2nd TinyG and X limit switch input and SpON not working?!

One possible problem with driving relays with a 3.3V output is that relay coils are inductors and have inductive kickback, ie. V = L di/dt. Outputs switch very fast and when the current changes rapidly (di/dt is change in current vs. change in time) across a coil (ie. inductor) the voltage goes very high. This is what may have blown the output, and other things on the board. The best way to power a relay is with a buffer gate like a relay driver. Another way is a diode from the output to 3.3 volts to clamp the voltage so the it does not go much higher than 3.3 volts, or a zener around 3.3 volts from the output to ground.

Dr:bs

• This reply was modified 8 years ago by Zootalaws.
• This reply was modified 8 years ago by Zootalaws.

Mitch

The relay was connected with the coil attached to SpOn and ground- linking the 12V+ and – spliced into the fan output which was set to 12V.

I read this to say you were attempting to use the relay to switch 12V on and off under SpOn control. Can I assume that was for test purposes? The current available from the fan regulator on tinyG will not be adequate to actually run a spindle.

The challenge with inductive spikes is that they affect circuits rather randomly, similar to ESD damage. It is possible that an inductive spike damaged the silicon chip in the area of of the SpOn output gate which possibly could have affected near by gates, perhaps the X limit inputs. That comment is about adjacent on the die, not necessarily on the pin-out (lead frame).

Based on the evidence so far in the thread, it seems as if the SpOn output port is no longer functional. I don’t know of any good options to recover it. Perhaps someone else has some ideas

is there any possibility to use the 4th axis and its limits instead and somehow change the programming to make A axis the new X?
Cheers

I actually pondered that last night, but I don’t see how to make it work, easily at least. Your could make the A axis behave like a linear axis, but then you would have to translate Gcode that has “X” commands into Gcode with A commands. Messy.
You could of course run without limit switch, but you would have no homing function either.

Have you tested any of the other I/O ports, such as coolant or Spindle Direction, just to gauge the extent of damage?
And to pile on the bad news (sorry), Electrostatic Discharge (ESD) and inductive overvoltage spikes often result in cracks in the oxide layer of the silicon device. Those cracks can then grow over time, due to oxidation of the underlying silicon. So it might work today, but not tomorrow.

You could just use a simple contact switch just to get you going – get a length of shielded twisted pair Ethernet cable (cheap as buggery) to run and you should be fine for interference.

I started with cheap contact switches from a stripped-down 3D printer and never replaced them, because they worked fine and never glitched. I bought a bunch of optical switches – they’re still in their packet, unopened.

And before you blow up another Tiny, make an opto-electrical isolation board to run all of your external voltages through. 🙂 #hindsightoftheboltedhorse

• This reply was modified 8 years ago by Zootalaws.
• This reply was modified 8 years ago by Zootalaws.