements could be tricky.
Didn't spend a lot of time at it on ebay but there's a bazillion 5A micro relays in that form factor for every 10A version.
Mind the coil voltage!

Cheers!

I fixed one by de soldering both relays and moving the working heating relay to the cooling side. Made it only a one stage controller but it's better than nothing!

I think I found some replacements on ebay back when repairing this one but never got around to ordering any.

SSRs don't need much current to trigger. You should be able to feed the coil leads to the ssr and be fine.

If you want the original relay:

http://www.futureelectronics.com/en...ductID=HF32FG012HS257HONGFARELAYS3010906&IM=0

http://www.aliexpress.com/item/Hong...2-G-012-f-the-HS-high-load-10/1927448867.html

Unfortunately, I bought the equivalent of the above relay before opening up my STC-1000, only to find that mine had a different part. Mine is the single pole single throw (SPST)/ Form 1A version of what's shown here:

http://www.futurlec.com/Relays/JQC-3FF-12.shtml

See the update 2 posts further down.

cbier60 said:

Unfortunately, I bought the equivalent of the above relay before opening up my STC-1000, only to find that mine had a different part. This is what's in mine:

http://www.futurlec.com/Relays/JQC-3FF-12.shtml

Click to expand...

Same relay as in my STC1000.Look at the spec sheets they might be interchangeable.
( not an electrician)

The HF32F-G/012-H and the JQC-3FF-12 are not compatible.

The former is is a four pin module with only a normally open switched contact.

The latter is a five pin module with both normally open and normally closed contacts.
And the fifth pin is the common for the switch, so it's not going to fit in the four pin footprint.

Aside from that, however, the JQC could replace the HF (or vice versa) with some surgical intervention.
The contacts and coil voltages are similarly rated for load and pick/hold levels, respectively...

Cheers!

day_trippr said:

The HF32F-G/012-H and the JQC-3FF-12 are not compatible.

The former is is a four pin module with only a normally open switched contact.

The latter is a five pin module with both normally open and normally closed contacts.

Click to expand...

Sorry, my link shows the SPDT (Form 1C) relay, but the datasheet covers both the SPDT (Form 1C) & SPST (Form 1A). The relay in my STC-1000 is JQC3FF/012-1HS(551). It is also 4 pin, but still not equivalent to HF32F-G/012-H. Here's a better reference to the datasheet and exact part. The datasheet covers all the parts in the family. The part needed s 12V and SPST (-1HS).

Bigdaddyale said:

Same relay as in my STC1000.Look at the spec sheets they might be interchangeable.
( not an electrician)

Click to expand...

day_trippr said:

Aside from that, however, the JQC could replace the HF (or vice versa) with some surgical intervention.

Click to expand...

I wouldn't recommend surgical intervention. I expect that both are standard configurations. I found several equivalents to the HF32F-G/012-H at parts sites like Digi-key and Mouser, so I expect the same could be done for the JQC3FF/012-1HS. It turns out my relay wasn't even bad, but the solder joints were, which I have now fixed. I'm not an electrician, but an electrical engineer. At ~$15 for a replacement, it's not really worth the time and effort to repair, unless you just like the challenge (like I foolishly do).