Lighting from Rayleigh Velo XC Display

[NeilP]

Just acquired a Ralleigh Velo XC ( now working) but with damagrd display case.

I see the display unit has a 'lights on/off' button and a Red LED indicator to indicate on/off.

But this bike not fitted with any lights

Anyone have any info or pics of the lighting circuit or how the display unit drives a light.

Does the display drive /feed the lamp direct or did it run through some electronic relay /switching /controller ?

Pictured is my 'display' with blue tape, and an internet photo of what I think it should be.

Thanks

 

[Deleted member 4366]

The display is powered by a wire with battery voltage. There's a small mosfet on the display's pcb that joins that battery wire to a separate wire in the didplay's harness when you press the lights switch so that wire gets battery voltage too. You can only take as much power for the lights as the mosfet and thin wire can handle.

These analogue displays usually have cpus, so the the switching is done by software. The switch is just a digital input to the cpu and the cpu gives a digital output to a transistor, which switches on the mosfet's gate.

Some of the digital displays don't do the switching. Instead, the same circuit is in the controller, and the display sends an instruction to the cpu down the comms wires for it to switch on the mosfet.

 

[NeilP]

thanks
Was thinking if I find the 'output wire' from the display unit it might be enough to run a small LED from lamp.

If not I may have to rig up an external MOSFET to it to run the current for the light.

Thanks

Oh..do you happen to know which PCB trace is the output? I see 5 or 6 unpopulated holes for wires

 

[Deleted member 4366]

As you have the top off, you should be able to check with a meter which one goes on and off when you press the button.

 

[NeilP]

Umm yes, of course

I'd hope 250mA would be reasonable. So @ 36volt.. 9W