Two power supplies together

Thread Starter

Luxten

Joined Aug 22, 2018
4
Hallo all

I need to drive the motor of a window courtain. It is 24V DC and has only two wires. The polarity between the two wires decides the direction of the motor movement.

I thought about using two cheap AC-DC power supplies, both wired to the two terminals of the motor, but with opposite polarity. A simple up-0-down switch would power on one of the supplies, or the other.

This would also have the advantage of not having a power supply always on, as was the case with the original control card, which is broken now.

I just wonder if the presence of the turned-off power supply could affect the functionality of the turned-on one, when the + terminal of one is connected to the - of the other, and the other way around.

Thank you very much
Luigi
 

Thread Starter

Luxten

Joined Aug 22, 2018
4
Thank you Albert.

That way, I would have to keep the power supply always powered on, or apply a second on-off switch, to power that on when it is needed.

Ideally, I think it would be cleaner to have a three-position switch, like the DPDT, but placed _before_ the power suppply, which not only provides the AC power to it, bu also decides the polarity of the output. Do you (or others) know of devices, or circuit, which does this? In absence, I'm thinkng about emplying thwo relays.

Thank you again,
Luigi
 

schmitt trigger

Joined Jul 12, 2010
243
Actually, you require a 3PDT dead center switch.
2 poles for the polarity reversal, one pole for the AC switching.
The dead center when the unit is off. The other pair of throws should be momentary.
 

KeithWalker

Joined Jul 10, 2017
907
Why would you not leave the 24 volt supply turned on? It will consume a negligible amount of power when it is not in use.
If you want it on only when it's in use, use a DPDT switch and momentary push switch. Set the direction with the toggle switch, then turn the supply on by holding the push switch down until the curtain is where you want it.
Regards,
Keith
 

Thread Starter

Luxten

Joined Aug 22, 2018
4
@schmitt and @albert: Thank you, I'll try the 3PDT solution.

@Keith: Thank you. Maybe it's just a paranoia, but indeed I have many motors like that in my house. When the controlling board broke, I had a look at another working one. And I found that the PSU was really really hot. So I'd like to have something normally switched off. Thank you, anyway.
 
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