[SOLVED] light 7 LED by timer of an AVR microcontroller

[matin-kh]

Hi everyone,
I have 7 LEDs in my board which I used them instead of 7segmnet. each of them are connected to an I/O port of AVR microcontroller. because of supply limitataion forexample for showing '8' all the LEDs could not be on all together and because of me supply source just one LED can be on at a moment. so I have to solve this problem by software. I have to use a timer which light just one LED at a moment.sth like below. my problem is the value of x, what can be the value of x which human eyes don't recognize that LEDs are blinking?
Best Regards
Matin

 

[Okada]

The code is like

PORTB = 0x01;
PORTB = 0x02;
PORTB = 0x04;
PORTB = 0x08;
PORTB = 0x10;
PORTB = 0x20;
PORTB = 0x40;
PORTB = 0x80;

Don't use any delays.

 

[matin-kh]

The code is like

PORTB = 0x01;
PORTB = 0x02;
PORTB = 0x04;
PORTB = 0x08;
PORTB = 0x10;
PORTB = 0x20;
PORTB = 0x40;
PORTB = 0x80;

Don't use any delays.

with this method, LEDS can being on? because LEDs need a time to start lighting but forexample with 8MHz frequency, the time for executing each line of code is too short and with this code LEDS have enough time to being on?

 

[KlausST]

Hi,

LEDs are very fast in switching ON.
If muxing, then I'd use a interrupt controlled muxing. Interrupt at least 1kHz. Delay beween LEDs.

But really...I'd just lower the LED current by changing the current limiting resistor to safe from muxing.

Klaus

 

[Okada]

If needed add 2 ms delay between each instruction.

 

[Easyrider83]

This is called dinamic segment-by-segment indication. You should switch between segments by using timer interrupt. That's simple. I can't undrestand what throubles do you have.

 

[matin-kh]

This is called dinamic segment-by-segment indication. You should switch between segments by using timer interrupt. That's simple. I can't undrestand what throubles do you have.

I know, If you see the picture which I attached in the first post, I want to khnow a reasonable value for 'x'.
Thanks
Matin

 

[Easyrider83]

Since 50Hz we can't see any switching. So, basicaly, you have to device 20ms to 7 (segments amount). So, 3ms is enought.

 

[Okada]

Which AVR Microcontroller are you using and what is the Crystal frequency ?