DIY Temperature Controller (Hot/Cold)
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Old 04-05-2014, 10:47 PM   #1
samwoo2go
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DIY Temperature Controller (Hot/Cold)


I decided to make a temperature controller unit that turns heating and cooling components on/off to ensure a stable temp for my Sulawesi cardinals tank.

The way I got it set up now is for the switch from hot to cold go off at 83F. My heater is set at 82F so under normal circumstances, the controller does nothing and the heater is going on and off. If the heater gets stuck or room temp goes over 83F, the controller shuts off power to the heater and turns on a fan, thus preventing cooking the tank.

Part List: (Total $30)
Controller:
Amazon.com: Elitech 110V All-Purpose Temperature Controller+ Sensor 2 Relay Output Thermostat Stc-1000: Home Improvement Amazon.com: Elitech 110V All-Purpose Temperature Controller+ Sensor 2 Relay Output Thermostat Stc-1000: Home Improvement

Electrical:
Amazon.com: Leviton 5325-SE 15 Amp, 125 Volt, Decora Duplex Receptacle, Residential Grade, Self Grounding, Black: Home Improvement Amazon.com: Leviton 5325-SE 15 Amp, 125 Volt, Decora Duplex Receptacle, Residential Grade, Self Grounding, Black: Home Improvement

Box: http://www.radioshack.com/product/in...ductId=2062284
AC Power Cord (18awg)

This is what the controller unit looks like, it's small



Take your project box and cut out 2 holes for the receptacle and controller unit.


Don't worry about making a perfect cut, because you'll cover it up with a cover plate and the controller has a lip that will cover up the edges. It'll end up looking like this. Yes, I know it's crooked.


Since you'll have separate heating and cooling controls, take some pliers and break off the connecting tab on the hot side (gold screws) of the receptacle. This way they can be independently powered. The neutral side (silver screws) can stay common.


Here's how to wire it all up. I am not going to explain, just follow my diagram.




I didn't take a pic of this but I ended up putting a piece of PVC pipe in the box under the receptacle because there's space there and without support, when you try to plug something in, the whole receptacle will flex inward.
Drill 2 small holes on opposite ends of the box for the power/temp prob wires to come out and it's done!



If you need additional help, this guy explains it pretty well in a YT video: https://www.youtube.com/watch?v=7I-iwFLykxs
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Old 04-06-2014, 03:14 AM   #2
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I like your design and your work. But then I have some doubts about the base unit and probe. I logged on to day to make a report on my experience with the small temperature controller. I had two and thought they were great as a fail-safe for my tank heaters.

But I now have to report that both have now failed due to bad probes. One failed in about three weeks and I swapped probes around to find it was, in fact, the probe rather than the unit itself. Now the second has failed and I can get the same failure on both units by switching the probe over. Both have failed in less than four months!
The question now is whether it is worth replacing the probes if I can't depend on them as a fail safe either. BAH! Cheap junk!
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Old 04-06-2014, 05:33 AM   #3
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Quote:
Originally Posted by PlantedRich View Post
I like your design and your work. But then I have some doubts about the base unit and probe. I logged on to day to make a report on my experience with the small temperature controller. I had two and thought they were great as a fail-safe for my tank heaters.

But I now have to report that both have now failed due to bad probes. One failed in about three weeks and I swapped probes around to find it was, in fact, the probe rather than the unit itself. Now the second has failed and I can get the same failure on both units by switching the probe over. Both have failed in less than four months!
The question now is whether it is worth replacing the probes if I can't depend on them as a fail safe either. BAH! Cheap junk!
Maybe try replacing with the Ranco probe? http://morebeer.com/products/replace...obe-ranco.html
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Old 04-06-2014, 04:57 PM   #4
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Those indicate they are water resistant but not water proof. That may have been the problem with the original probes. They seemed to work for a time but if I can't leave it in the water, It doesn't do the job. Also the $19 for a probe is about what I paid for my whole unit.
I want cheap but I want quality , too? Humm ! I may have to rethink my plan?
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Old 04-06-2014, 06:47 PM   #5
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Quote:
Originally Posted by PlantedRich View Post
Those indicate they are water resistant but not water proof. That may have been the problem with the original probes. They seemed to work for a time but if I can't leave it in the water, It doesn't do the job. Also the $19 for a probe is about what I paid for my whole unit.
I want cheap but I want quality , too? Humm ! I may have to rethink my plan?
I read the Amazon questions before buying, and there's a guy that said he used his in the tank for a few months without problems. Maybe they changed the design?

Ya, $19 is expensive for the Ranco probe, but it seems like it would make sense if the probe is the weak link. The unit itself seems solid, you are still looking at a $40 unit vs. $100 for a Ranco and it controls hot and cold.
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Old 04-07-2014, 06:50 PM   #6
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Yes, there are several reasons to go that way. I'm kind of hung with doing without which I have proved can kill my fish if the heater sticks or going for a probe that might/might not work for long. Since you have shown you are a bit of DIY guy, I ight ask about an idea.
What would be the expected result if I used a probe that might not be fully waterproof but put it inside some type of protection to keep it out of the water but the "sleeve" around it be fully in the water. Maybe like a soda straw that is thin to let the temperature follow pretty quick but still keep the probe dry?
Might work? Goofy idea? Any thoughts?
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Old 04-07-2014, 11:23 PM   #7
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Quote:
Originally Posted by PlantedRich View Post
Yes, there are several reasons to go that way. I'm kind of hung with doing without which I have proved can kill my fish if the heater sticks or going for a probe that might/might not work for long. Since you have shown you are a bit of DIY guy, I ight ask about an idea.
What would be the expected result if I used a probe that might not be fully waterproof but put it inside some type of protection to keep it out of the water but the "sleeve" around it be fully in the water. Maybe like a soda straw that is thin to let the temperature follow pretty quick but still keep the probe dry?
Might work? Goofy idea? Any thoughts?
Might work if you seal the top so it's like a little insulated capsule. The amount of air is so small, I expect it to be able to exchange heat with the water pretty quickly. Try it, doesn't hurt. The only problem is that the ambient temp might have an effect on the reading if the difference is too high.
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Old 04-08-2014, 12:27 AM   #8
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Good point that makes sense on sealing at the top, too. I had expected to seal the bottom shut but if I left the top open it might skew the water temperature reading with the air temperature.
A long length of heat shrimk sealed at top and bottom might keep it dry. There are lots of the probes for really cheap on the auction site. Gives me hope for a cure, anyway as I really did like the things.
Loved having a digital readout to see from across the room.
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Old 04-08-2014, 12:49 AM   #9
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I am not sure if wire heat shrink would be a good choice since it's designed to insulate heat. Might not be the best heat conductor. Maybe try shrink wrap? Like the packaging ones.
Amazon.com: 500 pcs 4"X6" PVC Shrink Film Wrap Flat Bags 100 gauge: Everything Else Amazon.com: 500 pcs 4"X6" PVC Shrink Film Wrap Flat Bags 100 gauge: Everything Else
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Old 04-09-2014, 11:30 PM   #10
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I picked one of these up a couple weeks ago from Amazon.
Do you have the plastic or metal probe?
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Old 04-09-2014, 11:36 PM   #11
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Plastic. Do you have a metal one?
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Old 04-11-2014, 04:13 PM   #12
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Both of mine were a small metal cylinder with the wires and components sealed in with what looked like a waterproof sealer. I now suspect it is more water resistant and not water proof. When I did my teardown on the first failure, the sealant seemed solid but the second seemed much more waterlogged. More like Elmer's glue, maybe?
Like this ? I may have had this same unit and probe.
http://www.ebay.com/itm/Fahrenheit-A...item58a62ba415

I'm disappointed to find the steady stream of probes that were for sale on the auction site seem to have left. There were bundles of 5-10 for really cheap but I don't find them now. Inertia has set in and I have not moved far on this.

Last edited by PlantedRich; 04-11-2014 at 04:17 PM.. Reason: additional info
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Old 04-11-2014, 09:11 PM   #13
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Wait is yours the Fahrenheit version. Does it say "STC-1000" on the bottom right? I've heard the Fahrenheit units aren't as reliable as the Celsius units.

Quote:
Originally Posted by PlantedRich View Post
Both of mine were a small metal cylinder with the wires and components sealed in with what looked like a waterproof sealer. I now suspect it is more water resistant and not water proof. When I did my teardown on the first failure, the sealant seemed solid but the second seemed much more waterlogged. More like Elmer's glue, maybe?
Like this ? I may have had this same unit and probe.
[Ebay Link Removed]

I'm disappointed to find the steady stream of probes that were for sale on the auction site seem to have left. There were bundles of 5-10 for really cheap but I don't find them now. Inertia has set in and I have not moved far on this.
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Old 04-11-2014, 10:17 PM   #14
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Mine are both the Fahrenheit type but I think the probes are the same. Both 10 K ohm and STC. I've just ordered a couple new probes that say they are "waterproof" but I will still seal them just so I know they are for sure. It may be a couple weeks to get them.
Guess it's all just a trip anyway?
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Old 04-11-2014, 11:00 PM   #15
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Have one of these sitting on my desk because I still haven't gotten around to wiring it up. My probe is a metal cylinder, thought I'd silicone where the wires enter the cylinder.
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