Electronics Help?

[Bailes1992]

I'd like to get inner door handle lights sorted on my Focus, great little feature on the MK2 Mondie.

Now my plan is to have them on bright when the interior light is on and on very dim when the ignitions on so they're only slightly illuminated.

This is the idea I drew up over lunchtime today...


Now in my drawing I have the relays switching the negative with a permenant live going to the LED's. Should I switch the Positive insetad? That way I could pick up the negative in the door instead of running two cables.

Also looking at 4v 30mA Super bright green LED's, how will I know what resistors to use? Or should I just buy a load and experiment?
I know how to work out the figures on resistors, not a clue how to work out what resistor to use

Also whats the best way of mounting all this? Looking to have a little control box with some electronics in it, but not a clue how to mount the relays, how to mount PCB's etc?

Cheers, Bailes.

[waue1978]

Not got much idea with electronics to be honest, but wouldn't it be just a lot easier to transplant the bits from a Mondy? Can be awkward to get hold of the bits as they were only in Mk2 Ghias upwards from 1996-1998 (although I have heard that the lesser models were prewired).

[Bailes1992]

Not got much idea with electronics to be honest, but wouldn't it be just a lot easier to transplant the bits from a Mondy? Can be awkward to get hold of the bits as they were only in Mk2 Ghias upwards from 1996-1998 (although I have heard that the lesser models were prewired).

The mondeo just has the lights on when the ignition is on, which I think is pointless.
When you switch the igntion off the lights in the car illuminate, so if I can get the LED's running off the same circuit as that AND with the ignition on aswell (but dimly) I think it would be a great partypiece

[lozz]

on the mondeo, you either wired into the footwell lights- they all had the wiring for them,
or, just patched into the lum side of the electric window switches,

fords dont spit there dummys out like french stuff,
if you want to see how there wired up on the Mondeys go on the Madmoles site plenty of how too guides onthere iirc,

[FarmerPug]

I would switch the positive, the negative is easier to wire up to the earth.

As for the LED's coping with 12v some are rated for 12v, the resistor will reduce the current and that affects the voltage which will affect the brightness.

here is a colour chart for resistors:

there is probably also apps available for finding the colour, here is an online calculator:
http://www.hobby-hour.com/electronics/r ... ulator.php

There is a bit of maths involved with selecting the right resistor, this site seems to explain it nicely
http://www.kpsec.freeuk.com/components/led.htm

R=(Vs-Vl)/I
R-resistor value, Vs-Supply voltage from car, Vl-voltage of the LED check with the maker normally between 2 and 4v, I-the current required by the LED in amps, not miliamps

so if for the purpose of examples you were to purchase these led's:
http://www.ebay.co.uk/itm/100-pcs-5mm-R ... 552wt_1143

then:
R=(12v-3.4v)/0.02 i think the current for the led is 20mA and thats 0.02Amps
R= 430 ohms (yellow, orange, brown, gold coloured resistor)

Although some ebay component sellers seem to include the right resistors in the sale.

[lozz]

if the wiring on the focus is anything like the wiring on a mondeo you shouidnt need any resistors,
iwired up floor lights doorlights etc on the mondey never had any probs,

anything french then the bsi is in the way, fecks everything up involving the need to be some electrical wizard,

heres some old skool guide for the Mondey:

http://www.mirez.co.uk/DoorLight.htm

[FarmerPug]

the resistors would be needed to protect the leds from the 12v, i think even with resistors
you would upset the bsi in the 406 although i dont think its easy to mount an led into a 406 door handle

[lozz]

Depends which leds you use:
ibought some from halfords the otherweek, no resistor on them ieven wired them direct to the car battery to test,and they didnt blow,
they use very little power,


The citreon seems to be alot more sensitive than the 406 so ifound out,

[steve_earwig]

Depends which leds you use:
ibought some from halfords the otherweek, no resistor on them ieven wired them direct to the car battery to test,and they didnt blow,
they use very little power

The LED route you need to wire yourself up an LED and resistor combination and then make another 3 for the other doors! Typical resistance value is 340? (orange-yellow-brown) If you are not happy with electronics then I suggest you buy 12volt LED’s – these have the resistor already in the housing and are more strait forward.

[steve_earwig]

If it helps:


Billy Brown ran out yelling "gor blimey, Violet's gone white!"

=or=

Black bastards rape our young girls but virgins go without

[FarmerPug]

that sounds a lot different than the rhyme we used about beetles.
although i remember mixing it up in a class test and using richard of york gave battle in vein which doesnt help with resistors

if you can try and download a circuit program you can build it on the computer and test it out livewire is good but it only seems to be available in maplin