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If we take I = E/R and we increase E then I would go up. Unless of course R goes down, but that is changing 2 variables. Does resistance change with increased voltage? This is DC so we aren't dealing with impedance (I don't think) so unless you are nearing the limits of what the wire in the circuit itself can handle I don't think resistance changes much. So in that case, if voltage goes up, so does current. I think. Electricity is not my thing.

 

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lets make sure we dont stray from the question. its all about DC voltage, not AC.

edited for stupidity

Edited by strangeduck
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I see many sporting their thinking caps here. This will be a fun exercise. Several have formulated their own hypotheses within their posts - IE, as voltage goes UP, current goes DOWN. Or . . . Inductive loads react differently than resistive loads.

This is the point of this post. Let's all stop guessing about stuff and prove / disprove our theories in an effort to learn the truth. At least one person has a tool at his disposal at which he could indeed prove / disprove the theory he laid out in his post . . .

I don't have a window motor on hand or else I would have done it the second I saw this post lol. All I have is resistors and not enough free time.

Edited by DubNDodge

 

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I have a variable voltage 50A power supply sitting on my desk. I should just rip out a window motor just to test this lol

Keep me posted if you do I'm curious of the results. Does it maintain a fixed current-voltage ratio as does a resistor? Logarithmic? Exponential?

I actually have a car door at work with a dc power supply wired up to test window switches, I might have to wait until my shift is over but I can record a quick video.

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Love it! However . . . one of the things that science teaches us is to eliminate all variables. In andru's video, the following are variables that can affect the outcome:

1. The friction the window, tracks, and door panel exert on the window. This is a constantly changing variable based on where the window is in its range of motion.

2. The window switch - age and use can tarnish its contacts. Although the window operates correctly in the video, the resistance across the contacts in the switch can be less of a factor when the window is going down and more of a factor when the window is going up.

3. The wiring, terminations, etc. between the power supply, window switch, and window. One less than ideal termination can skew all of the results.

4. The resolution of the display on the power supply. Even though it reads to a tenth of an amp, it's inconsistent so it can't be relied upon for good data.

1-3 obviously affect the "load" placed on the window motor. More load = more current as andru demonstrates by holding the window switch depressed with the window at the end of its travel.

Regardless, andru gets mad props for attempting to prove his hypothesis and that's what this thread is about. Although we're not there yet, we will be soon.

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1. this is an old junkyard door and the springs that serve as a counter weight for the weight of the glass are probably worn out, I did see much higher current was drawn while moving the window up.

2. The switches are good but the contacts might not yet be completely broken in yet. I can get my hands on the oem tolerances for contact resistance so I could test the switch

3. we just crimped some pins on 22awg wire and put them in the oem connector, I have no doubt that isn't ideal

4. that power supply is very cheap but i do have a Agilent(HP) N5745A coming in next week that has software so I should be able to graph it, still probably not fast enough to get the inrush current though

seems like the ultimate variable though is the door besides being old we also use it to test low volumes of replacement parts and before that engineering was using it so that switch connector is probably very worn out. automotive connectors aren't made to be connected and disconnected thousands of times let alone whatever wear might have happened to the motor.

My issue is that this was supposed to be a simple experiment but even this window motor ended up being more complexed than necessary. I could have just used a resistor and an inductor to simulate the load of a motor and connected directly to a power supply and 2 dmm's one for voltage the other for current

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