DC Polarity Switching - Power Supply Options

[Tico]

I'm installing at least 5 DC motor controlled blinds (12V) and wish to have individual control of each motor. I've read the Loxone documentation and see that there is a graphic on how to control DC motors using 4 relays for polarity switching.

This takes up more relay outputs than I would like and the best outcome I perceive is switching 4 motors before requiring an extension (see attached graphic).

It seems an external polarity reverser for the motor power supply would give the best 'bang for buck'. I would then need one relay output for the polarity reverser, leaving seven for blind control.

This option looks cost-effective -

http://www.ebay.com.au/itm/DC-MOTOR-REVERSE-POLARITY-SWITCH-DPDT-RELAY-CONTROLLER-MODULE-2A-12V-BUTTON-PUSH-/222142743896?_trksid=p2141725.m3641.l6368

Has anyone explored other options for DC motor polarity reversing? An even better option would be digital control of the polarity reverser to free up another relay.

[Christian Fenzl]

This (German) Wiki article explains a option with two DO's and two switching relays.

http://www.loxwiki.eu/display/LOX/Richtungswechsel+beim+Gleichstrommotor

[Tico]

Thankyou. That is very clever.

As an alternative, would you advise for or against using an Analogue Output for powering small switching relays? The device I linked to earlier has a minimum voltage requirement of 9VDC and a power draw of 0.2W.

10VDC from an Analogue Output would have a current draw of 20mA with this device. This appears to be sufficient to control the device and remain within the Miniserver limits?

That would free up all DO's for high current motor switching.