[SOLVED] Blinking 150 leds at 1sec delay using NE555 timer ic

[czabhinav]

I need to blink 150 leds at a rate of 1sec delay using NE555 timer ic. I have studied about the timer circuit and required calculation for achieving proper timing. I have used R1 as 1k and R2 as 150k with C = 10uF and its giving me 1sec on and off time. Now I need to drive 150 leds with 1sec on off time. I am planning to connect all the leds in parallel and give them 12v via 1k resistor. and connecting a MOSFET to the output pin of the 555 and then connecting this MOSFET with all the leds. I have not designed the circuit yet but I have tried simulating it and it seems to be working.
I have attached an image of the circuit. The image is just for the demo purpose so I have just connected 6 leds but I will be connected 150 leds in same way. I will be using yellow colored 5mm led. I want to if this circuit is fine and will work properly or is there any error in it.
Thanks.

 

[ud23]

you need aprroximate 2 to3amp 12v regulated power supply.

proper value resistor at mosfet gate terminal.

 

[BradtheRad]

Try to see whether you can put 2 or 3 led's in series. Each string needs a resistor (several hundred ohms).

Thus if your strings are 2 led's each then you'll need 75 resistors (maybe 400 or 500 or 600 ohms).
If 3 led's each then you'll need 50 resistors (maybe 200 or 300 or 400 ohms).

Brightness depends on how well the mosfet conducts, as well as led characteristics and resistor values.

 

[KlausST]

Hi,

typical LEDs need about 2V forward voltage. So the rest to the 12V is about 10V. These 10V are across the resistor and dissipated as heat (current multiplied with voltage).
This is a lot of wasted power.

As Brad says: use some LEDs in series. Then you need a smaller power supply, and less heat is generated.

What power supply do you use?

Example:
With your current configuration each LED runs with about 10mA. Making 150 x 10 mA = 1.5A at 12V.
If you have a regulated 12V supply you can run 5 LEDs and a 200Ohms resistor in a string .. and you need 30 strings. This makes 10mA per string giving only 300mA at 12V.
--> only 1/5 of the power before.

Use the LED datasheet to calculate the exact resistor.

Klaus

 

[schmitt trigger]

I don't remember whether it was discussed in this or another forum, but someone posted a similar idea, of using hundreds of LEDs to light up an area. To improve the efficiency, you know LEDs are very efficient.
Only that he had a similar scheme, where each individual LED was fed up via its own individual resistor from 12 volt.