Want to run DC 12V LED lights instant of 12v AC Halogen bulb

Thread Starter

tanvir21

Joined Nov 17, 2020
5
In my motorcycle I want to run DC 12V LED lights cut off Present AC 12V 35w halogen light. When I install Bridge rectifier and 4700uf capacitor output voltage 7 or 8 and LED Lights is flipping. When I accelerate my motorbike then LED light is OK. How to reduce problem. Please help.
 

bassbindevil

Joined Jan 23, 2014
150
Try a much bigger capacitor. Or, obtain LED lights that can run from a wider voltage range.

Or... make a voltage doubler circuit to convert the 12V to 24V; the cap will store 4 times as much energy, and the voltage will have to fall much more before the lights dim. (I had a look on ebay, and found a cheap "48W 16LED Mini Car Work Light Flood Truck Fog 12V 24V" that operates from 10V to 30V.) (there's also SMD LED bulb replacements that claim to be compatible with 12 to 24V) And, for what it's worth, a rectangular LED headlamp that I just opened up has 50V caps inside, but the switching driver chips are unmarked. The PC board markings point to a CM-5045 from Chiming, which does claim to work from 9V to 32V.

The MR11 and MR16 style LED lamps that are made for replacing halogen lamps in track lights and desk lamps are designed for 12V AC, but in my tests the ones with a single LED worked perfectly well down to below 6 volts. I tried one as a bike headlight, but didn't like the beam pattern the TIR optics produce. They could be adapted as tail lights or running lights, by replacing the white LED with a 20 mm 1W red or amber LED. The kind with a smooth machined aluminum housing should be easy to make waterproof. (The drivers in these LED lamps have a full-wave rectifier to get DC, then a constant-current switching chip that drives the LED at 300 mA (for a 1W lamp))
 
Last edited:

Tonyr1084

Joined Sep 24, 2015
5,802
output voltage 7 or 8 and LED Lights is flipping.
I'm assuming you mean "Flickering" when the engine is at idle. Isn't your bike running with a 12 volt battery? When the engine idles the battery isn't charging but the battery, assuming it's in good condition, should keep the light lit without flickering. Unless your bike doesn't have a battery.

Even still, my snow blower has a headlamp that is powered from a magneto. When the engine idles the bulb glows dimmer than when at full speed, but that's an incandescent bulb. They don't flicker as much or are as sensitive as an LED.

There's something up with your electrical system. Unless you're running something like a Briggs & Scrapiron motor with a magneto for powering lights. No battery, no storage capabilities at all. In that case, add a small 12V battery. Just make sure you can turn the light off when not riding.
 

Thread Starter

tanvir21

Joined Nov 17, 2020
5
T
Try a much bigger capacitor. Or, obtain LED lights that can run from a wider voltage range.

Or... make a voltage doubler circuit to convert the 12V to 24V; the cap will store 4 times as much energy, and the voltage will have to fall much more before the lights dim. (I had a look on ebay, and found a cheap "48W 16LED Mini Car Work Light Flood Truck Fog 12V 24V" that operates from 10V to 30V.) (there's also SMD LED bulb replacements that claim to be compatible with 12 to 24V) And, for what it's worth, a rectangular LED headlamp that I just opened up has 50V caps inside, but the switching driver chips are unmarked. The PC board markings point to a CM-5045 from Chiming, which does claim to work from 9V to 32V.

The MR11 and MR16 style LED lamps that are made for replacing halogen lamps in track lights and desk lamps are designed for 12V AC, but in my tests the ones with a single LED worked perfectly well down to below 6 volts. I tried one as a bike headlight, but didn't like the beam pattern the TIR optics produce. They could be adapted as tail lights or running lights, by replacing the white LED with a 20 mm 1W red or amber LED. The kind with a smooth machined aluminum housing should be easy to make waterproof. (The drivers in these LED lamps have a full-wave rectifier to get DC, then a constant-current switching chip that drives the LED at 300 mA (for a 1W lamp))
Thanks.
 

Dodgydave

Joined Jun 22, 2012
9,914
In my motorcycle I want to run DC 12V LED lights cut off Present AC 12V 35w halogen light. When I install Bridge rectifier and 4700uf capacitor output voltage 7 or 8 and LED Lights is flipping. When I accelerate my motorbike then LED light is OK. How to reduce problem. Please help.
What is the make/model of motorcycle, does it not have a battery for the lights ,, if not then you need a bigger value capacitor for smoothing.
 

Dodgydave

Joined Jun 22, 2012
9,914
Yes you use any regulating device you need ,but we need to know what voltage is outputted from the Alternator , at high and low revs.
 

Alec_t

Joined Sep 17, 2013
11,972
Is your 12V AC generated by a magneto or an alternator? Magnetos often have one end of the coil permanently grounded, which rules out using a bridge rectifier for full-wave rectificaton.
 
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