Print

Please login or register.
1 Hour 1 Day 1 Week 1 Month Forever
Login with username, password and session length

[laramie LC4]

trying to replace my signals with some smaller, LED's.

running into issues with the flasher load and getting the lights to work. currently i cant even get them to light, let alone worry about flashing to quick. i had been going off the advice and a crude schematic drawn by someone at another forum but just cant seem to get it to work.

i know i need to add diodes to the circuit, i just don't know where i guess. any input on location and voltage of the diode would be greatly appreciated.

please forgive my crude schematic, it's not pretty but it is accurate.

thanks,

laramie 

[Doug S]

I doubt you need to add diodes to the circuit to get it to work. LEDs are different than incandescent light bulbs; they will only flow current in one direction. My first guess would be that you've got them wired up backwards. Check for polarity markings, or just try reversing them.

The usual problem with LED lights is that they don't draw enough current to get the flasher to turn off, so instead of blinking, they'll just stay on continuously. Some people will add resistors in parallel with the lights so they'll draw enough current to make the flasher work correctly, but that seems ridiculous to me -- one of the nice things about LED lights is that they draw less current, which conserves power, which is especially nice on an EV (though in reality, the amount of power saved is extremely small overall). A far better solution is to simply replace the flasher with a more modern one which doesn't need high current to operate correctly. There are some vehicles which actually measure the current draw to determine when a light bulb goes out, in which case it makes some sense to use an external resistor, but the Zeros don't.

[MorbidBBQ]

You don`t need a diode, because thats what an LED is.  Light Emitting Diode.

Check the polarity, it might be backwards.

People add power resistors to make sure the flash rate is normal.  LEDs use so much less power, the flasher unit usually thinks its got a light out.

This all depends on the LEDs you're replacing it with.

My zero works fine when i replaced my rear signals with an LED light strip and an LED flush mount cluster.  No need for a power resistor (yet).

Ive used component high power LEDs in the past to make custom lights, and these needed power resistors.

Can you post a link to the products you are using?

[Fred]

You also need a current limiting resistor in series with an LED to limit the current that will flow through it. They're not like a bulb. LEDs will typically have a voltage drop off 2V or so. Put less than that across it and it won't light. Put more and the LED will probably draw enough current to self destruct. You need to know the forward voltage of your LEDs before you can start calculating the series resistor.

The resistor in parallel is something completely different and is just to waste power so the flasher thinks you still have a bulb.

[MorbidBBQ]

The current limiting resistor depends if hes using bare components or a prefabricated LED unit.

Theres an android app, `everycircuit` that lets you simulate a circuit.  I even contacted the programmer a few years ago to add in a few high power LED options.

As far as current limiting resistors, you want to limit it to about 75% of max.

If you have a 5w LED (star heatsink component, they go for ~$5/each), its probably rated to 2000mA, so use a resistor to limit the current to ~1800mA.

This all depends how many components you have in the series or parallel.

The free version of every circuit should work fine.  The full version is $10, and gives a few bells and whistles, nothing that you would need.

[Doug S]

You also need a current limiting resistor in series with an LED to limit the current that will flow through it. They're not like a bulb. LEDs will typically have a voltage drop off 2V or so. Put less than that across it and it won't light. Put more and the LED will probably draw enough current to self destruct. You need to know the forward voltage of your LEDs before you can start calculating the series resistor.

The resistor in parallel is something completely different and is just to waste power so the flasher thinks you still have a bulb.

Fred, any LED-based turn signal has current limiting built in. At least a series resistor, but these days it's almost always smart circuitry that keeps the light intensity constant across a wide range of voltages. They almost always use several LEDs, too.

[Fred]

Ah - OK. I didn't realise Laramie was taking about premade 12v units. In which case, ignore the series resistor bit. Just make sure they're the right way round and use a resistor in parallel to draw more current.

5W/2000mA sounds way too bright for a turn signal. That's more of a floodlight!

[MorbidBBQ]

Ah - OK. I didn't realise Laramie was taking about premade 12v units. In which case, ignore the series resistor bit. Just make sure they're the right way round and use a resistor in parallel to draw more current.

5W/2000mA sounds way too bright for a turn signal. That's more of a floodlight!

I looked it up because I was curious.
www.superbrightleds.com sells a 5w vollong LED with continuous forward current of 800mA (7v).

The peak forward current is 2000mA.

I did burn a few out before using a current limiting resistor.

After I built the diffuser for it, it was good for a turn signal.

[Doug S]

Ah - OK. I didn't realise Laramie was taking about premade 12v units.

I hope he is! If not, he may have already burned out the LEDs and/or blown a fuse. A single LED element running on 12V without a current limiter won't last very long...milliseconds at best.

5W/2000mA sounds way too bright for a turn signal. That's more of a floodlight!

It's bright but not too bad for a turn signal. A lot brighter than a standard turn signal, that's for sure. My pocket flashlight uses a Cree 5W LED.

[PL3]

These work great, 5 min install...

http://www.weisertechnik.com/shop/ultrabrights-extreme-motorcycle-led-turn-signal-indicator-upgrades

[mrwilsn]

You also need a current limiting resistor in series with an LED to limit the current that will flow through it. They're not like a bulb. LEDs will typically have a voltage drop off 2V or so. Put less than that across it and it won't light. Put more and the LED will probably draw enough current to self destruct. You need to know the forward voltage of your LEDs before you can start calculating the series resistor.

The resistor in parallel is something completely different and is just to waste power so the flasher thinks you still have a bulb.

A resistor in series will not reduce the amount of current flowing through the LED...the series resistor drops the voltage the LED sees.  The parallel resistor reduces current going to the LED.

Sent from my SAMSUNG-SM-G930A using Tapatalk

[Fred]

Sorry mrwilsn, but that's completely wrong. (I was talking about a single LED rather than an LED based indicator unit, if that's added to the confusion.)

[Doug S]

A resistor in series will not reduce the amount of current flowing through the LED...the series resistor drops the voltage the LED sees.

It does both things -- they're equivalent statements. If you apply 12V to an LED, it will draw massive current, until it burns out. The series resistor, by limiting the current that can flow, drops the voltage for the LED. That's what resistors do.

The parallel resistor reduces current going to the LED.

Uh, no. The parallel resistor has no effect on the current through the LED/series resistor combo. It just increases the current through the flasher, so the flasher will feel "normal" current and will operate normally.

[laramie LC4]

ok,

it's not polarity, just for giggles i reversed everything and still nothing.

i know the lights work, i can test them with 9v battery and they illuminate, it also tells me the polarity was correct the first time.

the LED's i am using are THESE. they do not mention anything about requiring additional resistors but who knows.

if i take 1 of the led's out of the loop (front), and use the stock bulb, everything works, just flashes quickly. so, once again wiring is correct, i just need to solves the resistance and location questions.

what resistor should i use, and where is best to tie in?

thanks,

laramie 

[pacificcricket]

How are you connecting the resistors (parallel vs series), and what resistance value do you have on them ? If you have a multimeter, you should measure the resistance of your flashers, or open them up altogether and see how those multiple LEDs are wired inside - that should help with figuring out the proper connectivity.

I am not an EE, but I believe like any semiconductor, LEDs have a threshold where if the current is too low, they won't light up even if the polarity is correct. So if you add a resistor in series that has too much resistance, the lights won't work.