LED indicator problem

[fence post]

so i suggest you check wether you are putting ac or dc thru the indicators,as this is relevant to the behaviour of the LED.[/QUOTE]

how do i check this? with a multimeter?
i borrowed a multimetre thing from a friend but am not too sure how to use it but im sure he show me how.

[fence post]

http://www.customled.com/products/fl...sher_relay.htm

this looks useful.

[glegge]

does this bike have a battery? if so the electrical system *should* (famous last words) be DC, if not the headlight etc may well run of AC direct from some coil under the flywheel..

in either case, if you unplug the flasher unit, and put a piece of wire in it's place, all things being equal and assuming it's DC etc, the leds should come on full strength and stay on (the flasher is just an interupter). (use an old piece of fuse wire just to be safe if you like)

but yeah, pull an LED bulb, and put the meter across the terminals of the socket, put the meter on DC and put the indicators on, see if what the meter reads (one with a needle would be best - rather than a digital meter). if the needle tries to go off the scale behind zero - reverse the leads, if it still does it - or swings from right to left (trying to pass zero to the left each time) then it's an AC system. all is not lost but it gets trickier from here.

[davereid]

hi,
ive just put new LED indicators on my bike and they dont seem to want to flash. they turn on when selected but dont flash.

OK, so everything worked OK until you put the LEDS in... so we know..

- The switch and wiring is OK
- The LEDS go so they are wired correctly
- They just dont flash.

This is because a standard flasher unit comprises a switch, constructed with two pieces of dissimilar metals riveted together.

When current is carried by the switch, it gets hot. But the metals have been chosen to have different rates of thermal expansion, so they curve, opening the contact. This breaks the current, turning the indicator off, allowing the switch to cool, and causing the cycle to restart.

Your problem is the flasher relay.

[avgas]

Funny reading this thread.
David Reid is right - and I am surprised no one sorted it quicker. Would be surprised if the supply was unregulated AC - but I suppose it is a bit trail bike - but this would mean it doesn't have a battery.

See how much a flasher unit is - if its too expensive a grass-roots solution could be to build one of these as I imagine the LED indicators would be low enough current.

R4 would be your indicator and current limiting resistance. Old school and works good.

[Laava]

I put an HD12 into my v strom and it flashes perfectly. I put this particular unit into my GPZ and it flashed perfectly. I went to supercheeseauto and bought another HD12 and put in the gpz and it pulses rather than flashes correctly as the other one does. Both bikes have LED's only. I don't know if they are just cheap and cheerful or weither they vary from one to the other. As an aside, the only one they had was in an already opened packet! Should have gone somewhere else eh! So Fence post, take it back and change it if you can?

[gammaguy]

Funny reading this thread.
David Reid is right - and I am surprised no one sorted it quicker. Would be surprised if the supply was unregulated AC - but I suppose it is a bit trail bike - but this would mean it doesn't have a battery.

not so

many bikes have an AC ignition system and a DC charging system(ie rectified and regulated)which charges a battery.This all runs from the same power source i.e the AC generator(usually called an alternator.)there are no hard and fast rules for this either,the best way is to refer to the manual if possible.

It just means that the owner of this one needs to find out which parts of his system goes to which components.

[Pixie]

OK, so everything worked OK until you put the LEDS in... so we know..

- The switch and wiring is OK
- The LEDS go so they are wired correctly
- They just dont flash.

This is because a standard flasher unit comprises a switch, constructed with two pieces of dissimilar metals riveted together.

When current is carried by the switch, it gets hot. But the metals have been chosen to have different rates of thermal expansion, so they curve, opening the contact. This breaks the current, turning the indicator off, allowing the switch to cool, and causing the cycle to restart.

Your problem is the flasher relay.

Most flasher relays are capacitive not bimetalic

[davereid]

Most flasher relays are capacitive not bimetalic

Nah.

Most are bimetalic, only a few are electronic and use a capacitor for timing.

Late model bikes may have electronic flashers, particularly those with self-cancelling features, but most bikes are just the humble bit of hot metal.

[bsasuper]

ebay has electronic flashers for leds, you can even adjust the flash rate, but it worked fine out of the box

[fence post]

ebay has electronic flashers for leds, you can even adjust the flash rate, but it worked fine out of the box

yea i might give that a go, were doing well enough against the us$ at the moment

[Juzz976]

Led's consume D.C to produce light and are generally meant to be operated on D.C. but they will operate on A.C. However with A.C. of equal voltage the value of the current limiting resistor will have to be adjusted to achieve the same brightness. This is because with A.C. the led will only be lit when the current flow is in the proper direction. When the current flow reverses the led blocks current flow and remains unlit. Thus A.C. applied to an led will cause it to blink on and off even though at high enough frequencies it will appear to be lit continuously. To make a blinking led appear as bright as constantly lit led the current limiting resistor's value is lowered to allow more current flow causing the led to be brighter when lit. This causes a greater average light output and thus a brighter appearing led. This trick of the eye is a phenomenon known as persistence of vision. This is also the reason the led appears to be continuously lit when actually blinking.

so i suggest you check wether you are putting ac or dc thru the indicators,as this is relevant to the behaviour of the LED.

When comparing DC voltages to sinusodial AC waveforms you need to factor that the peak voltage of the AC waveform is √2 times the RMS value. thus comparing 12VDC to 12VAC your peak voltage is going to be 16.97V which will give a higher peak current and reducing the series resistance will do as much, you may end up burning your LED's.
We use RMS values to compare the heating effect of Current where Impedance is = to Resistance. Also you could use 2 LED's oppositely polarised so you get illumination every half cycle.

[davereid]

When comparing DC voltages to sinusodial AC waveforms you need to factor that the peak voltage of the AC waveform is √2 times the RMS value. thus comparing 12VDC to 12VAC your peak voltage is going to be 16.97V which will give a higher peak current and reducing the series resistance will do as much, you may end up burning your LED's.
We use RMS values to compare the heating effect of Current where Impedance is = to Resistance. Also you could use 2 LED's oppositely polarised so you get illumination every half cycle.

Your maths is spot on, but it's internal heat that causes LED failure, so for practical purposes the difference can be ignored as (as you stated) 12V DC has exactly the same heating effect as 12v AC (rms).

In fact you can safely overrate an LED many times if you wish, as long as you do not allow it to get hot.

We commonly do this in devices like I.R. remote controls, where the peak current we push through the LED may be 10-40x its rated current, but we only do it for a few fractions of a second.

LEDs are not designed to be reverse biased, ideally they should be operated via a DC or rectified AC supply.

[Juzz976]

In fact you can safely overrate an LED many times if you wish, as long as you do not allow it to get hot.

We commonly do this in devices like I.R. remote controls, where the peak current we push through the LED may be 10-40x its rated current, but we only do it for a few fractions of a second.

Ah yes, stuck in work mode where we don't overrate anything. Don't see the point I would imagine the LED has a nominal current for acheiving its intensity, besides they mostlikey have a max instantaneous rating thats higher than their continuous.

If it were something I was looking at designing then apart from the 'not exceeding limits philosophy' I have, I would be slutted if a customer came back with a dead product because I didnt factor that no system is impervious to faults also any parallel capacitance that has its supply dropped at forward peak voltage would drain its charge through the LED and from memory they burn real quick.

Fine for consumer electronics I guess
would I exceed manufacturers recommendations for anything on my bike is what I'd be asking.

LEDs are not designed to be reverse biased, ideally they should be operated via a DC or rectified AC supply.

Did not know that, I thought being a diode they'd cope with reverse bias and why would they have a Max Rev Voltage rating in their datasheets. infact I'm looking at an omron 24VAC relay with LED indication and there is only a series resistor.

I know were only talking about an LED but its an attitude towards electrical equipment that carrys on to people who do not work in the trade. They're the ones who'll apply that theory to something that can cause a fire or shock hazard.

[Wiki Drifter]

If they wont light up at all then I bet they are connected the wrong way around. LEDs are polarised, and only work with the positive to the correct bulb terminal.
Steve

I've recently bought a pair of front LED turn signals and they don't light up at all. After I connect them, the rear signals (filament bulb) will flash fast on one side and flash normally on the other.

These LEDs came with factory socket terminals so the polarity should be correct as there's only one way of connecting them. Could low current draw prevent LEDs from lighting all together??