[SOLVED] pic16f876 and 500 LEDs

[tarekovitche]

hi everyone , i have a microcontroller pic16f876 and oscillator 20mhz and power supply 12v 10A
i want to light 500 LEDs blinking all in one , and i have regulator 7805 and transistor npn 2n2222
can i do this with this component and how ? thanks

 

[KlausST]

Hi,

it all depends on voltage, current power.

I don´t know the voltage, current, power of your LEDs.

But usually a LED needs a current limiting resistor. This is not on your stock list. Thus I assume it´s no simple standard solution.

Klaus

 

[tarekovitche]

my LEDs is work in 3 volt 20mA

 

[betwixt]

So you need more than 3V and a total current of 500 * 20mA = 10A. A transistor switch can be used but the 2N2222 is only rated to carry 0.8A maximum so it is far too small to do the job.

The best technical solution is to use the 7805 to power the PIC and to use the voltage BEFORE the 7805 to power the LEDs through suitable resistors. All the LED cathodes would be joined together and a MOSFET connected to ground would be used to switch them. You can drive the MOSFET directly from the PIC or better still, use your 2N2222 between the PIC and MOSFET to boost the gate voltage.

It may be possible to wire some of the LEDs in series then the series chains in parallel but we need to know more about your power supply before we can advise the best way to do it.

Brian.

 

[tarekovitche]

So you need more than 3V and a total current of 500 * 20mA = 10A. A transistor switch can be used but the 2N2222 is only rated to carry 0.8A maximum so it is far too small to do the job.

The best technical solution is to use the 7805 to power the PIC and to use the voltage BEFORE the 7805 to power the LEDs through suitable resistors. All the LED cathodes would be joined together and a MOSFET connected to ground would be used to switch them. You can drive the MOSFET directly from the PIC or better still, use your 2N2222 between the PIC and MOSFET to boost the gate voltage.

It may be possible to wire some of the LEDs in series then the series chains in parallel but we need to know more about your power supply before we can advise the best way to do it.

Brian.

thank you so mutch Mr.Brain my power supply is 12v 10A 60w, and i have also power supply 5v 40A can i use it?
I want to use as few component as possible
I also want to connect all LEDs in parallel
and thank you so much for your help

 

[d123]

Hi,

Maybe adding a few more components such as a few chained decimal counters or BCD chips could be combined with a fast 10% or 30% duty cycle to lower power consumption a lot. The human eye/human perception is very slow in comparison so it wouldn't be noticeable at all, only picked up by phone cameras, etc

 

[andre_luis]

Without mentioning the color, it will not be possible to perform an adequate calculation. the forward drop voltage of a visible light standard PTH LED varies between 1.8 (red) and 3.3 (blue) volts.

 

[KlausST]

Hi,

I want to use as few component as possible

500 LEDs are not a few.
If you want a few parts then use one high Power LED and a MOSFET.

Klaus