Have you ever hurt yourself from your own code?

My first ten minute as a lab instructor in a full intro to computing class. I was standing talking and backed up a bit stepping on the leg of my swivel chair. I fell right on my ass hard. Cracked a joke but the whole class of about forty students didn't laugh or say a word. Was rough and I was showing some code at the time and I blame this on the code to this day.

In the 90s I implemented a PWM motor controller in asm, for a robot with enough power to accelerate hard on soft grass, outside. Robot was rather over engineered by a team mate who previously worked on automated farm machinery. Tested the microcontroller on the breadboard with an oscilloscope, all looked well: nice PWM shapes.

For the first integrated test on the robot, I high-centered it on some bricks so the wheels would turn freely, on the bench. Didn't want to deliver too much torque with wheels up, so asked for 1% PWM duty cycle. The robot leaped into the air, tearing off its umbilicals, hit the floor spinning and generally smashing shit up, including bits of me.

Debugging revealed that the output PWM duty cycle was inverted when commanded <2%, so my 1% command was 99% power. My breadboard tests had never gone below 3%, which I guessed was the minimum to overcome stiction on soft ground. Poor robot. The chunks out of my hands were the price I paid to learn to test important corner cases.

Heh, you don't even need proper robotics.

Back in 2002, I was getting a package with a brand new Pocket PC (smartphone without the phone, running Windows). And I really wanted to know when it was delivered, but the UPS guy would regularly leave packages on the porch without ringing the bell or anything.

This was before you could get delivery alerts or anything like that. But I had a spare laptop with an integrated webcam (wow!), and I'd figured out how to make it run actions on motion detection.

My plan was to point the laptop at the door, and eject the CD drive when it detected motion. The tray of the drive would push a water bottle off the table. That would land on a seesaw, which would launch a deck of cards in a hard plastic case at the door and make a very loud noise.

It's unclear why I couldn't just play a really sound on the speakers instead. Anyway, I tested the program by standing in front of the laptop and waving my hand.

It worked perfectly! The CD tray ejected, and I watched as the water bottle slowly rolled off the table. It dropped onto the seesaw...... and instantly launched a hard plastic deck at my face and got me right between the eyes.

Never again have I been in so much pain and also so excited about my code working perfectly at the exact same time.

Not sure if this qualifies as my own code but I have a highly modified 3D printer, I had upgraded to more modern trinamic stepper drivers which have sensorless homing and I had forgotten to set a sane value for the torque limit to let the drivers know when it had hit the axis' limit when I ported over my existing firmware config and like an idiot decided to use my finger to test it... I learned that day even small stepper motors have finger crunching torque and that under sudden intense pain you will forget where the power switch you've operated 1000s of times is located.

It didn't happen to me personally, but I worked on a flight simulator. Not the fancy kind which moves around but it still used hardware from the real cockpit, including the stick and its actuators.

And if the controller is not properly initialized, the stick will slam left and back, hitting the leg of the guy in the pilot seat. For men, it can be much worse...

Another bench had a real aircraft gun mounted on a turret that is also controlled by software. No ammunition of course, but it is still a big metal pipe swinging around at great speed, thankfully, that one was fenced because that's the kind of thing that can easily break bones, maybe even kill you on a bad hit.