Car headlight projector for my son

Thread Starter

Nutcase1

Joined Feb 20, 2020
19
Hi I'm new to this site and yes I have very basic knowledge with electronics,

I'm hoping someone here might be able to help me, I'm trying to modify my sons car by installing projector headlights but the problem I'm having is converting the lights from a dual filament (H4) to a single filament (H1)

On the projector is a solenoid switch to control the high and low beam, in the other picture on my loom I have 3 wires brown (earth) white (low beam) blue (high beam), only white or blue has power at any one time.

I know I need a relay but can someone help me by telling or drawing me a diagram to make this work as low beam is ok but on high beam I need the switch to turn on as well
 

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Alec_t

Joined Sep 17, 2013
11,169
Welcome to AAC!
We don't know where in the world you are, but be aware that in most jurisdictions there are strict regulations on vehicle lighting. Check that what you are proposing is legal and is approved by the insurer.
 

Thread Starter

Nutcase1

Joined Feb 20, 2020
19
At the moment it has standard wiring as in if you turn the switch to low beam you get low beam and you get hi if you select hi

My trouble is the standard H4 bulbs has 2 filaments and the new bulb I will be using has only one so the bulb has to handle both low and high beam, but when high beam is selected it also has to trigger a switch to make the projector select the high beam setting

On the picture with the projector the red and blue wires are for the H1 bulb and the other red and black wires are for the solenoid switch to select high beam
 

Delta prime

Joined Nov 15, 2019
258
are you really sure you want to enable low beam with high beam?
Filament lamps have a very substantially higher "inrush current" when cold and relay contacts not rated to deal with this will not last as long.
I would use a two relay setup for this. The relays shall be parallel and one pin or the coil goes to the low beam switch and the one of the other relay to the high beam switch
Using a single pole single throw relay.
Connect one side of coil to ground.
Connect other side of coil to high-beam wire.

LConnect one side of contact to low beam wire.

Connect other side of contact to high beam wire.

Alternative - Connect other side of contact to Battery +ve. This is very slightly less desirable from a safety point of view (always live) but allows slightly less voltage drop as the high beam wiring does not have to handle twice the usual current.
enables the relay when high beam is on.
& 4. connect high and low beam wiring when high beam is on
 

Thread Starter

Nutcase1

Joined Feb 20, 2020
19
Basically what I need is, because I will low have one filaments to do both low and high beam, when low beam is selected I need just the light on but when high is selected I need the same light but with the solenoid switch turned on

Delta prime please can you do a basic draw please as I think I see you what are saying
 

Alec_t

Joined Sep 17, 2013
11,169
How does one filament provide high and low beams? Is there a mechanism to tilt the lamp or the lens? A properly dipped beam needs to deflect both downwards and to the side.
 

Thread Starter

Nutcase1

Joined Feb 20, 2020
19
The original bulb which was a H4 is a dual filament bulb, the projector lens requires a H1 Bulb which is a single filament bulb, the projector has a solenoid switch which flips between high and low Beam so only needing a single filament bulb
 

Thread Starter

Nutcase1

Joined Feb 20, 2020
19
The lens and bulb dont tilt but there is a mechanism which move with the solenoid switch to change the beam pattern
 

MrSoftware

Joined Oct 29, 2013
1,748
It sounds like the new headlights physically change the focus of the lens to switch between low and high beam.

Try drawing your wiring out on paper, and post it here if you can. Don't worry about figuring things out, just draw a picture of the old setup and the wires, and the new setup and the wires, and the wires from the car. It is possible that what you need might be as simple as a diode, but we need to see more details to say for sure.
 

shortbus

Joined Sep 30, 2009
7,623
It looks like Alec guessed correctly, the solenoid moves the bulb socket to change the direction of the beam.
Maybe a diode of a suitable value between the original high and low beam wires would work. That would keep the bulb lit in both high and low plus activate the solenoid.
 

Thread Starter

Nutcase1

Joined Feb 20, 2020
19
Thanks every one I've order a few diodes from Amazon as I dont have any electric hobby shops near me lol, will give it a go and let you know how it goes
 

Delta prime

Joined Nov 15, 2019
258
A diode will also work but will drop some voltage. A Schottky diode drops less than a silicon diode but may still be noticeable (or not).

A relay will work, and is liable to be cheaper than using a diode as automotive relays are a very well developed technology with an immense market.
 

Alec_t

Joined Sep 17, 2013
11,169
Doing a bit of googling I see that diodes are sometimes used in high-low systems, but since you already have an automotive relay I think this is how the wiring should go :-
BiXenonWiring.png
D1 is a back-emf suppressor. The example shown is a 3A Schottky diode, but is a tad OTT. Choice depends on the (unknown) solenoid current. Something in the 1N400x series should be adequate.
 
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