Electronic – Tomato Seed Warmer


I wonder if there is a very simple way to control one or two light bulbs in a box that are providing heat for my Tomato seed Propagator sitting on top … i.e. I need the heat underneath…It would be wonderful if I could get a static 80 degrees ???..I am not an electrical person and I live in New Zealand which is a drawback in many ways for trying to find off the shelf items…I would be sincerely grateful for any tips on how I could do this.


I found this on the NZ online auction. Would this be what one requires?

Best Answer

I just built something like this, actually it was for a much larger heat box to test some servers but the concept is the same. I bought one of these cheapo ($27) pid controllers on amazon. I think this one requires you to get the equally cheap AC relay a little further down the page but there is also another model that has a relay built in.

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Notice it comes with a nice thermocouple you can place where you want to monitor the temperature. Then I grabbed some ceramic light bulb fixtures from lowes, and wired everything together.

It's pretty simple this controller has a relay output and it has a built in PID loop to get to and maintain whatever temperature you set it to. I've found them really useful for all sorts of little projects.

Here's a page with the manual, some useful information, and more pics.

As usual be careful playing with AC it can kill you.