Watchdog/Charge Pump?

Hi,

For my CNC I built a simple charge pump circuit based on a HEF4538B retriggerable multivibrator. Mach3 outputs a 12.5khz square wave signal. and all the time this signal is present the relay is energised and power is supplied to the motors/spindle.

I think something similar for the Ormerod would be good. It could automatically power down after it has finished printing, or perhaps if a thermistor fails or temps get too high. Not sure if you could detect a motor jams, but there are all sorts of possibilities

So the first question is could the Duet output a nice reliable signal and what spare pins do we have to play with? Maybe something like this could be used. The only downside is that the duet would need to be powered from USB or some other 5v source.

Any thoughts?

Les
.

Quote
Pointy
Hi,

For my CNC I built a simple charge pump circuit based on a HEF4538B retriggerable multivibrator. Mach3 outputs a 12.5khz square wave signal. and all the time this signal is present the relay is energised and power is supplied to the motors/spindle.

I think something similar for the Ormerod would be good. It could automatically power down after it has finished printing, or perhaps if a thermistor fails or temps get too high. Not sure if you could detect a motor jams, but there are all sorts of possibilities

So the first question is could the Duet output a nice reliable signal and what spare pins do we have to play with? Maybe something like this could be used. The only downside is that the duet would need to be powered from USB or some other 5v source.

Any thoughts?

Les
.

Les, my versions of the firmware use the tick interrupt to check the temperatures, and the watchdog timer to reset the system if the tick interrupts stop. Do you think is anything to be gained from using an external watchdog as well?

---

Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Yes, the idea is to turn off the 12v, which would make me a more comfortable in leaving the printer unattended.


Regards,

Les