The controller of a two-color light cord Flexilight on the microcontroller. Scheme, description

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The controller of a two-color light cord Flexilight on the microcontroller. Encyclopedia of radio electronics and electrical engineering

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Encyclopedia of radio electronics and electrical engineering / Microcontrollers

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The controller is used with the Flexilight light cord to achieve various dynamic lighting effects. Flexilight is a flexible material for illuminated advertising, an alternative to "neon" advertising. Made from a solid PVC tube with a diameter of ~12 mm, filled with miniature light bulbs with a pitch of ~25 mm. Usually used to decorate and highlight the corners of buildings, roads, stairs, create inscriptions, pictures, etc. The controller provides a smooth change in brightness in color channels. There are three control buttons: two buttons - change the speed of the effects (faster - FAST, slower - SLOW) and the third button to switch between effects (PROG). Effects are switched in a circle: 1-2-3-..-1-2-3-.. The controller has a simple internal language for describing effects, which makes it easier to write them.

The first version of the controller is made on PIC16F84.

Fig.1. Schematic diagram of the Flexilight two-color light cord controller (first version) (click to enlarge)

To adjust the brightness, a phase-pulse method is used. At the beginning of the network half-cycle, the triac closes, then after the time interval set by the timer, the triac opens with a short pulse and remains open until the beginning of the next network half-cycle. The smaller the value loaded into the timer, the greater the brightness. Since the bulbs of the light cord are powered by an alternating sinusoidal voltage of 220 V, the dependence of the brightness on the moment the triac is turned on is non-linear. In order for the brightness change to look linear, the program has a table that contains the timer coefficients for each brightness gradation.

Attention! The controller does not have galvanic isolation from the 220 V network, therefore, appropriate safety measures must be observed during installation and operation. When using the triacs indicated in the diagram without radiators, the power of the switched load should not exceed 200..300 W, which approximately corresponds to 10 m of a light cord.

The second version of the controller, in order to reduce the cost, is made on the PIC12C509 using an internal RC generator.

Fig.2. Controller diagram for a two-color Flexilight light cord (second option) (click to enlarge)

A demo version of the program for the first version of the controller (for PIC16F84) is available for download. The firmware is in the file bi_demo.zip (2,151 KB). The demo version has 3 effects with a limited execution time. After this time, the controller stops the effect from executing. To continue working, press the PROG button.

Documentation (Datashit) for MK PIC16F84A

Author: Evgeny Soloshenko, solosh@ukr.net; Publication: cxem.net

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