# DIY Temperature Controller (Hot/Cold)



## samwoo2go (Apr 27, 2013)

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

Electrical: 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/index.jsp?productId=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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## PlantedRich (Jul 21, 2010)

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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## samwoo2go (Apr 27, 2013)

PlantedRich said:


> 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/replacement-probe-ranco.html


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## PlantedRich (Jul 21, 2010)

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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## samwoo2go (Apr 27, 2013)

PlantedRich said:


> 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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## PlantedRich (Jul 21, 2010)

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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## samwoo2go (Apr 27, 2013)

PlantedRich said:


> 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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## PlantedRich (Jul 21, 2010)

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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## samwoo2go (Apr 27, 2013)

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.


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## Beer (Feb 1, 2012)

I picked one of these up a couple weeks ago from Amazon.
Do you have the plastic or metal probe?


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## samwoo2go (Apr 27, 2013)

Plastic. Do you have a metal one?


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## PlantedRich (Jul 21, 2010)

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-...957?pt=LH_DefaultDomain_0&hash=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.


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## samwoo2go (Apr 27, 2013)

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. 



PlantedRich said:


> 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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## PlantedRich (Jul 21, 2010)

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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## devilduck (May 9, 2012)

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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## Beer (Feb 1, 2012)

samwoo2go said:


> Plastic. Do you have a metal one?


I have the plastic as well. This is going in salt water, I made sure it was the plastic probe. That is the ultimate reason of why I stayed away from the °F version, they all had metal probes. 
It looks as if the metal ones are the ones that are failing being submerged (from what I am gathering from this thread). The plastic looks like it seals pretty good to the cord, so it should eliminate the issue of water intrusion. I may add some black silicone just to be safe. It looks fairly tight under 30x magnification, but I'm not completely sure.

Keep us updated on how the plastic probe holds up.


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## PlantedRich (Jul 21, 2010)

I have a couple probes on order and will be sealing them. My current plan is in long tubes of heat shrink. Not due to the heat shrink factor but just because it is a very log cheap and waterproof tube. I don't worry much about the insulating factors as it is going to be in the tank full time and minutes by minute reading are not needed. So if it takes 10-15 minutes for the temperature inside to match the outside, it would still be all that I need. I would guess the heat/cold would transfer much quicker than that but either way, it should not bother my use. For greenhouse use I would want it to react quicker but then the water is not a factor in that plan. Still a way and see on whether I love these controlers or hate them! If they work, I'll love them!


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## Beer (Feb 1, 2012)

The initial setup may require a significant portion of time to equalize, but unless you had some rapid temperature swings of several degrees, I don't think that would pose much of an issue.
My concern would however be over the shrink tubing itself. Many of them have coatings on the inside of the tube that may be toxic in the tank. They ay also be made of materials that may leach toxins into the tank. How much, for how long, and how toxic, I couldn't say.
Something to think about.


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## PlantedRich (Jul 21, 2010)

For my purpose on this tank, the potential is very small. Large tank and lots of water changes. Before moving into live plants, I used heat shrink as a way to hold fake stems together when making plants for screens, etc.


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## majorwoo (Dec 25, 2012)

What controller are you using that is F based? I have a MH1210 (F) but it is single stage only compared to the dual stage STC-1000 (C). I've not found an inexpensive dual stage F based controller yet - and while I don't currently have a chiller/fan on my tank my brain refuses to accept using a single stage controller, and I want it in F because, dang it I do!


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## PlantedRich (Jul 21, 2010)

My controller is Fahrenheit and only does heating or cooling. It does both but only with rewiring and reprogram. The really odd part of the supply chain seems that Celcius is all that I find most of the time from US supply. And all the Fahrenheit seem to come from China. I would have expected more the opposite?


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## majorwoo (Dec 25, 2012)

Yeah that seems to match up with what I've found as well, I agree - odd!


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## magnum (Jun 23, 2011)

majorwoo said:


> What controller are you using that is F based? I have a MH1210 (F) but it is single stage only compared to the dual stage STC-1000 (C). I've not found an inexpensive dual stage F based controller yet - and while I don't currently have a chiller/fan on my tank my brain refuses to accept using a single stage controller, and I want it in F because, dang it I do!


Replace the controller with an inexpensive electronic thermostat (heating and cooling capable) and a couple relays. Literature can be found here http://www.homebrewtalk.com/f51/diy-temp-controller-build-133364/ That should fix your problem.


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## PlantedRich (Jul 21, 2010)

magnum said:


> Replace the controller with an inexpensive electronic thermostat (heating and cooling capable) and a couple relays. Literature can be found here http://www.homebrewtalk.com/f51/diy-temp-controller-build-133364/ That should fix your problem.


I was never able to get it to scroll on through to find out how he waterproofs the probe. Got any thoughts on that part?


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## NickMach007 (Aug 10, 2012)

Just to throw in my 2cents, I've been using this setup for a little while (Celsius), to be more precise, about 8 months, without any problem. You can see the unit I am using here:
http://youtu.be/BJxdzr11uVg
So far it has been perfect for me. Also, can I make one suggestion to this build? Add in a fuse for some extra safety-- I didn't see a fuse in the wiring diagram listed on the first page. If that is confusing, just watch the video and you will see what I mean. 
Hope this is helpful to someone.


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## PlantedRich (Jul 21, 2010)

magnum said:


> Replace the controller with an inexpensive electronic thermostat (heating and cooling capable) and a couple relays. Literature can be found here http://www.homebrewtalk.com/f51/diy-temp-controller-build-133364/ That should fix your problem.


 
Upon further study, this doesn't seem to be the answer for me. I was never able to see how they waterproofed the probe but I did look at the materials and that would stop me. They start with materials running about $38 or so. My two controllers only cost $30ish and they have some features I want. One is a digital readout that I can see from across the room and in the dark! When I do an early fishing trip, I can do a tank temp check without turning on the lights? 

I got the probes in the mail today so I'll report how that goes as I get them set up.


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## PlantedRich (Jul 21, 2010)

In spite of all going on with the Easter eggs and all, I was able to get the probes wired and setup. Both controllers are now back in operation. I also added heat shrink to one probe to make myself feel better about it being truly waterproof. 
It took longer to get the programming done than aany of the other stuff! What a bum set of instructions? 
I set them up to turn heat on any time it drops to 76 and off at 79 as I run my tank at 75-76. That should keep it from cooking anybody if the heater sticks. 










On the one on the left, I've added the end of an old extention cord to give me a plug/n/play setup as I may need to change the heater, etc. You can also see how I strapped the two probes and a glass thermometer together to get the temperature correction setting done. In doing this, I found the heatshrink may make the probe read just slightly slower by maybe 20-30 seconds when I changed temperatures but that is not any real problem. I stuck the one with the heatshrink probe on top of my canopy with a tab of Velcro and I'm all set again. Expecting this one to last longer??? Humm? 
Now I have the nice big bright readout and the fail-safe for any heater failures. 
Feeling better!


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## Naja002 (Oct 12, 2005)

Yes, necro! :thumbsup:

Just wanted to toss in here:

You can use this heat shrink to protect the probe:

Thermal Well For Aquariums - 3/8" Clear PVC Heat Shrink Tubing

Short version: My PCs are water cooled and chilled. I have used that heat shrink on a Ranco probe in a coolant reservoir (30 gal) for....4 or 5 yrs straight now. The coolant is a mix of water and anti-freeze, so I would assume that it would hold up indefinitely in an aquarium. 10-20 ft would last a lifetime for someone with MTS, I would think...


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## PlantedRich (Jul 21, 2010)

Since the posting has been revived, I can report that sealing the probe in common heat shrink for electrical work seems to work fine. I've forgotten the cost of the shrink but it is not high for an 18" length so squirting some silicone in the end and running the probe down to land in the silicone seems very easy. I did not fill the shrink all the way to leave the option of reusing it if I want to get the probe out for some reason. 
It's been working for 4 months now. The black shrink makes the probe pretty hard to see against my black background. 
Overall it makes a very nice small fail-safe controller that fits on top of my canopy in a way that I can see easily but is pretty hard to spot when not looking for it. A bit of Velcro on the bottom to hold it in place.


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## inkbird (May 18, 2016)

Good job.


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## thedood (May 30, 2015)

inkbird said:


> Good job.


I have two of these controllers and will be purchasing/building two more soon.


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## inkbird (May 18, 2016)

thedood said:


> I have two of these controllers and will be purchasing/building two more soon.


Have you DIY itc-1000, which has both F and C display.


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## thedood (May 30, 2015)

inkbird said:


> Have you DIY itc-1000, which has both F and C display.


I have two of the itc-1000 controllers mounted in project boxes. Right now they are just running heaters but I am working on hoods with fans in them that will be turned on for cooling as well.


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