- Joined Mar 24, 2008
I am not going to call this a completed project until I receive and install a new thermocouple (TC). The old one is a Teflon insulated unit. Teflon emits toxic gasses around 145°C so once I saw it had hit 200°C I shut it down until I have the right TC for it. Truth is, I was a little surprised it worked. But as a proof of concept it did its job. Most of the hard work is finished. Hope my other TC is OK. Walmart is cheaper than Amazon, but a 3 week lead time is an enthusiasm damper.
First step is to get the sheet metal. I got a .01” x 12” x 12” sheet metal and used the following pattern to cut 6 metal spacers shown in the .png(see attached) file (print this pattern using M$ Paint and the individual sheet is to scale). I have a centigrade thermometer but the Fahrenheit unit was more convenient to use. So after cutting and drilling the spacers to spec I started assembly. You will also need a separate unnotched top plate of a bit thicker material that won’t bend (I had extra steel from a previous project I used).
I bought 4 silicon 12V 25W heaters (calculates at 5.76Ω ± ?) I wired them as shown.
Do yourself a favor and crimp the lugs on before starting the stacking phase and if you are real adventurous cut the lead lengths too (I’m chicken and used the entire wire length). I labeled each lug with the resistor number. After the spacer plates are stacked on top of the top plate which does not have the notch for the heater pads internal connections (the thermocouple should be sandwiched between the top plate and the first spacer. Then stack the four heater pads between spacer plates as shown. Put a spacer plate on the bottom of the stack .
I found a small pack of lugs after I ordered a 100 pack, just as well since I ruined as many as I used. Hey, doing this with one hand ain’t easy, but I got er done. Then use the wrap around box(drawing attached) to give your hands a place to rest while solder your SMT components. Next the all important proof of concept test. This is my power controller.
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