Silicon ChipDisplaying digits using single RGB LEDs - March 2021 SILICON CHIP
  1. Outer Front Cover
  2. Contents
  3. Publisher's Letter: Older devices involved creative engineering
  4. Mailbag
  5. Feature: Hoarding: Urban Electronic Archaeology by Dr David Maddison
  6. Project: High-Current Four Battery/Cell Balancer by Duraid Madina
  7. Feature: Fetrons, and the All-Fetron Radio by Dr Hugo Holden
  8. Circuit Notebook: Low-noise microphone preamp by Petre Petrov
  9. Circuit Notebook: Two quartz crystal oscillators using a flip-flop by Ariel G. Benvenuto
  10. Circuit Notebook: Displaying digits using single RGB LEDs by Benabadji Mohammed Salim
  11. Circuit Notebook: The Omnidetector by Rev. Thomas Scarborough
  12. Feature: The History of Videotape – Quadruplex by Ian Batty, Andrew Switzer & Rod Humphris
  13. Serviceman's Log: If it isn't one thing, it's another by Dave Thompson
  14. Project: Mini Isolated Serial Link by Tim Blythman
  15. Feature: All About Capacitors by Nicholas Vinen
  16. Project: Battery Multi Logger - Part 2 by Tim Blythman
  17. Project: Electronic Wind Chimes - Part 2 by John Clarke
  18. PartShop
  19. Vintage Radio: Kriesler Triplex 41-21 portable transistor radio by Ian Batty
  20. Subscriptions
  21. Product Showcase
  22. Ask Silicon Chip
  23. Market Centre
  24. Advertising Index
  25. Notes & Errata: USB SuperCodec, August-October 2020; Car Altimeter, May 2020; 6GHz Touchscreen Frequency Counter, October-December 2017
  26. Outer Back Cover

This is only a preview of the March 2021 issue of Silicon Chip.

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Items relevant to "High-Current Four Battery/Cell Balancer":
  • High Current Battery Balancer PCB [14102211] (AUD $12.50)
  • ATSAML10E16A-AUT programmed for the High-Current Battery Balancer [1410221B.HEX] (Programmed Microcontroller, AUD $15.00)
  • Firmware for the High-Current Battery Balancer [1410221B.HEX] (Software, Free)
  • High Current Battery Balancer PCB pattern (PDF download) [14102211] (Free)
Articles in this series:
  • High-Current Four Battery/Cell Balancer (March 2021)
  • High-Current Four Battery/Cell Balancer - Part 2 (April 2021)
Items relevant to "Displaying digits using single RGB LEDs":
  • Firmware for the Digit display with single RGB LEDs (Software, Free)
Articles in this series:
  • The History of Videotape – Quadruplex (March 2021)
  • The History of Videotape - Helical Scan (April 2021)
  • The History of Videotape – Cassette Systems (May 2021)
  • The History of Videotape – Camcorders and Digital Video (June 2021)
Items relevant to "Mini Isolated Serial Link":
  • Mini Isolated Serial Link PCB [24102211] (AUD $2.50)
  • Complete kit for the Mini Isolated Serial Link (Component, AUD $10.00)
  • Mini Isolated Serial Link PCB pattern (PDF download) [24102211] (Free)
Items relevant to "Battery Multi Logger - Part 2":
  • Battery Multi Logger PCB [11106201] (AUD $5.00)
  • PIC16F1455-I/SL programmed for the Microbridge [2410417A.HEX] (Programmed Microcontroller, AUD $10.00)
  • PIC32MX170F256B-I/SO programmed for the Battery Multi Logger [1110620A.hex] (Programmed Microcontroller, AUD $15.00)
  • DS3231MZ real-time clock IC (SOIC-8) (Component, AUD $10.00)
  • DS3231 real-time clock IC (SOIC-16) (Component, AUD $7.50)
  • SMD resistor - 15mΩ ±1% M6332/2512 3W (CRA2512-FZ-R015ELF or similar) (Source component, AUD $2.00)
  • 2.8-inch TFT Touchscreen LCD module with SD card socket (Component, AUD $25.00)
  • Matte/Gloss Black UB3 Lid for 2.8-inch Micromite LCD BackPack (PCB, AUD $5.00)
  • Battery Multi Logger software [1110620A.hex] (Free)
  • Battery Multi Logger PCB pattern (PDF download) [11106201] (Free)
Articles in this series:
  • Battery Multi Logger (February 2021)
  • Battery Multi Logger - Part 2 (March 2021)
Items relevant to "Electronic Wind Chimes - Part 2":
  • Electronic Wind Chimes PCB [23011201] (AUD $10.00)
  • PIC16F1459-I/P programmed for the Electronic Wind Chimes [2301120A.HEX] (Programmed Microcontroller, AUD $10.00)
  • Pair of CSD18534KCS logic-level Mosfets (Component, AUD $6.50)
  • Electronic Wind Chimes software [2301120A.hex] (Free)
  • Electronic Wind Chimes PCB pattern (PDF download) [23011201] (Free)
Articles in this series:
  • Electronic Wind Chimes (February 2021)
  • Electronic Wind Chimes - Part 2 (March 2021)

Purchase a printed copy of this issue for $10.00.

Displaying digits using single RGB LEDs With embedded systems these days, engineers must often deal with very small PCB footprints, so suitable displays (especially for debugging) can be difficult. My idea is to display multidigit numbers using just a few RGB LEDs, where the digital value of 0-9 is shown using standard resistor colour codes (black, brown, red, …, white). The circuit shown in Fig.1 is minimalistic, using just one high-brightness RGB LED controlled by a tiny PIC10F200 (the world’s smallest 6-pin microcontroller). It uses three simultaneous PWM pulse trains, each with an independently controllable duty cycle. By varying the duty cycles, the intensity of the red, green and blue elements within the RGB LED create different colour mixes. While seven of the required colours are easy to obtain: red, green, blue, yellow (red+green), purple (red+blue), white (red+green+blue) and black (led off), achieving the three remaining colours required some experimentation and fine-tuning of a look-up table (see the table at right). The current-limiting resistors have also been individually adjusted to obtain the same brightness precisely, using a lux meter. The RGB led should be used with a white diffuser to mask the individual red, green, blue elements (even with SMD RGB LEDs, these elements are distinctly visible). Pin 6 in the circuit shown monitors the status of pushbutton S1, which allows you to cycle through the available digits values/colours (Fig.1). This pin has an internal pull-up enabled for that micro pin so that it can detect button presses. As shown in Fig.3, this circuit can be used in cascade, with discrete logic OR gates, creating a multi-digit display. Alternatively, a single 8-pin microcontroller can drive a four-digit LED display, as shown in Fig.2. The source code (1dgtRGB.ASM and PWMLEDS.INC) is available for download from siliconchip.com. au/Shop/6/5781 This suits the 6-pin PIC10F200 and would need to be modified for the PIC12F617 or other micros. Its size is optimised, and it uses macros to ease understanding. It occupies just 116 program words and nine data bytes. The code is fully commented, to make it easy to adapt to other microcontrollers. Benabadji Mohammed Salim, Oran, Algeria. ($100) Fig.1 Fig.2 Fig.3 siliconchip.com.au Australia’s electronics magazine March 2021  41