google me this: Potentiometer

I have been having a hard time finding the correct one for what I need.

My rx7 has 0 original wiring and right now I'm trying to enhance my wiring on a particular circuit, the wiper blades.

How it works via factory (and how I have mimic'd it) is that the wiper motor always receives power and the ground controls on/off/speed.

Right now I just have it wired to full speed with a toggle switch, what I'm trying to have a variable resistor with a knob that I can interrupt the ground circuit with. The only ones I can find are a knob that needs a screwdriver to adjust or something with a bizzare ohm range that is useless to me.

IE: I'd like a simple one that goes from 0 ohms to open (or very high resistance) that I can use with me finger to turn, so it will act as a basic on/off switch and any "speed" in between.

I'm a long way from certain, but off the top of my head, I suspect that the average finger-twiddlable potentiometer isn't going to want to put up with the kind of current a wiper motor pulls...

From the Wikipedia article on pots (not that this is probably a great source of info...):

Potentiometers are rarely used to directly control significant power (more than a watt), since the power dissipated in the potentiometer would be comparable to the power in the controlled load.

Also, and I'm guessing you already know this, it sounds like you'd just be operating the motor at different speeds, and not actually having a delay...

What I wish I had was a simple idea for you. Wouldn't be surprised if wiper control boxes are out there in the aftermarket...

Hrm... Wish Summit gave some more technical details on this Hella switch...

In reply to ransom:

but in ,y wiring it doesn't control voltage or load, it is only controlling the resistance. The motor has a constant KOEO feed.

I'm not trying to set a few different speeds, just change the resistance on the ground to vary the speed.

It's probably easier to wait for someone to identify a car that has an easy to remove wipe controller.

Radio Shack!

The first one has an on-off switch integrated. Knobs are expected.

For that type of a load you want a Rheostat. for on the cheap try. grab a 70's vintage dodge head lamp switch and wire wipers to the dash dimmer built in.

fidelity101 wrote: I have been having a hard time finding the correct one for what I need. My rx7 has 0 original wiring and right now I'm trying to enhance my wiring on a particular circuit, the wiper blades. How it works via factory (and how I have mimic'd it) is that the wiper motor always receives power and the ground controls on/off/speed. Right now I just have it wired to full speed with a toggle switch, what I'm trying to have a variable resistor with a knob that I can interrupt the ground circuit with. The only ones I can find are a knob that needs a screwdriver to adjust or something with a bizzare ohm range that is useless to me. IE: I'd like a simple one that goes from 0 ohms to open (or very high resistance) that I can use with me finger to turn, so it will act as a basic on/off switch and any "speed" in between.

I don't think you want to vary the resistance of the ground, you want to interrupt it on/off with a timer circuit. Varying the resistance will only have it run full speed until it drops below a certain point and then make it stop working completely. here's a kit that would add delay to it:

http://store.qkits.com/moreinfo.cfm/MXA041

but really any timer that has an output relay that turns on/off and is adjustable should work.

Usually you want full speed and something slower that still works (there will be a threshold where the voltage is too low and the motor can't push/pull the wiper), then a delay between wipes. Infinite variability in speed but still wiping all the time is not going to work as well. This is the reason delay wipers are the norm.

Use a single value power resistor (switched, with DPDT toggle) and then a delay circuit borrowed from the JY (or whip up a 555 timer relay circuit) and put the pot on the delay function :)

In reply to dculberson:

hmmm I see your point, good to know. Thanks for the support all!

I see a lot of methods here to add an intermittent speed but having 1 speed that is infinitely variable would be key.

I know it is for the Volvo 850.. but this might be something you could look into

Smart Wiper Delay

44Dwarf wrote: For that type of a load you want a Rheostat. for on the cheap try. grab a 70's vintage dodge head lamp switch and wire wipers to the dash dimmer built in.

^^^ What he said^^^

fidelity101 wrote: In reply to dculberson: hmmm I see your point, good to know. Thanks for the support all! I see a lot of methods here to add an intermittent speed but having 1 speed that is infinitely variable would be key.

I am still not understanding the value in 1 speed being infinitely variable. I could see being able to control the delay between wipes in an infinitely variable manner being very useful though. Maybe a delay timer that is controllable by a potentiometer?

In reply to szeis4cookie:

Let me rephrase

Normal wipers have the following function: intermittent speed 1 (low) speed 2 (high)

What I'm looking for is any speed in-between 1 to 2 (including slowest and full blast)

Turn the knob down its speed one, I move it up a higher a bit its about speed 1.235, I turn the knob to decrease the resistance and the speed is now somewhere around 1.754.

and yes I am making arbitrary numbers.

if that made things more confusing then I'll leave with this one. on your dash, the backlit has a knob where you can turn the intensity down or up with a knob changing the brightness of the dash lights. I'm trying to do this but with my wipers. Instead of lights to low brightness to high brightness I am trying to use wipers from low speed to high speed.

I think we understand what you're trying to achieve. What's not so clear is why that's the specific operation you're looking for, since it seems harder to do and less effective. But we may not understand all the criteria yet.

I think 44Dwarf and HappyAndy might be on the right track, but again, dash lights don't pull nearly the power that a wiper motor does.

If you have the old wiring around (or a manual?), I would look for the resistor which used to give you "speed 1". The value of that resistor will tell you what the highest resistance is that you'll need on your rheostat, and it'll also give you an idea how much power it needs to be able to dissipate.

Forgive me if I'm misinterpreting, but it sounds like you might be thinking that because the control is on the ground side that it doesn't deal with power. However, it is still part of the circuit, and is still very much involved in that circuit (Google Ohm's Law). You're adding a variable resistor to that circuit, and it's going to have to be able to dissipate an amount of energy affected by input voltage, the resistance of the motor, and the resistance of the rheostat.

HappyAndy wrote:

44Dwarf wrote: For that type of a load you want a Rheostat. for on the cheap try. grab a 70's vintage dodge head lamp switch and wire wipers to the dash dimmer built in.

^^^ What he said^^^

In the '60's, the time before intermittent wipers, Ma Mopar had a variable speed wiper available. The cars used the 2-speed wiper motor and a rotary switch. My Barracuda has this setup.

The normal 2-speed switch routed power through a ceramic resistor mounted to the motor for the low speed setting, and full 12v for high. I suspect the variable setting was routed though the resistor as well, but I never looked that close at the wiring.

That kinda sounds like heater fan wiring, Rob.

dculberson wrote:

fidelity101 wrote: I have been having a hard time finding the correct one for what I need. My rx7 has 0 original wiring and right now I'm trying to enhance my wiring on a particular circuit, the wiper blades. How it works via factory (and how I have mimic'd it) is that the wiper motor always receives power and the ground controls on/off/speed. Right now I just have it wired to full speed with a toggle switch, what I'm trying to have a variable resistor with a knob that I can interrupt the ground circuit with. The only ones I can find are a knob that needs a screwdriver to adjust or something with a bizzare ohm range that is useless to me. IE: I'd like a simple one that goes from 0 ohms to open (or very high resistance) that I can use with me finger to turn, so it will act as a basic on/off switch and any "speed" in between.

I don't think you want to vary the resistance of the ground, you want to interrupt it on/off with a timer circuit. Varying the resistance will only have it run full speed until it drops below a certain point and then make it stop working completely. here's a kit that would add delay to it: http://store.qkits.com/moreinfo.cfm/MXA041 but really any timer that has an output relay that turns on/off and is adjustable should work.

crikey!!!!

THANKS!!!

you just solved a problem for me in a way that i like. i was wondering how to convert my duster to intermittant wipers when i tear the wiring harness out of it. for 10 bucks, im willing to give it a wack.

michawel

In reply to fidelity101:

Controlling a single coil motor speed with a resistor (variable) is a bad idea in general. It requires a large rheostat (high current/power potentiometer), is hugely wasteful of available power and will result in an uneven speed motor during operation. A PWM switching controller like used in model trains and RC cars is a much better solution. Here is something on ebay that might do: http://www.ebay.com/itm/12V-30A-DC-Motor-Speed-Control-PWM-HHO-RC-Controller-/221021510531

Keith Tanner wrote: That kinda sounds like heater fan wiring, Rob.

Yea it is. Wiper wiring probably was thought up by the same electrical guys in Highland Park.

wclark wrote: In reply to fidelity101: Controlling a single coil motor speed with a resistor (variable) is a bad idea in general. It requires a large rheostat (high current/power potentiometer), is hugely wasteful of available power and will result in an uneven speed motor during operation. A PWM switching controller like used in model trains and RC cars is a much better solution. Here is something on ebay that might do: http://www.ebay.com/itm/12V-30A-DC-Motor-Speed-Control-PWM-HHO-RC-Controller-/221021510531

This.

Dusterbd13 wrote:

dculberson wrote:

fidelity101 wrote: I have been having a hard time finding the correct one for what I need. My rx7 has 0 original wiring and right now I'm trying to enhance my wiring on a particular circuit, the wiper blades. How it works via factory (and how I have mimic'd it) is that the wiper motor always receives power and the ground controls on/off/speed. Right now I just have it wired to full speed with a toggle switch, what I'm trying to have a variable resistor with a knob that I can interrupt the ground circuit with. The only ones I can find are a knob that needs a screwdriver to adjust or something with a bizzare ohm range that is useless to me. IE: I'd like a simple one that goes from 0 ohms to open (or very high resistance) that I can use with me finger to turn, so it will act as a basic on/off switch and any "speed" in between.

I don't think you want to vary the resistance of the ground, you want to interrupt it on/off with a timer circuit. Varying the resistance will only have it run full speed until it drops below a certain point and then make it stop working completely. here's a kit that would add delay to it: http://store.qkits.com/moreinfo.cfm/MXA041 but really any timer that has an output relay that turns on/off and is adjustable should work.

crikey!!!! THANKS!!! you just solved a problem for me in a way that i like. i was wondering how to convert my duster to intermittant wipers when i tear the wiring harness out of it. for 10 bucks, im willing to give it a wack. michawel

Fiat used something similar in the 124. But it was a relay that would click "off" when it got too hot and then make the contact again when it cooled. Not bad for a 60s design.

What was fun, it worked in both and low speed settings

They used to sell exactly what you're looking for in the 80's, but I haven't seen the kit since every econobox came with interval wipers. I installed a ton of them into Subaru's, worked great with the variable knob. This might work for you:

http://www.quasarelectronics.co.uk/smart-kit/1093-windscreen-wiper-speed-controller.htm

so i ordered one of the q-kits switches for the 64 as the wiper switch died. ill let you know how it works in the real world. heres to hoping it comes with wiring diagrams.....