led chaser pwm

Posted on Feb 5, 2014

This neat little circuit provides 8 LEDs directly driven from the PIC along with a single mode control switch. The firmware elsewhere on this page drives the LEDs with a 5 bit PWM signal providing each of the 8 LED channels with four levels of intensity; off, dim, mid, bright. A number of sequences are programmed into the firmware to provide some

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interesting visual effects and chase sequences, including the classic effect seen on the car in the Knight Rider TV series. The software has sequential, random and manual sequence run modes and manual advance to the next sequence in any mode. The selected sequence and mode are also saved to non-volatile memory so it will always restart in the selected mode. The design is deliberately simple with each LED being directly driven from a PIC I/O pin. This and the inclusion of an in-circuit programming header (ICSP) make the circuit ideal for teaching/learning introductory PIC assembly language programming. You can use it with different sized LEDs and mixed colours, as well as fewer than 8 LEDs. As well as using it as a LED chaser it is great for adding effects to toys and models. See FAQ However, if you just want a cool LED chaser without having to write any code, a ready written LED chaser program including 34 chase effects with source code and programmer ready HEX files is provided at the bottom of this page. Here`s a couple of variations I`ve built based on the basic PWM LED chaser described on this page. They run exactly the same base code, just use different sequences to suit the layout of the boards. The heart of the LED chaser is the PIC 16F628A microcontroller, IC2. The program that runs on this chip controls the LEDs attached to the output port pins. Resistors R1 thru R8 limit the current through LED1 - LED8 to a safe...

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