Installing dash cam behind rear view mirror?

Discussion in 'Gen 4 Prius Accessories and Modifications' started by Danny Troy, May 12, 2017.

  1. Danny Troy

    Danny Troy Member

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    Has anyone hardwired their dash cam to the overhead light switches? If so, how do you disassemble the covers, to get at the available leads. I read somewhere a while back that there is a 12v source at that location, which is switched on and off with the ignition switch. That's how I plan to connect my camera. I had this camera on my Chevy Volt, and ran the wiring along the window and down a pillar. I'm looking to avoid going that route. Any ideas?
     
  2. Danny Troy

    Danny Troy Member

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    Disregard. After a more extensive search I found what I was looking for. The best part is that my camera requires 5v (if not using the cigarette lighter plug, which has a 12v->5v step down) and there is a 5v source already available in the car's wiring. I pulled down the assembly already and will finish the installation tomorrow (in daylight!).
    If anyone is interested, here's a video showing how to pull the assembly down. It's harder than shown in the video, but not too difficult. At least I didn't break any parts in the process!
     
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  3. Elektroingenieur

    Elektroingenieur Senior Member

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    If you don’t mind my asking, where did you find 5 volts? Other than the USB connector in the console, I wasn’t aware of any 5-volt sources exposed outside of individual ECUs.
     
  4. Danny Troy

    Danny Troy Member

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    Yes, I was surprised to find it also, although it was mentioned in another thread. On my car, a Four, there are two harnesses plugged into the overhead console. The red and white leads on the smaller connector are the (+) and (-) 5v leads.
     
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  5. Elektroingenieur

    Elektroingenieur Senior Member

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    Thanks for the explanation, and now I understand why I didn’t remember it from the Electrical Wiring Diagram: that’s a dedicated power supply for the microphone in the Map Light Assembly, used by the navigation and Safety Connect systems.

    The Repair Manual says (under Audio / Visual / Telematics: NAVIGATION / MULTI INFO DISPLAY: NAVIGATION SYSTEM: Microphone Circuit between Microphone and Navigation Receiver Assembly) that the red wire (O2-1 or O4-17) is the “Microphone power supply,” which should have 4 to 6 V, switched with ACC; this is provided by the Navigation Receiver Assembly, or if your car has Safety Connect, the Telematics Transceiver.

    I don’t know, however, how much current this circuit was designed to provide, and I’m not sure I would connect an additional load, for fear of causing a malfunction or perhaps even damaging the Navigation Receiver Assembly or Telematics Transceiver.

    The white and black wires (O2-4 or O4-15 and O2-2 or O4-16) are the ”Microphone voice signal,” and I would be hesitant to tap into them, especially since Toyota used a shielded cable, suggesting that it’s necessary to keep electrical noise out of this circuit.
     
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  6. Danny Troy

    Danny Troy Member

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    I hear you, in that it might not be able to handle the additional load. The wires in this harness appear to be of a lighter gauge than the other larger harness. I suppose I can use the original 12v receptacle plug that came with the dash cam, and utilize the 12v supply. There is pretty good room available in the compartment, so fitting the additional wiring shouldn't be a problem.
     
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  7. krmcg

    krmcg Lowered Blizzard Pearl Beauty

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    I had my dash cam hooked up to the light fixture over a year ago with no negative issues.
     
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  8. Danny Troy

    Danny Troy Member

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    Good to hear. Hopefully, the rain will let up tomorrow enough to allow me to finish the installation. I decided to go with the 12v light source, and not mess with the 5v (mic power).
     
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  9. Danny Troy

    Danny Troy Member

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    Just finished the installation. I realized there are no switched 12v sources in the harnesses after all. I wound up using the 5v mic power. I'll be the guinea pig on this one. My power supply adapter had a 1A fuse, so I'm thinking it's drawing very little current, and hopefully the mic power will power it safely. So far it's working great. I made sure I added a 1A fuse in a fuse holder, just to play it safe. So, if anyone is installing a dash cam, the video link I posted is how you take off the console. It's just a lot harder than shown in the video. You really have to tug it hard to unplug the front two connectors. The rear two seem to come off easy after you have the front two free.
     
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  10. Elektroingenieur

    Elektroingenieur Senior Member

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    I’m sorry not to have posted this in time for it to be of use to you, but for other readers, there is switched 12-volt power above the headlining, but it’s controlled by the DOME CUT relay, which acts after a 20-minute delay, not the IG or ACC relays. As the Repair Manual explains:

    The main body ECU (multiplex network body ECU) controls operation of the DOME CUT relay in order to supply power to the interior lights. When the battery saving function operates while the interior lights are on, the main body ECU (multiplex network body ECU) opens the DOME CUT relay to turn off the lights.​

    The Electrical Wiring Diagram shows the connections. Interior lights are supplied through the 7.5 ampere DOME fuse, which feeds the DOME CUT relay, which feeds (among others) positions 12–22 on junction connector O16; positions 1–11 on this connector are wired to ground point FA. Connector O16 is above the headlining, to the left of the opening for the map light assembly; on my car, the connector housing is made of black plastic. The housing has part number 90980-12B54, so new terminals could be added to the open positions using repair wires, part number 82998-24290 (0.64 II series), or with Sumitomo TS 025 terminals crimped to your own wires.

    Of course, I’d suggest doing a load study before deciding to connect new loads to the DOME circuit, but since the existing load consists of lamps with known wattages, this wouldn’t be difficult.
     
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  11. Danny Troy

    Danny Troy Member

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    Since I would imagine any dash cam that uses a USB type connector, is probably running on 5v, having a 5v switched source in the overhead console is very handy. Question is, how much amperage can you safely draw from that source? In my case, my dash cam is running off less than one amp, but others might require more juice. I'd love to know the limit on that mic power line. I haven't fried anything yet in my installation, and I hope it stays that way!
     
  12. Elektroingenieur

    Elektroingenieur Senior Member

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    As far as I know, the maximum current isn’t published; proprietary design information like this isn’t needed or useful for repair, so it’s unlikely to be available from Toyota or its suppliers, who if asked would probably just refer you to the general warning against modifications in the Owner’s Manual.

    It would be challenging to determine a value through reverse engineering, without knowing the design criteria, such as the worst-case undervoltage on the 12-volt bus. You would also need to consider what else is powered from the 5-volt supply and its behavior in case of an overload: does it just shut down and then restart, or are there internal fuses or other components that would fail permanently?
     
  13. Danny Troy

    Danny Troy Member

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    Well, for whatever reason my dash cam isn't working properly using the 5v connection. I'll have to re-wire using a 12v source.

    ELEKTRO.... Is the 12v source you mentioned reachable with the overhead console removed? Any idea of what the connector looks like and how many wires it contains? To clarify, this source provides 12v and remains energized for some time sfter the ignition is switched off?
     
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  14. Elektroingenieur

    Elektroingenieur Senior Member

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    Yes; on my car, connector O16 is mounted to the headlining with a plastic clip, just to the left of the opening for the map light assembly.
    It’s black, not natural, but otherwise the same as this connector sold by hi-1000.com. (I’ve bought from that store, by the way—a small company in Osaka with parts that are otherwise tricky to find in small quantities. My order was carefully packaged and delivered quickly by Japan Post EMS.) You can also see part number 6098-3925 on page A-05 of Sumitomo’s Connectors for Automobiles catalog (12.8 MB PDF).
    It’s a 22-position connector, but there are vacant positions on both rows (12 volts and ground). I encourage you to subscribe to techinfo.toyota.com ($15 for two days) to see the Electrical Wiring Diagram for your Prius, but the European left-hand drive version is very similar; see pages 4 and 8 for O16.
    The DOME circuit and DOME CUT relay are for the interior lights. The Owner’s Manual says:
    • Illuminated entry system: The lights automatically turn on/off according to power switch mode, the presence of the electronic key, whether the doors are locked/unlocked, and whether the doors are opened/closed.
    • If the interior lights remain on when the power switch is turned off, the light will go off automatically after 20 minutes.
    Here are a few more tips to consider:
    • Measure the current used by your dashcam when it’s powered by an AC adapter or bench supply, and then figure the total current for all the other lamps on the DOME circuit. If the dashcam plus the lamps exceeds 70% of the fuse rating (7.5 A × 70% ≈ 5.3 A), use a different circuit or add a new one.
    • Loads on the DOME circuit, rather than circuits fed from one of the IG relays, are part of the parasitic drain on the auxiliary (12-volt) battery, if only for a few minutes. It’s hard to give specific advice without design information Toyota doesn’t publish, but it would be good if your dashcam has a battery-saving feature, so if the battery voltage is low, it will turn off automatically.
    • Rather than tapping into existing wires, use the Toyota repair wires (pigtails) I mentioned earlier to add new terminals to the connector, so you can remove everything later, if necessary, leaving the factory wiring harnesses intact. The current Electrical Wiring Diagram is the best source, but this 2007 edition of the Wire Harness Repair Manual (8 MB PDF) explains how to handle the connectors.
    Note: I don’t know the details of your added load, nor your skills as a technician, so consider the above as general information, not an engineering design. I recommend against modifying your Prius at all, except perhaps by installing Genuine Toyota Accessories.
     
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  15. Danny Troy

    Danny Troy Member

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    Elektroingenieur..... Thanks for that detailed explaination. I finally located that connector, and I would have seen it if I wasn't sitting on the driver's side while doing the installation. I switched sides and was able to free the connector from the snap in mount. Unfortunately, I couldn't figure out how to unplug it, and there isn't enough room to manipulate the wires (I have big hands!). I gave up on the idea of using that connector and will go back to the un-switched 12v connector. I will monitor how much of a draw it is on the vehicle's battery by testing it when I park it for the night, and when I start it the next morning. If it's too much of a drain, I'll have to install a simple toggle on-off switch. Question: will the car start with a dead 12v battery, by taking juice from the hybrid battery? I have a 12v lithium booster pack in the glovebox, so I suppose worst case scenario I'll use that to start if needed.
    I found some info on amp draw on my unit, with is the Mini0801 Ambarella A2S60 FHD 30FPS G-sensor GPS (from it's eBay listing)
    1. GPS locked, recording, screen on, led blue flashing, 0.50A
    2. GPS locked, recording, screen off, led blue flashing, 0.38A
    3. No GPS, recording, screen on, led blue/red flashing, 0.40A
    4. No GPS, standby, screen on, led blue, 0.32A
    5. No GPS, standby, screen off, led blue, 0.26A
    6. No GPS, motion detection on, screen on, led blue flashing, 0.39A
    7. No GPS, motion detection on, screen off, led blue flashing, 0.31A
    8. No GPS, motion detection on, screen off, led solid blue, 0.22A
     
  16. Elektroingenieur

    Elektroingenieur Senior Member

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    You’re most welcome.
    Alas, no—the electronics controlling the hybrid system operate on 12-volt power, which is available only from the auxiliary (12-volt) battery until the hybrid system is started.
     
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  17. randomwalk101

    randomwalk101 DYI'er

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    Just run the wire up from the fuse box. I monkey around looking for that 12v ignition on about a year ago and couldn't find it so I gave up. Running the wire up only took me 5 mins.
     
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  18. Danny Troy

    Danny Troy Member

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    Just a follow-up on my installation. Using the red and green 12v wires from the larger connector in the over-head console, I had issues where the dash cam stopped working. Turns out that the headlight switch setting feeds those 12v leads. If you turn the light switch to the off or auto setting, they get 12v. If you turn the switch to the parking light setting, or full-on lights, they lose voltage. So, for those that use the red and green 12v leads and are concerned about leaving the car with the dash cam pulling voltage, you actually have an on-off switch for the dash cam built into the car. Unfortunately, I like to use the full on switch setting when towing my utility trailer, so I have my trailer lights on at all times (someone already hit my trailer). I have to forfeit having the trailer lights on, or having the dash cam working, but not both in the daytime. One option is to cover up the light sensor when towing the trailer, but it's just a bandaid fix.
     
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  19. Danny Troy

    Danny Troy Member

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    Another update. Using leads in the overhead console didn't work out at all. Too unreliable and I couldn't figure out exactly why the 12v power would sometimes drop. I wound up using Jorge L's hookup, using the 12v power to the rear-view mirror. Post 5 in this link shows the hookup. Turned out to be a lot easier than messing with the other harness. Dark blue wire is +12v ignition switched, and the striped wire is ground. Hard wiring a dash cam | PriusChat
     
  20. randomwalk101

    randomwalk101 DYI'er

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    Do you have the powered auto dim mirror pre-installed on your car? I don't think the plug/wire is there if the car doesn't have the auto dimming mirror (as in my case). I pulled the overhead console out and there isn't one that I can see.
     
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