Nu Relic power window issue

[colorado80439]

So I've installed a complete set of Nu Relics power windows in a 69 Camaro coupe and I have to say I'm pretty impressed. There is one issue I've been trying to solve. The door windows power/roll down too fast for my liking. Up speed is fine and quarter windows are awesome. I've spoke with the folks at Nu Relics, they are helpful but do not have an answer. I installed a 10K potentiometer rated for DC, which slowed the window speed but burned up in the process. I think I'm on the right track with a variable resister to control the down speed, just not having much luck finding the correct product.
I'm thankful for all the help I've received from everyone on this site.
Thanks again

[Spiffav8]

I too was a bit surprised by that when mine where installed.

[dhutton]

A resistor is going to affect the power available to raise the window. It’s not a good idea imho unless you get clever and place a schottky diode in parallel with it such that the resistor is bypassed by the diode in the up direction. 10k is pretty far off the mark imho, I think you are probably looking for something less than one ohm, certainly less than 10 ohms. It also needs to be rated for high current, around 20 amps.

The kit I installed in my 69 Camaro several years ago did not drop quickly but the ones I have installed recently do have that characteristic. It seems they changed something....

Don

[colorado80439]

Oh ya the old schottky diode trick, lol. Thanks Don, I guess I have no concept of resistance because I have no idea what voltage drop it will take to marginally slow it down. I'll let you know what I come up with! Thanks gain

[dhutton]

Originally Posted by colorado80439

Oh ya the old schottky diode trick, lol. Thanks Don, I guess I have no concept of resistance because I have no idea what voltage drop it will take to marginally slow it down. I'll let you know what I come up with! Thanks gain

Well, those motors draw around 20 amps. A .5 ohm resistor will drop the voltage 10 volts. Going down the current is likely lower, but you get the idea.

Voltage drop = Current x Resistance

Don

[colorado80439]

So if this is correct
watts=amps x volts, I need a resistor to handle 300 watts at least

If E= IxR then 20 amps at 10 ohms would be a 200 volt drop?

I think there will be some trial and error to determine the correct resistance.
I would try a variable but they are over $300 for that power rating

I'll start with .5 ohms and see where that leads

According to Nu Relics low load is 5A, high load 11A, and stall is 20amps
I'm assuming low load is window down mode and high load windows up.

Thanks Don, let me know if that doesn't add up

[dhutton]

Originally Posted by colorado80439

So if this is correct
watts=amps x volts, I need a resistor to handle 300 watts at least

If E= IxR then 20 amps at 10 ohms would be a 200 volt drop?

I think there will be some trial and error to determine the correct resistance.
I would try a variable but they are over $300 for that power rating

I'll start with .5 ohms and see where that leads

According to Nu Relics low load is 5A, high load 11A, and stall is 20amps
I'm assuming low load is window down mode and high load windows up.

Thanks Don, let me know if that doesn't add up

Pretty much all sounds right.

Also, Watts = amps squared x ohm

Or power = I^2 x R

Your load on the resistor is very short term so you will be able to get away with a power rating smaller than the calculation would tell you.

You can make 1 ohm putting two .5 ohm in series and .25 ohm placing two .5 ohm in parallel...

Those up down currents foreshadow the problem I was predicting, the voltage drop will be higher going up than it is going down and the window won’t raise properly. You can try the Schottky diode if you find that to be the case.

Don

[blitzer454]

Hmm, I use the New-Relics power windows in my car and they only draw around 2A when moving up or down. When the window hits one of the stops the current will shoot up. I have my over-current limit (stall) set to around 3A on my automatic up/down circuit.

I don't recall that they gave the current limit specs when I purchased my motors, I wonder if they did change to a different motor.

I think you are right that the low load is window going down, high load is going up and stall is when the window reaches one of the stops.

You probably should design around the 5A low load spec when choosing the resistor, but know that current can get as high as 20A if you leave your finger on the switch too long after the window hits the stop.

I would shoot for a variable resistor under 10 ohms rated for 300W or more. Like the AVE030020E8R00KE. Try it without the diode first you might get lucky.

[dhutton]

Oddly enough I’ve had 30 amp fuses blow with my Nu Relics power windows...

This always help me understand electricity....

Don

[colorado80439]

Originally Posted by dhutton

Pretty much all sounds right.

Also, Watts = amps squared x ohm

Or power = I^2 x R

Your load on the resistor is very short term so you will be able to get away with a power rating smaller than the calculation would tell you.

You can make 1 ohm putting two .5 ohm in series and .25 ohm placing two .5 ohm in parallel...

Those up down currents foreshadow the problem I was predicting, the voltage drop will be higher going up than it is going down and the window won’t raise properly. You can try the Schottky diode if you find that to be the case.

Don

Great advice, again, Thanks Don