LED Headlight for Motorcycle

[boyrekta]

Hi Guys,

I saw a diagram of a LED Headlight for a Motorcycle. So I tried following it's instructions.

I've used these:

72 pcs 5mm LEDs
120 ohms 1/2 watt 12 pcs

also created a rectifier to convert the AC to DC:
50v 100uF Cap
4pcs IN4007 diodes

so here is the diagram: ( sorry I just did it in mspaint )





The lights are so bright and I tested them on standby for 2-3 minutes.

The problem is the resistors heats up that you can't touch them. I'm worried if I use my bike that these resistors might burn.

Can you please tell me what resistor should I use or what are other options I can do? Thanks!

[smeezekitty]

Re: LED Headlight for Motorcycle

What kind of LEDs?

Measure the voltage drop across the resistor.
I would also measure the current going to each string to make
sure it is within the LED's spec (although you can calculate this from
the voltage drop)

[SteveNielsen]

Re: LED Headlight for Motorcycle

"I saw a diagram of a LED Headlight for a Motorcycle. So I tried following it's instructions."

It might help if we coud see that diagram and instructions.

[boyrekta]

Re: LED Headlight for Motorcycle

What kind of LEDs?

Measure the voltage drop across the resistor.
I would also measure the current going to each string to make
sure it is within the LED's spec (although you can calculate this from
the voltage drop)

hi thanks for the reply!

they are 3v to 3.3v LEDs
drop is 4.2v
unfortunately I don't have a tool to measure the current, my tester is crappy

[boyrekta]

Re: LED Headlight for Motorcycle

"I saw a diagram of a LED Headlight for a Motorcycle. So I tried following it's instructions."


It might help if we coud see that diagram and instructions.

Thanks for the reply!
here is the original diagram, i did not include the 3 big LEDs though, they are not available from our stores here

[boyrekta]

Re: LED Headlight for Motorcycle

OMG im sorry guys I had the LEDs in parallel.......

I'll give you guys an update after I put them in series...im so emabrrassed

these LEDs came from flashlights and I didn't bother removing them from their mini PCB so I assumed they're in series.

sorry.. just a noob in electronics

[eccerr0r]

Re: LED Headlight for Motorcycle

What's with the bridge rectifiers? Automotive/Motorcycle electrical systems should be DC so they can recharge the onboard battery, and except if you're worried about plugging in backwards and having to disconnect and reconnect in the right way (or there is no battery system), the bridge shouldn't be necessary.

I noticed you had 9 LEDs in series, and this 9 corresponds to the Harbor Freight Tools 'free' flashlight offer... Yes these are hooked up in series and no wonder why the 120 ohm resistor was burning up as it had to dissipate about 3/4 W per on a 12V system. You should use at least a 1W or better a 2W unit.

Hooking up these things in parallel like in the HFT flashlight isn't recommended of course but it may be the cheapest way to light the LEDs. You probably could hook up three of these 9-LED clusters in series for a 12V battery and reduce the resistor resistance down to 10 ohms or so... Here a 1/2 W unit would be sufficient for 27 LEDs...

[boyrekta]

Re: LED Headlight for Motorcycle

What's with the bridge rectifiers? Automotive/Motorcycle electrical systems should be DC so they can recharge the onboard battery, and except if you're worried about plugging in backwards and having to disconnect and reconnect in the right way (or there is no battery system), the bridge shouldn't be necessary.

I noticed you had 9 LEDs in series, and this 9 corresponds to the Harbor Freight Tools 'free' flashlight offer... Yes these are hooked up in series and no wonder why the 120 ohm resistor was burning up as it had to dissipate about 3/4 W per on a 12V system. You should use at least a 1W or better a 2W unit.

Hooking up these things in parallel like in the HFT flashlight isn't recommended of course but it may be the cheapest way to light the LEDs. You probably could hook up three of these 9-LED clusters in series for a 12V battery and reduce the resistor resistance down to 10 ohms or so... Here a 1/2 W unit would be sufficient for 27 LEDs...

hi thanks for your reply, I was told that the headlight supply of the motorcycle has AC and that is the reason why there is a rectifier so that it will be converted to DC, ( it does light up though ). But I will try to series it first and use the same resistors, maybe I'll copy the same 3 LEDs in 1 series with a 120 ohms 1/2 watt. I'll do it when I arrive home ( still at work )

[boyrekta]

Re: LED Headlight for Motorcycle

hey guys I did this and the resistors are still hot but not as hot as before. Still thinking they might burn when I give it a long ride. Any suggestions?

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[SteveNielsen]

Re: LED Headlight for Motorcycle

The orig schem does not specify what the R values are. Where dd you come up with 120 ohms?

[boyrekta]

Re: LED Headlight for Motorcycle

The orig schem does not specify what the R values are. Where dd you come up with 120 ohms?

hi,

here is the site where I tried to copy it.

http://www.instructables.com/id/DIY-...ens-Headlight/

I just used less LEDs

[SteveNielsen]

Re: LED Headlight for Motorcycle

hi,

here is the site where I tried to copy it.

http://www.instructables.com/id/DIY-...ens-Headlight/

I just used less LEDs

That explains it. You changed the circuit, eliminating some LEDs. That increased current flow throught the circuit, overheating the resistors. You need to increase the value of the series resistors to compensate but I'm not doing the math.

[eccerr0r]

Re: LED Headlight for Motorcycle

It would also be interesting: what motorcycle. Though in the thread may hint at it being AC I am not convinced unless that motorcycle does not have battery start. You'll then also need to measure voltage, is it really generating around 20 volts ? What was the spec of the original bulb? Does the alternator have a regulator on it? You may need to incorporate a regulator as for the same amount of light, the LEDs will use less power (if designed properly) and the voltage may shoot up.

[boyrekta]

Re: LED Headlight for Motorcycle

That explains it. You changed the circuit, eliminating some LEDs. That increased current flow throught the circuit, overheating the resistors. You need to increase the value of the series resistors to compensate but I'm not doing the math.

hmmm maybe ill just copy the exact diagram then...

thanks!

[boyrekta]

Re: LED Headlight for Motorcycle

It would also be interesting: what motorcycle. Though in the thread may hint at it being AC I am not convinced unless that motorcycle does not have battery start. You'll then also need to measure voltage, is it really generating around 20 volts ? What was the spec of the original bulb? Does the alternator have a regulator on it? You may need to incorporate a regulator as for the same amount of light, the LEDs will use less power (if designed properly) and the voltage may shoot up.

My MC is a Yamaha Mio 110cc. When I tested the headlight pins while engine is on, it reads 18-24v when I rev it.

[kc8adu]

Re: LED Headlight for Motorcycle

dont waste your time with 5mm leds.
since they came from flashlights in paralell this means they are crap.
only cheap n nasty flashlights are built like that.
the ones i have built use lumileds altilons.
note to be safe and road legal your modded headlight must have the proper cut off.
otherwise you just blind oncoming drivers and your eyes never adjust right due to the bright spill near you.

[boyrekta]

Re: LED Headlight for Motorcycle

hey guys I used a LED resistor calculator which a searched in google and ended up on this circuit, resistors aren't heating up ( although warm ).



Thanks for all your replies!!

[boyrekta]

Re: LED Headlight for Motorcycle

dont waste your time with 5mm leds.
since they came from flashlights in paralell this means they are crap.
only cheap n nasty flashlights are built like that.
the ones i have built use lumileds altilons.
note to be safe and road legal your modded headlight must have the proper cut off.
otherwise you just blind oncoming drivers and your eyes never adjust right due to the bright spill near you.

I've adjusted the headlight so it won't affect others

So far these LEDs are ok for now.