Help with motor control

[Dennis]

Hi there I was wondering if someone could help me, im trying to make an an auto open and closer which will require a motor to wind up when it gets dark and unwind when it gets light, ive found a few kits online that can do the up bit but was wondering how i could make the motor reverse when it gets light again.
will this kit do both
http://www.anykits.com/catalog/product_ ... cts_id=295

I have a little bit of electronics knowledge but very basic.

Thanks in advance for any help.

[Dumbo]

Hello Dennis, A lot depends upon what equipment you have and how far the motor has to wind. If only a short travel is needed, like a window opening/closing then it might be worth using a mechanical means to reverse. Using a large pulley with a crank throw equal to half the travel required you could rotate the motor enough to give a half rotation of the pulley and use a limit switch to stop it at the half rotation point. When closing, the motor still rotates in the same direction but the window or whatever moves in the reverse direction stopping when the "reverse" limit switch is reached. You would need two relays, arranged to be "self-latching", one for each direction of travel wired in series with the appropriate limit switch which would break the circuit to stop the motor. Much will depend on the light detector you will use and what sort of signal it gives and you would need to use an op-amp with hysteresis to prevent "hunting" due to variations in light level. Dependent upon the signal level (high or low) the appropriate up or down relay could be energised.
Failing the mechanical solution, you will almost certainly need a DC motor and use a "cross-over" switch to reverse the polarity of the stator winding whilst leaving the rotor winding as originally arranged. If you have a motor with a permanent magnet for the stator, you just need to reverse the current flow. I have used this system with a windscreen winder motor very successfully. You seem to have chosen quite a complex project here, similar to one I embarked on for curtain opening/closing.

Best of luck!

[CCH Concepts]

this i quite oftern done using a MosFet H-Bridge. check out this link http://en.wikipedia.org/wiki/H-bridge