Well...I'm driving down the road in my converted
bus to RV and started to notice more and more
cars have running lights. Some lights even look
like the cars logo. So why can't I have running
lights on my 89 bus!
Well, I tried but failed in the next step.
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Step 1: Failed 5mm White Led
I ordered 100 leds and made a jig. I was very careful
to add resistors that would only allow 10ma. Automotive
voltage can reach 14-16 volts. So I wired up each led
with its own resistor. 6 hours later I hooked it to
a solid 12.6 volt supply and went to bed. The next day
5 leds were out. I thought I got them too hot while
soldering and replaced them. Back on the 12.6 volts...
Next day 3 were out. Then 4...then 2. You get the
message. The leds were junk and never came close to
their rated MA of 20. So I shelved the project for
6 months and when I had another order I got some
white and red SMD leds.
Step 2: SMD So Easy ... No Bending
I made a pc board and included a place for each led
and resistor. My first pc was small enough to fit
inside the blinker lens but at 10 feet it just
looked like a light not a logo. The chevy logo
needs to be at least 6x4 inches to be seen at
any distance. I included a pdf of my logo. This is
a mirror copy for printing to a pc. The center
is negetive and the outside ring is positive.
There is a pad for a 12volt wire at top left.
Leds mark goes to ground but some rejects are
marked wrong so test first before you solder
then unsolder 44 leds. The edges look like the
layout is wrong, but if you place the leds first...
in the logo pattern then you will see where to
place the resistors. Just to be sure...the
Chevy logo 'tips' point right and up.
This unit has about
44 leds and draws .6 amps. Which is close to 11ma
per led. Way below the 20ma a led usually draws.
As you can see from the photos even at a lower ma
they are still daylight bright. The actual resistor
I used is 150 ohm which is too low (but it works).
Here is the actual formula... R=( Vs- Vu)/ I.
Vs is supply voltage, Vu is the unit voltage,
I is amps so 20ma is .020 amps
So most led stats are 20ma, 1.8 volts.
Lets plug this into the formula.
R= (12.6 - 1.8) / .02
R= 10.8/.02 is 540. Around 470 ohm will do.
(Even though I used a 150 ohm.)
I used one resistor for one led. Looking at so
many traffic lights that have 3-5 leds in a string
that burn out. I do not understand why they have to
tie a string of leds together! If one goes they all
go out. So I have one for one...resistors cost
about .002 cents each.
Step 3: Finish Remarks
So after soldering and testing for 3 days I spray
with black paint. These are not behind a lens so
a good paint is needed. Then I whipe off the paint
with a T shirt and lacquer thinner. Test again for
3 days. I never have put a clear coat on my lights
but it may be a good finishing touch
as well as another layer of protection.
Mounting the pc to the bus was easy but I know
not many cars have a 'BIG FLAT BUMPER' to mount to.
Here is where you need to be creative.
My best advise is NOT to use a screw through the
copper on the pc for a connection. (either
ground or 12v). You MUST have a wire soldered to
a pad ON the pc and attach that wire to your
sourse. Weather will take a toll and a screw WILL
develope a poor connection. My bus lights are
over a year old. With over 15,000 miles. They have
eaten bugs, hail, rain and worst of all
my wifes driving! Not one led has failed !
If you read this far I want to say thanks and some PC advise.
The hit and miss on dry ink transfer from laser machines is
very frustrating. But for two years I kept close records and
the I know one secret is PRINT only on dry days. It seams that
humidity causes less ink and poor dispersement. I have what is
rated as the worst printer and ink... a Brother ninty nine dollar
special. I now get great results if I print on dry crisp days.
I tried many papers too and the best paper is
Everyday with Rachel Ray magazine.
If you see my bus...wave.