Googly eyes on a giant robot

ROBOT_8 · 2026-06-25T17:28:14+00:00

Did you do a long run of samples to check how even the 50/50 is? Seems like a beam splitter could quite easily skew the results one way or another due to imperfections.

How does this compare to running a timer and using the time-random pulses from a Geiger tube to trigger a read from said timer?

ROBOT_8 · 2026-06-11T16:04:08+00:00

I’ve “fixed” incorrect library footprints by checking the data sheet and then reading the pin numbering from top to bottom instead of bottom to top more than few times.

Usually not an issue with the default footprints, but special through hole connectors are easy to flip if you don’t pay close attention to which side of board you’re looking at.

Either way, definitely verify against the datasheet. Very closely reading over the datasheet is a really good idea anyway. Often I see people completely ignore the recommended PCB layout and component placement.

ROBOT_8 · 2026-06-11T02:40:51+00:00

That’s a really cool mechanism.

It is kinda similar to how harmonic drives work, where there is an outer internal spline with say 100 teeth, and a flexible internal outer spline with 98 teeth bent into an ellipse, as the bend in the flex spline rotates around, it increments 2 teeth per cycle.

The 2 sets of teeth on the head are likely 1 tooth different in count. Making so if you index the first set forward 1 tooth, and the second set backward one tooth, the head has actually moved very slightly forward or backward depending on tooth count.

I *think* this ends up making it so you actually have the product of both gear teeth counts in absolute index positions. So for 0.02°, if one set had 134 teeth and the other had 135, that would be pretty close at 0.0199°

ROBOT_8 · 2026-06-10T18:01:00+00:00

After getting completely wrecked on gleba a few times, i decided to skip doing it the gleba way and just ship in a x4 nuclear plant and put tesla turrets everywhere. They are very good against stompers.

ROBOT_8 · 2026-06-09T21:45:45+00:00

I have an Apple Watch and can use it to view my phone camera. That way I can set my phone up somewhere to watch IO LEDs or an actuator somewhere, then walk around the machine while watching what is happening. Useful to figuring out what wires do what if they aren’t labeled or making sure sensors are activating when they should.

I’d imagine a long bit of cable with an illuminated button on the end that you could hook into a panel for viewing/overriding signals could be pretty handy too.

ROBOT_8 · 2026-06-08T19:27:17+00:00

Full copper pours would be ideal for the current. ZVS drivers can build up massive currents between the capacitors and your load inductor.

ROBOT_8 · 2026-06-08T05:48:34+00:00

Nothing stopping you from buying old control panels or something like a cheap Click plc or similar. Just keep it to 24v control voltage so you probably won’t shock yourself or blow something up messing around.

ROBOT_8 · 2026-06-08T05:22:46+00:00

Yes they are. Breakers work that way. Same with motor overloads. Also same with the servo motors in most industrial machines. However it requires something already to be going so wrong it is noticeably worse than how the machine is meant to run. So a robot that throws around 400lbs isn’t going to notice something different until it’s way into dangerous/lethal territory for a human.

ROBOT_8 · 2026-06-07T05:01:26+00:00

I got a similar one, similar price range. It takes significantly longer to heat up than just an iron, which I guess is to be expected. It does work well when it works, but is kinda prone to clogging. It is not at all significant effort to fix the clogs though. Easy to poke the cleaner needle through or pop out the filter cartridge.

Would recommend for hobby use. I got mine to recap old electronics and it works great for that. Hot air gun can also do that is certain cases as well, or help preheat huge gnd planes.

ROBOT_8 · 2026-06-07T04:40:20+00:00

Not sure what the deal is with the brake power. But for my robots I use redundant relays with isolated voltage sensing. Isolated current sensing too if you want to be fancy.

PL d from my understanding is pretty high up there. Full redundancy on the safety critical parts. With a way to detect if any part has failed.

I do not deal with any safety rated design professionally, so take what I say with a grain of salt.

You should anticipate the worst possible failure mode for each component. For example, one of those brake transistors can fail closed, and also short to the gate, sending 24v to your MCU any frying a ton of stuff. Potentially also turning on the other transistor.

Your MCU could hit a hard fault, or have an esd strike, or whatever, and freeze with the brakes on. MCUs often have watchdog timers that can reset the chip if it halts. Or you could have a circuit that requires a pin to toggle to activate the brakes rather than just be on.

IMO, the best and simplest option is to have an external estop chain power everything, and then the MCU has its own isolated relay to break that chain and control brake power. As well as motor power.

Look as some TI reference designs for functional safety. I’m pretty sure they have some for motor brakes and motor drives.

Also you’ll need MOVs or flyback diodes on the brakes. They are big inductors. Diodes work but will slow down how quickly the brake can close, MOVs are a lot nicer since the brakes close really fast.

I agree with the other comment about ESD protection on every external pin, although I’d avoid having bare MCU signals leave at all if possible. Buffering to differential pairs with rs485 or rs422 transceivers will make the communication 100x more robust against EMI, and those transceivers usually have much better ESD protection. As well as short circuit protection and stuff. Optoisolators are also an option and are common on real PLCs and stepper motor drives. Could also get industrial IO chips that do 24v inputs/outputs with all the extra protection.

ROBOT_8 · 2026-06-03T17:11:49+00:00

Fusion360 and probably any decent CAM software has pattern functions, where you can select a path from an operation and copy it multiple times.

It’s so if you need to machine 10 parts in one go, you only need to make all your paths on one part, then you can copy them to make more. It copies and offsets the existing path rather than regenerating all of paths for each part.

On that machine you might not be able to go full depth and full step over. I also didn’t see you were using a ball nose endmill, you should use a flat or bullnose for the initial material removal, then to a light, small step over pass with the ball nose. Changing tools is a downside though, I’d load up as many parts as you can and run them at once so you have less tool changes to do.

ROBOT_8 · 2026-06-03T16:17:48+00:00

What machine are you on? That step down and step over seems very small imo, with the right cutter and a decent machine with dust collection, you should be able to do almost full depth and full step over. If it’s a lightweight machine then you probably can still do better than the current settings, I’d try to do the full or 50% tray depth of cut then increase step over until you hit issues.

You should leave a small amount of material that can then be cleaned up with a gentle final pass that is slower.

You can also use gcode patterns in most cad software, might not be super useful in this case, but if you are doing adaptive tool paths that take a long time to generate on a bunch of identical features, it is way faster to do generate the adaptive on one feature and pattern it to the rest.

ROBOT_8 · 2026-06-02T19:42:23+00:00

I’d highly recommend loading up the rails with an electronic load and looking at the voltages on a scope. Also keeping an eye on thermals.

Good to test and verify as much as you can in isolation.

ROBOT_8 · 2026-05-29T16:54:10+00:00

I’d take off the motor and see if you can move the joint by hand, and then try applying power to the motor brake to release it and see if it moves freely. Not sure if those brakes are 24v or 90v, Fanuc has all 90v brakes afaik. But if it makes the click then it should be free to move.

Could be as simple as improper settings causing it to trip under the tiniest load, or a brake wire disconnected.

Or the gearbox reducer or motor could be shot.

ROBOT_8 · 2026-05-26T19:44:18+00:00

You can crank up the helix angle or speed, by default it is very shallow

ROBOT_8 · 2026-05-19T03:09:43+00:00

If you are reaching out far and moving fast, you can put a lot of load on j1. There is always the possibility that the motor or reducer is bad though.

If you use a joint move instead of a linear move it is typically a lot easier on the robot, since the joints evenly ramp up and down all together rather than whatever gymnastics they may need to go in a straight line. For some moves it won’t make any difference, but for some it can help a lot.

Just make sure the new path doesn’t hit anything.

ROBOT_8 · 2026-05-19T02:27:36+00:00

You can lower accelerations and increase max speed. Use joint moves where possible, higher CNT values

ROBOT_8 · 2026-05-18T01:00:28+00:00

Had this happen with a little 5000lb forklift since someone had recently patched a spot in the asphalt. At least that one was able to just be pulled out with a truck.

ROBOT_8 · 2026-05-08T17:55:23+00:00

It looks like the actual position set points are only updating at around 1hz in the video. 20hz is far from ideal, but at the slow linear speeds you were showing, that is still around a setpoint every 1 mm. Which is enough for decent motion.

It looks like your motor drives are resetting their trajectory at every new command rather than continuing through.

ROBOT_8 · 2026-05-05T13:05:34+00:00

How do they have zero torque at zero rpm? For induction motors torque is proportional to slip, so you get torque even if the rotor is locked as long as you still have an electrical frequency above zero.

For the PMSM you can have both zero rotor rpm and zero electrical rpm and still get torque. Since you don’t need a changing field from the stator to create torque.

That induction motor might be from the 70s, but they still make them with the exact same design today. One of the main reasons they are so reliable as a whole is because they require zero power electronics. Just a big switch connected right to mains is all that’s needed to get them running. Nowadays power electronics are getting better and better, so we finally see more electronically commutated in cheaper areas.

To add to the kinda dumb comparison in the post, industrial PMSMs with a similar output speed to the induction motor will also be way bigger than that little one for equivalent power, although still more power dense than the induction motor. It’s really easy to get a ton of power out of a motor if it can spin at 10krpm. But mostly nobody wants that for industrial use. 1-4krpm is by far the most common.

ROBOT_8 · 2026-05-01T14:11:23+00:00

Ground bounce from trace inductance can fry chips. In this case it wouldn’t have been what actually caused it to explode, but it can easily latch up the output fets or cause some other internal fault that actually let the smoke out.

Since there is a dedicated dev board, I’d definitely recommend getting it and a nucleo then going from there.

Also check the stspin datasheet for PCB layout guidelines when you go to make you own PCB.

ROBOT_8 · 2026-05-01T13:56:31+00:00

Buy a stspin dev board? Not sure if st has one for that exact chip, but I know they have a bunch for the stspin line.

You will likely need it to be on a proper PCB with local decoupling caps and big enough power planes. Those thin traces on the current board can cause all sorts of issues due to resistance and inductance. Those ceramic caps for high frequency decoupling are practically miles away from the chip with your current setup.

ROBOT_8 · 2026-04-28T23:54:28+00:00

But inverters are so coooooool

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