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Making small PC boards

P

Palmer

Jan 1, 1970
0
I'm looking at either finding or making some small PC boards. They need to
be about a 1/2 inch square. I'm wanting to mount an LED on each board but
I'll need to connect 4 LED boards in series but each board will be connected
to the next with insulated wires. I could either have a board with 4 holes
right down the middle but then I would have a long length of wire for the
negative side of the source. I was thinking of having a board with four hole
on the upper half and two on the bottom half. The bottom two holes would
just be a place for the negative wire coming in and one going out to the
next board. The two center holes on the top half would be for the LED wires
and the outer holes on either side would be for the positive coming in and
one going out to the next board.
So would it be easier to make a board as such or find something to work? I'm
new at this so I'm looking for help and direction. The only thing is that
the side the LED is mounted on to remain smooth so that means all the wires
and LED legs to be soldered on the back side.
Thanks for your comments and help.
Palmer
 
H

hamilton

Jan 1, 1970
0
Palmer,

OK, the cost of a 1/2" x 1/2" PCB will cost a lot.
Building a larger board and cut up into small pieces will be good.

Using a vector board with the wireing you are looking for would be the
easiest.

If I understand your circuit each board would look like this:

LED LED LED LED
o--o-|<-o--o o--o-|<-o--o o--o-|<-o--o o--o-|<-o--o
o----------o o----------o o----------o o----------o
board 1 board 2 board 3 board 4
Are the LEDs surface mount ?

This would put all the LEDs in series.
What does you power supply look like ??

PS: Got to www.digikey.com and search for "vector board".
 
Why are you making a PCB if all that is going on it is a single LED? It
would be more efficient to mount the LEDs in some kind of fixture (e.g.
a matrix of holes drilled in a piece of metal, wood or styrene).
Although you can etch a PCB to do this (I recommend Olimex,
www.olimex.com, for this, since they charge by panel area rather than
by number of PCBs). Or you could build it on snippets of regular matrix
board. But as I said, I don't understand why you need a PCB for this
application.
 
P

Palmer

Jan 1, 1970
0
You are correct on how the boards will look and be arranged. ( I could have
never drawn that on the computer)
The power will be coming from the car in which they will be installed.....
so it will be a 12 volt to 13.6 volt source. What I have seen are the LEDs
that are bought at places like Radio Shack. They look like a small dome with
a small flared bottom. What I am after is being able to drill a hole the
same size as the LED and inserting it from the back side of the hole and the
flared bottom and or the PC board stopping the LED from going any further
in. That is also why would like all the wires and LED legs to be on the
back side of the board.
I tried searching for vector board but not too sure what that is and what
I'm looking for. I've seen boards at R.S. that are just a bunch of drilled
holes that I could cut down but I wasn't sure how to apply the connections
between the holes...like a circuit board is. Like in your drawing ....the
"--" are connected via copper trace...if that is what it is called.
Again thanks for your help.
 
T

Tweetldee

Jan 1, 1970
0
Palmer said:
I'm looking at either finding or making some small PC boards. They need to
be about a 1/2 inch square. I'm wanting to mount an LED on each board but
I'll need to connect 4 LED boards in series but each board will be
connected to the next with insulated wires. I could either have a board
with 4 holes right down the middle but then I would have a long length of
wire for the negative side of the source. I was thinking of having a board
with four hole on the upper half and two on the bottom half. The bottom
two holes would just be a place for the negative wire coming in and one
going out to the next board. The two center holes on the top half would be
for the LED wires and the outer holes on either side would be for the
positive coming in and one going out to the next board.
So would it be easier to make a board as such or find something to work?
I'm new at this so I'm looking for help and direction. The only thing is
that the side the LED is mounted on to remain smooth so that means all the
wires and LED legs to be soldered on the back side.
Thanks for your comments and help.
Palmer

Well, you could do something like this...
Arrange your boards so that you have right angle 2-pin female headers on one
side, and mating 2-pin male headers on the other side. Then, you could join
as few or as many as you like. No connecting wires except for the ones
supplying power.

--
Dave M
MasonDG44 at comcast dot net (Just subsitute the appropriate characters in
the address)

Never take a laxative and a sleeping pill at the same time!!
 
H

hamilton

Jan 1, 1970
0
Palmer said:
You are correct on how the boards will look and be arranged. ( I could have
never drawn that on the computer)

A picture is worth a thousand words.
Also tell others what you have in mind without knowing the terms.
The power will be coming from the car in which they will be installed.....
so it will be a 12 volt to 13.6 volt source. What I have seen are the LEDs
that are bought at places like Radio Shack. They look like a small dome with
a small flared bottom. What I am after is being able to drill a hole the

"Radio Shack" means you are in the US.
Good, Yes you are correct, getting the boards and LEDs from Rat shack
will get this done quickly.
same size as the LED and inserting it from the back side of the hole and the
flared bottom and or the PC board stopping the LED from going any further
in. That is also why would like all the wires and LED legs to be on the
back side of the board.

Just like the drawing, a few holes to insert the LEDs or the wires will
make it easy to mount.
I tried searching for vector board but not too sure what that is and what
I'm looking for. I've seen boards at R.S. that are just a bunch of drilled
holes that I could cut down but I wasn't sure how to apply the connection

Yes, a "vector board" is a board full of holes.
between the holes...like a circuit board is. Like in your drawing ....the
"--" are connected via copper trace...if that is what it is called.

Yes, you are also correct in that the "--" are the "wires" on the vector
board. Pushing the leads of the LEDs thru the vector board and bending
them over to solder to the ends of the interconnecting wires can be done
in no time. How long the interconnecting wires is up to you.

The next thing to look at is the voltage drop across each LED.
If you bought the LEDs from R.S., then on the back of the package will
be the voltage and current rating for that LED.

Most LEDs are about 2.0 volts each. ( more or less, check the packaging )

At 12.0 volts, 6 LEDs can be strung together with out damaging them.
If however your supply goes to 13.6 volts, some of the LEDs may get
damaged. ( burn out ) Maybe not right away, but one may burnout and then
the whole string will go out.

It seems to me that this is a simple wiring problem. This "thing" your
drilling thru can be used to mount the LED and the interconnecting wires
can be soldered directly to the legs of the LED. Using some hot melt
glue to cover the connections will protect the connections.

No PCB necessary.

How many LEDs will you need in any single string ?
As mentioned above, 6 is a good number.

You many want to insert a voltage regulator before you connect the
string to the battery. This will help regulate the voltage to the LED so
any varation will not kill your work.

R.S. also sells voltage regulators. Look for a LM317.
This is a 3-Terminal Adjustable Regulator, which means you can control
the output voltage with a potentiometer.

Here is a link: http://www.national.com/pf/LM/LM317.html

Good Luck.
 
D

Dmitri

Jan 1, 1970
0
A PCB is not going to be smooth on both sides unless you are using SMD
LEDs, and all your soldering as well as parts are on one side of the PCB
only. The layout of the PCB looks so simple (with SMD parts) that you
don't even need to etch it, craft knife would be sufficient to cut the
copper and separate those limited amount of pads you'll need from each
other. Use gull-wing type SMD LEDs, they are easier to solder than a
chip-type SMD LEDS. Make your power pads as large as practically possible
considering the size of the board so they don't easily de-laminate if you
accidentally pull on the wires hard.
Good luck!
--
Dmitri Abaimov, RCDD
http://www.cabling-design.com
Cabling Forum, color codes, pinouts and other useful resources for
premises cabling users and pros
http://www.cabling-design.com/homecabling
Residential Cabling Guide
-------------------------------------

Palmer wrote:

I'm looking at either finding or making some small PC boards. They need
to
be about a 1/2 inch square. I'm wanting to mount an LED on each board
but
I'll need to connect 4 LED boards in series but each board will be
connected
to the next with insulated wires. I could either have a board with 4
holes
right down the middle but then I would have a long length of wire for
the
negative side of the source. I was thinking of having a board with four
hole
on the upper half and two on the bottom half. The bottom two holes
would
just be a place for the negative wire coming in and one going out to
the
next board. The two center holes on the top half would be for the LED
wires
and the outer holes on either side would be for the positive coming in
and
one going out to the next board.
So would it be easier to make a board as such or find something to
work? I'm
new at this so I'm looking for help and direction. The only thing is
that
the side the LED is mounted on to remain smooth so that means all the
wires
and LED legs to be soldered on the back side.
Thanks for your comments and help.
Palmer







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R

Rich Grise

Jan 1, 1970
0
.
The next thing to look at is the voltage drop across each LED.
If you bought the LEDs from R.S., then on the back of the package will
be the voltage and current rating for that LED.

Most LEDs are about 2.0 volts each. ( more or less, check the packaging )

At 12.0 volts, 6 LEDs can be strung together with out damaging them.

Only if you are very, very lucky.

Do not attempt to drive LEDs with a constant-voltage source, without
a current limiting resistor. In this case, if we take battery voltage
as a nominal 13.6, then that's 1.6 V you have to drop, at 20 mA is
1.6/.02 = 80 ohms. So 82 ohms, 1/4 watt will work, but at 14.2V,
you'll have 27 mA. So go for 20 mA at 14.6V (this is how high the
voltage gets when it's charging), you want 14.6-12, 2.6/.02= 130R;
RS has a 100 and a 220, so two 220s in parallel will give you 110R;
2.6/110=23.6 mA, so you should be OK.
If however your supply goes to 13.6 volts, some of the LEDs may get
damaged. ( burn out ) Maybe not right away, but one may burnout and then
the whole string will go out.

With no current limit, you are guaranteed to destroy LEDs.

Also, if the LEDs are going to be in fixed positions relative to your
holes, just do one board and line them up right. :)

Good Luck!
Rich
 
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