Pneumatic Gripper Intermittent Disconnect
Intermittent disconnect from PC (COM5). I’ve removed and checked the diode and it test OK. Polarity is correct. Resetting the HMI 5v IO Board Com Port back to COM5 works for a little while longer. Seems to always be on D0 off. New install - never worked correctly.
MK3
HMI v6.3
Nano Sketch v1.3
Hi Ron,
The fact that it seems to disconnect specifically when the output turns off is helpful. That makes me suspect electrical noise from the solenoid valve when it de-energizes. The diode is there specifically to suppress that transient and prevent the Nano from dropping its USB connection, so even though the diode tests good I think we should isolate that circuit first.
Could you temporarily disconnect the solenoid valve coil from the relay, leaving the Nano and relay connected, and then repeatedly toggle D0 ON/OFF in the HMI? If COM5 stays connected with the solenoid disconnected, that would tell us the problem is coming from the solenoid/diode/power wiring rather than the Nano or HMI.
Also, when it disconnects, could you check Windows Device Manager and see whether COM5 actually disappears from Windows, or whether COM5 remains present and only the HMI loses communication?
Since this is a new installation and has never worked correctly, if you can also post a couple clear pictures of the diode, relay, solenoid and Nano wiring I can check the connections.
Hi Chris,
After looking at the circuit a bit, I realized that the flyback diode should be directly across the inductive load - in our case the pneumatic solenoid, not from +24v to ground. I made this change and all works now.
In answer to your questions above, with the solenoid disconnected there were no disconnects. When it disconnects the computer beeps (like when you unplug the USB) and the Device Manager window refreshes, but COM5 still is there. At that point the HMI still shows COM5, but doesn’t work. If I reselect the COM5 entry all works again.
Thanks.
Ron