Donations help to keep the site running:
Home
Projects
LED Open Sign
Controller Board
LED Open Sign Controller Board
Created on: 25 September 2012
An ATtiny2313 8-bit AVR microcontroller from Atmel is used on the controller board to control the sequencing of the LEDs.
The controller board shown below consists of the ATtiny2313 microcontroller, ten NPN transistors for driving the LEDs, a 5V regulator circuit and a pin header for programming the microcontroller in-system.
Board Design and Construction
The board has been designed using the open source EDA software, KiCad. Because the board is single-sided, it can easily be made at home using the toner transfer method or other home PCB manufacturing method.
The circuit diagram shows 12 channels for driving LEDs (CH1 to CH12) as well as two push buttons with supporting resistors. It is not necessary to use channel 11 and 12 or the push buttons for the open sign. These can be left off as shown in the board photo above.
These extra channels and push buttons have been put on the board to make it more versatile and may be used with a different sign that needs more LED channels.
The board as shown basically consists of 10 open-collector outputs for driving the LEDs. This means that the anode of the LED will be connected to +12V (off board), the cathode will be connected to a current limiting resistor (off board) which will then be connected to one of the controller board's open collector outputs.
LED Open Sign Component List
The unused transistors, push buttons and supporting components have been left off this list.
| Qty | Part | Designator | Notes | Type |
|---|---|---|---|---|
| 1 | 10k | R15 | 1/4W, 5% or better | Resistors |
| 10 | 2k or 2k2 | R1 to R10 | ||
| 1 | 470 ohm | R16 | ||
| 1 | 330 ohm | R17 | ||
| 1 | 270 ohm | R19 | ||
| 1 | 10 ohm | R18 | ||
| 1 | 470uF | C1 | Electrolytic, 25V or more | Capacitors |
| 1 | 220uF | C2 | Electrolytic, 16V or more | |
| 1 | 100uF | C6 | Electrolytic, 16V or more | |
| 3 | 100n (0.1uF) | C3, C4, C5 | Non-polarized, X7R | |
| 1 | 1N4007 | D1 | Silicon rectifier | Semiconductors |
| 1 | LM317T | U1 | Variable voltage regulator | |
| 1 | ATtiny2313-P | U2 | 8-bit AVR microcontroller from Atmel | |
| 10 | KSP2222A | Q1 to Q10 | Or similar NPN transistor e.g. PN2222 | |
| 6 | PCB screw terminals | P1 to P4, P6, P7 | 5mm or 5.08mm PCB mounting screw terminals | Connectors |
| 1 | 3 by 2 pin header | P5 | 6 pin (3 pins by two rows) 2.54mm spaced pin header (ATtiny2313 ISP header) | |
| 1 | 20 pin DIP IC socket | U2 | 20 pin DIP IC socket for U2 (ATtiny2313) |
Power Supply
A 12V power supply will also be needed to power the controller board and sign. It should be able to deliver 2A or more.
When measured, it was found that the sign drew less then 1.2A with all the LEDs on. It is still recommended to use a power supply that can deliver at least two Amps or more as the amount of current drawn could vary depending on the characteristics of the LEDs used.
Circuit Diagram and PCB Files
Here are the source files for manufacturing and modifying the board.
The circuit diagram (pdf):
schematic_os_sign_controller.pdf
The PCB bottom layer (for toner transfer PCB):
PDF file: os_sign_controller-Back.pdf or PostScript file: os_sign_controller-Back.ps
The PCB top silkscreen layer(for toner transfer silkscreen):
PDF file: os_sign_controller-SilkS_Front.pdf or PostScript file: os_sign_controller-SilkS_Front.ps
The compressed KiCad files (for modifying the board or producing Gerber files):
os_sign_controller.zip or os_sign_controller.tar.gz