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Mystery LED's in Series

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kenny782

New Member
I've got 11 - 5V LED's wired in parallel.
Positive coming into the first LED and ground on the last.
But nothing comes on.

I tested each LED on it's own, they all work.
I've triple checked make sure nothing is reversed.

Then I moved up and down the line, process of elimination.
1 LED - Good
2 LED's - Good
3 LED's - Good
4 LED's - Dead

I retested this using different LED's in the row and every time it died at 4.

Even though the power consumption is neglegable, my first PSU was very smallI don't recall the exact number.
So I found a 5V - 1amp brick thrown in my closet, wired it up and I'm still seeing the same behavior.
So it's not a shortage of power.

Any ideas? I know it's probably something simple I'm too dumb to figure out.

Thanks,

Kenny
 
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audioguru

Well-Known Member
Most Helpful Member
If "Positive coming into the first LED and ground on the last" then they are in series, not in parallel. They need 25V.
I don't know if they have built-in current-limiting.
 

kenny782

New Member
Yeah sorry I was going to change that to series and forgot :)

It doesn't look like it's supposed to be that way anyway.
I was just working on this hookup for the led's, giving me a headache lol

8929-kitt12led.gif
 

audioguru

Well-Known Member
Most Helpful Member
The LEDs are not in parallel and they are not in series.

You are driving each LED in a bridge. One output of the micro goes high at the anode of an LED and another output of the micro goes low at the cathode of the LED.
Then the LED is forward biased and lights.

You said the LEDs are 5V types. Then maybe they have built-in current-limiting resistors.

Please explain what you are doing to test the LEDs where one to three work and the fourth LED doesn't.
 

kenny782

New Member
Well I'm waiting for a part to come in so I can program the controller.
For right now I was just trying to get the LED's wired properly, ready to connect to the chip when I get it mounted.

I just read something on google about a similiar led config that shed a little light on things (no pun intended lol)

I don't know if it's right or wrong, but based on what I read here's where I am now.
1) I have 4 groups of 3 led's
2) Within each group the led's are wired in series.
3) all groups share a common ground
4) I have the 4 resistors mounted.
5) Resistor 1 connects to group 1, res. 2 to group 2 and so on.
6) Each resistor is receiving 5V+ from my PSU.

All LED's light up.

Now I know each resistor needs more inter connecting but it's some progress I think?

Thanks,

Kenny
 
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audioguru

Well-Known Member
Most Helpful Member
The LEDs are not in series.
They do not share a common ground.
The resistors do not connect to the +5V supply.

To test the LEDs you can connect one resistor to +5V and another resistor to ground.

When one micro output goes high and another micro output goes low then one LED will light.
The four micro outputs can have 12 combinations of high and low.
 

kenny782

New Member
ok then one more question, the top two led's. See how the connection on the left is in the center of the led's.

What does that mean, I jump that connection to the + on both led's?
 

kenny782

New Member
I made up this crude and painfully simple wiring.
Hopefully you can make sense of it, it's late and my brain is fried.

Depending on the combination of the four resisitors I get get the first LED on with most combinations.
One combination i get the first and 8th I believe it is on.

Thanks,

Kenny


removed horrible diagram
 
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Mr RB

Well-Known Member
It's a standard charlieplexing array.

The best way to draw a 4way charlieplex is like a square. Each corner of the square is a node, which connects by a resistor to the PIC pin. And in between every 2 nodes there are 2 LEDs (forward/reverse).

A 5way charlieplex looks exactly like a pentagram.

The math for the max number of leds charlieplexed is;
leds = pins * (pins-1)

so 4 pins gives 12 leds, 5 pins gives 20 leds, 10 pins gives 90 leds.
duty cycle is (unfortunately);
duty = 1 / leds
 

audioguru

Well-Known Member
Most Helpful Member
Each two sets of LEDs are wired "back-to-back" so that the anode of one connects to the cathode of the other.
Then one LED lights if the polarity is one way and the other LED lights if the polarity is the other way.
 

kenny782

New Member
okay, based on what you said I found this, I laid out the led's exactly as shown.
and connected the led's exactly as shown, I went over it twice.

Though I wasn't quite sure of the purpose of the black dots, compared to the rest of the wires. I simple ran the wires from each pin one at at a time using different colors.
For example where Pin2 passes between LED 2 and 4.
1) I jumped the appropriate pins on each led to a common location and then tapped that location from pin2.
2) I did the same for the next pair as but I connected the previous common point to the new one.
3) From there I connected the new common group to the positive side of led 6, and then jumped that to the negative side of led 7

As I connected Pin 0 I connected the opposite sides of led 6 and 7 thereby both sides where connected between pin 0 and 2.

With 3/4's of the combinations it gives give me single led's. Of the remaining 6 combinations I get 4 - 4 light combo's and 2 - 3 light combo's.

8933-12ledwspecs.gif


I doubt this helps but here are my test results.
Constant Pin 0 - 5V+
GND to Pin1 - LED 3
GND to Pin2 - LED 9
GND to Pin3 - LED 11


Constant Pin 0 - GND
5V+ to Pin1 - LED 0
5V+ to Pin2 - LED 8,0,1,5 (5 really dimm)
5V+ to Pin3 - LED 10


Constant Pin 1 - 5V+
GND to Pin0 - LED 0
GND to Pin2 - LED 4
GND to Pin3 - LED 7


Constant Pin 1 - GND
5V+ to Pin0 - LED 3
5V+ to Pin2 - LED 1
5V+ to Pin3 - LED 1,2,3,6


Constant Pin 2 - 5V+
GND to Pin0 - LED 0,1,5,8
GND to Pin1 - LED 1
GND to Pin3 - LED 1,5,7

Constant Pin 2 - GND
5V+ to Pin0 - LED 9
5V+ to Pin1 - LED 4
5V+ to Pin3 - LED 2


Constant Pin 3 - 5V+
GND to Pin0 - LED 10
GND to Pin1 - LED 1,2,3,6
GND to Pin2 - LED 2

Constant Pin 3 - GND
5V+ to Pin0 - LED 11
5V+ to Pin1 - LED 7
5V+ to Pin2 - LED 1,5,7


I don't know why the hell I can't get this, I work in IT I've solved the most complex of problems. And I've taken on these electronics projects before, I have the rest done.
It's just this wiring that's killing me, I thought it looked simple enough.

Anyway, thanks -Kenny
 
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Mr RB

Well-Known Member
You schematic above looks fine.

However the Text you posted ov which LEDs light sup has lots of issues. I think you have some LEDs reversed/numbered wrong and most likely a short or two... ;)
 

kenny782

New Member
lol, I'll go over it all again.

But can you tell me what the deal is with the black dots?
Maybe that's what's throwing me off.

I mean look at led 6 and 7.
6 has a dot on pos and neg, and 7 only has one on the positive side.

If I were to only connect the black dots for example 7 would have nothing on the negative side.

Thanks,

Kenny
 

audioguru

Well-Known Member
Most Helpful Member
The black dots are soldered connections in the circuit. Where a wire passes another wire without a black dot then the wires are not connected in the circuit.

You must connect the polarity of the LEDs correctly.

Here is an example of how wrong your connections are. Here is your results and the correct results:

Constant Pin 0 - 5V+
GND to Pin1 - LED 3 No, LED 0.
GND to Pin2 - LED 9 No, LED 6.
GND to Pin3 - LED 11 No, LED 8.

Constant Pin 0 - GND
5V+ to Pin1 - LED 0 No, LED 1.
5V+ to Pin2 - LED 8,0,1,5 (5 really dimm) No, LED7.
5V+ to Pin3 - LED 10 No, LED9.
 

kenny782

New Member
Okay I cut new wires and made it look nice and neat.
So at least you can see what I have and make sense out of it.

I burned out the last 3 led's since the beginning of this whole process.
So I'm using 3 led's I pulled out of an old pc case for now.

8938-cleanlayout.jpg



Constant Pin 0 - 5V+
GND to Pin1 - LED 0/4/7
GND to Pin2 - LED 8
GND to Pin3 - LED 0/6

Constant Pin 0 - GND
5V+ to Pin1 - LED 3
5V+ to Pin2 - LED 3/4
5V+ to Pin3 - LED 3/5/7


Constant Pin 1 - 5V+
GND to Pin0 - LED 3
GND to Pin2 - LED 1
GND to Pin3 - LED 6

Constant Pin 1 - GND
5V+ to Pin0 - LED 0/4/8
5V+ to Pin2 - LED 4
5V+ to Pin3 - LED 4/5/7


Constant Pin 2 - 5V+
GND to Pin0 - LED 3/4
GND to Pin1 - LED 4
GND to Pin3 - LED 4/6/9/10

Constant Pin 2 - GND
5V+ to Pin0 - LED 8
5V+ to Pin1 - LED 1
5V+ to Pin3 - LED 5


Constant Pin 3 - 5V+
GND to Pin0 - LED 3/5/7
GND to Pin1 - LED 4/5/7
GND to Pin2 - LED 5

Constant Pin 3 - GND
5V+ to Pin0 - LED 0/6
5V+ to Pin1 - LED 6
5V+ to Pin2 - LED 4/6

Thanks,

Kenny
 
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audioguru

Well-Known Member
Most Helpful Member
You still have many LEDs lighting wrong.
You didn't label your LEDs on your breadboard and didn't show their polarity so mayby you made more mistakes.
 
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