Thread: Wiper motor with speed controller

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Has anyone used a speed controller to operate a windshield wiper motor? I like to know if a Traxxas XL-1 speed controller would work. I currently have a BOC (board of chuckie) operating perfectly but I would like to animate waist movement by turning the torso of the prop back and forth, this is where I would like to use the wiper motor which has good torque and the Traxxas XL-1 speed controller would operate the back and forth movement on the wiper motor.

1) Would this work?
2) How would it be connected to BOC?
3) Do I still need to provide separate power to the wiper motor or is the power from BOC sufficient (currently running 5V@4amps)

Are you planning to animate the torso to be synchronized with the rest of the routine? For example: torso turns left, skull talks to animatronic A... then torso later turns right, and skull talks to the audience. If this is what you're after, the speed controller method won't work. The reason is that, even if you tell VSA to move the motor for the same time duration each direction, the speed will be ever so slightly different. After 20min or so, the torso will have 'walked away' from its cues - it won't be facing the audience or the animatronic... it'll be facing the tree and the wall.

If servo control of the torso is what you're after. This is what you want. You can use one of these, and a potentiometer attached to your torso, to turn a wiper motor into a servo.

On the other hand, with a speed controller, you could just have the torso oscillating back and forth - using a offset crank mech (like a Christmas animated deer). Although I'm not sure whether that speed control would cut it or not - I didn't see a datasheet for it online.

Hope this helps...
- Hook

Yeah I was planning to animate the torso with the rest of the routine. Here is a copy of image, specs, and diagram

http://www.servocity.com/assets/imag..._Schematic.jpg

So in the diagram it looks like the servo is powered by a separate battery pack from the speed control. The speed control would be powered by a 12vdc source and the servo by some 5-7vdc source. Seems to me that this would work. I'm curious though about the "receiver". How does this connect to your BOC or is it a separate servo controller board?

It's a motor speed controller made for R/C vehicles. An R/C receiver receives the radio signals from the transmitter, and sends the control pulses to each of the controlled servos (or the ESC, in this case).

The specs I was interested in are the input voltage and output current limits that the speed controller can tolerate. Although, I don't have a great guess as to how much current a wiper motor will draw under load. Maybe someone who's actually hooked one up can chime in?

- Hook

Below are the specs.

Input: 4-7 Cells (4.8-8.4V)
Output: 75Amp Continuous Max.
Peak Output: 100amps
Voltage Drop: .019V
Operating Frequency: 1.5KHz
Battery Eliminator Voltage: 5V/1Amp
Low Voltage Cutoff: 4V
Dimensions: 2.4 x 1.5” x 1.4"
Weight: 3.4 oz with wires
Maximum Motor Size: 500 Size - 17 turn

@Bucaneerdude the speed controller has a servo connector that would plug into one of the BOC servo channels, there is a red and black wire that would be connected to the motor, another black and red with connector for power, and an on and off switch

fright props sells a speed controller for the wiper motors it works good I used one on animated meat grinder I made

If you want to run the wiper motor off of 12V (like originally intended), the ESC won't handle the voltage. You could probably run it at lower voltage, but finding a high-current power supply at that voltage range might be tough (except for 5V, which might be lower than you want - speedwise).

But again... it sounds like you've confirmed you're trying to animate the angle of the torso. Speed control won't accomplish that. It may work for a few minutes, but eventually the torso won't come back to the same angles you intend. If you really want angle control on the torso, I think the Pololu board + wiper motor, or a big servo, are the only ways to do it.

- Hook

Thanks hook

I experimented with it via separate 5 volts for the motor and the signal through the boc.
Just like you mentioned in your first reply it will not work. I do need a position feedback via a potentiometer to determine it's position.
When I was testing it the motor started jittering when I wanted it to stop at a certain point. I may have to consider the Pololu option you mentioned in your earlier post.

@esbit regarding the frightprops speed controller...what are you using it for arm movement, torso, etc.
I don't think it would work for my routines because..correct me if I am wrong...but I believe you have to pre-record the event in the speed controller. My application I want to rotate a torso left and right but in sync with my animations playing via VSA. With the pre-recorded frightprops speed controller it may not stop when I need it to on cue with the routines playing via VSA.

A while back Dr. Moribus built a "servo" from a wiper motor. I think there is a thread on here for that , he used it on a ground breaker if I remember correctly. I'll try to find the link. Hope this helps....