Welcome to Netrider ... Connecting Riders!

Interested in talking motorbikes with a terrific community of riders?
Signup (it's quick and free) to join the discussions and access the full suite of tools and information that Netrider has to offer.

Featured LED resistor

Discussion in 'Technical and Troubleshooting Torque' started by Doch, May 7, 2015.

  1. Ahoyhoy
    I lobbing some led blinkers at my Guzzi and of course I'm getting the hyperflashing. I know I need to slow them down but I can't replace the flasher relay as it's electronic and part of the dash. I will be using a relay to solve my problem but what I don't know is 1) how many do I need and 2) how are they fitted, do they fit across the + 've and - 've wires or inline in the +ve wire only

  2. You mean you will be using resistors to fix the problem not a relay.

    What you are trying to achieve is to put the same load, i.e. draw the same current on the flasher circuit as would usually be seen with globes. You need one resistor on each side in parallel with the globe circuit. Assuming the globes in the old system are 5Watts each front and back together would be 10 watts.

    Power = Voltage x Current or Current = Power/Voltage
    Current = 10watts/12volts = 0.834 amps.

    So with your resistor and LED lamps together you need to draw 0.834 amps. Note this calculation is based on having replaced both front and rear blinkers with LEDs. The resistor has to go in parallel with the globe circuit from the sitched positive to ground. Note it can connect to this circuit anywhere in the loom that is convenient it does not need to be next to the globe. A power take off crimp can connect your resistor into the globe circuit.

    The LEDs will probably draw 200 - 300 milliamp so you need a resistor to draw about 0.8 amp or 800millamp. Ohms law V = IR or R = V/I

    Resistance = 12volts/0.8 amp = 15ohms.

    You also need to take into account that the power the resistor has to dissipate is Power = VI = 12 x 0.8 ~ 10 watts. It is an intermittent load so you can come down on wattage a bit.

    Possible Resistor

  3. If you can't replace the flasher can then a relay won't help you.

    You need load resistors in PARALLEL with the LED bulbs. Start with one a side. If it still flashes fast, put them front and back.
  4. I meant to say resistor not relay. Thanks for your help. I'll start with 2 and see what happens.
  5. Remember those resistors are dissipating quite a lot of power, they may get warm or hot. Bear this in mind when you zip tie them to bits of your bike.
  6. Yep, you had me up until on each side and in parallel. Does that mean one one each side of the bike ie left and right and parallel is connected to the +'ve only.
  7. I'm looking at part of the frame behind an air vent.

  8. See my drawing above, generally in bikes the positive goes through the flasher can then to the indicator switch. From there it splits into the left circuit and the right circuit. You need to have your resistor across that part of the circuit.
  9. Jeez cjvfrcjvfr All we wanted was a yes or a no. :)
  10. It's the didactic nature of me, I can't do yes/no ;)
  11. A couple too many zero's, did you mean 20 - 30 mA.

    Also I prefer to use 14v as the vehicle supply in calculations, 12v is a little too low, though in this case it doesn't change the figures too much, i.e: 20Ω at 9.7w. Although it may reasonably be argued that the voltage drop through wiring, connectors and switches could easily chew up a couple of volts :oldman:
  12. Sorry yes you are right, brain fart, the LEDS are generally in series to cope with the voltage so the current is low. As you say the calculations are not critical as long as you are pulling more current.
  13. Hi wot thewot the, have you checked any other bike forums on this issue ? Or similar.
    If your bike already has an electronic relay then it may already be sorted for LED indicators too.
    I've seen some where you just need to change / add or remove a link on the PCB or computer to set the right timing for the new LEDs.
    Have a look around first before you add the resistors.
  14. Have a ship load of resistors for free, looking for a good home just need a post pack to send them. Got them with my indicator bulbs but don't need them as I could replace the indicator relay with after market.