Relay or transistor for Motorcycle (on/off)

Discussion in 'Homework Help' started by jjmaia, Jun 15, 2010.

  1. jjmaia

    Thread Starter New Member

    Jun 15, 2010
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    Hi there.

    My motorcycle have a very unstable voltage/current, so it always burn any LED I use, and I can't use xenon.
    What I have done is not use LED's (which are cooler, more visible and low consuming) and I have the Xenon connected directly to the battery which I don't like because is a nuisance to turn it on and off each time I board or dismount the bike...

    So, it seems the solution is to have something where I'll connect the 12v source from the battery, directly to the LED's and the Xenon kit, but that would only allow electric current to pass only when i turn on the ignition.

    So the solution seems to be a Relay or a Transistor.

    Could you give me some help regarding this matter?

    My thanks in advance.
     
  2. jjmaia

    Thread Starter New Member

    Jun 15, 2010
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    After some research and trying to learn how it works, it seems i need this type of relay:
    (its not 7 ~ 5v, but 7 ~12v)
    [​IMG]

    Bassically i'll conet the 2nd to the (+) terminal of the battery and the 4th pin to the xenon kit and LED's, etc, and 3rd to the headlight live cable and the 1st to the ground.
    Is that correct?

    Two more question, will the relay consume around how much power?
    And would be better to find a Transistor to d the same?

    Thank you!
     
  3. retched

    AAC Fanatic!

    Dec 5, 2009
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    Wow. EXACTLY 24 hours later!

    Your first post was at 2:43 PM Yesterday (My time)
    and your second was 2:43 PM Today.

    Neat.

    As for your question. You will want to use a relay rather than a transistor for the amount of current you will be needing.

    As for the relays usage, you need to read the datasheet on the relay you choose to see how much power the relay needs to energize and hold. It is usually a pretty small amount.

    check online suppliers for automotive relays. They will be manufactured to handle the weather and rough conditions involved with automobiles, including motorcycles.

    You could even just use a switch. No relay or transistor needed.
    Get a 12v switch that is rated for the current that the xenon bulb needs. Then you just turn the lamp on and off as you wish.

    Battery + to switch.
    Switch to bulb
    other side of bulb to battery -
    done.
     
  4. jjmaia

    Thread Starter New Member

    Jun 15, 2010
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    Thanks for your answer.

    Has i have said on the first post, i already have a switch, but its boring to turn it on and off every time i board (on and off) the bike...
     
  5. retched

    AAC Fanatic!

    Dec 5, 2009
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    Sorry. I read it as "directly connected to the battery" meaning you were pulling a wire off the battery to turn it off.

    What are you going to use to energize the relay coil?
     
  6. jjmaia

    Thread Starter New Member

    Jun 15, 2010
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    It is connected to the battery, but if i don't use a switch the lights would be always on, killing the battery.

    I'm going to use the "unstable current" from the headlights.
     
  7. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
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    Not sure how easy parts are to come by in Portugal.. But here in the US we simply go to the auto parts store and pick up a typical automotive 30A Bosch relay. Auto parts stores typically have tons of different ones. Thats all you need.
     
  8. jjmaia

    Thread Starter New Member

    Jun 15, 2010
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    I already found the right one, but i got back at the beginning...

    Starting over:
    I've bought the xenon kit and installed it (already with relay) but when i give a little gas, the light blinks and goes off, and you can year the relay going on and off.

    So i have connected the entire kit to the battery i used a switch.

    Now i have used a relay connect it properly and the same happened. Because of the bike (not battery) current instability the relay goes on/off constantly when i give gas to the bike.

    How do i get over this?

    Thank you.
     
  9. retched

    AAC Fanatic!

    Dec 5, 2009
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    You may need to regulate the voltage. And/or a cap to smooth the voltage.
     
  10. Georacer

    Moderator

    Nov 25, 2009
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    Is there any chance the vibrations of the motor are swinging the relay's core on and off position? Or the mmf is too strong for that?
     
  11. jjmaia

    Thread Starter New Member

    Jun 15, 2010
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    The vibration of the motor is out of the question.

    But how do i regulate the voltage? I have used a voltimeter and sometimes it reads 7v other times 0v, and i have already used 2 diferent multimeters...
     
  12. jjmaia

    Thread Starter New Member

    Jun 15, 2010
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  13. jjmaia

    Thread Starter New Member

    Jun 15, 2010
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  14. retched

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    Dec 5, 2009
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    Yes, the COIL or control is 6vDC.

    The contacts for the LOAD side (Your lamp) is rated UP TO 10A at UP to 28vDC.

    So as long as that headlight is pulling UNDER 10A, you are good.

    However, this is a PCB relay. It can NOT handle the bumps of the road or the temperature changes incurred from outdoor driving.

    I would get yourself a AUTOMOTIVE relay that is rated for a 6vDC coil and around or above the same LOAD rating of 28vDC 10A..Even 100vDC 100A would work. Just make sure the coil can energize with your available voltage.

    As for spikes, they WILL fry that coil. You want to get an AUTOMOTIVE relay that is designed to handle the voltage spikes incurred with load dumps like turning the light off.

    Also, You didnt measure the voltage to the circuit when you are at higher RPMs.

    DO NOT try to drive the bike and read the meter at the same time.

    Put it on a stand and see what voltages you are getting at higher revs.
     
  15. jjmaia

    Thread Starter New Member

    Jun 15, 2010
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    I have accelerated and the voltage doesn't grow beyond 7.xx volt.
    The load is not greater than 5A @ 12v.

    The thing is that i can't find a car relay at 6v on ebay...
     
  16. sceadwian

    New Member

    Jun 1, 2009
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    e-bay isn't the greatest site to go to for specific electronics components. Try a site like www.digikey.com
     
  17. jjmaia

    Thread Starter New Member

    Jun 15, 2010
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    I know, but unfortunately i live in Europe's tail :D

    Could you recomend a relay for me? I don't know the diference betwin "Logic Supply Voltage (Output)" and "Voltage - Input", neither the style...

    Thank you.
     
  18. retched

    AAC Fanatic!

    Dec 5, 2009
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    Friend, you will be blowing parts like mad without protection for back-emf and environmental protection. A little rain or a puddle and you will have a mess.

    Do you have standard automotive stores around your house? Dont limit yourself to the internet, especially ebay.

    As sceadwian said.
     
  19. retched

    AAC Fanatic!

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    Last edited: Jun 20, 2010
  20. jjmaia

    Thread Starter New Member

    Jun 15, 2010
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    If you could point one from the digikey i would appreciate since they seem to have good prices and they send to Portugal.
     
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