Lilliput buttons light up with car lights on?

**dtran01** · 02-24-2005, 09:38 PM

I did a

on this and didnt find anything...

but does anyone know if there's a way to rig the lights on the lilliput to turn on with your car light? the car is a 12V supply and the leds are probably 3.8 or so, so with a resistor, i could see this being a real possibility.

Alternatively, i woudn't mind the lights to be "always on" instead of "on-during-press".

I dont have the electrical background for insight into this problem. Can anyone help?

**Rundell** · 02-24-2005, 10:21 PM

I remember reading about someone doing this and posted how they did it... can't seem to find it, maybe someone else knows of this post or perhaps I'm dreaming.

Edit: I'm not dreaming here it is that someone talks about it: Lilliput blue lights

**Quattro** · 02-24-2005, 10:29 PM

To keep the Blue LEDs on all the time, connect pin 12 to pin 8.

This information was taken from http://www.tmz.com/wrx/lilliputLCD.html close to the bottom of the page.

**Squid** · 02-24-2005, 10:41 PM

If you throw a relay between the connection from pin 12 to pin 8 (as shown on this site,
you could then trigger the relay when the headlights are on.
This would give you the blue LED's only when the lights are on...

**antimatter** · 02-25-2005, 02:31 PM

What if you wanted them controled by the headlight switch. couldn't you just take a lead from your headlight switch add a resistor to step it down to ~4.5 volts and solder it to one of the pins.

The question is what pin would apply the 4.5 volts to, to make the blue LED's stay on based on the head light switch.

Any EE want to help out here

**dtran01** · 02-25-2005, 06:39 PM

hm, pat (wrx webmaster) seems to live near me.

i think i may pay him a visit.

Thanks for the suggestions guys.

I think antimatter has an interesting suggestion. If we go with the same resisters that are typically used for car led conversions, then could i wire a tiny 471 resister in series to the connection point (pin 8?) from my parking light 12v power?

Or would it be better to do the relay route with the same line as squid suggested?

**Squid** · 02-25-2005, 06:42 PM

Do you mean you want them to dim with the headlight switch or just come on with it?

Cause my solution above will do the latter. You have the 12 volts coming from switch trip
the relay which closes the line between pins 12 and 8 thus turning your blue LED's on.

I feel this is alot safer also, because your not adding grounds or voltage to the lilliput
circuitry which avoids any accidental shorts

As far as dimming goes, that's another whole circuit... LED's don't dim easily..
very small voltage area where the light actually dims some before it just shuts
off. That's where the E.E. steps in and this M.E. steps out

**antimatter** · 02-25-2005, 06:47 PM

Originally Posted by Squid

Do you mean you want them to dim with the headlight switch or just come on with it?

Cause my solution above will do the latter. You have the 12 volts coming from switch trip
the relay which closes the line between pins 12 and 8 thus turning your blue LED's on.

I feel this is alot safer also, because your not adding grounds or voltage to the lilliput
circuitry which avoids any accidental shorts

As far as dimming goes, that's another whole circuit... LED's don't dim easily..
very small voltage area where the light actually dims some before it just shuts
off. That's where the E.E. steps in and this M.E. steps out

I was referring to the on off switch not the dimmer

After discussing this with a couple of EE at work here your relay idea is the best.

I have never used relays... ever. Would anyone care to draw me up a diagram or point me to a suitable relay?

Thanks

**Dexter** · 02-25-2005, 07:16 PM

use PWM for the dimming. how to actually implement that is a different story

**Squid** · 02-25-2005, 07:56 PM

Relays are a very powerful tool... (lol.. that statement kills me)

But really are useful...

You can learn the fundamentals at the12volt which will get you started...

My own words...
Relays are just "switches" that you throw with another "hot" line.
You spec a relay for whatever voltage you need to trip it, and that the current
you will be flowing thru it will not destroy it. (basically)
It keeps different circuits separate. i.e. I use a 5 volt relay hooked to the ps2
port on my laptop to trip a 12volt circuit from letting the laptop shut off...
And most relays (not all) have NO or NC (normally open or normally closed)
which allows your result to either disconnect the line or connect the line however
it's wired...

Now after my ramblings... u should be confused..

just goto the the12volt page
and the pictures will show u right

I'm sure others will join in with their explanations...