Homebrew power lead for Garmin

Anythingwithaplugon

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For info. Just made up a lead to run my 55 from a 5 volt supply. The camera seems to follow the Garmin practise of needing a 17.3K ohm resistor between pins 4 & 5 of the micro USB connector to force into operational mode.
Works a treat.
 

DC55User

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Hi. Please explain this to me! You may have just solved an issue I have been troubleshooting with my DC55. I bought an invisicord in order to 'self install' my dashcam, but it will not charge/operate the camera. (Yes, I get the message on the camera that it is not the correct cable, but had seen on other forums that it did indeed charge the DC45). Is there something special about the Garmin cables where the DC55 will only work with that?
 
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Anythingwithaplugon

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Hi. Please explain this to me! You may have just solved an issue I have been troubleshooting with my DC55. I bought an invisicord in order to 'self install' my dashcam, but it will not charge/operate the camera. (Yes, I get the message on the camera that it is not the correct cable, but had seen on other forums that it did indeed charge the DC45). Is there something special about the Garmin cables where the DC55 will only work with that?
I found out about the resistor when I first bought a Garmin Sat Nav, a Drive 51, a few years ago. I couldn't fathom out how it went into navigation mode only when you used the supplied 'cigar lighter' power adaptor and not when using an ordinary A-micro USB lead. I checked the lead and found there was a resistor between pins 4 and 5 on the micro USB. I thought initially it was 22K but then Goggled and came across a sight that said it was actually 17.3 K. I think its 17.4k but why such a bizarre value baffles me. When I found the same issue with the dash cam out came the meter and that lead is the same 17.4K between 4 and 5. Added the resistor and works OK
 

DC55User

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I guess this is something a normal (non-electrician) could not do then? I have no idea how to add a resistor between pins. Is this something a person can google?
 
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Anythingwithaplugon

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I’m afraid else you’re adept at fine soldering work it’s a no-go. Micro USB connectors have very fine pitch connections. You’ll also need a very small size resistor, less than 0.125 watt, to fit in the connector shell. Your best bet would be to enquire locally if there are any ‘electronic’ clubs that could do it for you. Sorry.
I guess this is something a normal (non-electrician) could not do then? I have no idea how to add a resistor between pins. Is this something a person can google?
 

DC55User

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Thanks. It's good to know this is just a proprietary thing with Garmin. I'll look at other options.
 
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Can't you just wire the + and - wires to your power source and put the resistor on the other wires? You wouldn't have to mess with the actual plug. You'd have to adjust the resistance according to your cable length though
 
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Anythingwithaplugon

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Can't you just wire the + and - wires to your power source and put the resistor on the other wires? You wouldn't have to mess with the actual plug. You'd have to adjust the resistance according to your cable length though
You can if the cable you're using has 5 conductors, 4 + screen where the screen is negative. Quite often they only have 4 including the screen as pin 4 is classed as an 'ID' and doesn't carry 'data' or 'power'. You would use the same resistor value as the cable resistance is so low. The cable that comes fitted to the Garmin 'cigar lighter' has 2 conductors, red and green, and a screen. The red and green are joined in the micro USB and are ‘+’, with the screen being negative. The resistor is moulded into the plug . It’s interesting as the green is thinner than the red and think it may be a ‘sense’ conductor to measure volt drop down the cable. I joined both together on my 5V psu and no smoke as yet :)
 
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You can if the cable you're using has 5 conductors, 4 + screen where the screen is negative. Quite often they only have 4 including the screen as pin 4 is classed as an 'ID' and doesn't carry 'data' or 'power'. You would use the same resistor value as the cable resistance is so low. The cable that comes fitted to the Garmin 'cigar lighter' has 2 conductors, red and green, and a screen. The red and green are joined in the micro USB and are ‘+’, with the screen being negative. The resistor is moulded into the plug . It’s interesting as the green is thinner than the red and think it may be a ‘sense’ conductor to measure volt drop down the cable. I joined both together on my 5V psu and no smoke as yet :)

Well that's a bummer. I guess the original cable does have the nice right angle which is a benefit. So since the resistor is in the plug that means you can cut the 12V off and wire it to a standard USB plug? I wonder if the Garmin adapter puts out extra voltage to get it down the long cable and still have 5v
 
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Anythingwithaplugon

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Well that's a bummer. I guess the original cable does have the nice right angle which is a benefit. So since the resistor is in the plug that means you can cut the 12V off and wire it to a standard USB plug? I wonder if the Garmin adapter puts out extra voltage to get it down the long cable and still have 5v
The Garmin adapter gives out 5 volts exactly. I’ve had a play with the green lead coming from the adapter, pulling it to ground with a resistor but the output volts don’t change. I’m reluctant to break it open and trace the circuit as may wreck it.
I made my own 5v psu and works ok so shouldn’t be an issue with cutting off, soldering on a A type USB plug shorting the red and green together, and running from a USB adapter, at your own risk ;)
You’ll need an adapter that provides at least 1 amp. A ‘standard’ 500mA one could cause issues
 

lacibaci

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Putting resistor between pins 4 and 5 is a common practice to signal "power only" arrangement and it is not exclusive to Garmin.
 

olav

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I’m afraid else you’re adept at fine soldering work it’s a no-go. Micro USB connectors have very fine pitch connections. You’ll also need a very small size resistor, less than 0.125 watt, to fit in the connector shell. Your best bet would be to enquire locally if there are any ‘electronic’ clubs that could do it for you. Sorry.

Thanks so much for all this info!

I used two micro usb breakout boards (one male right angled, the other female) to wire up power, ground and a 17.4kohm resister on the ID pin. Now I just use a regular micro usb cable to deliver power to the dash cam 55 from a regular usb-car power adapter. Works like a charm! (I can't use the garmin car adapter since I also want my phone on the single charger ....)
 
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Are 17.4K resistors hard to find? They seem expensive compared to others, and aren't included in any assorted packs
 

olav

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In August, I paid $1.78 on eBay for 20, including shipping from Erie, PA. Search for “KOA 1/4 watt”
 
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