Led matrix Power issue


Im new to Arduino and im having a bit of trouble with my 8x8 LED matrix.
Im using a breadboard power supply unit to supply the power to the LED matrix. when I flip the switch the entire matrix lights up. However The program only sets one led to HIGH. Everything works fine if I use the Arduino board to power it. is there something else im meant to do if I use a separate power supply ?

What type of matrix are you talking about?
How is this wired up?

Have you connected the ground of the power supply to the ground of the Arduino.

Hi everyone

I'm quite new to Arduino and im having some trouble with my breadboard power supply. When I use it to power my joystick module it gives random readings. I also tried using it to power an LED matrix. it just sets all led's high and doesn't respond to the program.

Is there something else I need to do when using a breadboard power supply to make it work properly ?

Yes, get a bigger one preferably with voltage and current meters. I have no clue as to what you have or doing however each of the things you have connected draw power of which you have a finite supply. I have seen this before when the supply voltage drops to low. There is also a phenomena of feed back via the power supply.
Good Luck & Have Fun!

You haven't told us anything of value in solving the issue. You might as well be talking to a wall for all we can do.

  1. vendor link for power supply
  2. Schematic of led matrixcircuit
    (handrawn on blank sheet of printer paper
    photographed and uploaded)
  3. closeup photo of power supply
  4. Describe your electronics experience
  5. do you have a multimeter ?
  6. power supplies don't "give readings"
    They just supply power.
    be specific . What kind of reading ?
    Obtained how ?
  7. There is no such thing as a "breadboard power
    supply" , with one exception: Many years ago
    they sold a metal box with a triple power supply
    built in and a breadboard mounted on top.
    That was a true breadboard power supply. I
    seriously doubt you have obtained one of those.
    If you have, I'll buy it from you. That being the
    case , you need to do a better job of describing the power supply.
  8. What the joystick have to do with anything?
    Does it "give strange readings " too ?
  9. Do you have any good news ?
    Goodbye and good luck !

(just kidding)

Hi, Sorry I realize now that my post was very undescriptive. By breadboard power supply module I meant this :


  • Im trying to use it to power a Joystick module and a MAX7219 led matrix at the same time for a project. But I can't seem to get either the joystick or LED matrix to work properly. The led matrix ignores the program and all LED's stay lit. as for the joystick readings. The readings I mentioned are the x and y values my program would take from the joystick module. I made a program to read and display the values in the serial monitor every 2 seconds. The values would be different and random every time ( even when the joystick was not being moved). The result is the same if I connect either module separately.

  • Sorry I don't know the schematic for the LED matrix.

  • I have a very basic knowledge on electronics. I'm a first year engineering student and just completed an introductory unit to electrical systems. the unit includes introduction to basic DC and AC circuit analysis, Diodes, Op-amps, Transistors.

  • I do own a multimeter.

I think I know what I did wrong. I didn't have a common ground for all the components. I connected the ground pin on my Arduino to the ground on the adapter and so far everything is working fine.

Hi , I have a KY-023 joystick module. I made a simple program to record the x and y values every 2 seconds. When using the Arduino mega board to power it I have no problems, I get the same values consistently ( When the joystick is in the resting position). However when I use a breadboard Power supply adaptor

shown here : https://core-electronics.com.au/3-3v-5v-solderless-breadboard-power-supply-module-adaptor.html

the readings from the joystick vary very slightly ( up to +- 2 ). Im just wondering what is causing it, if its normal and if it isn't how can i fix it ?


How are you powering the power supply PCB?

What does the 5V and 3.3V measure on your DMM when you select the appropriate voltage?

Tom… :slight_smile:

Maximum Output Current: <700ma

It has the same type of voltage regulators as Arduino and the same limitations, the higher the input voltage, the less current can be drawn before overload. With 12V on the barrel jack, the maximum current is down to 200 ~ 300 mA.

The most accurate name for the Makerbot Breadboard Power Supply is "3.3V/5V/700mA
Power Supply Breakout Board". That would
cover any similar products that might emerge

What would your Electronics Engineering
professor say if you told him you forgot to
connect the GND ? Would he consider that
"acceptable" for an engineering student ?
(or would he look shocked and roll his eyes ?)

What is supplying the supply (what is plugged into the barrel jack)?

For stability (ratiometric behaviour), the joystick (pots) MUST be powered from the same supply as Vref of the A/D.
That means the joystick MUST be powered from the Mega’s 5volt pin.

Why are you using a breadboard supply.
They are, generally speaking, not any better or more powerful than the 5volt supply of the Mega.

Why did you start a new thread for the same project (wasting yours and our time, and against forum rules).

Hi, thanks for responding. Sorry about it being somewhat the same problem, but before ( before I found out that I need a common ground between the Arduino and the joystick ) the values were very erratic (upto +500) when the joystick was in the resting position. Now with common ground the values only vary by (+- 10). I'm just using the breadboard power supply to learn how to use different power sources for components. I would really appreciate it if you could tell me a bit more about ratiometric behaviour and why the joystick must be powered by the Arduino or refer me to a source where I can learn more about it


As said, pots MUST be powered from the same supply as the Arduino A/D.
And "supply" means two wires. Power and ground.
So the pots must have dedicated (not shared) supply and ground to the Arduino to be stable and independent of other power users. No way around that.

A pot (voltage divider) outputs a ratio of it's voltage on the wiper.
If you power the pot with 5volt, and turn it to the center position, then it outputs 2.5volt.
But if the supply suddenly drops to 4.8volt, then the wiper voltage drops to 2.4volt (same 50% ratio).
The A/D has the same behaviour, but opposite.
Half of the supply on the input always returns 512, but 2.5volt does not always return 512.
Because of the same and opposite behaviour of pot and A/D, returned values stay the same with supply variations.
That is, if you power both from the same supply.

Thanks for explaining I understand why the joystick needs to have the same supply as the Arduino now however I still don't understand why it needs a dedicated ground and power. why can't things be connected in parallel with the joystick , isn't voltage across parallel elements the same ?

however I still don't understand why it needs a dedicated ground and power.

Not strictly needed, but wise if you want to avoid problems.
Wires and (breadboard) connections have some resistance. If (high) currents from other devices/sensors travel over the same VCC/GND wires, than a possible resulting voltdrop could affect pot readout.

It appears you are drawing to much current causing the on board regulator to fault. I would bet it gets hot enough to burn your finger. Use a driver (a transistor will work) and another power supply for the LEDs. You are driving 64 leds at 20 mills each that requires 1.28 Amps way beyond the Arduino capacity. at 10 mills that is 640mA.
Good Luck & Have Fun!



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