LED indicator advice

sorry its a curvey (2000)

on the pointy (well k3) its next to the fuse box, black box about inch and a half square.

[SoulKiss]

People looking to sort out LED indicators, please do a search.

There is a VERY good post that tells you how to do it.

Resistors will cost as much as a flasher relay, will require soldering skills an generate heat in use (ok not much but needs to be considered)

Controling the flash rate is only part of the job the SV Relay does - it also looks after the side-stand switch, so you cant just swap it over. You need to wire an aftermarket flasher relay into the wires going to the SV one.

As said, full instructions are on the site - I know because I followed them

David

Originally Posted by SoulKiss

Resistors will cost as much as a flasher relay, will require soldering skills an generate heat in use (ok not much but needs to be considered)

Note: I haven't read the thread that SoulKiss suggested people search for. In the context of that thread my next comments may make me look like a numpty. That said...

Crumbs what resistors are those then? I've no idea how much a flasher relay is but I'd have thought it was more than the few pence a resistor costs.

All adding a resistor into the circuit does is alter the time constant of the circuit. A variable speed flasher unit is going to contain a variable resistor.

I assume that the reason aftermarket LED units flash wrongly (ie not within MOT spec) is that they have a different (lower) resistance than the bulbs they replace. Not a terribly supprising situation as a bulb wouldn't work very well if it didn't have a resistance and an LED wouldn't work very well if it did.

So my very basic assumption of things (and I accept there may well be more to it but I'll read that when I'm not halfway through posting in my break on a training course ) is that measuring the resistance of the bulbs being removed and adding a resistor in series to the LED replacement would be all that was needed.

Ok. Now you can start kicking me.

[SoulKiss]

Originally Posted by 2mths

Note: I haven't read the thread that SoulKiss suggested people search for. In the context of that thread my next comments may make me look like a numpty. That said...

Crumbs what resistors are those then? I've no idea how much a flasher relay is but I'd have thought it was more than the few pence a resistor costs.

All adding a resistor into the circuit does is alter the time constant of the circuit. A variable speed flasher unit is going to contain a variable resistor.

I assume that the reason aftermarket LED units flash wrongly (ie not within MOT spec) is that they have a different (lower) resistance than the bulbs they replace. Not a terribly supprising situation as a bulb wouldn't work very well if it didn't have a resistance and an LED wouldn't work very well if it did.

So my very basic assumption of things (and I accept there may well be more to it but I'll read that when I'm not halfway through posting in my break on a training course ) is that measuring the resistance of the bulbs being removed and adding a resistor in series to the LED replacement would be all that was needed.

Ok. Now you can start kicking me.

Regular 0.5W or 1W resistors, are, as you say pennies each.

However with the application we are looking at you need 10W + resistors.

These, when I looked into it, came in at about £3-£4 each - and you need one on each LED unit.

A flasher relay is about £15-£20, and only involves the soldering of 2 wires, so easier and less messy, and produces less heat.

Both methods work, you just choose the one that works best for you.

David

Another Pre-Note: I don't have LED indicators and am not looking at fitting them. I'm just interested in the electronics side of things.

I think I know the resistors you're talking about. And now I understand the cost.

What I don't understand (seriously) is why so much power needs to be dissipated by the resistor?

i sorted my bike out by flogging the aftermarket indys on ebay and putting my OE one back on

[fizzwheel]

Originally Posted by kwak zzr

i sorted my bike out by flogging the aftermarket indys on ebay and putting my OE one back on

I bought mini indicators with bulbs in, almost as easy but not quite

[embee]

Originally Posted by 2mths

What I don't understand (seriously) is why so much power needs to be dissipated by the resistor?

In very simple terms, normal indicator lamps are around 21W nominal rating, which on (again nominal) 12V means a current draw of 21/12= 1.75Amps per lamp, so 3.5A total when two lamps are lit.

On this nominal basis each lamp works like a resistor of R=V/I or about 6.8 Ohms. Note that if you measure the resistance of a lamp filament when cold it will be a lot less than 6.8 Ohms, the resistance increases as the filament heats up.

An LED takes minimal current (and therefore power).

Flasher relays are designed intentionally so that if the current draw isn't what it should be, then it will flash at a fast rate to let you know something is wrong (a lamp has failed).

With LEDs on a standard relay you need to provide the extra load, so an extra 6.8 Ohm resistor (which happens to be a standard value, often termed 6_R_8 at each lamp position will do it.

Remember that each lamp was rated at 21Watts, so you're looking at that sort of heat dissipation when they are powered. But of course the lamps are only on about half the time, so the average power is around 10W. This will load 10W rated resistors pretty heavily but they'll probably survive. 25W might be a better choice if the oncost isn't too much.

The alternative is a relay intended for LEDs without the 3.5Amp expected current feature.

Call me old fashioned , but incandescant indicator blubs generate light other road users can see! From a 'be seen' POV, I don't go a bundle on LED indies. And another thing , VAG seem to be fitting rear light clusters where the indicator is toally surrounded by stop/tail lights! The red light swamps the indicator light. Maybe it's my eyes...