darlington array uln2803a help

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i have a uln2803a darlington array and have no idea how to use it. i
am trying to use it to power a 12volt train set lamp. it has a small
circle/indentation at the top left or bottom right, depends on how
you look at it. in relation to this "dot" whats the top of this
thing or where is this dot in relation to the +supply.
can anyone supply a code i can work with? do i have to tell the
uln2803a to supply output1 with 12volts somewhere in the code?
thanks for any help. mark

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>Do a google search for uln2803a you will need to look for the data
>sheet. It will tell you what pins are what. You will need this for hook up.


Brian G.

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<markmcleod50@y...> wrote:
> i have a uln2803a darlington array and have no idea how to use it.
i
> am trying to use it to power a 12volt train set lamp. it has a
small
> circle/indentation at the top left or bottom right, depends on how
> you look at it. in relation to this "dot" whats the top of this
> thing or where is this dot in relation to the +supply.
> can anyone supply a code i can work with? do i have to tell the
> uln2803a to supply output1 with 12volts somewhere in the code?
> thanks for any help. mark

Hi Mark,

I guess I didn't realize just how much data you needed.

The top left of the chip is pin #1. that is indicated by the
recessed circle. the top of the chip has a half round bite mark in
it. this is common for almost all chips.

look at the picture on the lower right of this link
http://www.nelnick.com/datasheets/ULN2803-D.pdf

you will notice the little bite mark at the top of the chip.

The UNL2803 is an 18 pin chip.

since you found pin #1, you count down to pin 9 on the same side,
then jump directly across to pin 10 and then start counting up to pin
18. Pin 18 is closest to pin #1 on the top of the chip. (reference
above link)

The important pins.

1-8 are all signal inputs.
pin 9 is ground
pin 10 is your power
pins 11 thur 18 are the power collectors.

you connect one side of your lamp to your power supply.
the other side to pin 18.

connect your power to pin 10 and your ground to pin 9.

So far you only have 4 wires conected to this thing. one in each
corner of the chip.

connect the loose wire on pin #1 to the +DC voltage and then remove
power by pulling the wire off. this is just using the wire like a
switch. as you touch and let go, the light will go on and off.

pins 1-8 are signal you can control with a Stamp or the 595 chip.

This chip is used in an NPN fashion meaning you connect your +5V DC
to the thing you want to power, then connect the ground of that thing
to this chip. This chip completes the circuit by connecting the
ground line of your light to ground.

directly across the SIGNAL INPUTS of the chip are the power lines for
that circuit so this is an easy chip to know where the things are
connected.

Hope this helps.

Dave