I decided to separate the high voltage mains from the low voltage components via a dividing wall and power the temperature controller off 24V. ![]() The temperature controller can be powered off mains AC or 24V DC. The CAD models for all the Omron parts were supplied by Omron on their website. It just fits the power supply, temperature controller and the MOSFET board. Naturally, I wanted to print the enclosure on the Cetus and so I put something together in F360 which can be found here. After remounting the bed I was pleased to see that it all just fits without needing to make any further changes. The wires and the thermocouple were attached with capton tape. Note that the MOSFET board requires 12V to turn on and so I used a simple voltage divider to drop the 24V down to 12V. ![]() The MOSFET board was connected directly to the power-supply and switched with the relay output of the temperature controller. Note that you can use a bi-metal switch as a method of temperature control on its own but that they tend to become stuck after a few thousand cycles. In series with the input to the heated bed was placed the bi-metal switch so that in the even that it becomes stuck on full power it should still stay within a safe temperature range. The resistors were wired up in a 4S-2P configuration so that the current draw from the power supply was around 4.2A for a total of 100W output. After many dozens of hours of printing this method appears to be working just fine. The power resistors were attached with two part epoxy as I did not have any thermal adhesive on hand.
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