Circuit diagram:
Parts:
R1,R5____________1K 1/4W Resistors R2______________33K 1/4W Resistor R3_____________100K 1/2W Trimmer Cermet R4_______________1M 1/4W Resistor R6,R7,R8________10K 1/4W Resistors R9_______________4K7 1/4W Resistor R10_____________33R 1/4W Resistor (See Notes) C1_______________1µF 63V Polyester Capacitor C2_____________100nF 63V Polyester Capacitor C3_____________470µF 25V Electrolytic Capacitor D1______________LED (Any dimension, shape or color) D2,D3________1N4002 100V 1A Diodes D4--D15________LEDs High brightness, high efficiency red types (See Notes) Q1___________2N3819 General-purpose N-Channel FET Q2____________BC337 45V 800mA NPN Transistor Q3____________BC547 45V 100mA NPN Transistor IC1____________7555 or TS555CN CMos Timer IC IC2,IC3________4094 8-stage shift-and-store bus register IC SW1____________SPST Brake/Turn Lights Switch
Comments:
This circuit, designed on request, allows up to 16 LED clusters illuminate in bar-mode sequence. LED sequencing will start when the Brake pedal is pressed (or Turn Lights are switched-on) and, when the last cluster illuminates, all LED clusters will remain steady on until the Brake pedal is released or Turn Lights are switched-off.
Notes:
- R5 and D1 are optional: they could be of some utility in monitoring the sequence frequency set by means of R3.
- Clusters can be formed by up to 12 LEDs as shown in the circuit diagram, right side. Common cluster types usually range from 5 to 10 LEDs.
- Up to 16 of these cluster driver circuits, each formed by the LEDs, two transistors and three resistors can be built and connected to the progressively numbered outputs of IC2 (the first eight clusters) and IC3 (the remaining clusters).
- If a number of clusters up to 8 is required, IC3 can be omitted.
- Constant output current value for the LEDs can be changed by varying R10.
The formula is: R = 0.6/I (I expressed in Amperes). - Use high brightness, high efficiency red LED types of suitable size and change R10 value to suit LED's Absolute Maximum Ratings.
- The main circuit, formed by the three ICs and related components is permanently wired to the supply (and D1 will flash) but its 12V positive supply can be wired after the main switch of the car, or an on/off switch can be added.
