Solenoid Driver Board Layout Preview

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.

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Pinball Cabinet Beginnings

I was getting to the point where I really needed to build on something. I have numerous pinball parts but have nothing to attach them to. I managed to find some pinball plans for a Williams Widebody pinball machine. All the measurements are in mm sadly even though all pinball cabinets are in inches. I converted and change it all to the nearest quarter inch. Well sort of. The guy who measured this was intending on using 45 deg cuts in the corners. My skill saw is too cheap for that so I changed the measurements for butted joints. The interior is set for a 23.5" wide playfield. The length of the cabinet is 51.5" in total. I used 3/4 inch plywood so the bottom would be 50" long for example. You can pretty much dimension the rest from there. I did get a little chipping of the plywood but I went out and bought a blade with more teeth for finer cuts. It's a 60 tooth saw blade and my skill saw doesn't really have enough power for it so I have

MOSFET Driver Board

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 quickly. Driving 48V from a separa

Pinball Solenoid Control

Pinball solenoids come with designations like 23-800. The first number, 23 in this case, represents the American Wire Gauge (AWG) used. The second number, and the more important number, is the number of windings which is related to its power rating. A solenoid with less windings, say 400, is more power and is used for such applications as actuating the flippers. These solenoids get very hot very quickly, which increases the resistance of the solenoid thereby decreasing the current and therefore the power. To avoid overheating, these high powered solenoids will have two coils. One for the main actuation of the solenoid, and another to maintain the position. The second solenoid will have a smaller wire gauge and more windings. In example, my flipper 'coils' are 15-411, 15 AWG and 411 windings. They are quite strong and found in some of the latter Williams pinball machines such as the popular Adams Family machine. You can find a lot of good additional information

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