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BMW 3-Series (E90 E92) Forum
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12v reversing power source
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08-29-2010, 03:03 PM | #1 |
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12v reversing power source
quick question...
does anyone know any other back up power source i can use for my back up camera other than the 2 reverse tail light?? tried both the back up tail light but for some reason it was not stable camera will turn on for 4-5 sec then turned off... but if i tap on any other power source the camera will work perfect. while i'm searching through the internet might as well posted here try my luck thanks |
08-29-2010, 03:41 PM | #2 | |
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This is what you should do: - Go pick up a generic 4-pin relay from any local auto parts store, should be $5 or less, something that looks like this: - The pins will be clearly marked on the relay packaging. - one pin will be for ground - one pin will be for the power source, you should wire it to any 12V source (fusebox, battery, accessory line under shifter, etc, something you know for sure is 12V unlike the reverse light power line) - One pin will be to provide power/connect to the backup cam - One pin will be for the remote trigger, you want to wire this to the reverse light, either one, that before didn't have the voltage to power the cam The end product will be when you throw the shifter in reverse, the relay will sense the power to the reverse lights, and draw power from the other 12V source to power up the backup cam. When you shift out of reverse, the relay will close the circuit providing power to the back up cam, so it will then shut back off. Identical end result but a bit of a workaround to get it going. Hope this helps. Out of curiosity, what camera are you using? Last edited by jjoseph7; 08-29-2010 at 03:49 PM.. |
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08-29-2010, 03:49 PM | #3 |
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why do you need a backup camera on an e90
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08-29-2010, 03:55 PM | #4 |
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Once you try one, you'll realize how useful they are. It makes parallel parking/judging depth when backing into a tight spot much easier, even on a compact sedan. IMO, it was well worth the $50 i spent on the the camera+DIY install. I don't think anyone who has installed one on an E90 will tell you it hasn't been at least slightly more convenient to have.
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08-29-2010, 03:58 PM | #5 | |
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08-29-2010, 04:04 PM | #6 |
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thanks jjoseph7
thats some valuable info...i bought it for 30 bux on ebay... didnt wanna waste 500 for the kit here offered much more.... i just want a simple view of the back while parking.... reason i bought it b/c i cant really park... i used to have pdc installed but was removed after mtech rear install now just wanna try it the camera out ( after all its only 30 bux) |
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08-29-2010, 04:06 PM | #7 | |
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08-29-2010, 04:48 PM | #8 |
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08-31-2010, 10:42 AM | #9 |
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You have to be careful when trying to "power" things on circuits that weren't originally intended to power anything but for example in this case a brake light... It's just as bad as "upgrading your fuses" if you've ever seen people power fog lights off their main headlights by changing the 20amp fuse to a 30amp... Eventually the wiring heats up and melts the entire harness or blowing a computer. 12v electronics are very sensitive to current draw, and switched circuits are the most delicate. Car electronics are built to carry just enough power for the cable diameter they use, and not much more, so when you start pulling extra power, only bad things happen.
The current is often limited by transistors, and easily smoked/burned; as a general rule of thumb, always use a relay when pulling a signal from something and power from a dedicated or non-switched circuit. It may work fine initially, but over time pulling more power through circuits not designed for it has a tendency to overheat transistors passing power and blow... Especially things that are switched, like dashes, lights, etc... I just have seen too many people try and power lights and things off of their dash lights, just to have them burn out their entire dash. I've done it, and it's very expensive to repair, just a word of warning. This isn't meant to be a slight on anyone in particular, just it's not that obvious, and as someone who has helped others tinker for many years with their car electronics, a bit of knowledge ahead can prevent catastrophe. Cheers |
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08-31-2010, 02:28 PM | #10 |
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this is my current plan...dont know if it work yet
4 pin spst relay from radioshack pin 85 connect to ground pin 86 connect to tail light pin 87 connect to back up camera pin 30 will be connecting to 12v + battery in the trunk ( with a 15amp fuse in between) or should i get 20amp? |
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08-31-2010, 09:50 PM | #11 | |
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08-31-2010, 11:07 PM | #12 | |
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09-17-2010, 04:20 PM | #14 | |
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Weeks later, how are things with the camera? I've done this to my current car but I had an aftermarket flip-up Pioneer with backup cam ready. Does the e90 allow for "extra" plug-ins? I checked out modmynav.com and that's pretty cool but $450 more. |
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09-17-2010, 04:41 PM | #15 |
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the camera are working nicely... i dont know whats the different from the camera sold here for 130 dollar than the camera for 30 dollar from ebay... from what i can tell they both offer the same feature with the distance line and see clearly at night as well....
making me wonder if they got their camera sources from the same company.... so is 15amp an over kill for this set up? can someone confirm it. |
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09-17-2010, 08:02 PM | #17 |
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i;m using a 3.5" monitor that find layin around my room... i use a ipod holder to hold it on to the air vent....i wanna to connect it to my idrive but it seem way too much work.... maybe i'll try it when my warranty runs out.
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12-12-2011, 12:28 PM | #18 |
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I just picked up a relay today and hopefully this will be the end of the headaches the camera has been causing me.
The only relays the shop had were "5 pin 12v 30A SPDT". I believe the camera only needs 300ma to run, is a 30A relay just overkill? I want to make sure nothing is going to go epically bad. |
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12-12-2011, 02:32 PM | #19 |
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30A relays are pretty much the car-stereo-install-bay standard, but yes, a relay with 30A-capable contacts is overkill (but really irrelevant). The coil (the "motor") of the relay uses around 80-100ma of current to stay energized. Varies depending on the coil temperature.
But that's the relay that an installer would use. The real question is whether or not the wire you found can supply 100mA. The 30A contacts are irrelevant. If you are using the wire feeding 12V(+) to the actual reverse light bulbs, then you should be fine. |
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12-13-2011, 12:10 PM | #21 |
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FINALLY, it works perfectly with no static/interference at all.
I did however run into one little hicup, the relay would click super loud non-stop when I put the car into reverse, it got so loud that it just did not sound normal. Exchanged it for a new one and voila! Must have been a defective relay |
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12-15-2011, 02:31 AM | #22 | |
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In any case, soldering in a protective diode might be a good idea to protect transitors/ICīs in your car if your using a standard electromechanical relay.
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