How to create a pulse for an emitter follower circuit which will drive a dc motor

[suave-o]

The circuit is a position control circuit. A pulse has to be created (between +12v and -12v) which would be fed into the DAQ in order to drive the emitter follower circuit (made up of 1 npn and 1 pnp transistors) if the output is positive the dc motor will drive it one way and negative the other way. could pwm be used? can any other type of pulse creation work?

[johnsold]

Many analog output devices are not able to produce +12 to -12 V outputs.  I suggest that you consider using a digital output (from a digital port or a counter) and build the necessary level-shifting circuits to drive your emitter follower.  You may also need to consider adding some dead time when both transistors are off.  If the turn on time of the transistors is shorter than the turn off time then both will be on simultaneously.  This produces a short circuit across the power supply.  It could damage or destroy the power supply or the transistors.

Certainly PWM can be used.  The digital outputs probably give you more versatility in pulse timing than you would have with analog outputs, but that depends on the type of DAQ device you are using.

Lynn 

[suave-o]

sounds good! ive been trying to locate counters on labview 8.2 but cant find .........

[johnsold · Accepted solution]

Do you have the DAQ drivers installed?  What DAQ device are you using and which drivers?  Several different versions exist.

There should be some examples of using counter if you have installed the DAQ drivers.  Have you searched the examples?

Lynn 

[suave-o]

no problem i will try this. it is a new project that my university has set me. i dont have 24/7 access to the labs which have the DAQ but i will find out the answers to those questions