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Topic: MAX7219 problem (Read 1 time) previous topic - next topic

avalon66

#45
Apr 23, 2019, 10:38 am Last Edit: Apr 23, 2019, 11:25 am by avalon66
Ok, apologies for wasting everyone's time with my problem, but I have now finally understood how to power the project.

I have a + wire from a female barrel jack to a vcc pin on the pcb board. This pin is next to the vcc pin and wire from the Arduino Uno. I then connected the gnd wire from the barrel jack to the gnd pin on the pcb board, which is next to the gnd wire to the Arduino Uno.

I am now using a 5v 2.5 amp power supply connected to the female barrel jack to power the project which is working.

When you say :
Under no circumstances should the "barrel jack" on the UNO be used in an attempt to power the circuit.

Do you mean this particular circuit, or any circuit.

adwsystems

#46
Apr 23, 2019, 11:47 am Last Edit: Apr 23, 2019, 11:50 am by adwsystems
There is no Vcc pin on a genuine Arduino. The are 3.3V, 5V, and Vin pins.

You don't have to read the schematics to see what each are for. Just the description of the board tells you
Quote
Vin: The input voltage to the Arduino/Genuino board when it's using an external power source (as opposed to 5 volts from the USB connection or other regulated power source). You can supply voltage through this pin, or, if supplying voltage via the power jack, access it through this pin.

5V: This pin outputs a regulated 5V from the regulator on the board. The board can be supplied with power either from the DC power jack (7 - 12V), the USB connector (5V), or the VIN pin of the board (7-12V). Supplying voltage via the 5V or 3.3V pins bypasses the regulator, and can damage your board. We don't advise it.

3V3: A 3.3 volt supply generated by the on-board regulator. Maximum current draw is 50 mA.

GND: Ground pins.
As you see, using the Vin pin or the barrel jack does the same thing. Both go through the regulator.

You can use the barrel jack to power the Arduino or is you are careful you can use the 5V pin. But if you use the barrel jack for power, your CANNOT use the 5V power to power anything else. The regulator between the barrel jack and the 5V pin has just enough to run the Arduino. Attaching anything to the 5V when using the barrel jack (or Vin in pin) causes the EXACT issues you have described.

If I was standing next to you, I would have reached over and yanked out the red wire connected to the 5V pin, 10 posts back.

Your power supply, which is 5V, should be connected DIRECTLY to both the Arduino and the display. The daisy chain you have, power supply to Arduino and the Arduino to the display, is causing your problem.

avalon66

I knew something would be wrong withe way I have it connected and working.

i am not seeing any problems, and I have not had it connected this way before. It was however connected to the vcc pin on the display, Then there was a problem.
 
If I pull out the red wire to the arduino 5v pin and connect the red wire from the power supply to the 5v pin on the arduino, how do I then connect directly to the display, use 2 wires??


adwsystems

If I pull out the red wire to the arduino 5v pin and connect the red wire from the power supply to the 5v pin on the arduino, how do I then connect directly to the display, use 2 wires??
Yes. You have to.


I knew something would be wrong withe way I have it connected and working.

i am not seeing any problems, and I have not had it connected this way before. It was however connected to the vcc pin on the display, Then there was a problem.
Vin is the input power. I will admit the 5V pin is a bit confusing as it has two purposes. 5V is either 5V output when 7-12V is supplied to Vin or the barrel jack; OR 5V is 5V input to the board. As it is, putting the 5V power supply into the Vin pin is only causing you a voltage drop across the regulator that is between the Vin and 5V pins, that doesn't have enough voltage supplied to operate properly. Essentially, you are using the device (voltage regulator) out of its specified range.

All of the issues you describe point to one thing. The Arduino and display are not correctly connected to the power source. You need to pick one of the three power input points to use:
1. Barrel Jack
2. Vin
3. 5V

You can pick only one of the three to connect to. The other two will be unused.

If you have a 7-12V power supply, you can connect that to either Vin or the barrel jack. But you CANNOT connect the display to the 5V (output) pin, there isn't enough power.

If you have a (good) 5V power supply, you can connect that to both the display and to the Arduino 5V pin. You CANNOT connect that to Vin/barrel pin. Then you can connect the display directly to the power supply. Yes, the connection is a "V" on both the 5V and ground of the power supply.

The power supply 5V should be connected directly to:
1. Arduino 5V
2. Breadboard +
3. LED display Vcc

Ground should follow the same rules. This is the proper way to distribute power in most designs, direct connection of the power/ground pins of the load directly to the power source. This simplifies trouble shooting. You are now 48 posts into fighting a basic design technique.

If you have it working, then good luck on it staying that way. If you want to substitute luck for experience, then open your mind and update your design.


Paul__B

You can use the barrel jack to power the Arduino or is you are careful you can use the 5V pin. But if you use the barrel jack for power, your CANNOT use the 5V power to power anything else. The regulator between the barrel jack and the 5V pin has just enough to run the Arduino. Attaching anything to the 5V when using the barrel jack (or Vin in pin) causes the EXACT issues you have described.
Which is to say, if you are going to do anything useful with the UNO (or Nano, Leonardo, Mega 2560), because anything useful requires connecting other devices, just forget the "barrel jack" and "Vin" pin exist:smiley-roll:

When you say :
Under no circumstances should the "barrel jack" on the UNO be used in an attempt to power the circuit.
Do you mean this particular circuit, or any circuit.
I believe this has been answered.  :smiley-lol:

Quote
5V: This pin outputs a regulated 5V from the regulator on the board. The board can be supplied with power either from the DC power jack (7 - 12V), the USB connector (5V), or the VIN pin of the board (7-12V). Supplying voltage via the 5V or 3.3V pins bypasses the regulator, and can damage your board. We don't advise it.
This from the Arduino literature is terribly misleading.  It is simply nonsense!  :smiley-eek:  But we - the users - are unable to correct it.

avalon66

I connect 2 red wires to the female barrel jack, correct or not.
Then connected 1 red wire to the arduino 5v, and the other red wire to the display. If the first one is not correct then this wil be also
I connected the black gnd wire from the female barrel jack to the gnd pin / socket on the arduino
Then I connected the male barrel kack of the 6v power supply and hoped. The display flashed on, then off .

Thanks

avalon66

If I was standing next to you, I would have reached over and yanked out the red wire connected to the 5V pin, 10 posts back.

I wish you were standing next to me then you could see what I w as doing and then correct me.

adwsystems

#52
Apr 23, 2019, 05:02 pm Last Edit: Apr 23, 2019, 05:47 pm by adwsystems
I connect 2 red wires to the female barrel jack, correct or not.
Then connected 1 red wire to the arduino 5v, and the other red wire to the display. If the first one is not correct then this wil be also
I connected the black gnd wire from the female barrel jack to the gnd pin / socket on the arduino
Then I connected the male barrel kack of the 6v power supply and hoped. The display flashed on, then off .

Thanks
Where did you get a 6V power supply? Typo? Per you reply in post #48, you are using a 5V 2.5A power supply.

It is no surprise to me that it did not work. The instructions in post #48 have not been followed.

I will summarize.

You can only use one of the three following connections:
1. Barrel Jack (for 7-12V power supplies)
2. Vin (for 7-12V power supplies)
3. 5V (for 5V power supply)

Pick the one that fits.

Per your reply as post #45, you are using a 5V power supply. Therefore you CANNOT use the Barrel Jack and you CANNOT use Vin. You can only connect to 5V pin. That will only power the Arduino.

Now you have to get 5V power from the power supply to the LED display and to the breadboard. Make the connections and send us a picture of your solution.


avalon66

#53
Apr 23, 2019, 05:30 pm Last Edit: Apr 23, 2019, 05:47 pm by avalon66
It was a typo,. sorry

What is a 5C power supply, as I can't say i've heard of them.

Ok if I use a 5v power supply which has a barrel connector, and plug that into the female jack plug on the arduino,  how do I get a 5v supply to the display

adwsystems

#54
Apr 23, 2019, 05:46 pm Last Edit: Apr 23, 2019, 05:54 pm by adwsystems
What is a 5C power supply, as I can't say i've heard of them.
It was a typo,. sorry. Fixed.

Ok if I use a 5v power supply which has a barrel connector, and plug that into the female jack plug on the arduino, which now does not power the display, but did so yesterday, how do I get a 5v supply to the display
What is the voltage requirement for the barrel connector and the Vin pin? I have listed it at least three times. Then return to Paul__B post #23 for your answer.

Per your reply as post #45, you are using a 5V power supply. Therefore you CANNOT use the Barrel Jack and you CANNOT use Vin. You can only connect to the 5V pin. That will only power the Arduino.

avalon66

So I can use a 7v to 12v on the barrel socket/connector, and the Vin is the same from what I have read.

Alright then, I will use a 7v power supply, and I have a 5v wire to the display, which gives 5v, well 4.92v , on the display.

adwsystems

So I can use a 7v to 12v on the barrel socket/connector, and the Vin is the same from what I have read.

Alright then, I will use a 7v power supply, and I have a 5v wire to the display, which gives 5v, well 4.92v , on the display.
You will be working with two powers upplies which means you MUST connect the grounds together (at some point) or you will run into a whole new set of issues.

avalon66

You will be working with two powers upplies which means you MUST connect the grounds together (at some point) or you will run into a whole new set of issues.
Two power supplies?
I just said i'll use a 7v power supply, only 1. The 2 grounds are together

adwsystems

#58
Apr 23, 2019, 06:55 pm Last Edit: Apr 23, 2019, 09:02 pm by adwsystems
So I can use a 7v to 12v on the barrel socket/connector, and the Vin is the same from what I have read.

Alright then, I will use a 7v power supply, and I have a 5v wire to the display, which gives 5v, well 4.92v , on the display.
When you wrote this I assumed (I know, I made an ass out of me, at least), that you were going to use the 7V in the barrel jack and the 5V for the display.

Based on this

Two power supplies?
I just said i'll use a 7v power supply, only 1. The 2 grounds are together
I was wrong. You actually intend to ignore all the posts go back to what didn't work and have been told won't work.

So I will write this again.

You can only use one of the three following connections:
1. Barrel Jack (for 7-12V power supplies)
2. Vin (for 7-12V power supplies)
3. 5V (for 5V power supply)

PICK ONE and ONLY ONE.

Based on my new understanding of this post
Alright then, I will use a 7v power supply, and I have a 5v wire to the display, which gives 5v, well 4.92v , on the display.
You are going to use two of the three pins. You intend on using both the barrel jack and the 5V pin. THAT WON'T WORK.

You need 7-12V to use the barrel jack. You need 5V to run the display. The 5V pin of the arduino does not provide enough power to run the display. You already figured that out.

Plug the 7V supply into the barrel jack. Plug the 5V supply into the display. Connect the grounds. DONE. PROBLEM SOLVED. Your do-dad works.

Paul__B

I have said it in post after post, most recently in #49.

If you do not believe me, well, we await #99.  :smiley-roll:

So I will write this again.
You can only use one of the three following connections:
1. Barrel Jack (for 7-12V power supplies)
2. Vin (for 7-12V power supplies)
3. 5V (for 5V power supply)
PICK ONE and ONLY ONE.
I really wish you would not confuse the poor fellow with such unhelpful nonsense!  :smiley-eek:

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