Nu Relic power window issue

[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

[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

[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 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.

Thanks for chiming in!
I haven't seen that variable resistor in my search, it's reasonably priced so I bought it for testing.
I'll reply with the results

By the way, any issues with your window speeds?

Thanks again

[dhutton]

You are a glass alignment god if you only need 3 amps to raise and fully seal repop glass on repop weatherstripping....

Don

[blitzer454]

Originally Posted by colorado80439

By the way, any issues with your window speeds?

My windows are quick but I don't feel they are excessively fast.

You are a glass alignment god if you only need 3 amps to raise and fully seal repop glass on repop weatherstripping....

Okay I went back and double checked my measurements and I did screw them up. I have my over current A/D count value set to 0x200 (hex) which translates to 2.5V (10 bit A/D counter with 5V reference). I was mistakenly taking that voltage value as the current forgetting that I have a voltage divider on the A/D channel such that 5V scales to 30A. So 2.5V is actually 15A. On a side note I have the rear window over-current set to 0x115 which translates to 8.11A. Sorry for the confusion.

So I guess the Nu-Relics spec values are actually pretty close to what I'm seeing in the real world.

I would like to say that my windows are perfect, but they're not. They like to leak around the seal at the top of the window when I hit them with the water hose, but they're not to bad in the rain.