What kind of device/controller for application?

[joeysmalls]

Help,

I know nothing about electronics. I am trying to help my 11 year old with a school project. We need a device or controller that can power on/off several 12 volt motors in a series. Only 1 motor could be on at a time. So Motor A would be on, while Motors B, C, D, E, F would be off. Then Motor B would be on while all others are off; and so on. The order would always be the same. I had my daughter research this first and then I took over. We have been unable to come up with anything. It must be rather simple (Christmas lights use something like this, right?). If anyone can tell us where to start, any help will be most appreciated. Thanks.

 

[electric101]

Hi,

Are you attempting to avoid using multiple toggle switches for a reason? If willing, I'd wire a line that has power to all the motors and control the operation of each motor separately with a switch controlling ground. Does this work for what you are trying to do?

 

[electric101]

Help,
It must be rather simple (Christmas lights use something like this, right?). If anyone can tell us where to start, any help will be most appreciated. Thanks.

Forgot this part:

No and yes. Older x-mas lights used series circuits. Remember when you had a bulb go out the entire strand would, too. That was because current would stop at the bulb that was bad. Now they are wired in parallel. This means that current doesn't have to go through the previous bulb to make it to the next bulb.

So I think you are looking to wire your motors in parallel rather than series. Make sense?

 

[joeysmalls]

Oops. I left out a major requirement. The speed of the transition from one motor to the next, has to be variable and controllable. I envision using some sort of rotary dial to make this happen. I need to be able to "fire" each motor one at a time, in sequence. So it would look like this: A, B, C, D, E, F, A, B, and so on. And the on/off cycle would increase/decrease in speed by turning the dial. Thanks for your help.

Oh, to answer your question: yes, I envisioned wiring the motors independent of each other (is that what you consider parallel?).

 

[electric101]

Oops. I left out a major requirement. The speed of the transition from one motor to the next, has to be variable and controllable. I envision using some sort of rotary dial to make this happen. I need to be able to "fire" each motor one at a time, in sequence. So it would look like this: A, B, C, D, E, F, A, B, and so on. And the on/off cycle would increase/decrease in speed by turning the dial. Thanks for your help.

Oh, to answer your question: yes, I envisioned wiring the motors independent of each other (is that what you consider parallel?).

I think I understand correctly. And I am assuming your 12 volt motors are basic DC motors; with two wires? If this is the case, they vary in speed by the amount of voltage given to the motor. 12 volts will spin the motor at a speed twice as fast as 6 volts would (in theory). This being said; most motors like this are controlled through PWM or Pulse Width Modulation. It's essentially turning the motor on and off quickly a bunch of times, thus lowering the speed. Am I making sense?

For your project, I would say skip the PWM and just vary voltage with a potentiometer (it's a dial, like you referred to) which will vary the voltage output to the motors. This is quick and easy. I think Radio Shack has them.

Now, for the starting ("fire") of each motor. I'm confused about what you need to happen. Are you wanting the motors to start up and turn off in sequence automatically or can you manually start each one? Because manually; this project can be done with 6 motors, 7 on/off toggle switches, potentiometer, battery and some wire. But if you want to just flip and switch and have a "control module" turn each motor on and off while you vary the speed; it just got a lot more complicated

Hope this is making sense!

 

[(*steve*)]

Well... I might approach this using a 555 to generate the pulses, a 4017 to switch up to 10 lines on, one at a time, mosfets to switch the motors, and a diode protecting each one.

The other option id to use a PIC (or PICaxe) to control the motors (also need mosfets and diodes), with the ADC input used to read a potentiometer.

Bus with no knowledge of electronics, either solution is a big ask.

 

[joeysmalls]

Thanks guys. So basically, this project is going to require some sort of program? I looked up PWM, the 555 timer, 4000 series circuit and think I would be in way over my head building something like this from scratch. The PICaxe device looked like it was maybe more manageable. Do you think that RadioShack's Mircrocontroller Stamp Kit would be a good place to start? I also found something online that does what I am looking for. Here's the link:

http://www.chaselights.com/wl_models.htm

Do you think that this uses a PIC?

Thanks again guys. I know these questions are probably pretty inane.

 

[electric101]

Thanks again guys. I know these questions are probably pretty inane.

Sorry, as I hinted in my previous post; this kind of stuff is beyond my knowledge. But you are in the right area; lots of these guys know this stuff in and out. Good luck and sorry I couldn't ultimately help!!