Silicon ChipIlluminated doorbell press switch circuit - March 2022 SILICON CHIP
  1. Outer Front Cover
  2. Contents
  3. Publisher's Letter: RIP Brendan James Akhurst, cartoonist extraordinaire
  4. Mailbag
  5. Feature: The History of Transistors, part one by Ian Batty
  6. Project: Capacitor Discharge Welder, part one by Phil Prosser
  7. Project: Raspberry Pi Pico BackPack by Tim Blythman
  8. Feature: All About Batteries, part three by Dr David Maddison
  9. Serviceman's Log: The oven with a mind of its own by Dave Thompson
  10. Project: Amplifier Clipping Indicator by John Clarke
  11. Circuit Notebook: An alternative version of the Arduino Power Supply by Stephen Gordon
  12. Circuit Notebook: Illuminated doorbell press switch circuit by David Worboys
  13. Circuit Notebook: Reading three digital signals with a two-channel oscilloscope by John Rich
  14. Feature: Advances in Drone Technology by Bob Young
  15. Project: Dual Hybrid Power Supply, part two by Phil Prosser
  16. Feature: A Gesture Recognition Module by Jim Rowe
  17. Vintage Radio: Phenix Ultradyne L-2 by Dennis Jackson
  18. PartShop
  19. Ask Silicon Chip
  20. Market Centre
  21. Advertising Index
  22. Notes & Errata: Vintage Radio, February 2022; USB Cable Tester, November & December 2021
  23. Outer Back Cover

This is only a preview of the March 2022 issue of Silicon Chip.

You can view 0 of the 112 pages in the full issue.

For full access, purchase the issue for $10.00 or subscribe for access to the latest issues.

Articles in this series:
  • The History of Transistors, part one (March 2022)
  • The History of Transistors, Pt2 (April 2022)
  • The History of Transistors, Pt3 (May 2022)
Items relevant to "Capacitor Discharge Welder, part one":
  • Capacitor Discharge Welder Power Supply PCB [29103221] (AUD $5.00)
  • Capacitor Discharge Welder Control PCB [29103222] (AUD $5.00)
  • Capacitor Discharge Welder Energy Storage Module PCB [29103223] (AUD $2.50)
  • IRFB7434(G)PBF‎ N-channel high-current Mosfet (Source component, AUD $5.00)
  • Hard-to-get parts & PCB for the Capacitor Discharge Welder Energy Storage Module (ESM) (Component, AUD $20.00)
  • Hard-to-get parts & PCB for the Capacitor Discharge Welder Power Supply (Component, AUD $25.00)
  • Validation spreadsheets for the CD Spot Welder (Software, Free)
  • Capacitor Discharge Welder PCB patterns (PDF download) [29103221-3] (Free)
Articles in this series:
  • Capacitor Discharge Welder, part one (March 2022)
  • Capacitor Discharge Welder, Pt2 (April 2022)
Items relevant to "Raspberry Pi Pico BackPack":
  • Raspberry Pi Pico BackPack PCB [07101221] (AUD $5.00)
  • DS3231MZ real-time clock IC (SOIC-8) (Component, AUD $10.00)
  • DS3231 real-time clock IC (SOIC-16) (Component, AUD $7.50)
  • 3.5-inch TFT Touchscreen LCD module with SD card socket (Component, AUD $35.00)
  • Raspberry Pi Pico BackPack kit (Component, AUD $80.00)
  • Matte/Gloss Black UB3 Lid for Advanced GPS Computer (BackPack V3) or Pico BackPack (PCB, AUD $5.00)
  • Matte/Gloss Black UB3 Lid for Micromite LCD BackPack V3 or Pico BackPack using 3.5in screen (PCB, AUD $5.00)
  • Raspberry Pi Pico BackPack software (Free)
  • Raspberry Pi Pico BackPack PCB pattern (PDF download) [07101221] (Free)
Articles in this series:
  • All About Batteries - Part 1 (January 2022)
  • All About Batteries – Part 2 (February 2022)
  • All About Batteries, part three (March 2022)
Items relevant to "Amplifier Clipping Indicator":
  • 500W Amplifier Module PCB [01107021 RevD] (AUD $25.00)
  • Hard-to-get parts for the 500W Amplifier (Component, AUD $200.00)
  • 500W Amplifier Module PCB pattern (PDF download) [01107021] (Free)
  • Amplifier Clipping Indicator PCB [01112211] (AUD $2.50)
  • Amplifier Clipping Indicator PCB pattern (PDF download) [01112211] (Free)
Articles in this series:
  • Fan Controller & Loudspeaker Protector (February 2022)
  • Amplifier Clipping Indicator (March 2022)
  • 500W Power Amplifier, Part 1 (April 2022)
  • 500W Power Amplifier, Part Two (May 2022)
  • 500W Power Amplifier, Part 3 (June 2022)
Items relevant to "Dual Hybrid Power Supply, part two":
  • Intelligent Dual Hybrid Power Supply PCB set (AUD $25.00)
  • Intelligent Dual Hybrid Power Supply regulator PCB [18107211] (AUD $7.50)
  • Intelligent Dual Hybrid Power Supply front panel control PCB [18107212] (AUD $2.50)
  • PIC32MZ2048EFH064-250I/PT programmed for the Intelligent Dual Hybrid Power Supply [0110619A.HEX] (Programmed Microcontroller, AUD $30.00)
  • 128x64 Blue LCD screen with KS0108-compatible controller (Component, AUD $30.00)
  • Hard-to-get parts for the Intelligent Dual Hybrid Power Supply regulator board (Component, AUD $125.00)
  • Hard-to-get parts for the Intelligent Dual Hybrid Power Supply CPU board (Component, AUD $60.00)
  • LCD panel bezel for the Dual Intelligent Hybrid Power Supply (PCB, AUD $5.00)
  • Intelligent Dual Hybrid Power Supply firmware [0110619A.HEX] (Software, Free)
  • Intelligent Dual Hybrid Power Supply PCB patterns [18107211/2] (Free)
  • DSP Active Crossover/DDS/Reflow Oven PCB patterns (PDF download) [01106191-6] (AUD $3.00)
Articles in this series:
  • Dual Hybrid Power Supply – Pt1 (February 2022)
  • Dual Hybrid Power Supply, part two (March 2022)
Items relevant to "A Gesture Recognition Module":
  • MMbasic software for the PAJ7620U2 gesture recognition module (Free)
Articles in this series:
  • El Cheapo Modules From Asia - Part 1 (October 2016)
  • El Cheapo Modules From Asia - Part 2 (December 2016)
  • El Cheapo Modules From Asia - Part 3 (January 2017)
  • El Cheapo Modules from Asia - Part 4 (February 2017)
  • El Cheapo Modules, Part 5: LCD module with I²C (March 2017)
  • El Cheapo Modules, Part 6: Direct Digital Synthesiser (April 2017)
  • El Cheapo Modules, Part 7: LED Matrix displays (June 2017)
  • El Cheapo Modules: Li-ion & LiPo Chargers (August 2017)
  • El Cheapo modules Part 9: AD9850 DDS module (September 2017)
  • El Cheapo Modules Part 10: GPS receivers (October 2017)
  • El Cheapo Modules 11: Pressure/Temperature Sensors (December 2017)
  • El Cheapo Modules 12: 2.4GHz Wireless Data Modules (January 2018)
  • El Cheapo Modules 13: sensing motion and moisture (February 2018)
  • El Cheapo Modules 14: Logarithmic RF Detector (March 2018)
  • El Cheapo Modules 16: 35-4400MHz frequency generator (May 2018)
  • El Cheapo Modules 17: 4GHz digital attenuator (June 2018)
  • El Cheapo: 500MHz frequency counter and preamp (July 2018)
  • El Cheapo modules Part 19 – Arduino NFC Shield (September 2018)
  • El cheapo modules, part 20: two tiny compass modules (November 2018)
  • El cheapo modules, part 21: stamp-sized audio player (December 2018)
  • El Cheapo Modules 22: Stepper Motor Drivers (February 2019)
  • El Cheapo Modules 23: Galvanic Skin Response (March 2019)
  • El Cheapo Modules: Class D amplifier modules (May 2019)
  • El Cheapo Modules: Long Range (LoRa) Transceivers (June 2019)
  • El Cheapo Modules: AD584 Precision Voltage References (July 2019)
  • Three I-O Expanders to give you more control! (November 2019)
  • El Cheapo modules: “Intelligent” 8x8 RGB LED Matrix (January 2020)
  • El Cheapo modules: 8-channel USB Logic Analyser (February 2020)
  • New w-i-d-e-b-a-n-d RTL-SDR modules (May 2020)
  • New w-i-d-e-b-a-n-d RTL-SDR modules, Part 2 (June 2020)
  • El Cheapo Modules: Mini Digital Volt/Amp Panel Meters (December 2020)
  • El Cheapo Modules: Mini Digital AC Panel Meters (January 2021)
  • El Cheapo Modules: LCR-T4 Digital Multi-Tester (February 2021)
  • El Cheapo Modules: USB-PD chargers (July 2021)
  • El Cheapo Modules: USB-PD Triggers (August 2021)
  • El Cheapo Modules: 3.8GHz Digital Attenuator (October 2021)
  • El Cheapo Modules: 6GHz Digital Attenuator (November 2021)
  • El Cheapo Modules: 35MHz-4.4GHz Signal Generator (December 2021)
  • El Cheapo Modules: LTDZ Spectrum Analyser (January 2022)
  • Low-noise HF-UHF Amplifiers (February 2022)
  • A Gesture Recognition Module (March 2022)
  • Air Quality Sensors (May 2022)
  • MOS Air Quality Sensors (June 2022)
  • PAS CO2 Air Quality Sensor (July 2022)

Purchase a printed copy of this issue for $11.50.

Illuminated doorbell press switch circuit This circuit allows you to add an illuminated doorbell press switch to a new or existing wireless chime setup. You can also use it to upgrade an existing illuminated press switch to longlife LED lighting. No more costly and hard-to-get specialised light bulbs for your favourite bell switch! Four 3mm super-bright LEDs of any colour are connected in series and housed within the body of the pushbutton switch. They should be arranged to shine through the switch sides; in my case, a Friedland D534 Lightspot. The LED current is limited to a safe level by the 150W 2W resistor, although the resistance of the wires leading to the switch has an effect too, depending on their length. When the button is pressed, the LEDs are effectively shorted and the voltage at the inverting input of the LM393N comparator (pin 2) drops below the reference voltage at the non-inverting input, set by trimpot VR1. This causes the LM393N’s output transistor to turn off, switching on NPN transistor Q1 due to the 10kW pull-up resistor and energising the small relay. The normally-open contacts of the relay can be used to adapt a wireless doorbell transmitter by bridging its pushbutton switch, or simply used to control a bell or chime in a conventional wired doorbell. The circuit can be easily constructed on a small piece of veroboard, powered from a small 12V plugpack and housed in a small plastic case. The only setup required is the adjustment of VR1. With the circuit wired and powered up, the LEDs in the pushbutton switch should be illuminated. First measure the voltage at pin 2 of IC1 with a DVM, then monitor the voltage at pin 3 while adjusting VR1 until it is about 1V lower. The exact setting is not especially critical, but setting it too low can give trouble if the pushbutton switch contacts become more resistive due to corrosion. Setting the voltages too close can produce unwanted spurious chime operation. David Worboys, Georges Hall, NSW. ($70) Reading three digital signals with a two-channel oscilloscope I needed to watch three different digital signals (SPI chip select, clock and data) but only have a two-channel analog scope. So I came up with the idea of using resistors to mix the clock and data signals, as shown, then feeding the combined signal into one of the scope channels. As you can see from the scope grab, it works surprisingly well – the clock pulses ‘ride on’ the data pulses. You can identify the clock pulses and see whether the data bit is high or low during that pulse. The other channel is free to be connected to the chip select line, so it can be used as a trigger to capture the SPI packet. You could change the value of the resistors to suit the job; 22kW is a reasonable middle ground as it will not overly load digital signals while still providing reasonable signal integrity to the scope for moderately fast signals (up to a few MHz perhaps). John Rich, Petersham, NSW. ($60) 74 Silicon Chip Australia's electronics magazine siliconchip.com.au