Question about using PIC OR ATMEL

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kobre98

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I want to make a Rotating led display in which I will connect 30 leds that will light at the same time,
I tried to this with PIC but it miss function cause of current drain !!!
Could this be done with ATMEL AT89C51 ?!?!
 

it's not ready yet, but it involve 30 led with 220 resistor for each connected to 30 pins of the micro-controller
 

kobre98 said:
it's not ready yet, but it involve 30 led with 220 resistor for each connected to 30 pins of the micro-controller
Click to expand...
so 30 pin use then which micro controller u used ? and what is your resistor value? and your goal is light up all L.E.D right ?
 

I used PIC18F and PIC16F
with resistor value 220 ohm
it didn't work
I heard that I can use AT89C51 and it can provide more power
 

Do you want to turn ON/OFF each LED individually or or you multiplexing some or all of them? You can use 4 X 74HC595 to drive 32 LEDs and it connects to micro with 3 pins. You need micro with 3 digital IO pins and some 2KB ROM. You can also use any 14 pin IC with I2C/SPI and use 2 X MCP23017/23S17. If you can get any 8 pin micro with I2C/SPI then it is also ok or you can use 8 pin micro with software i2c/spi.

**broken link removed**
 
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thanks for your reply but I really need something compact, I don't need more ICs to be attached to the system, I just want a controller and the LEDs
since it will be rotating using a motor and I can't afford additional weight on the motor head
 

rotating using motor means input as a motor and led blink as a rotate motor state ?
 

Last edited:

kobre98 said:
thanks for your reply but I really need something compact, I don't need more ICs to be attached to the system, I just want a controller and the LEDs
since it will be rotating using a motor and I can't afford additional weight on the motor head
Click to expand...


Hi,

You still have not answered the key question, how many leds will be on at any one time ?

A typical Pic 16F or 18F micro can handle up to 25ma per output pin BUT the total load on the chip is about 200-300ma so that limits how many leds you can drive directly.
Thats a different current load if you are multiplexing the leds, which again you do not say.
 


I want to light the 30 leds at the very same time, and does ATMEL support only 200-300ma as well ?!
 

Hi check the sinking current limitation and connect the current limiting resistors as to divide the current to 30 individual LEDs....
 

This is the best circuit for you. LEDs and resistors packs are needed for circuit using any micro. The space taken by 2 X port expanders and micro is less than that of 40 pin micro.

Another method is using one 74HC595, PIC12F1823, ULN2803 or 4 PNP transistors. Each transistor will drive 8 LEDs. 4 pins for transistors, 3 pins for 74HC595 (total 7 pins in micro). Multiplexed display. 8 leds turn ON at a time for a short period and then turn OFF.



 

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