8 x 16 (red green) led matrix project

[tubos]

- I would like to make a battery operated project
- with 2 8x8 red green led matrix modules.
- run by pic with some sw pwm coding.

- one of the requirements is that most of the time the project should
be sleeping and draw almost no current < 100uA.

- That leaves out using the TLC5940 as a driver .

- I was thinking of using a 64 pin pic and connect all columns to separate pins ( 32 pins)
then use a row driver like the TPIC...

Any other ideas or tips ?

 

[ronsimpson]

I don't see the math! 32 pins.
You are thinking about using (8xa pins +8ya pins)=(8xb Pins +8yb pins)=32 pins.

1) Your Idea using 32 pins.
10000000 Data to be displayed 10000000 Data to be displayed2
01000000 Data to be displayed 01000000 Data to be displayed2
00100000 Data to be displayed 00100000 Data to be displayed2
00010000 Data to be displayed 00010000 Data to be displayed2
00001000 Data to be displayed 00001000 Data to be displayed2
00000100 Data to be displayed 00000100 Data to be displayed2
00000010 Data to be displayed 00000010 Data to be displayed2
00000001 Data to be displayed 00000001 Data to be displayed2

2) Using 24 pins.
10000000 Data to be displayed Data to be displayed2
01000000 Data to be displayed Data to be displayed2
00100000 Data to be displayed Data to be displayed2
00010000 Data to be displayed Data to be displayed2
00001000 Data to be displayed Data to be displayed2
00000100 Data to be displayed Data to be displayed2
00000010 Data to be displayed Data to be displayed2
00000001 Data to be displayed Data to be displayed2

3) Use 3 pins on the PIC that drive a 3 to 8 decoder IC. The IC inputs a number 0 through 7 on three pins and drives 1 of 8 pins.
0 10000000 Data to be displayed Data to be displayed2
1 01000000 Data to be displayed Data to be displayed2
2 00100000 Data to be displayed Data to be displayed2
3 00010000 Data to be displayed Data to be displayed2
4 00001000 Data to be displayed Data to be displayed2
5 00000100 Data to be displayed Data to be displayed2
6 00000010 Data to be displayed Data to be displayed2
7 00000001 Data to be displayed Data to be displayed2

4) I have also used a ring counter to step through the columns. The counter has a reset pin that takes you to 10000000 and a clock pin that increments the count by 1. If I remember right CD4022 or a CD4017 for 10 outputs. Also see MC14022, MC14017.

 

[tubos]

there are 32 columns 16 green and 16 red.
As stated in topic i need ultra low current sleep mode.

So i can not use TLC5940 or other drivers that use current themselves
when nothing is displayed.

any other helpful answers?

 

[ronsimpson]

there are 32 columns 16 green and 16 red.
As stated in topic i need ultra low current sleep mode.

8 x 16 (red green) led matrix project
with 2 8x8 red green led matrix modules.

I don't understand. How many LEDs? matrix or no matrix?

8x8 matrix=64 LEDs

 

[tubos]

Its all in the title

8 x 16 (red green) led matrix project

so there are 8 x 32 leds in a matrix .

 

[tubos]

No takers?

 

[ronsimpson]

I don't know how much current you want to run in the LEDs.
In a matrix the current will be high. The LEDs will only be on 1/8 of the time. If you want very bright; you might need 50mA for 1/8 of the time.
The PIC can not drive 50mA. If the current is too high you will need a N-channel logic level MOSFET to switch the current.
On the top side (8 pins) use P-channel logic level MOSFETS. These MOSFETs will control 32 LEDs at a time so the current will be very high.

(you could reverse that and have 8 N-channel logic level MOSFET and 32 P-channel logic level MOSFETS.

 

[4pyros]

Have you looked at charlieplexing?

 

[tubos]

I will only be running 20mA per led .

 

[nickelflippr]

Any other ideas or tips ?

Continue on with the 32 soft PWM idea and use the high side PFETs per ronsimpson for row drivers.

OR

Use the CC PWM led driver chip of choice and use the micro software to switch off/on a high side PFET switch to the driver supply line when going to sleep, and on wakeup.