Motorcycle Flasher Issue

Discussion in 'Circuit Help' started by gturbo7, Oct 27, 2012.

  1. gturbo7

    gturbo7

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    I recently purchased a 1971 kawasaki enduro motorcycle with a 6 volt electrical system. I have to install turn signals on the bike to make it street legal. I couldn't find 6 volt turn signals to easily install on it so I decided to install 12 volt led turn signals since they are readily available and very inexpensive. I used a 6-12 v converter board to bump the voltage up and I bought a 12 volt electronic led flasher. When I turned the key to the on position the turn signals worked flawlessly. When I started the bike the turn signals just stayed on steady. I then made my own flasher using a 555 timer and that one flickers very quickly when the bike is running. I am thinking the problem is noise from the ignition system or the magneto on the bike, I'm just looking for an easy way to isolate that from the flasher circuit so my lights can flash like they do on battery power alone.
     
    gturbo7, Oct 27, 2012
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  2. gturbo7

    CDRIVE VIP Member

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    Posting your schematic would be best. This way we can better assess where noise decoupling and surge protection will be most effective.

    Chris
     
    CDRIVE, Oct 27, 2012
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  3. gturbo7

    duke37 VIP Member

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    It may be interference as you surmise but it may also be excess voltage. Motor cycle voltage control is primitive to say the least.
     
    duke37, Oct 27, 2012
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  4. gturbo7

    gturbo7

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    Here is the a link to the diagram for the bike. https://docs.google.com/open?id=0B2gBjUuRY9-PR0U4aUs4ZmJFSVU

    And here is a link to the flasher diagram I used. https://docs.google.com/open?id=0B2gBjUuRY9-PWlhPSnczYjBuWVE

    There is a brown and an orange wire that go to the optional turn signal flasher on the bike diagram. I have the brown wire and circuit ground feeding a bridge rectifier in attempt to eliminate negative voltage swings. The rectifier feeds the 6v-12v converter. I don't have a diagram for that as it is a board that I purchased. The output of the converter feeds the flasher that you see on the diagram and the leds are connected in the same way the light bulb in the diagram is connected.
     
    gturbo7, Oct 27, 2012
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  5. gturbo7

    CDRIVE VIP Member

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    There's no Vcc decoupling there and there's probably none on the input to your converter either. It's also not a bad idea to precede the input to the converter with a low value resistor followed by a 9V Zener with anode connected to Gnd.

    Are you really using a 2N3055 power transistor? This is a very high power model with very low beta. With an automotive lamp in the collector circuit that 1K base resistor would not provide enough base current to saturate it. It would not be my choice for diving high current LEDs either.

    Chris
     
    CDRIVE, Oct 27, 2012
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  6. gturbo7

    gturbo7

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    What size decoupling cap would you recommend? How low of a resistor are you thinking and what is the purpose of that with the zener? I am using the 2n3055 transistor and it works fine when I'm just using battery power. The leds are running at about 350mA with 12v across them to give you an idea of how much power they are consuming.
     
    gturbo7, Oct 27, 2012
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  7. gturbo7

    CDRIVE VIP Member

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    Before we go there, what's the specs on the converter? 6-12V converter doesn't tell us much. What's the min-max input range, max output current, input current demands? Do you have a link to it?

    EDIT: Did you measure the bike's 6V line while the bike was running? Also, while a DMM is slow, you might be able to switch the DMM to AC and see if it picks up any readable noise or ripple on the line.

    Chris
     
    Last edited: Oct 28, 2012
    CDRIVE, Oct 28, 2012
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  8. gturbo7

    gturbo7

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    Here is the link for the 6-12v converter i am using. http://www.ebay.com/itm/Classic-car-6V-to-12V-voltage-converter-power-power-/350436684000

    I have measured the voltage at the brown wire, it reads between 6.2-6.5v dc while running, which is slightly higher than with just battery power. I did try measuring for ac while running, my meter doesn't pick much of anything up, maybe .1 or .2 v

    As a side note, i did try bypassing the 6-12v converter and the leds do light up they're just very dim and they do the same flicker as when i have the 6-12v converter connected.
     
    gturbo7, Oct 28, 2012
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  9. gturbo7

    CDRIVE VIP Member

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    See attachment for addition of noise filtering. I also recommend that you lower R2 as shown. Even this value is high for a 3055 but it ultimately depends on what the LED current is in the collector circuit. The general rule of thumb when saturating a transistor is that the Base current should be Ib = Ic/10 or times less than the collector current. Admittedly, this rule isn't that relevant when the collector is switching light load currents though. Do you know what your LEDs draw.?

    Chris
     

    Attached Files:

    CDRIVE, Oct 28, 2012
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  10. gturbo7

    gturbo7

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    They draw about 350mA, so I should shoot for about 35mA base current?
     
    gturbo7, Oct 28, 2012
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  11. gturbo7

    CDRIVE VIP Member

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    Yes, a 330 Ohm should put you close enough to the ball park. I suspect you will see an increase in the LEDs brightness too. By the way, to give you an idea of how different a 3055 is from a common small signal switching transistor, the 3055 has a max base current of 7A! No, that's not a typo. ;)

    Chris

    Edit: I didn't want R2 to go any lower than 330 Ohms because I stuck that 10 Ohm decoupling resistor in the Vcc leg. I didn't want the Vcc to dip too much when the output is driving the base.
     
    Last edited: Oct 28, 2012
    CDRIVE, Oct 28, 2012
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  12. gturbo7

    gturbo7

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    Yea, i was pretty surprised to see that the max power dissipation for this thing is 115W when i went to radioshack to get parts. That is probably more than the whole electrical system on the bike consumes lol. Thanks for all the help, I will let you know how it goes when I make these changes.
     
    gturbo7, Oct 28, 2012
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  13. gturbo7

    CDRIVE VIP Member

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    Yes, it's big time overkill for your needs. Your 350mA load would have been best handled with a small power MOSFET. My second choice would have been a TIP120 Darlington.

    Chris
     
    CDRIVE, Oct 29, 2012
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  14. gturbo7

    gturbo7

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    I made the changes with the exception of using a 33uF cap in place of the 10uF that you suggested as that was a size that I had handy. It works when it is just battery power but it is a slower flash now, like on for 3-4 seconds and off for 3-4 seconds. When the bike is running it still just flickers, at seemingly the same frequency that it did before. This problem may have to wait until I get a scope so I can get a better look at whats happening.
     
    gturbo7, Oct 29, 2012
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  15. gturbo7

    CDRIVE VIP Member

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    Sorry that those mods didn't help. Perhaps a photo of the board and the interconnects to the bike might help. I think ignition noise is getting in there. It can be very severe and difficult to eliminate. Wire length, grounding points, decoupling cap lead length, all can play a part here. Spark noise extends well into the RF bands. If it gets onto the Trigger and Threshold pins it can make a 555 very erratic. You may have to resort to a metal case with RF feed - through caps..

    Chris
     
    CDRIVE, Oct 30, 2012
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  16. gturbo7

    Mongrel Shark VIP Member

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    Ive seen people try to run Motor bike blinkers from a magneto before. Rarely (never in my experience) goes well. Unless its OME.

    Could I suggest a new approach? Get a small secondary 6v battery, maybe 4 rechargeable AAA's. Or maybe even a super cap. Charge it from the magneto, then when you turn the blinker on, have the magneto disconnect from the battery and run a flasher circuit, isolated from the rest of the electronics. If you don't need blinkers a lot, I would consider a small solar panel and not have it connected to the bikes circuit at all.
    You might even get away with 4 AAA's(6v) to your boost circuit then run the lights you have...


    If you find another solution, please PM me, as I have come across this problem 20-30 times in the last 20 years... Never seen a solution work with the magneto... Whats the rectifier look like? If it's not FWBR (doesn't look like one in your circuit diagram) You might want to try putting one between original battery and boost circuit. Look for one that can handle a few hundred volts...

    I wouldn't be surprised if the magneto killed you boost circuit either. They can put out some wacky voltages... Ive seen headlights blow at high rpm... Especially with enduros from the 70's. Not so much with modern bikes.
     
    Mongrel Shark, Oct 30, 2012
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  17. gturbo7

    gturbo7

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    I thought about the separate battery, there just isn't any space for anything on this bike. I thought of another way to keep the circuit separate on the way to work this morning. I'm gonna put two relays, one on positive wire to battery and one on negative wire so that the normally closed position connects the battery to the rest of the circuit and the normally open will connect the battery to my circuit when I hit the turn signal switch. The bike does run without the battery so I think this should work.
     
    gturbo7, Oct 30, 2012
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  18. gturbo7

    CDRIVE VIP Member

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    I've been thinking about it too. Early in the thread you said that the boost converter is connected to the battery through a bridge that you added. Long shot, but have you tried eliminating the bridge? A storage battery is a very low impedance device that filters garbage well close to its terminals. I'm wondering about the necessity of the bridge and it's effect on this noise. Is it an aid or hindrance? Is there a large filter cap on the output of the bridge?

    Chris
     
    CDRIVE, Oct 30, 2012
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  19. gturbo7

    gturbo7

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    I did try eliminating the bridge at the same time I eliminated the 6-12 converter, same flickering. I do have a pretty large cap on the output, 3300uF.
     
    gturbo7, Oct 30, 2012
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  20. gturbo7

    CDRIVE VIP Member

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    You've certainly done a good job of trying to isolate the problem. You're consistently one step ahead of me. ;)

    Have you tried connecting both the + & - input of the boost converter directly to the battery?

    Grabb'n at straws.

    Chris
     
    CDRIVE, Oct 30, 2012
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