Hello, I am struggling with something that feels as that it should have a simple answer.
I have created a system that operates the blinds at home. The blinds are lowered and raised by pulling a rope and I have attached a motor for each direction. However, the dc motors I attached to the ropes have worm gears which means that i need to run the 'up' motor backwards when I lower the blind and vice versa. This creates problems and I need a more elegant solution that allows the motor to spin freely in the reverse direction. I looked for freewheels but they are too big for my setup.
Are there dc motors that allow the free motion backwards or should i look for an external thing like a freewheel (but maybe I am doing the wrong search)?
Thank you.
Most applications like this would use one reversible DC motor.
An “H” bridge or simple DPDT relay is used to reverse the current that flows through the motor.
What is a freewheel ?
Why 2 motors? That is almost a hopeless design that is not good for the other parts like the pulleys and the rope
Perhaps they mean a sprag clutch (one way clutch).
That would appear to be the basic problem. 
No, he really means just a clutch - which releases when the motor is not activated. But the design is clearly all wrong! Part of it is that he presumably also wants to be able to operate the blind manually. 
One guy building several modell railroad locomotives once installed 2 motors to give the new loco more pulling force. It moved like a snake having too small shoes... Removing one of the motors, the loco worked perfectly.
Worm drive of course.
I think it was, yes. Hopeless....
A drawing of your motor / pulley / rope arrangement and the forces required to raise / lower the blinds would help.
Not just "help".
Completely essential prerequisite for further discussion.
Seem to remember that old commercial laser printers had quite a few electromagnetic clutches/couplings.
They were mostly 24v dc but only around 25mm diameter and quite powerful.
Used a few on a couple of my workshop machines I built here for miniature ic engine building.
Think some of the online stores would have them relatively cheap also.
Thank you all for the answers.
I admit that the whole design was not great to begin with. I did not realise that there is actually an easy way to use a single motor by using a pulley system, which is what I did last night and it looks like it will work well.
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