MAKE | Make: Projects – Water Bath Thermostat

This project was inspired by Cooking for Geeks author Jeff Potter’s quick DIY sous-vide hack. My plan, initially, was to just hack the controller into an enclosure with an A/C outlet, the idea being that you could just plug any heater you wanted into the outlet.

Looking around for cheap temperature controllers, however, I happened across the STC-1000 on eBay for $25. It’s not PID, but it has proven to be accurate enough for almost any practical purpose. And since the STC-1000 has both heating and cooling functions built-in, the logical next step seemed to be to split a single A/C outlet so that you could plug a heater or a cooler (or both) into it and use it for all kinds of stuff.

The STC-1000 will regulate at any temperature between the freezing and boiling points of water, which opens up all kinds of potential applications in chemistry, aquaculture, zymurgy, hydroponics, cooking, etc., etc. And unlike most other water temperature controllers I’ve seen around, this one can operate in heat only, cool only, and heat-or-cool-as-necessary modes.

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20 Responses to Make: Projects – Water Bath Thermostat

Matthew Miller on August 2nd, 2011 at 8:34 pm said:

I could build this and use it to cook individual servings of beef stew for lunches.

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David Bell on August 2nd, 2011 at 8:38 pm said:

Sean, is the STC-1000 on eBay actually 120 VAC?
I see in the description section the seller mentions both 110V and 220VAC±10%, 50/60Hz

Dave

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- Sean Michael Ragan on August 3rd, 2011 at 4:35 pm said:
  
  I think what the eBay sellers do is look at your mailing address and include the version of their controller that is appropriate for your national power system.
  
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David Bell on August 2nd, 2011 at 8:38 pm said:

Sean, is the STC-1000 on eBay actually 120 VAC?
I see in the description section the seller mentions both 110V and 220VAC±10%, 50/60Hz

Dave

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Mikey Sklar on August 2nd, 2011 at 9:22 pm said:

While I like the idea of a inexpensive temperature controller the STC-1000 does not seem to have a food grade probe. Depending on what you want to do this could put you back in the market for a $60 open hardware temperature controller kit that does heating/cooling and includes the stainless steel food grade probe.

http://screwdecaf.cx/yatc.html

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- Sean Michael Ragan on August 3rd, 2011 at 4:39 pm said:
  
  The STC-1000 uses an NTC thermistor temperature probe. I am in the process of taking the necessary measurements to determine its K value, at which point it should be possible to buy an aftermarket food-grade stainless thermistor probe that will work with the STC-1000, if it is necessary for your application.
  
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- Sean Michael Ragan on August 3rd, 2011 at 4:39 pm said:
  
  The STC-1000 uses an NTC thermistor temperature probe. I am in the process of taking the necessary measurements to determine its K value, at which point it should be possible to buy an aftermarket food-grade stainless thermistor probe that will work with the STC-1000, if it is necessary for your application.
  
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  Tim Tan on November 23rd, 2011 at 1:45 am said:
  
  Did the author do this so we can use aftermarket SS probe or at least a replacement? Thanks.
  
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Mikey Sklar on August 2nd, 2011 at 9:22 pm said:

While I like the idea of a inexpensive temperature controller the STC-1000 does not seem to have a food grade probe. Depending on what you want to do this could put you back in the market for a $60 open hardware temperature controller kit that does heating/cooling and includes the stainless steel food grade probe.

http://screwdecaf.cx/yatc.html

Reply ↓
Mikey Sklar on August 2nd, 2011 at 9:22 pm said:

While I like the idea of a inexpensive temperature controller the STC-1000 does not seem to have a food grade probe. Depending on what you want to do this could put you back in the market for a $60 open hardware temperature controller kit that does heating/cooling and includes the stainless steel food grade probe.

http://screwdecaf.cx/yatc.html

Reply ↓
Anonymous on August 3rd, 2011 at 8:59 pm said:

So how does the performance of this compare to a PID approach? Anyone know just how this is different?

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- Derrick Boudwin on August 19th, 2011 at 1:16 am said:
  
  PID uses an algorithm to prevent temp overshoot and undershoot. This rig simply turns the outlet off when the target temp is reached. I tested my rig out last night and since my crock pot has a slow temperature response it overshot by about 2 degrees. If I had a PID on it and calibrated it, it would know to turn the outlet off (or start pulsing it) before the target temp was reached to compensate.
  
  Reply ↓
- Derrick Boudwin on August 19th, 2011 at 1:16 am said:
  
  PID uses an algorithm to prevent temp overshoot and undershoot. This rig simply turns the outlet off when the target temp is reached. I tested my rig out last night and since my crock pot has a slow temperature response it overshot by about 2 degrees. If I had a PID on it and calibrated it, it would know to turn the outlet off (or start pulsing it) before the target temp was reached to compensate.
  
  Reply ↓
- Derrick Boudwin on August 19th, 2011 at 1:16 am said:
  
  PID uses an algorithm to prevent temp overshoot and undershoot. This rig simply turns the outlet off when the target temp is reached. I tested my rig out last night and since my crock pot has a slow temperature response it overshot by about 2 degrees. If I had a PID on it and calibrated it, it would know to turn the outlet off (or start pulsing it) before the target temp was reached to compensate.
  
  Reply ↓
- Derrick Boudwin on August 19th, 2011 at 1:16 am said:
  
  PID uses an algorithm to prevent temp overshoot and undershoot. This rig simply turns the outlet off when the target temp is reached. I tested my rig out last night and since my crock pot has a slow temperature response it overshot by about 2 degrees. If I had a PID on it and calibrated it, it would know to turn the outlet off (or start pulsing it) before the target temp was reached to compensate.
  
  Reply ↓
- Derrick Boudwin on August 19th, 2011 at 1:16 am said:
  
  PID uses an algorithm to prevent temp overshoot and undershoot. This rig simply turns the outlet off when the target temp is reached. I tested my rig out last night and since my crock pot has a slow temperature response it overshot by about 2 degrees. If I had a PID on it and calibrated it, it would know to turn the outlet off (or start pulsing it) before the target temp was reached to compensate.
  
  Reply ↓
- Derrick Boudwin on August 19th, 2011 at 1:16 am said:
  
  PID uses an algorithm to prevent temp overshoot and undershoot. This rig simply turns the outlet off when the target temp is reached. I tested my rig out last night and since my crock pot has a slow temperature response it overshot by about 2 degrees. If I had a PID on it and calibrated it, it would know to turn the outlet off (or start pulsing it) before the target temp was reached to compensate.
  
  Reply ↓
Anonymous on August 3rd, 2011 at 8:59 pm said:

So how does the performance of this compare to a PID approach? Anyone know just how this is different?

Reply ↓
Anonymous on August 3rd, 2011 at 8:59 pm said:

So how does the performance of this compare to a PID approach? Anyone know just how this is different?

Reply ↓
Derrick Boudwin on August 18th, 2011 at 2:12 am said:

Is the thermistor that comes with the STC-1000 waterproof?

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