Automation, sensing and robotics • Re: How to control low voltage AC motors

"read the state from the "comm" terminal", what do you mean with this?

Oops, I thought it had this feature. Other Belimo actuators do (e.g. "2 to 10 VDC feedback signal shall be provided for position indication"), but this one does not.

The datasheet only mentions AC, but there is a photo attached of the motor. On the label of the motor is "24VAC / DC". This also explains the "COM -24V"; the minus sign would not make sense for AC operation only.
Perhaps doublecheck with the company about this.

Yeah, I noticed this too, and already sent them a message. I would much rather deal with DC if I can.

For DC usage:
Use a 24V DC powersupply. Build a high side transistor switch with an optocoupler connect to the RPi. Eventually use a 'high current' optocoupler only for these low currents, e.g. 4N30M or PS2702-1.

Anything off the shelf that would work with this? I assume I could use a motor hat with an h-bridge and treat "forward" and "backwards" as separate motors. Do you see a simpler way?

For AC usage:
Use a 24V AC powersupply.
Switching AC with transistors is complicated, use relay instead. These also solve the 'isolation problem' between RPi and the 24V side.
The usual solid state relay SSR will wot work with these small currents.
A simple solution would be to use two usual relay for each of the open, close connectors.
The relay contacts should be rated prox 40VAC min, 0.1A min.

Thanks, this is good info. (I'm assuming "will wot work" -> "will not work".)

Statistics: Posted by Sentre — Sun Sep 15, 2024 8:35 pm

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