Wrong component value, R7 should be a 1K, not a 10 ohm resistor

[rondlh]

I know this is old, but just in case anybody want to build or trouble shoot this parts, I think there are some issues:

1. The value of R7 seems wrong. A 10 ohm resistor would immediately blow the opto-coupler input when you connect 12 or 24V. The max rating for the input LED is 50mA. I think this should be a 1K resistor.

2. Vdd(Bed supply power) and Vcc(Motherboard bed power output) are connected. I doubt the original circuit is like this, it will cause big issues if you want to use a separate bed power supply for the bed and the printer motherboard.

3. PWR_FLAG seems to short circuit the bed output pins. It connects pin 2, 3 and 4 together of the power screw terminals.

Just my 2 cents.

I guess the actual schematic is probably something like shown below: