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> Electrical Q, Voltage at the USB connector ?
jim_hoyland
post Mar 23 2024, 10:16 AM
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What is the voltage output at the end of a USB connector. The input plug is at the cig lighter receptacle.
I assumed it would be 12v, but, heard it might be 5 v ???


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FlacaProductions
post Mar 23 2024, 10:48 AM
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USB power is always 5v

USB 2.0 - 5V - Max output 2.5W
USB 3.0 / USB3.1 - 5V - Max output 4.5W
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windforfun
post Mar 23 2024, 10:49 AM
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(IMG:style_emoticons/default/popcorn[1].gif) (IMG:style_emoticons/default/popcorn[1].gif) (IMG:style_emoticons/default/popcorn[1].gif)
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jim_hoyland
post Mar 23 2024, 11:31 AM
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Thanks, thought it
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SirAndy
post Mar 23 2024, 12:34 PM
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Looks like USB can go up to 48V for power delivery but is 5V otherwise:
https://en.wikipedia.org/wiki/USB

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worn
post Mar 23 2024, 07:34 PM
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QUOTE(jim_hoyland @ Mar 23 2024, 09:31 AM) *

Thanks, thought it

I did it myself for a USB outlet. Turns out that I had to make resistor connections to keep the data pins at the right voltages to suit Apple.
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jim_hoyland
post Mar 23 2024, 08:04 PM
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QUOTE(worn @ Mar 23 2024, 06:34 PM) *

QUOTE(jim_hoyland @ Mar 23 2024, 09:31 AM) *

Thanks, thought it

I did it myself for a USB outlet. Turns out that I had to make resistor connections to keep the data pins at the right voltages to suit Apple.

What size resistor would drop 12v to 5v. ?
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fixer34
post Mar 24 2024, 08:01 AM
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QUOTE(jim_hoyland @ Mar 23 2024, 09:04 PM) *

QUOTE(worn @ Mar 23 2024, 06:34 PM) *

QUOTE(jim_hoyland @ Mar 23 2024, 09:31 AM) *

Thanks, thought it

I did it myself for a USB outlet. Turns out that I had to make resistor connections to keep the data pins at the right voltages to suit Apple.

What size resistor would drop 12v to 5v. ?

Depends on the current load you are expecting to pull. At a minimum you need two resistors in series to tap the middle point, or resistor/zener diode combination.
Rather than build it yourself though, go buy a couple cigarette lighter adapters and open them up to see what they use for circuitry. Build that into a USB port if you want.
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windforfun
post Mar 24 2024, 08:52 AM
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QUOTE(jim_hoyland @ Mar 23 2024, 07:04 PM) *

QUOTE(worn @ Mar 23 2024, 06:34 PM) *

QUOTE(jim_hoyland @ Mar 23 2024, 09:31 AM) *

Thanks, thought it

I did it myself for a USB outlet. Turns out that I had to make resistor connections to keep the data pins at the right voltages to suit Apple.

What size resistor would drop 12v to 5v. ?


Goggle “divider network.”
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Montreal914
post Mar 24 2024, 09:42 AM
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Why not use something like this?

First one that came up with initial search, I am sure many other can be found. (IMG:style_emoticons/default/smile.gif)

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https://www.amazon.com/Cllena-TOYOTA-Dashbo...vD_BwE&th=1
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Retroracer
post Mar 24 2024, 10:16 AM
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@jim_hoyland a better question might be: what device are you trying to get power to?

- Tony
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lierofox
post Mar 24 2024, 11:22 AM
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A USB charger that plugs into a cigarette lighter plug already does the voltage step down process for you.

Unless a device plugged into the USB port specifically requests a higher voltage (like a tablet, or a laptop), USB will ALWAYS default to outputting 5v.
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jim_hoyland
post Mar 24 2024, 01:52 PM
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QUOTE(Retroracer @ Mar 24 2024, 09:16 AM) *

@jim_hoyland a better question might be: what device are you trying to get power to?

- Tony

I’m going to power a HUD directly to the fuse panel. The HUD say max voltage is 5v.
So, I want to step the v down under the dash.
This is A MPH HUD, not the fancy ones that plug into an OB receptacle
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windforfun
post Mar 24 2024, 02:54 PM
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QUOTE(jim_hoyland @ Mar 24 2024, 12:52 PM) *

QUOTE(Retroracer @ Mar 24 2024, 09:16 AM) *

@jim_hoyland a better question might be: what device are you trying to get power to?

- Tony

I’m going to power a HUD directly to the fuse panel. The HUD say max voltage is 5v.
So, I want to step the v down under the dash.
This is A MPH HUD, not the fancy ones that plug into an OB receptacle


https://en.wikipedia.org/wiki/Voltage_divider
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jim_hoyland
post Mar 24 2024, 03:23 PM
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QUOTE(windforfun @ Mar 24 2024, 01:54 PM) *

QUOTE(jim_hoyland @ Mar 24 2024, 12:52 PM) *

QUOTE(Retroracer @ Mar 24 2024, 09:16 AM) *

@jim_hoyland a better question might be: what device are you trying to get power to?

- Tony

I’m going to power a HUD directly to the fuse panel. The HUD say max voltage is 5v.
So, I want to step the v down under the dash.
This is A MPH HUD, not the fancy ones that plug into an OB receptacle


https://en.wikipedia.org/wiki/Voltage_divider


Interesting; if I go to the electronic shop, what should I be buying ?
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SirAndy
post Mar 24 2024, 03:39 PM
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QUOTE(jim_hoyland @ Mar 24 2024, 12:52 PM) *
I’m going to power a HUD directly to the fuse panel. The HUD say max voltage is 5v.
So, I want to step the v down under the dash.
This is A MPH HUD, not the fancy ones that plug into an OB receptacle

What does the power connector for the HUD look like?
How does it normally get power?
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fixer34
post Mar 24 2024, 05:24 PM
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No affiliation, but I don't think you can build something for this price...

https://www.temu.com/ul/kuiper/un9.html?sub...YBoCb5oQAvD_BwE
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r_towle
post Mar 24 2024, 05:32 PM
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Buy a 5 dollar cigarette lighter converter and break it open.
There will be the circuit and resistor
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technicalninja
post Mar 24 2024, 06:08 PM
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QUOTE(fixer34 @ Mar 24 2024, 06:24 PM) *

No affiliation, but I don't think you can build something for this price...

https://www.temu.com/ul/kuiper/un9.html?sub...YBoCb5oQAvD_BwE


That's sort of cool if it really can deliver 5a at 5v.
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FlacaProductions
post Mar 24 2024, 06:45 PM
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Why not just use the power supply that came with it?
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