LED indys.

[Rich]

Just a quick question, i've got LED indicators with resistors in the rear tail light. If i was going to fit LED indicators allround would i need to put resistors to each LED indicator or would just the two for the rear tail light be enough?

Baph help maybe please

Cheers Rich!!

Yup. You'd be needing resistors in the front.

However, might be easier to replace (or add to) the resistors in the back.

The reasoning for this comes back to the stock flasher relying upon the resistance of the bulbs to sort its timing out. LEDs don't have the same resistance (much lower) therefore the indicators will flash fast.

Two schools of thought on this, if it's below the magical 120 flashes per min, do you want to go to the hassle? A fast indicator is more noticable, and so long as you're not breaking the law (and it'll pass an MOT) then why worry about being noticed more?? However, there's also the possible problem that if you pass too much voltage through the LED's that they'll blow (as SoulKiss recently found out). If you have a designed LED indicator, it should run at 12v though. Worth checking.

If you do want to get the timing sorted out, you'll need to know the resistance offered by your current setup on the rear, then adjust from there. You'll need to know the power usage of the system as a whole (mine is 2x 23W bulbs when I'm indicating), then you'll need to match that power usage with resistors to sort out the timing.

[Rich]

Cheers baph, so i need to add some too the front. The ones i put in the back for the integrated indys won't be enough then. I read somewhere that aslong as theres resistors in the indy wiring somewhere that should be enough!!! Thanks Baph, where about do you put them in the front then?? not many places i can see!!

On a curvy I've no idea, but thankfully you ride a pointy from your avatar.

Lift the tank, then take off the airbox. Look just behind the forks (on the inside of the frame - near the engine). There's multiple connectors there, and all the speedo/neutral lights/horn etc wiring goes here. Your indicators also go here. Nice weather protection.

You can get to it without removing the airbox, but you'd better have a russian midget on hand because that's a mighty small hole!! Even with my snorkel removed I couldn't fit my hands down there without removing the airbox (not just the top either!!).

Now do you see what I was saying about adding to or replacing the ones at the back??

[Rich]

Originally Posted by Baph

Now do you see what I was saying about adding to or replacing the ones at the back??

Thanks Baph, muchly appreciated

No problem, the rear indicators are linked to the front by the ground (-ve) wire IIRC. So any changes made here will also affect the front.

My suggestion, hook up the front indicators, get a stop watch out, are they illegal? If not, are you that fussed that they flash a little faster (it might not be all that much faster - depending on the resistor you already have in there).

EDIT: Ensure they're 12v LEDs before doing this!!

Blimey Baph, is there anything you don't know about bikes?!?

I tried led's at the rear of my bike. Even with the resistors they worked fine but then the front indy's would not work at all. The front's were standard. Weird.

Originally Posted by HooliganDan

Blimey Baph, is there anything you don't know about bikes?!?

I tried led's at the rear of my bike. Even with the resistors they worked fine but then the front indy's would not work at all. The front's were standard. Weird.

There's lots I don't know, mainly the mechanical side. I'm steadily learning though

I know about where the connectors are in front of the airbox because I've been down there dealing with my horns.

In your situation, if your back indicators worked, but your fronts didn't, that's either one or the other of:
1) You shorted the fronts somehow when putting the back in. Quite possible if you put the resistor in yourself I suppose.
2) They did work, but overall circuit voltage was so low that the front's were too dim to see. The rears, being LEDs didn't need as much voltage, so you saw them flashing. Problem there is the resistance is too high.

I posted a wee guide to this years ago, but can't find it anymore so...

A regular lamp, say 21 watts 12V will draw 1.75Amps.
An LED has a much higher impedance, (fancy word for resistance), which will only draw about 0.02Amps for every individual LED in the indicator. Say 0.2 Amps in total for a 10 LED indicator.

As the flasher rate changes depending on the amount of current being pulled, we need to make it think the regular indicators are still in circuit.

You can do this by adding resistors to mimic each indicator lamp. But what size? I'll do this twice, for 21W, and 23W lamps.

21W Lamp

R=V/I V=12 I=? (R - resistance in Ohms, V - Voltage in Volts, I - current in Amps, W - wattage in Watts)

I=P/V = 21/12=1.75

R=12/1.75 = 6.8 Ohms

23W lamp

I=23/12 = 1.9 Amps

R=12/1.9 = 6.3 Ohms

Not a huge difference between the resistor sizes for the two different lamp sizes.

Resistors only come in certain sizes anyway, and the two sizes closest are 6.8 Ohms or 7.5 Ohms.

You might have noticed that I haven't adjusted the calculation to take account of the current, (Amps), being drawn by the new LED indicators, which will draw current through the same circuit as the resistor. However I am going to look at this now to help influence the choice of resistor, 6.8 or 7.5 Ohms.

I'll look at the 7.5 Ohm resistor.

I=V/R = 12/7.5 = 1.6Amps + 0.2Amps (rough guesstimate for the LED indicator) = 1.8 Amps - Right in between the two sizes of bulbs which pulled 1.75Amps and 1.9 Amps.

So I'd recommend the 7.5 Ohm resistor. But what wattage?

P=IV = 1.6 x 12 =19.2 Watts. This is your minimum wattage. You could use a 7.5 Ohm 25Watt or 50Watt resistor if you wanted to.

So that's a 7.5 Ohm, 20 or higher Watt resistor - per LED indicator. Just wire them across the same wires as the LED indicators. Doesn't matter which end goes to negative or positive, they're not polarity conscious components. Jobs done.

20 Watts is a standard size, and relatively easy to get hold off. Be aware though that running a resistor on it's limit like this will produce some heat, and could get bit hot if you don't allow it to cool off, either by switching it off, (remember it's never on for more than a second or two as it flashes), or by cooling it in some way. Depending on the type of resistor you buy, clamping it to a metal surface can be a huge help in dissipating any heat generated.

If you struggle to get this size you can use 8.2 Ohm 20 watt resistors. Or use two resistors in "parallel", (wired side by side, not one after the other). To do this double the resistance to 15 Ohms, another standard size, and half the minimum wattage to 9.6Watts. Again 10 Watts is a standard size.

If you want to you can fit the resistors for the front indicators in "Parallel" with the resistor for the rear indicator, which could make it easier to tuck away, especially on a naked bike. So that means both resistors for the left hand indicators are fitted in "parallel" with each other, at the left hand rear LED indicator. Same idea for the right hand pair of indicators and resistors.

Another option if you only want to fit one resistor for the left pair, and one resistor for the right pair, would be a 3.3 Ohm or 4.7 Ohm 50 Watt resistor, (again standardised sizes), fitted across the rear OR front LED indicators only. A bit harder to get hold of these sizes of resistor though, and not as close to matching the power consumption of the standard lamps. Although it would still be damn close in terms of flash rate.

If you did go for this option you would need to make sure your flasher unit could handle the 43.2 Watts consumed by the 3.3 Ohm resistor. Because the 3.3 Ohm standard size is less than the desired 3.75 Ohms, it pulls a bit more current and consumes a bit more power. Safer option is the 4.7 Ohm resistor.

OR...

You can just buy a replacement flasher unit for LED indi's!!!

Originally Posted by Philbo

I OR...

You can just buy a replacement flasher unit for LED indi's!!!

Prob the easiest option!! And would have saved your typing fingers!!