Workbench and Some New Toys

My extra room in my condo was getting a little overrun with electronic components. It was time to build a proper workbench instead of littering my computer desk with all sorts of junk. Also, it was an excuse to buy some new tools such as a skill saw. Cheaped out on the skill saw and got a $60 7 1/4 inch saw. Ah, it works. I did purchase a plywood blade, ie. many teeth, to make smooth cuts through plywood. It made a huge difference compared to the rip blade that came with the saw. I also have a mastercraft jigsaw I purchased on sale at Canadian Tire for $45 bucks. That's for later though when I need to make odd cuts for the playfield.

My workbench covered with... stuff.

My trusty new skill saw.

Here is my workbench. Evidently I've been using it. I made it myself using 3 2x10's for the top and 2x4's for supports. I used drywall screws because they work and are cheap. Drywall screws are more brittle than wood screws but for most stuff they work fine except for that phillips head. What a terrible design for a screwdriver! The Robinson head is a much better design.

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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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