Experience is what you get…

meltdown

There is a great quote – “experience is what you get…when you didn’t get what you wanted”

My most recent project is providing me LOTS of experience…

That dark & crunchy component on the right is a high-current P-Channel MOSFET that dutifully did its job driving a pinball solenoid…until the solenoid melted down, shorting, and pulling so much current that I hear the MOSFET POP.

Solenoid meltdown

Now, this took the right combination of things to go wrong. I’d terminated the code, but not realized that it left an output high, I left the power supply on, AND I left the room. I’m used to working with microcontrollers where you’d pull power and the WHOLE circuit would go down. In this case, I’m using a Raspberry Pi, so I terminated the python app, but the computer and the I/O expanders stay powered – meaning that any outputs that were high…stay high.

Until this point, I’d really not thought about the fact that with the power levels available (15A @ 24V), I could easily start a fire…

The solenoid is $10, the driver components are another $2 or $3, but I’m thinking the lesson here – while VERY frustrating today, is worth much more.

I’m still thinking of how to safeguard the system and have some good ideas… I’ll implement one of them very soon.

Now, for the better part of the day… here’s some video of the system working as intended…

For those paying attention, you only saw 3 solenoids in the video (left slingshot, right slingshot, ball kicker) the two pop bumper solenoids are on the table below the playfield since I’m rebuilding the pop bumpers…

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