Here is an image of my solenoid driver board. It is 99% autorouted but I did make the traces for the positive inputs for the solenoids much larger for the 10 amps peak they might see. The current is very brief so the traces are probably larger than they need to be. The traces for the solenoid inputs are 100 mils, the rest at 16 mils and I have the entire top and bottoms of the board as ground. There are five vias but I do not think I can avoid them. I also probably need to line the ICs in a way that is more pleasing to the eye and I have to add the silk screen layer to label everything.
Final version? I hope so. I have gone back and redesigned my solenoid driver board several times. In previous versions I attempted to offload some of the logic from the microcontroller. For example, I used a Schmitt-Trigger [74HC14] with an RC network to provide a single pulse to the solenoid. Also, I added in a PWM signal to set the average voltage 'seen' by the solenoid. This worked but was very limiting to have the pulse length hardwired in and it was difficult to adjust without more expensive precision potentiometers. I chose to simplify my circuit to make it a general MOSFET driver for flexibility. Since I have more than enough space inside my pinball cabinet, it was not a problem to have the extra boards. The boards were designed to have 4-channels since by default I would get a minimum of 10 boards for the same price from Seedstudio. Also, the cheapest board option was restricted to 10cm x 10cm otherwise the price balloons ...
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