About the article

Two-Colour Running Light

with microprocessor control

Two-Colour Running Light
Lighting effects are always popular and we frequently publish such projects in the pages of Elektor Electronics. Here is a circuit that uses a microcontroller to drive up to 96 bicolour LEDs in a wide range of patterns. A particular feature of the design is the way it exploits the persistence of human vision.Instead of `regular’ LEDs this running light uses so-called bicolour LEDs which can emit two different colours, usually red and green. These are available in versions with three connections (a common cathode and separate anodes) or with two connections. We use the second type in this circuit, where the two LEDs are connected in antiparallel so that one LED or the other lights according to the direction of current flow.
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Gerber file

CAM/CAD data for the PCB referred to in this article is available as a Gerber file. Elektor GREEN and GOLD members can exclusively download these files for free as part of their membership. Gerber files allow a PCB to be produced on an appropriate device available locally, or through an online PCB manufacturing service.

Elektor recommends its business partner Eurocircuits as the company of choice for its own prototypes and volume production in selected cases.

Component list
Controller board
R1 = 4-way10k? SIL array
R2 = 2k?2
R3 = 22k?
R4 = 10k?
R5,R6 = 1k?
C1,C2 = 33pF
C3 = 10µF 16V radial
C4 = 470µF 16V radial
C5 = 100µF 16V radial
C6 = 100nF
D1 = 1N4148
T1 = BC547B
IC1 = AT89C2051-12PC, programmed, order code 010134-41
IC2 = 7805
K1 = 9-way sub-D socket, angled pins, PCB mount
K2-K5 = 5-way SIL pinheader
K6 = mains adaptor socket, PCB mount
PCB, order code 010134-1
Disk, order code 010134-11
LED board
R1-R24 = 390?
C1,C2,C3 = 100nF
D1-D24 = bicolour LED, 2 pins, 3mm dia.
IC1-IC6 = 74HC164
K1 = 5-way SIL pinheader
PCB, order code 010134-2
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