sp0rk
Mayor of Pooptown
No I just meant one of their $10 SSRs pulled apart as an exercise to see how good they are, because I'm sure your electrical pixie wrangling skills are better than mine
STC-1000 went bang
- Thread starter Pataka
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I've re-wired it up the way I originally did it. Here's what it looked like. I also tested with a multimeter to ensure everything was connected as it should, and not shorting where it shouldn't.
The connector is rated for 30 amps (they didn't have any 10 amp ones, so I thought I'd be on the safe side).
The connector is rated for 30 amps (they didn't have any 10 amp ones, so I thought I'd be on the safe side).
alphaomega
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My $0.05
Thee unit is an STC model with a switching power supply and not a transformer. That could explain why it is said to accept both 110v and 220v. The units I use (A400_P) use a transformer and needs to be the right one for the intended voltage.
Switching power supplies are awesome, but they are a bit troublesome. Lets just say I have more confidence in the units with transformers...
While it is not unlikely that your unit blew up due to some component(s) being out of spec or failing, I do think the fact that you powered it up ok and did some more wiring and then it blew, suggests that the unit was not faulty, but it was due to something you did (for lack of better words, I don't wan't to assign blame or anything, shit happens, I just want to add my theory to this).
It could have been anything, like a loose strand of wire, or if you put the bare PCB on your workbench, it picked up some loose wire, or dirt/water or whatever and burned out the next time you powered up.
Not all STC's are created equal and the quality control can be kind of lax (though the A400_P ones I'm familiar with are surprisingly good, with only a couple of units not being 100% functional, of the hundred plus I've worked on, and only one being a non starter).
TL;DR
While it is plausible the unity was faulty, I think it is equally plausible that an unintentional (partial) short during wiring is equally plausible.
Finally, it sucks that our unit died. But I also think that the chinese retailers can't be held accountable in the same way a local/domestic store can. They just don't have much margin.
Best of luck in your further STC-1000 adventures
Thee unit is an STC model with a switching power supply and not a transformer. That could explain why it is said to accept both 110v and 220v. The units I use (A400_P) use a transformer and needs to be the right one for the intended voltage.
Switching power supplies are awesome, but they are a bit troublesome. Lets just say I have more confidence in the units with transformers...
While it is not unlikely that your unit blew up due to some component(s) being out of spec or failing, I do think the fact that you powered it up ok and did some more wiring and then it blew, suggests that the unit was not faulty, but it was due to something you did (for lack of better words, I don't wan't to assign blame or anything, shit happens, I just want to add my theory to this).
It could have been anything, like a loose strand of wire, or if you put the bare PCB on your workbench, it picked up some loose wire, or dirt/water or whatever and burned out the next time you powered up.
Not all STC's are created equal and the quality control can be kind of lax (though the A400_P ones I'm familiar with are surprisingly good, with only a couple of units not being 100% functional, of the hundred plus I've worked on, and only one being a non starter).
TL;DR
While it is plausible the unity was faulty, I think it is equally plausible that an unintentional (partial) short during wiring is equally plausible.
Finally, it sucks that our unit died. But I also think that the chinese retailers can't be held accountable in the same way a local/domestic store can. They just don't have much margin.
Best of luck in your further STC-1000 adventures
No blame taken whatsoever. The reason I'm not happy with my diagnosis is because of that same question - why did it work fine before the probe was connected? What changed? The wiring.
The only thing with the 'loose wire' theory is that the unit was in its case the whole time. Dismantling only started after the event. The only place where there could have been a loose wire is on any of the terminals. Given the relays are designed to create a short between 5&6, or 7&8, a loose wire on those terminals wouldn't have mattered. Also, given the distance between the probe terminals and the neighbouring ones, I'd say the chances of a loose wire sending current into those is very low. The only remaining possibility is that there was somehow a short between 1&2. Whether that would have been enough to destroy the unit (as opposed to simply tripping the breaker at my distribution board) isn't something I can answer.
The only thing with the 'loose wire' theory is that the unit was in its case the whole time. Dismantling only started after the event. The only place where there could have been a loose wire is on any of the terminals. Given the relays are designed to create a short between 5&6, or 7&8, a loose wire on those terminals wouldn't have mattered. Also, given the distance between the probe terminals and the neighbouring ones, I'd say the chances of a loose wire sending current into those is very low. The only remaining possibility is that there was somehow a short between 1&2. Whether that would have been enough to destroy the unit (as opposed to simply tripping the breaker at my distribution board) isn't something I can answer.
alphaomega
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@Pataka: Righto Then I'd suspect one component (the resistor?) being out of spec.
Then I'd suspect one component (the resistor?) being out of spec.
megabyte
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That resistor is probably not out of spec. i.e. It could have a large error in its value without affecting the circuit too much. I'd suspect the LNK564 controller IC caused the issue. Maybe it didn't get the right feedback from the transformer, maybe it got zapped with some static, or maybe it's just faulty. If it (for whatever reason) switches on and stays on (for more than a few milliseconds), your resistor will go bang.
alphaomega
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@Michael Burton: That makes a lot of sense.
Hi all.
To close the loop on this, I thought I'd post my experience with the InkBird ITC-308.
The thing is fabulous. It just works. Easy to program, easy to follow instructions on, plenty of length in the cables, and perhaps most importantly, doesn't go bang
My only qualm is that the adjustment buttons feel like they are the wrong way around (up is on the left, down is on the right) but that's a very minor issue. The controller arrived about a day and a half into the fermentation of my latest small batch (a standard kit Coopers Dark Ale), so I was able to switch it out and run with a much more robust temperature from then on. I find the Coopers standard kit yeast, while relatively ordinary, does perform pretty well when you run it cool. I'm at 16.8 degrees at the moment, but will raise it up once the high krausen stage passes.
Thanks to those who suggested it to me. It's the solution I really needed from the beginning.
To close the loop on this, I thought I'd post my experience with the InkBird ITC-308.
The thing is fabulous. It just works. Easy to program, easy to follow instructions on, plenty of length in the cables, and perhaps most importantly, doesn't go bang
My only qualm is that the adjustment buttons feel like they are the wrong way around (up is on the left, down is on the right) but that's a very minor issue. The controller arrived about a day and a half into the fermentation of my latest small batch (a standard kit Coopers Dark Ale), so I was able to switch it out and run with a much more robust temperature from then on. I find the Coopers standard kit yeast, while relatively ordinary, does perform pretty well when you run it cool. I'm at 16.8 degrees at the moment, but will raise it up once the high krausen stage passes.
Thanks to those who suggested it to me. It's the solution I really needed from the beginning.
A compressor kicking over through a relay isn't ideal, a fridge seems like too big a load to be dropped across the contacts of those tiny relays. Is there a current rating printed on top of them? I can't see it properly in the photos.
megabyte
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Given that the compressor motors are inductive I don't think it's as bad as you might expect when the contacts close as the current takes a few milliseconds to ramp up. The trouble is when the contacts open and there's nowhere for that current to flow, it causes arcing in the relay contacts that can wear them out. Any controller that's been designed to operate an inductive load (like a motor) should have a snubber network included (a resistor and capacitor) across the relay, but this adds cost and takes up more board space so the STC1000's don't have them in my experience.kunfaced said:
I've annotated a photo of the old controller I designed way back. Not to gloat, but just to illustrate what components to look for. As you can see they're pretty big when rated for the task and they do add a bit to the build costs. That's why I only included them on the cooling relay and not on the heater relay that will generally never see an inductive load.
I'd love to see a pic of the internals of the Inkbird but I dare not ask Pataka to rip apart his new acquisition!
You never know your luck. I did quickly glance at the case for that reason, and seem to recall it was held together by screws, with nothing stopping a relatively straightforward disassembly. I'll have a closer look when I get home.Michael Burton said:I'd love to see a pic of the internals of the Inkbird but I dare not ask Pataka to rip apart his new acquisition!
Not my unit, but I found this post on HomeBrewTalk, which shows one that has had the back taken off it. Not a particularly large image, however:
http://www.homebrewtalk.com/showthread.php?t=541662
Let me know if you still need bigger photos.
http://www.homebrewtalk.com/showthread.php?t=541662
Let me know if you still need bigger photos.
megabyte
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I'd love to know what the microcontroller chip is. In those photos on HBT it was far too blurry to make out. It might just be a shift register in which case the microcontroller would be on the back of the PCB.
If it's a PIC, AVR or anything common I'll probably pick up one of these controllers to play around with. That said, please don't go out of your way to open it up just on my behalf, like it's no biggie, I'm just curious is all.
If it's a PIC, AVR or anything common I'll probably pick up one of these controllers to play around with. That said, please don't go out of your way to open it up just on my behalf, like it's no biggie, I'm just curious is all.
Thanks for the info, I hadn't heard of a snubber network before. I use the cooling relay to drop a contactor for my fridge. Probably overkill but my workplace is a great resource.Michael Burton said:Given that the compressor motors are inductive I don't think it's as bad as you might expect when the contacts close as the current takes a few milliseconds to ramp up. The trouble is when the contacts open and there's nowhere for that current to flow, it causes arcing in the relay contacts that can wear them out. Any controller that's been designed to operate an inductive load (like a motor) should have a snubber network included (a resistor and capacitor) across the relay, but this adds cost and takes up more board space so the STC1000's don't have them in my experience.
I've annotated a photo of the old controller I designed way back. Not to gloat, but just to illustrate what components to look for. As you can see they're pretty big when rated for the task and they do add a bit to the build costs. That's why I only included them on the cooling relay and not on the heater relay that will generally never see an inductive load.
snubber - 1.jpg
I'd love to see a pic of the internals of the Inkbird but I dare not ask Pataka to rip apart his new acquisition!
