Page 1 of 3 123 LastLast
Results 1 to 10 of 27

Thread: Reverse Camera

  1. #1
    Junior Member
    Join Date
    Jan 2019
    Location
    westbury wiltshire
    Posts
    4
    Post Thanks / Like

    Reverse Camera

    Sorry. posted this yesterday but in the wrong group.
    I have an XJ 2.7 diesel and have fitted a dash cam with a built in rear camera but to get the rear view up in reverse I need a live feed from the reverse light bulb but the bulbs are perminate live. Any idea where I can tap into to make it work i.e. reverse light switch?

  2. #2
    Senior Member
    Join Date
    Dec 2013
    Location
    Berkshire
    Posts
    2,303
    Post Thanks / Like
    I don't have an electrical manual to hand at the moment to be entirely sure, but I am pretty certain that the reverse switch is not on the gearbox - probably on the gear lever module.

    I have a reversing camera on my SType, I got round the same problem by making a signal (voltage) inverter. Effectively this is just a PNP transistor - this type of transistor is different to the more normal type in that it is switched on with Zero or negative voltage, which is what you want. I.e. Put zero volts on the transistor input (base) and it will switch +12v.

    Having said all that my camera stopped working a few weeks back so it may be this gadget that has failed !

    I don't expect you to be able to use the above - just answering your question - it is possible !
    S Type 4.2 SE Plus 2002 original spec: Xenon HID/SatNav/Voice/Cassette Player/CDC/TV/GSM Phone/Sun Roof/Rear Blind/CATS.
    Retro-fitted: CD Player/Bluetooth Phone/Aux Power Socket, USB & Volt Meter in Boot/Reversing Cam/Dash Cam & PSU/Dual USB sockets in Armrest/
    Wireless Phone Charger under Instrument Surround.
    Pictures of technical stuff

  3. #3
    Senior Member FastEddie's Avatar
    Join Date
    Apr 2017
    Location
    Milton Keynes
    Posts
    1,549
    Post Thanks / Like
    You will need to drive a relay from the permanent live of the bulb cluster , and the switching negative from the reverse bulb / rear ECM.

    Also connect the permanent live to the common of the relay , the output will then be switched +12 as you require for the application.

    Let me know if you need a picture to understand better , I'll post shortly if you do.
    2009 X358 XJ LWB 2.7 Tdvi , Liquid Silver , 100k+ and going strong.
    Bumper reflectors drilled and fitted with 3W side marker lights.
    Fog lamps / DRL running with HID colour match of dipped beam.



  4. Thanks C16RKC thanked for this post
    Likes xjrecosse, C16RKC liked this post
  5. #4
    Senior Member Nimiq1's Avatar
    Join Date
    Apr 2015
    Location
    Bradford
    Posts
    317
    Post Thanks / Like
    If you could post a picture that would be most helpful, as I was about to do this today, never realising that the lights would have a permanent live feed....

    Cheers
    2006 XJ6, X356, 2.7 TDVi Sport Premium Auto
    2002 X Type, X400, 2.5 L Auto

  6. Likes FastEddie liked this post
  7. #5
    Senior Member Partick the Cat's Avatar
    Join Date
    Apr 2013
    Location
    Thornbury, Gloucestershire
    Posts
    1,084
    Post Thanks / Like
    It's way that control modules detect failed bulbs. When the switched (return) line is not connected to earth, ie the lamp is off, then the return line will sit at 12v if the bulb is okay, but at 0v if it's failed (ie it's open circuit).
    "The jaguar is a compact and well-muscled animal." (Wikipedia on Panthera Onca)
    2008 XJ Sovereign 2.7 Tdvi,
    LWB, Sunroof, 19" Polaris, Botanical Green
    2008 Hyundai Getz 1.4
    Previous: 2004 Hyundai Getz; 1990 Merc 190E 2.6; 1987 Nissan Prairie ... 1954 Mk-C 197cc Bond Minicar

  8. #6
    Senior Member FastEddie's Avatar
    Join Date
    Apr 2017
    Location
    Milton Keynes
    Posts
    1,549
    Post Thanks / Like
    Quote Originally Posted by Nimiq1 View Post
    If you could post a picture that would be most helpful, as I was about to do this today, never realising that the lights would have a permanent live feed....

    Cheers
    You can do this with any standard 4 or 5 pin automotive relay , fuse is optional as the ECM is happy enough see 12v +ve normally.

    The permanent live /+ve of the cluster is already fed through a fuse so another is not required , connect this to pins 86 and 30 of the relay.

    The switched -ve of the reversing light needs to be connected to pin 85 of the relay , relay will now operate when in reverse.

    When the relay closes , pin 87 will become live so this will be your switched live / +ve 12v that you require.

    Pin 87a will be permanently live and go off when the relay closes , just cap this with another blade receptacle as not required.

    On a 4 pin relay you will not have the 87a so nothing to worry about and it won't be there at all.

    You can use this for any application requiring a switched live from normal operation of a sunk earth system , -ve switched.

    2009 X358 XJ LWB 2.7 Tdvi , Liquid Silver , 100k+ and going strong.
    Bumper reflectors drilled and fitted with 3W side marker lights.
    Fog lamps / DRL running with HID colour match of dipped beam.



  9. Thanks JimC64, C16RKC thanked for this post
    Likes fat controller, C16RKC liked this post
  10. #7
    Senior Member
    Join Date
    Dec 2013
    Location
    Berkshire
    Posts
    2,303
    Post Thanks / Like
    You must be very careful of what you connect the "-ve of the lamp" as this uses the lighting control module to sink current - albeit on the 'negative side'.

    If you are going to use a relay then you need a reverse EMF diode (AKA a flyback diode) to provide a path for the current when the relay is off (some relays have this built-in) to avoid damaging any electronic devices in the circuit. To give an analogy an ignition coil uses the voltage surge to produce a spark when the coil is switched off and the electro-magnetic field in the coil collapses.

    Also, if you are going to use a relay then why not use a power transistor as a switch instead - minimal (micro-amps) current drain.
    S Type 4.2 SE Plus 2002 original spec: Xenon HID/SatNav/Voice/Cassette Player/CDC/TV/GSM Phone/Sun Roof/Rear Blind/CATS.
    Retro-fitted: CD Player/Bluetooth Phone/Aux Power Socket, USB & Volt Meter in Boot/Reversing Cam/Dash Cam & PSU/Dual USB sockets in Armrest/
    Wireless Phone Charger under Instrument Surround.
    Pictures of technical stuff

  11. #8
    Senior Member FastEddie's Avatar
    Join Date
    Apr 2017
    Location
    Milton Keynes
    Posts
    1,549
    Post Thanks / Like
    With two bulb filaments across the relay coil there will no back emf generated. Additionally, most automotive relays have had a back emf diode in with a series resistor for years. The series resistor is for when the polarity of 85 and 86 is not observed correctly.
    Last edited by FastEddie; 12-01-19 at 15:23.
    2009 X358 XJ LWB 2.7 Tdvi , Liquid Silver , 100k+ and going strong.
    Bumper reflectors drilled and fitted with 3W side marker lights.
    Fog lamps / DRL running with HID colour match of dipped beam.



  12. #9
    Senior Member
    Join Date
    Dec 2013
    Location
    Berkshire
    Posts
    2,303
    Post Thanks / Like
    Quote Originally Posted by FastEddie View Post
    With two bulb filaments across the relay coil there will no back end generated.
    Quite possibly, I should have made the point that this is one of the situations where extreme caution is always advised - car electronics (especially this lot !) can be very sensitive to spurious voltages etc.

    Quote Originally Posted by FastEddie View Post
    Additionally, most automotive relays have had a back emf diode in with a series resistor for years.
    Quite probably true - I made that point myself - but in this instance such a relay (10-30A) is complete overkill as the likely current is likely in the milli Amps range

    Quote Originally Posted by FastEddie View Post
    The series resistor is for when the polarity of 85 and 86 is not observed correctly.
    A resistor will reduce the voltage at the relay by creating a resistor ladder but the total voltage across the relay will not change - the resistor will now have to dissipate the heat generated, diodes are used to protect against reversed polarity at the loss of approx 0.7 volt drop.
    S Type 4.2 SE Plus 2002 original spec: Xenon HID/SatNav/Voice/Cassette Player/CDC/TV/GSM Phone/Sun Roof/Rear Blind/CATS.
    Retro-fitted: CD Player/Bluetooth Phone/Aux Power Socket, USB & Volt Meter in Boot/Reversing Cam/Dash Cam & PSU/Dual USB sockets in Armrest/
    Wireless Phone Charger under Instrument Surround.
    Pictures of technical stuff

  13. #10
    Senior Member FastEddie's Avatar
    Join Date
    Apr 2017
    Location
    Milton Keynes
    Posts
    1,549
    Post Thanks / Like
    Graham,

    The original post requesting some help was clearly from someone with less electrical knowledge than others may have.

    The solution was simple , with easy to follow details and with parts that would be readily available from Halfords etc.

    There would be little chance of any back emf as you suggested , unless of course they removed both bulbs and the relay was very old.

    Your alternative solution would be of little help to them without any additional supportive information for them to follow , feel free to elaborate more.

    Mark / Nimiq,

    Obviously up to you and at your own risk if you choose to follow any of the above.

    If Graham can post an informative diagram for a switching transistor as an alternative solution , the choice is then yours.

    BR, Eddie
    2009 X358 XJ LWB 2.7 Tdvi , Liquid Silver , 100k+ and going strong.
    Bumper reflectors drilled and fitted with 3W side marker lights.
    Fog lamps / DRL running with HID colour match of dipped beam.



  14. Thanks C16RKC, Nimiq1 thanked for this post
    Likes C16RKC, Nimiq1 liked this post
Page 1 of 3 123 LastLast

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •