Building a bread /dough Proffer for my sourdough

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I need to make a proffer for my sourdough. I have box but need the following:
1 A means os heating the box to 26C
2 A thermostat and probe that will control the heat to 26C
3 The “box” is approx 300 mm x 300 X 300 and insulated.
4 Power supply is 240V and could use usb.
All suggestions would be appreciated, including the source of parts.
Norm

2

Hi Norm, welcome to the forum!

  1. A small heating pad should suffice I think, though this depends on how well insulated the box is. That model draws about 0.83 amps at 5V, so a regular phone charger should cut it.
  2. We don’t have standalone thermostats, but we have all the gear to build your own. You just need a good temperature sensor, a relay or MOSFET to switch the pad on and off (or in between if you pick a MOSFET), and a way to connect that all. Here’s what I found:
  1. I suppose the question that decides how big the heating pad is, is how fast does it need to heat up, and how insulated your box is, though you could always start this thing early to get it nice and toasty before you proof.
  2. 5V should do fine I hope, working with 240V directly would likely mean employing a contractor with the relevant qualifications.

Let me know if this sparks any followup questions

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Hi Norm
How accurately do you need the 26ºC.
If you are in Australia you might find you need cooling as well or is 26ºC a minimum.
If you need heating and cooling you could consider a “Peltier” device. This is a plate which transfers heat from one side to the other depending on the direction of current flow. So if you want heating you pass current in one direction and if cooling simply reverse current flow. Can be a bit power hungry though although I think any sort of heating or cooling system is going to be beyond USB capability.
The car units that both cool and heat use these things I think.
I made myself a car cooler by cutting a rectangular hole in the lid of a small “esky”, attaching a peltier device to an aluminium plate (to get some effective surface ares) with some heatsink compound. Mounted a finned heatsink and fan on top of this and fitted the whole thing through the hole in the lid making sure of a snug fit so no leaks. Worked well but I only needed cooling.

If you need to maintain an even 26ºC you might need a PID controller as if you use simple on/off switching you will get some thermal overshoot and will need some hysteresis anyway. The amount of overshoot will depend to some extent on the load.
Cheers Bob

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Hi Norm
Add on.
This is the sort of thing I had. Have a look and you will see what I am talking about.Core SKU ADA1335.

Peltier Thermo-Electric Cooler Module+Heatsink Assembly - 12V 5A

The heat sink and fan get rid of unwanted heat while the heatsink acts like a heat gatherer when heating. While heating the fan is best switched off. As I described I attached an aluminium plate to the peltier device using heat sink compound for good thermal transfer and more surface area but with your small box this may not be required (but could work better). You will have to mechanically attach any plate, do not use the compound as a glue, I don’t think that would work.

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