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Topic: Control 5 7-segment display (Read 595 times) previous topic - next topic

jirkap95

Hello, I have got 5 7-segment display and i need to control them with arduino yun. The 7-segment displays are HD-AD16RD with common anode they need 30mA current and 10V. i was thinking about TLC5940NT, but im not really sure about that. Thanks for any idea.

Wawa

Big displays are usually controlled with TPIC6x595/6 shift registers.
Recent thread here.
TPIC chips are 5volt only, but it seems the Yún has 5volt I/O.
Leo..

CrossRoads

Yes, TPIC6C595 for sure.
Take a look at this schematic which uses a similar TPIC6B595 (can sink more current).
You'll need current limit resistors for each segment, approximately (10V - 2.2)/.03A = 270 ohms.
30mA may be really bright, you may want to consider higher value resistors to tone the display down some, like 10-15mA.
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.

CrossRoads

Here's the board I offer, with a '328P built in to run things vs a separate Arduino.
http://www.crossroadsfencing.com/BobuinoRev17/
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.

jirkap95

Very thanks for that. If can i ask, im not sure about my circuit, if i understood good. If you will be so kind and check it. Many thanks

PaulRB

#5
Nov 10, 2017, 04:58 pm Last Edit: Nov 10, 2017, 05:06 pm by PaulRB

Looks pretty good. The resistors may be a little low. 330R would be safer.

If you do not need maximum brightness, you could consider reducing the number of chips required from 5 to 2 by multiplexing the display. 5 pnp transistors such as bc327 would be needed to control the digit commons, with 10K base pull-up resistors and 330R series resistors. One tpic chip would connect to the segments of all digits and the other tpic chip would drive the transistor bases.

jirkap95

#6
Nov 10, 2017, 06:06 pm Last Edit: Nov 10, 2017, 06:15 pm by jirkap95
Thank you for check my circuit. Multiplexing is really good idea, can i use only one tpic chip like on this circuit ? if this ok to connect transistors on digital pin of YUN. thanks for checking it again :D

PaulRB

#7
Nov 10, 2017, 07:44 pm Last Edit: Nov 10, 2017, 08:05 pm by PaulRB


Yes, you can use the Yun pins instead of the second tpic chip, but you will need another 5 transistors, and these should be npn such as bc337.

The base pins of the PNP need to be pulled up to 12V, not 5V, otherwise they will never switch off. This means you cannot connect the Yun pins to the PNP bases, because they would be damaged by the 12V. So the 5 npn are needed between the Yun pins and the PNP bases. 4K7 between the Yun pins and the npn bases should be ok. You also need those 330R to limit the PNP base current.

jirkap95

#8
Nov 11, 2017, 09:19 am Last Edit: Nov 11, 2017, 09:44 am by jirkap95
OK, so here is circuit with 2 tcip, hope than i got it right. Thanks all of you for so many informations.

PaulRB

#9
Nov 11, 2017, 10:58 am Last Edit: Nov 11, 2017, 11:16 am by PaulRB


Looks ok. I'm not sure if it makes much difference, but I would put the 10K pull-up resistors direct to the PNP bases, on the other side of the 330R compared to your diagram.

Can anyone else provide a double-check for us please?

jirkap95

Last changes. I hope for that :D

PaulRB

Please learn to insert your own images, I am doing it for you every time!

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