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Topic: Is it necessary to put resistors attached to pins of a 7 segment display ? (Read 1 time) previous topic - next topic

firashelou

hello guys,
sorry for this question but i didn't need to rush with my project and wire the display without asking if it's necessary to connect every pin of a 7 segment display to a 1K resistor for protection or directly to arduino without any resistor ?
Aiming for the unreachable !

CrossRoads

Depends how you are controlling it.
If you desire to sink/source current from all segments at the same time, then a resistor is needed on each segment pin.
If you will only sink/source current from 1 segment at a time, then only a single resistor is needed on the common pin.
1K might be on the dim side.
270 would ne brighter, allowing ~10mA to flow (depends on LED color).
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

firashelou


Depends how you are controlling it.
If you desire to sink/source current from all segments at the same time, then a resistor is needed on each segment pin.
If you will only sink/source current from 1 segment at a time, then only a single resistor is needed on the common pin.
1K might be on the dim side.
270 would ne brighter, allowing ~10mA to flow (depends on LED color).


let me explain what i need to do because i didn't know that i must explain:

what i want to do is to go from 0, 1, 2, 3, 4, 5 and the display i have i guess it's common anode because HIGH to all pins makes it off
and it's RED color so ?
Aiming for the unreachable !

CrossRoads

Then put a resistor on each segment.
Keep pins 0, 1 free for serial downloads if you can.
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

firashelou


Then put a resistor on each segment.
Keep pins 0, 1 free for serial downloads if you can.


ok first i meant by 0 to 5 the numbers i need to display not the pins i am sorry for not saying that :S
but what do u mean by serial downloads ?
Aiming for the unreachable !

Grumpy_Mike

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but what do u mean by serial downloads ?

Putting software onto the Arduino.

firashelou

ok good attached to ground and by the way a 150 Ohms do you think is good ? or i should put a 1K ? i mean is it same , it won't let the component be damaged ?
Aiming for the unreachable !

Grumpy_Mike

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i mean is it same

It is not the same 1K will let too little current through 150R is about as low as you can go and might exceed the group pin current limits. I would go with 220R to 330R.

firashelou


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i mean is it same

It is not the same 1K will let too little current through 150R is about as low as you can go and might exceed the group pin current limits. I would go with 220R to 330R.


ok thank you :)
Aiming for the unreachable !

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