Question: [![enter image description here](https://i.stack.imgur.com/Hio4d.png)](https://i.stack.imgur.com/Hio4d.png)

Hi Guys .. I am designing a few panels using LEDs for backlighting. Some of these panels have over 20 leds, using a 5v power source. So only one of these panels can draw around 500mA alone. I am planning on using the same PSU to power them all, but need a dimmer circuit to dim them all at once, but most of the dimmer circuits I have seen can only really do lower current draw, i.e. 2N2222 can only handle 800mA.

Any idea if this is possible with one high current dimmer, or do I have to build multiple dimmers ?

Answer: 
Pulse width modulation (PWM) is the most efficient way to do this. The basic principle is that you cycle the LEDs on and off at a speed fast enough that the eye can't detect a flicker - say 50 times a second. By varying the % on-time from 0 to 100% the LEDs can go from 0 to 100% brightness. The advantages are:

* The power circuit is very simple.
* No power is used while their off.

We need to know what is going to control the dimmer if we are to provide further information.
You can use a circuit like this one (from [here](https://learn.sparkfun.com/tutorials/led-light-bar-hookup/example-circuits)): (operated from +5V only)

[![enter image description here](https://i.stack.imgur.com/I1afr.png)](https://i.stack.imgur.com/I1afr.png)

Use a CMOS version of the 555 (eg. TLC555) rather than the NE555, and reduce R3 to 100 ohms. 

Q1 must be a logic-level MOSFET such as an [AOD476](http://aosmd.com/res/data_sheets/AOD476.pdf). The circuit as described will easily handle several amperes.