I've been looking at sources for relatively inexpensiver options for motors for various projects and one of the things I came across was windshield wiper motors from cars. They presumably have quite high torque as the operating radius is across the blade length at least and even demonstrably capable of moving a modest weight of snow.
I am entirely spitting in the wind as a very rough guess, but I vaguely believe a linear actuator with a similar torque ability and probably much slower rate, would cost several times more. As an example of a windshield wiper motor, the "Super Auto WPM1025X" can be found on ebay for $20USD shipped.
I am here asking if anyone has had any experience or even educated speculations on how these things work in terms of control signals.
When you adjust the wipe frequency in your car, does your car handle the timing of when to power on the wiper motor to perform a cycle of a single wipe?
Or is the wiper motor always powered and has a separate control signal?
Is the wiper motor internally programmed to only perform whole wipe cycles (forward and back) each time it gets power? In other words, if I rig up a 12V battery with a momentary button to the wiper motor, would it rotate from start to end, and then return to start, every time i press the button?
Very simply:
Wiper motors have an internal set of contacts that close when the motor rotates off the home position. These contacts supply power to the motor until the motor is once more at home position. In delay mode, the wiper control provides a pulse of power long enough to ensure the motor turns far enough to close the internal contacts, which take over the sweep until home position. When the delay period ends another pulse is sent to the motor. Under constant wipe the control remains on and the wipers merrily fly back and forth until you turn them off, which is usually in mid-wipe. The internal contacts make sure the wipers return home.
How is speed controlled, then? I could be wrong, but it sure seems like the blades move slower when the frequency is lower. I.e., it's not simply one wipe speed only spaced by activation.
INTP:
How is speed controlled, then? I could be wrong, but it sure seems like the blades move slower when the frequency is lower. I.e., it's not simply one wipe speed only spaced by activation.
Perhaps if you tell us what car you are referring to, someone might Google the information for you.
You can easily bypass those contacts by just powering the correct wires. You shouldn't need to disassemble anything. Most wiper motors I have seen will run in reverse too. So yes, it does make a good actuator for some projects.
The travel available from the motor unit will be small. Maybe 1 or 2 inches max. If you need a linear actuator to go 3in or 6in then you need to add levers and linkages and that gets expensive quickly unless you own a welder. Plus that is no longer "linear" so it may not suit your project.