This project came about because I had a need for a simple dimmer for a small LED light fixture (1Watt). But by the time I was done, I had 4 different versions. Unlike my Super Dimmer project, these dimmers are all stand-alone (that is, they don't need additional components).

One dimmer is actually an adaption of my Super Dimmer project, but it is self contained, so it can be used in a stand-alone situation. It includes option for RF remote control, but it cannot handle quite as much load as the Super Dimmer.

The chart below shows the 4 dimmers and their differences:

Dimmer SC1: This is a "clone" of sorts of the Super Dimmer project. It uses the same ATTiny85 microcontroller to perform the functions, and in fact - it is interchangeable. For this reason, how to program the microcontroller will not be discussed here. Rather, I am providing a Link where you can read the details, download the sketch (software), and other matters involved in programming the ATTiny85. The remaining three dimmers do not require programming.

Dimmer SC2: This is a low-power PWM dimmer, and can handle about 3Watts, or one typical RV "puck light". My original need for this dimmer was for a single 1Watt LED fixture - used in my console upgrade project.

Dimmer SC3: Since only two components differ, I decided to also construct a high-power PWM dimmer on the same circuit board. I have no immediate use for it, but who knows what the future will hold. This dimmer is useful for up to four 4Watt RV Puck Lights, or a string of monochrome LEDs.

Dimmer SC4: Along with building the original low-power dimmer, I tried a Linear version. This is the result. However, since the output is linear, the voltage drop of the LED being driven is critical. When using this dimmer, even within the 6Watt specification, make sure the dimmer is not overheating.

All of the dimmers were tested with a constant current load to determine how much current they could supply. The ratings were chosen at the point where the dimmer does not heat up more than a few degrees over ambient. Also, different LED light fixtures may affect the heating characteristics of the dimmer. While the components may actually handle more current, the circuit board is limited to the rated capacity. Observe all cautions and monitor temperatures to ensure the dimmer does not oveheat.

SC-1 wiring. There are 4 terminals that connect the dimmer to the circuit. The two input terminals provide 12V to the dimmer, while the two output terminals provide connection to the LED fixture. Note that this is a LOW side dimmer, which means the switching occurs on the negative side of the LED. Therefore, the LED fixture cannot be connected to ground.

The wiring for SC-2, SC-3, and SC-4 is identical so all three will be covered together. The 12V input from the battery is provided by the top connector. The bottom connector consists of a LED-, LED+, and LED Limit (+) lead. This is also a LOW SIDE dimmer, so the LED- lead goes to the negative side of the LED fixture. The LED + provides the full output current of the dimmer to the LED fixture.

The LED limit is useful if you need to drive LEDs that do not have their own driver and need current limiting. It is an optional connection.

Finally, the LED pilot light is an optional LED that is on whenever the driver is powered.

The PWM frequency of Dimmers SC-2 and SC-3 can be changed. This is covered in the build documentation PDF file above with a table of several options. However, the basic formula to determine PWM frequency is:

For example, using a 0.047uF Capacitor, the result would be: 1/(0.7 x 50000 x 0.000000047) = 607Hz