Controlling Double A Battery Powerd Motor

jpalme5

I need to turn on a motor which was taken from a hand held drink mixer with a Basic STAMP II. The motor uses TWO Double A batteries and I would like to be able to turn it on and off to mix a solution in a reaction chamber for my senior design project. I have the motor mounted above the chamber with the stirrer bellow and the wiring exposed above.

My entire setup (stamp, micropumps, etc..) is being powered by a common 12V DC battery. I have a 5V regulator for the stamp.

Should I use a relay that just tells the motor to turn on (I assume that I will need to use the double A batteries to power the motor)? If so could you recommend a relay that would work?

I thought that this would be the simplest way to accomplish the task with out building a new circuit with regulators and transistors but is there better way for me to do this?

Thanks for the help everyone.

Chris Savage

If the pump runs off 2 AA batteries you could probably switch it with a simply transistor or a FET if you have one. Here are a couple of schematics to demonstrate this. I hope this helps. Take care.

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Chris Savage
Parallax Tech Support

jpalme5

I have three micropumps that run off 12VDC. These are the main components of the system and I have them working with TIP120 transistors between the stamp and the battery. For this reason, the stamp is powered by the 12V battery so that the the entire setup is not running off of a separate power source.

The motor/mixer that runs off the AA batteries is secondary. This may be a off the wall question for here, but I assume that the two AA batteris that power the motor are in series, therefore the motor uses 3V to run. Is this assumption correct?

The reason I ask is because I am wondering if it would be possible to just use a single 5V to 3V regulator to power the motor (from the stamp to the motor and to into a common ground for the 12V battery)?

I would like to just use a relay that switches on the motor using the AA batteries. Do I have any other options?

I am in biomedical engineering, not electrical, so I am not well educated in all of this circuitry.

Thanks again for the help guys...this forum has been a life saver in the past.

Mike Green

Yes, the motor probably runs off a 3V supply. It is generally not a good idea to have a large voltage drop across a linear regulator since all that extra power (voltage times current) has to get turned into heat. The Stamp has its own regulator on the Stamp itself. It is not designed to handle the current (or the power dissipation) needed by the motor. I suggest you get a simple 8V regulator (like an LM2940-8.0) that you'll run off the 12V supply. You'll run the Stamp off the 8V output of this and a 3.3V regulator (like the LM1086-3.3) which will run the motor. The LM2940-8.0 you'll need to use with a small heatsink. You might put the 3.3V regulator on a small heatsink as well.

Look at the datasheets for the regulators for suggestions for filter capacitors and wiring diagrams.