First Integration Test

A project log for Small Programmable Kiln

A small kiln with big expectations: Fusing PMC, Solder PCBs, Harden/Temper/Anneal/Carburize Steel, Pottery, Glass, Melting Precious Metals

myburamybura 05/01/2020 at 14:340 Comments

Great news! First integration test went okay. Hooked one set of coils up to the assembled controller box and fired it up to 108 deg C. Held it for about 1H.

Only two things got hot: The inside of the oven and the 9V PSU in the controller box. Didn't have the 80mm fan on so hoping it will keep the PSU temperature in check. It was hovering around 50 degrees with ambient at 18.

Had some teething issues with noise in the I2C bus and the GPU controller ran out of RAM causing random things to show on the display. Don't think it is all fixed but getting close.

Before running the test I limited the PWM to 25% of its max capacity. This translates to the coil only ever getting power 25% of the time max.

Some measurements while cruising at 108C (18C ambient):

- Coil at 65 Ohms

- Max Temp 110.1C/Min Temp 106.7C

- Max Power 500W / Min Power 270W

- Power meter power factor of 50

- Power meter 4A max

- Multi meter AC Voltage over coil Min 40V Max 80V

- Clamp meter Amps at 0.3A - 0.45A

To the untrained eye these numbers don't add up. The trained eye doesn't care to do the math to recon why not :)

Not sure what's next. Really want to check the controller box can handle full on state for 8 hours. That needs a couple of small problems solved before it can be executed (like the stuck terminal block screw for the second coil, lugs and insulation for the remaining coil wires and more schedules to ramp the temperature to various intermediate levels).

The PID needs some serious tuning but 2.5 degrees swing around the target is not bad for an initial guess.

Wonder how one can calculate the efficiency of the insulation and oven design using the results from above?