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M2 Technical Topics > Navigation, iDrive, Audio, Video, Bluetooth, Phone, Cameras, Electronics > Help with dash cam fuse taps

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      04-23-2020, 12:17 AM   #23
Nezil
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Originally Posted by digimattic View Post
Dude - you're a legend. That's awesome. I am not sure about my ability to do that kind of soldering, but it's inspiring. I haven't got a USB port in my cupholder, so I'd have to think about cutting. Does the Pi pass through enough power to keep your phone running with Waze/spotify etc. running?
According to this page: https://www.raspberrypi.org/document...ower/README.md, the RPi 3B that is used for the BM3 OBD Agent draws 400mA typically, and can supply a max of 1.2A (5v x 1.2A = 5.1W) to peripherals like a phone; not fast charge by any means. That adds up to 1.6A, which isn't much.

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I was thinking of using one of these to feed the Pi. https://mausberry-circuits.myshopify...-supply-switch
That looks like overkill for our application, but I do like that it shuts down the RPi cleanly.

I ended up buying a bag of these: https://www.ebay.com/itm/5pcs-MP1584...72.m2749.l2649, and though that results in power being yanked from the RPi, I've never had any issues with file corruption or not booting etc. in the 2 years I've had it set up. I still have some of these sat on my desk from my build!

If you're happy to pay for the parts, I'll make you up a cable with the DC/DC converter built in and a micro USB cable etc.

You'll need to run a wire from the back of the front fuse box to the OBD port but I could provide you with a cable with the correct crimps on each end for that as well.
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Last edited by Nezil; 04-23-2020 at 12:25 AM..
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      04-23-2020, 11:19 AM   #24
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I just might take you up on that, though I think the price of shipping from SF to TO will make things prohibitively expensive.

I also had a thought - Running power through those pins; could that potentially fry some shop's diagnostics device? I know that BMW doesn't use the pins, but presumably something will. Last thing I want to do is take the car in and nuke their machine.

I think I am going to try a Pi 4, if the firmware doesn't work, I will repurpose it and pick up a 3+. I really appreciate you taking the time to respond, and your kind offer of making the mods, though.
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      04-23-2020, 12:01 PM   #25
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well since I hardwired the cam has gone mental and bricked. Think it's just coincidence.

Otherwise I appeared to have hardwired correctly. Even with no dashcam the hardwire kit draws some power, to the extent battery warning lights have come on the dash.

So given the dash cam isn't working have reverted to stock with no taps in situ.
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      04-23-2020, 01:36 PM   #26
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I just might take you up on that, though I think the price of shipping from SF to TO will make things prohibitively expensive.
I doubt it. I know it's technically another country, but I'd have thought the shipping cost is less than $10, but your call, just let me know.

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I also had a thought - Running power through those pins; could that potentially fry some shop's diagnostics device? I know that BMW doesn't use the pins, but presumably something will. Last thing I want to do is take the car in and nuke their machine.
I thought about that, but the official pin-out of the OBD connector actually defines a pin for permanent 12v and accessory 12v, BMW just didn't populate it.

Having said that, I do usually remove my RPi and cabling before visiting the dealer. I need to do that anyway because it's plugged into the the OBD port that they want to use, and I'd rather not alert them to a tune unnecessarily.

When I remove all of this stuff. I unplug the fuse that runs to that pin. It shouldn't be necessary, but I do it just in case.

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I think I am going to try a Pi 4, if the firmware doesn't work, I will repurpose it and pick up a 3+
It didn't used to work, but that might have changed. The 3B might even be difficult to get hold of these days...
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      04-23-2020, 01:38 PM   #27
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Quote:
Originally Posted by 3t3p View Post
well since I hardwired the cam has gone mental and bricked. Think it's just coincidence.

Otherwise I appeared to have hardwired correctly. Even with no dashcam the hardwire kit draws some power, to the extent battery warning lights have come on the dash.

So given the dash cam isn't working have reverted to stock with no taps in situ.
It's interesting to me that a lot of people are getting warnings on the dash when running a dash cam. I did move over to a separate battery that is only charged while the car is running, but even before that, I never once had a warning on the dash.

I can flick a switch in the trunk and have my dash cam battery charge from the car battery for 12 hours after I stop before it starts to discharge, increasing run-time. Even when I do this, I still don't get any warnings.
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      06-05-2020, 02:48 PM   #28
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Back again! I finally got my RPi 4 and PSU. The PSU has this screwless jumper/terminal block. Anyone have an idea how to get the wires out without breaking it? It's rather delicate. I'd prefer one clean cable run from the power to the PSU, rather than using crimp connectors etc.
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      06-05-2020, 02:49 PM   #29
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Quote:
Originally Posted by digimattic View Post
Back again! I finally got my RPi 4 and PSU. The PSU has this screwless jumper/terminal block. Anyone have an idea how to get the wires out without breaking it? It's rather delicate. I'd prefer one clean cable run from the power to the PSU, rather than using crimp connectors etc.
I'm not 100% sure, but it looks like the white terminal block at the top has wires that can be released by pressing in the dimple part on the top and pulling the wire out at the same time.
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      06-05-2020, 03:13 PM   #30
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Yeah, that was the first thing I tried, unsuccessfully, along with gently lifting up the tab. No joy - at least with the level of pressure I felt comfortable applying.
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