# Current not being completely sunk?

I don't know the correct terminology for this but it seems to me that there is still a small amount of current present in one of the rows. What could cause it to remain present? The row is connected with stranded wire, sourced by a PNP and sunk by the Arduino. 150 Ohm resistor at each cathode. 5v and ground provided by Arduino.

It is the second to last row.

I updated my post.

Short?

I created an 8x8 matrix with PNPs sourcing current and Arduino Pins sinking current.

Here is the Schematic:

Here is the code:

``````int DS_pin = 6;
int STCP_pin = 7;
int SHCP_pin = 12;

int rowArr[8] = {2,3,4,5,8,9,10,11};

int cathodeArr[8][8] = {
{0,0,0,0,0,0,0,0},
{0,0,0,0,0,0,0,0},
{0,0,0,0,0,0,0,0},
{0,0,0,0,0,0,0,0},
{0,0,0,0,0,0,0,0},
{0,0,0,0,0,0,0,0},
{0,0,0,0,0,0,0,0},
{0,0,0,0,0,0,0,0}};

int diamond2[8][8] = {
{0,0,0,1,1,0,0,0},
{0,0,1,0,0,1,0,0},
{0,1,0,0,0,0,1,0},
{1,0,0,0,0,0,0,1},
{1,0,0,0,0,0,0,1},
{0,1,0,0,0,0,1,0},
{0,0,1,0,0,1,0,0},
{0,0,0,1,1,0,0,0}};

void setup(){

pinMode(DS_pin,OUTPUT);
pinMode(STCP_pin,OUTPUT);
pinMode(SHCP_pin,OUTPUT);

for(int i = 0; i < 8; i++){
pinMode(rowArr[i],OUTPUT);
}

for(int i = 0; i < 8; i++){
digitalWrite(rowArr[i],HIGH);
}

setArray(diamond);

}

int time =1000;

void writereg(int x){

digitalWrite(STCP_pin, LOW);
delay(time);
for(int i = 7; i >= 0; i--){
digitalWrite(SHCP_pin, LOW);
if(i == x){
digitalWrite(DS_pin, LOW); // Switch PNP On
}else{
digitalWrite(DS_pin, HIGH);
}
digitalWrite(SHCP_pin, HIGH);
}
digitalWrite(STCP_pin, HIGH);
}

void setArray(int x[8][8]){

for(int i = 0; i < 8;i++){
for(int j = 0; j < 8;j++){
cathodeArr[i][j] = x[i][j];
}
}

}

void loop(){

for(int i = 0; i < 8; i++){
delay(time);
writereg(i);
for(int j = 0; j < 8; j++){
if(cathodeArr[i][j] == 1){
digitalWrite(rowArr[j],LOW); // Sink Current
}else if(cathodeArr[i][j] == 0){
digitalWrite(rowArr[j],HIGH); // Do nothing
}
}
}

}
``````

Here is the Schematic:

You sure.
It looks all shorted out in the matrix.

This is why we hate fritzing here, most people can’t drive it and produce rubbish like this. There is no way that will function at all. By overlaying wires in the same place you can’t see what the circuit is. Take Q8,7 & 6. It looks like all the base resistors are connected on the same signal, which is of course rubbish.

I should probably fix that. It's my first Schematic lol. But do you have any idea why I'm getting those LEDS lit?

Is there any hope for Fritzing? What a useless diagram!

What makes a schematic useful? How do I make a good schematic?

A properly drawn schematic makes it absolutely clear which components are used and exactly how they are wired together.

Do you see why it is impossible to understand how your LEDs are wired in post #5?

I use and recommend the free LTSpice program, which is not hard to learn and also accurately simulates the behavior of many useful circuits.

Hi,

Can you please post a copy of your circuit hand drawn circuit in jpg, png?

Using dots when wires connect to each other, and label the components?

Its free, has not stupid limits or pop-ups and is well supported. Just spend some time playing with it.

Do you have a DMM?

Tom... :)

Grumpy_Mike: This is why we hate fritzing here

Objection m'Lud!

We hate Fritzing because beginners post "breadboard views" all the time and call them schematics. Bruce's first attempt at a proper schematic would have been just as bad if he had used Eagle, LTspice, ExpressPCB or whatever. You can't really blame it on Fritzing. I used to use Fritzing and was able to produce some perfectly respectable schematics. At the time, Fritzing was at quite an early version, and there was not a large library of parts, which was frustrating and the reason I switched to Eagle. Eagle's UI took a lot of getting used to compared to Fritzing.

Well while I must admit that the schematic posted here was neater than many you see, but it was even more useless than the tangle of wires you often see. Yes we do hate fritzing here mainly for the physical layout being touted as a schematic, but also for stupid component substitutions and poor schematics.

Yes I have a multimeter and I used it. I tested the defective row and there is a small voltage present. I will try to remake my schematic. My apologies for creating an atrocity but you have to learn somewhere right?

My apologies for creating an atrocity but you have to learn somewhere right?

Yes that is quite right. Thanks for taking in in the spirit it was meant. Good luck.

As a general rule try and keep the high voltages at the top and low voltages ( ground ) at the bottom with the signal flow going from left to right.