reversing motor motion direction MyDAQ

[Haidar92]

Hi I need help with the following:

Time detection and shading: The LDR (photoresistor) sensor should be able to detect whether it is day or night (light or dark) . During the day, if the sun is so bright, special curtains should automatically shade the temperature sensors by the means of a motor. During night, the curtains should be automatically retrieved. Note that the user should have the ability to override whatever decisions the system might make regarding deploying or retrieving curtains.

I have done some work on the vi program. However I don't know how to reverse motor direction through labview. I am controlling the speed of the motor through DAQmx write counter freq (1 chan. 1 sample) function by a control knob. So I can't specify a negative duty cycle. Any suggestions?

my labview code is attached.

[apok · Accepted solution]

Use a double pole double throw relay connected to your daq dig out and driver and reverse the connection through the relay..

a True on the dig out will reverse the polarity

note: realized that i had connected Daq GND to motor and source...DO NOT CONNECT due to motor's coil induction reflex, ULN has a built in 'flyback diode' for the relay coil induction.

Spoiler

[Haidar92]

of course... the instructor mentioned it quickly during the lecture but I forgot about it... 

thanks a lot