Need a simple XOR for Car turn signal

Discussion in 'The Projects Forum' started by brandini, Feb 25, 2008.

  1. brandini

    Thread Starter Member

    Feb 25, 2008
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    I own a Mazda 6 which has a turn signal in the front headlight assembly. It also has a side marker light on the side of the front quarter panel. I'm annoyed with Mazda since when operating the turn signal, only the front lamp flashes and cars next to me are oblivious.

    I've figured out after dusting off old logic maps knowledge that what I need is an XOR. The two inputs are the turn signal and the parking light lead and the output with be the side parking lamp (to be turned into a turn signal).

    I'm here to ask you gurus what components do I need to make this work? The bulbs are 12v and run at about .4A each. I will later be switching them out for LED side parking lamps but the front turn signal will probably remain bulb due to size constraints.

    Thanks for all your help!
     
  2. thingmaker3

    Retired Moderator

    May 16, 2005
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    You'll need two transistors, four diodes and five resistors:

    XOR gate built with 1 each OR, AND, and NAND gates: http://hyperphysics.phy-astr.gsu.edu/hbase/electronic/xor.html#c2

    OR gate from two diodes and a resistor: http://hyperphysics.phy-astr.gsu.edu/hbase/electronic/or.html#c2

    AND gate from two diodes and a resistor: http://hyperphysics.phy-astr.gsu.edu/hbase/electronic/and.html#c2

    NAND gate from two 2N2222A transistors and three resistors: http://hyperphysics.phy-astr.gsu.edu/hbase/electronic/nand.html#c2
     
  3. brandini

    Thread Starter Member

    Feb 25, 2008
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    The 2N2222A you mentioned is pulling up as .6A max. Will this truly handle a .8A load reliably? If not, are there any suitable replacements that do?
     
  4. jpanhalt

    AAC Fanatic!

    Jan 18, 2008
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    The KSC1173 will handle plenty of current (http://www.fairchildsemi.com/ds/KS/KSC1173.pdf ).

    To find more, go to Digikey.com, search on transistor, there will be several thousand hits. Then use the search filters to find what you want/have available. The KSC1173 handles 3 A , is in a TO-220 package, and costs $0.47 in single units. Digikey has a minimum charge of $25.
     
  5. thingmaker3

    Retired Moderator

    May 16, 2005
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    There are 2N2222A and there are 2N2222A :)

    Many manufacturer's 2N2222A will handle 800 milliamps.

    As noted, other transistors can handle more. Nearly any old NPN will do.
     
  6. Ron H

    AAC Fanatic!

    Apr 14, 2005
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    Is there some reason he can't use an IC XOR gate (CD4030 or CD4070), and a MOSFET driver?
    EDIT: Schematic below.
     
  7. nomurphy

    AAC Fanatic!

    Aug 8, 2005
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    You could just use a SPDT relay. Wire the side light through the normally closed contacts, and run the +12V coil between the front blinker hot and ground.

    The side light will be on as normal (through closed relay contacts), but whenever the front blinker is on it will turn off the side-light. When blinking, the front and side-light on/off phases will be opposite of each other.
     
  8. Ron H

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    Apr 14, 2005
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    That's a great idea. One thing I just thought of, though. The turn signal modules that I'm familiar with rely on bulb current for their timing. With low current, they flash at a lower than normal rate. This would be a problem with a relay, and even more so with the XOR approach. Have the newer cars replaced these with electronic timers?
     
  9. nomurphy

    AAC Fanatic!

    Aug 8, 2005
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    I doubt that a 12V coil is going to add much load to the front blinker light.
     
  10. Ron H

    AAC Fanatic!

    Apr 14, 2005
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    I think that's the problem. The only load the flasher module sees is the relay coil. With the XOR, it's even worse.
    I guess you could put a dummy bulb or resistor in parallel with the coil. :(
     
  11. brandini

    Thread Starter Member

    Feb 25, 2008
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    The problem with this is that when my headlights are off (parking lights off), the side marker will stay off even though the relay will be clicking away. Leaving those around me clueless to my turn signal intentions :(

    I think the diode option is what I'll be going with. My question is that when picking diodes or transistors, do I have to take into account the load's power draw (like I asked about above, which points to yes)?

    The worst case scenario is that when the parking lights are off, the turn signal rate would be slower (by about 50% I'm guessing off cuff). I rarely drive with my headlights off so this is not abig issue and in the future the sidemarker will be replaced by http://www.therpmstore.com/product_info.php?cPath=26_32&products_id=727 and the LEDs should be less load.
     
  12. thingmaker3

    Retired Moderator

    May 16, 2005
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    You'll want to make sure the current drawn by the load is not more than the components can handle. You might also want to check maximum and minimum operating temperatures on the components - could be a bummer if the turn signals don't work in August or January.
     
  13. Ron H

    AAC Fanatic!

    Apr 14, 2005
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    Brandini, if I understand you correctly, you are basically combining the parking light signal and the turn signal logically, and then driving the lamps with a transistor. If this is correct, you will never get lamp current through the flasher module, so it will run very slow (assuming it is the bimetal switch type). Am I not understanding what you are doing?
    I think there are solid state flashers also.
     
  14. nomurphy

    AAC Fanatic!

    Aug 8, 2005
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    Remove the standard bulb and holder from the side panel, install one with a double filament. Connect one filament to the headlight circuit, and the other to the blinker circuit.
     
  15. brandini

    Thread Starter Member

    Feb 25, 2008
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    Then, as I posted above, http://www.therpmstore.com/product_info.php?cPath=26_32&products_id=727 would not be a plug and play upgrade in the future...

    Ron, I am leaving the headlight bulb intact and its circuit the same except I'm using it as an input for this new system. Put simply, the module I'm building will use the turn signal simply as a status input, and will be intercepting the parking light lead to the side marker. Therefore just switching off the parking light if it is already lit (parking lights on), but powering it from the turn signal if not (parking lights off - rare).

    The original in headlight turn signal will not be an output of this system.
     
  16. brandini

    Thread Starter Member

    Feb 25, 2008
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    Well I've found out that my amperage requirements will be going up since the front turn signal is 28W (1157 bulb) and the side is 5W (168 bulb). That being said I have pieced together one version and found another that may work and will be able to piece together these from the useful digikey search. I do have a question regarding the resistors, I read that they should all match. What ohm resistor should I get and would it have to be able to handle nearly 32 watts?

    Note: Voltage shown and components in diagram are untrue. I was looking at using a KSC1173YTSTU-ND Transistor. I am trying to decide to rule out diodes (via the diagrams in a previous post) since Schottky diodes say they are temperature dependent and it affects their breakdown voltage.
     
  17. brandini

    Thread Starter Member

    Feb 25, 2008
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    And to add another '?' in there, since the output of this circuit is only the 5 watt side marker, I should be able to spec for that, not both bulbs (33 watts) right?
     
  18. lupisak

    New Member

    Oct 3, 2012
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    I know this is an old tread, but the question is timeless, so I'm replying for the benefit of future readers.

    I've always solved these things using SPDT (Single Pole Double Throw) relays in the past, but because non-American cars tend to disconnect a wire when off instead of connecting it to ground (so you get either 12V or floating, while you need 12V or ground), you end up with quite a few relays.
    You do this by connecting the coil of the relays to ground and the other side to each of the signals (right turn signal, left turn signal and parking light), the Normally Closed pin to ground and the Normally Open pin to 12V. The common pin if the new output.

    You can now connect the new output from one of the turn signal relays to one side of the coil of a relay and the new parking light output to the other side. The relay will then switch on if either parking light or turn signal is on, but off if none or both are on.

    Hence, in this case you end up with 5 relays (7 if you also want to combine brake light and rear turn signals in one bulb as well).

    I recently learned another trick. If you first use 3 SPDT relays to convert the floating/12V signal to ground/12V, you can use a simple rectifier or diode bridge in place or a relay or an XOR gate to produce the wanted effect with the marker lights.
    Connect the (ground/12V) parking light wire to one of the AC inputs of the rectifier and the (ground/12V) turn signal wire to the other, then connect the plus and minus output from the rectifier to the marker light. This will work both with LED lights and normal bulbs (provided you use a strong enough rectifier).
     
  19. spinnaker

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    Oct 29, 2009
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  20. Kermit2

    AAC Fanatic!

    Feb 5, 2010
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    It is from 2008

    Back when people were wild and reckless and electronics was conducted like gunfights in the OK corral.

    :)
     
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