Fast window mod - motor relays on a PCB!

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Lead Head said:
So what's the deal? Why not change the gauge of wire to better suit the terminal?
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These motors draw several amps, and undersizing the wiring is a recipe for heat. That's a very poor design choice. So you want the biggest wire necessary, smallest possible. The gauge I selected is exactly that (18AWG)

I can DIY a connector with no issue with the gauge specified, and despite going back and forth with the vendor a few times and explaining some techniques on how to do this (including offering to buy them additional crimping tools, no charge), I was told that they just can't do it.

Maybe I'll just end up DIYing them myself :)
 
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mtndogdad said:
Ill let OP keep on trucking through this project for us but i'm an electrical engineer and happy to jump in any help where I can. My day job involves working with tons of quick-turn development harness shops
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I’ll pm you!
 
jonnyd42 said:
These motors draw several amps, and undersizing the wiring is a recipe for heat. That's a very poor design choice. So you want the biggest wire necessary, smallest possible. The gauge I selected is exactly that.

I can DIY a connector with no issue with the gauge specified, and despite going back and forth with the vendor a few times and explaining some techniques on how to do this (including offering to buy them additional crimping tools, no charge), I was told that they just can't do it.

Maybe I'll just end up DIYing them myself :)
Click to expand...
I can understand the desire to use the biggest, fattest wire possible - but it's actually really not necessary. It really only matters on long wire runs, or when trying to keep heat down on sustained loads. Voltage drop is V=I*R, and R is relative the length of wire and its diameter. The ~2 foot total circuit length your harness adapter cables will add is really inconsequential.

Just some napkin math:
12AWG Copper Resistance: 0.001588 ohms/foot
2 feet of wire total = 0.003176 ohms
15A * 0.003176 ohms = 0.05V drop across the wire

18AWG Copper Resistance: 0.006085 ohms/foot
2 feet of wire total = 0.01277 ohms
15A * 0.01277 ohms = 0.19 V drop across the wire

And yes, something as small as 18AWG wire pushing 15A is completely fine in this application since power windows are an intermittent application and the NEC doesn't apply to cars. As always, ultimately it's your project (that I'm interested in once it's done), and you can spec out whatever wire you want but for the short lengths we're talking here, wire gauge almost doesn't matter. The math suggests that basically anything 18AWG and larger would have very minimal voltage loss.

FWIW: When I was re-assembling my doors for my re-build, I was testing the power windows with a small battery and 2ft of ~24 AWG clip leads. Those windows flew up and down.
 
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Lead Head said:
I can understand the desire to use the biggest, fattest wire possible - but it's actually really not necessary. It really only matters on long wire runs, or when trying to keep heat down on sustained loads. Voltage drop is V=I*R, and R is relative the length of wire and its diameter. The ~2 foot total circuit length your harness adapter cables will add is really inconsequential.

Just some napkin math:
12AWG Copper Resistance: 0.001588 ohms/foot
2 feet of wire total = 0.003176 ohms
15A * 0.003176 ohms = 0.05V drop across the wire

18AWG Copper Resistance: 0.006085 ohms/foot
2 feet of wire total = 0.01277 ohms
15A * 0.01277 ohms = 0.19 V drop across the wire

And yes, something as small as 18AWG wire pushing 15A is completely fine in this application since power windows are an intermittent application and the NEC doesn't apply to cars. As always, ultimately it's your project (that I'm interested in once it's done), and you can spec out whatever wire you want but for the short lengths we're talking here, wire gauge almost doesn't matter. The math suggests that basically anything 18AWG and larger would have very minimal voltage loss.

FWIW: When I was re-assembling my doors for my re-build, I was testing the power windows with a small battery and 2ft of ~24 AWG clip leads. Those windows flew up and down.
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Also not all wire is the same
 
Lead Head said:
I can understand the desire to use the biggest, fattest wire possible - but it's actually really not necessary. It really only matters on long wire runs, or when trying to keep heat down on sustained loads. Voltage drop is V=I*R, and R is relative the length of wire and its diameter. The ~2 foot total circuit length your harness adapter cables will add is really inconsequential.

Just some napkin math:
12AWG Copper Resistance: 0.001588 ohms/foot
2 feet of wire total = 0.003176 ohms
15A * 0.003176 ohms = 0.05V drop across the wire

18AWG Copper Resistance: 0.006085 ohms/foot
2 feet of wire total = 0.01277 ohms
15A * 0.01277 ohms = 0.19 V drop across the wire

And yes, something as small as 18AWG wire pushing 15A is completely fine in this application since power windows are an intermittent application and the NEC doesn't apply to cars. As always, ultimately it's your project (that I'm interested in once it's done), and you can spec out whatever wire you want but for the short lengths we're talking here, wire gauge almost doesn't matter. The math suggests that basically anything 18AWG and larger would have very minimal voltage loss.

FWIW: When I was re-assembling my doors for my re-build, I was testing the power windows with a small battery and 2ft of ~24 AWG clip leads. Those windows flew up and down.
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We have the same napkin math :)
I spec'd this to 18 AWG from the very beginning, the vendor couldn't do that, despite the molex female crimp terminal being designed specifically for that
 
FYI - I have reached out to 6x quick turn wire harness shops, and one vendor on mud as well. Stay tuned
@mtndogdad - forum won't let me message you (says you hit your inbox max), so feel free to message me
 
After a few calls & a lot of research, I've placed an order for 350x of the harnesses with a US-based quick turn wiring harness shop. They have the design requirements now & I explicitly requested the "pull test" quality control step on every single wire+crimp placed into the molex connectors.

Estimate is 20-30 days before they show up at my door since they have a large backlog. Will keep everyone updated.
 
jonnyd42 said:
After a few calls & a lot of research, I've placed an order for 350x of the harnesses with a US-based quick turn wiring harness shop. They have the design requirements now & I explicitly requested the "pull test" quality control step on every single wire+crimp placed into the molex connectors.

Estimate is 20-30 days before they show up at my door since they have a large backlog. Will keep everyone updated.
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Amazing. How long until you have a shop setup to take pre-orders?
 
DaveGins said:
Amazing. How long until you have a shop setup to take pre-orders?
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I actually have the Shopify site done but I don't want to take any $ until inventory is in hand. There's no faster way to piss people off than taking their money and then telling them to wait an indefinite amount of time to get a product lol
 
jonnyd42 said:
I actually have the Shopify site done but I don't want to take any $ until inventory is in hand. There's no faster way to piss people off than taking their money and then telling them to wait an indefinite amount of time to get a product lol
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Right on.
Sending positive juju to you and this endeavor.
Thank you for your efforts and communication.
Still very excited about this and all the energy you are putting into it.
Thank you.
 
I just stumbled on this thread. As the owner of a HJ61 this got me very excited. Thanks jonnyd42! Looking forward to the shopify website

Cheers
 
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