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High Beam PWM to regular Voltage Ideas

4K views 2 replies 1 participant last post by  paulmackie 
#1 ·
Has anybody any ideas on how to use the headlight high beam DRL PWM voltage to power a relay or LED lights.

Some ideas:
470uf capacitor across the coils of the relays; supposed to stop relay chattering.

Converting PWM to voltage
Arduino?s AnalogWrite ? Converting PWM to a Voltage

Using a Solid State relay.


I found the Truck Lite PWM adapter harness 96830; do you think that would work to power my LED lights and HID projector high beam solenoids?

Has anybody tried any of these ideas and had them work?

I have a post in electrical, but no replies.
 
#2 · (Edited)
I spoke with a dealer here in Canada and they use the Putco anti flicker device on Jeeps, but he said the WPM output is 9 to 12 volts and burns out the device if the headlight and LED circuitry is not designed for the device. He also said that it is illegal to run LEDs off the PWM voltage as you have to have the high beam.

I checked the Traffic Safety Act here in Canada and it basically says this:
Headlamps

Location

(2) A headlamp must be mounted so that the centre of the headlamp is not more than 1.4 metres and not less than 560 millimetres above ground level when the motor vehicle is not loaded.

(4) The light from a headlamp must be white, and the lens and bulb of the headlamp must be made of clear, untinted glazing.
This means that most "ricer bulbs" and yellow headlight bulbs are ILLEGAL

(5) A person shall not attach or apply anything that colours the light from a headlamp to the headlamp, part of the headlamp or a bulb in the headlamps.

High and low beams

(2) A headlamp must have a low beam that can reveal a person or another vehicle that is at least 30 metres ahead.

(3) A headlamp must have a high beam

(b) that does not shine in the eyes of an approaching driver.

Daytime running lamps

12 The daytime running lamps on a motor vehicle may emit amber or white light.

It is my understanding that:
you are not allowed to have forward facing red lights; red devil eyes will probably be illegal.
you can only have two fog lamps, which can be used as DRLs.
and a maximum of four white lights facing forward.

So at this point I need to change the PWM to a fixed voltage and run that through a relay coil and switch 12 volts to my LEDS. I should be able to maintain my High beams, but only when my low beams are on, usually at night.

I have some research:
Headlights on with engine running: 78% duty cycle; 90Hz

I found someone that used 470uf capacitors across the coils of the relays.

Depending on the relay's cutoff voltage you may have a very tiny gap with a 470uF, the relay may not even respond fast enough to it.

If the frequency is correct you have 1s/90 = 11ms for each pulse on and off.
With a 20% off time you have a window of about 2.22ms.
Using the current draw of your relay and assuming 12V, you can divide the voltage by current to get resistance.
The simplified Discharge formula for a capacitor is Resistance * Capacitance. 470uF is 0.000470. The time will be the result in seconds to discharge to 37% of the original voltage.

The same information could be used for those wanting to use LED lights direct from the factory harness, just consider a bit more current draw from the light when getting parts.

The Morimoto Capacitor Link utilizes a 10,000μF electrolytic capacitor, 14 gauge wiring.

Has anyone resolved using the PWM voltage to run a relay or LEDs and still maintained high beam use?

I am using Morimoto X DRL 5 LEDswith power draw 417mA and possibly an LED strip in both headlights, not sure what draw is.

I would need the information to fit into the calculator ((Sample)RC Low-pass Filter Design for PWM - Result -) to get a resistance and capacitor value

fPWM=Hz
Duty Step 0%→[%]
PWM signal voltage:
VL = [V] VH = [V]
R and C values of filter | Cut-off frequency
Cut-off frequency fc = [Hz]
R and C values
R=Ω C=F
p:pico, n:nano, u:micro, k:kilo, M:mega

or if someone can figure it out or best guess from the research above.


Thanks for any replies.
 
#3 ·
I have not tested this circuit yet, has anybody any comments?



Here in Canada,the DRLs come on when the car is put in drive, with HIDs this means I have low beam HIDs with the projector solenoid being energized, giving high beam also. This situation is resolved by turning on the low beams and a high beam that works off the stalk switch.

I want to have LEDs on during the day when the car is put in drive, with no HID lights; and at night low beams, with no LEDs and a high beam option.

From what I have learned another way is to fit a capacitor with a zenner diode in the high beam circuit.
 
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