Silicon ChipPortable amplifier built from modules - August 2021 SILICON CHIP
  1. Outer Front Cover
  2. Contents
  3. Publisher's Letter: Productivity Commission report on the Right to Repair
  4. Mailbag
  5. Feature: Advanced Medical & Biometric Imaging – Part 1 by Dr David Maddison
  6. Project: Second Generation Colour Maximite 2 – Part 1 by Geoff Graham & Peter Mather
  7. Feature: Automated PCB Assembly for Home Constructors by Geoff Graham
  8. Feature: The History of Op Amps by Roderick Wall & Nicholas Vinen
  9. Project: Nano Pong using an 8-pin PIC by Tim Blythman
  10. Serviceman's Log: Rocking Raucous Retro Roland Repair by Dave Thompson
  11. Project: Multi-Purpose Battery Manager by Tim Blythman
  12. Circuit Notebook: Portable amplifier built from modules by Sid Lonsdale
  13. Circuit Notebook: Frequency meter with non-contact mains reading by Mahmood Alimohammadi
  14. Product Showcase
  15. Feature: El Cheapo Modules: USB-PD Triggers by Jim Rowe
  16. Project: Simple Linear MIDI Keyboard by Tim Blythman
  17. PartShop
  18. Vintage Radio: Bush VTR103 AM/FM radio by Ian Batty
  19. Ask Silicon Chip
  20. Market Centre
  21. Advertising Index
  22. Notes & Errata: Ultra-LD MK.4 Amplifier, July-August 2015
  23. Outer Back Cover

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

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Articles in this series:
  • Advanced Medical & Biometric Imaging – Part 1 (August 2021)
  • Advanced Imaging - Part 2 (September 2021)
Items relevant to "Second Generation Colour Maximite 2 – Part 1":
  • Second-generation Colour Maximite 2 PCB [07108211] (AUD $15.00)
  • Colour Maximite 2 software and documentation (Free)
  • Second-generation Colour Maximite 2 PCB pattern (PDF download) [07108211] (Free)
Articles in this series:
  • Second Generation Colour Maximite 2 – Part 1 (August 2021)
  • Second Generation Colour Maximite 2 – Part 2 (September 2021)
Items relevant to "Nano Pong using an 8-pin PIC":
  • Nano TV Pong PCB [08105212] (AUD $2.50)
  • PIC12F1572-I/SN programmed for Nano TV Pong [0810521B.HEX] (Programmed Microcontroller, AUD $10.00)
  • Nano TV Pong short form kit (Component, AUD $17.50)
  • Firmware for Nano TV Pong (Software, Free)
  • Nano TV Pong PCB pattern (PDF download) [08105212] (Free)
Items relevant to "Multi-Purpose Battery Manager":
  • Battery Manager Soft Switch PCB [11104211] (AUD $5.00)
  • Battery Manager I/O Expander PCB [11104212] (AUD $2.50)
  • Battery Multi Logger PCB [11106201] (AUD $5.00)
  • PIC32MX170F256B-I/SO programmed for the Battery Manager [1110620B.hex] (Programmed Microcontroller, AUD $15.00)
  • PIC16F1455-I/SL programmed for the Microbridge [2410417A.HEX] (Programmed Microcontroller, AUD $10.00)
  • 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 Manager software [1110620B.hex] (Free)
  • Battery Manager Soft Switch PCB pattern (PDF download) [11104211] (Free)
  • Battery Manager I/O Expander PCB pattern (PDF download) [11104212] (Free)
  • Battery Multi Logger PCB pattern (PDF download) [11106201] (Free)
Items relevant to "Frequency meter with non-contact mains reading":
  • Firmware for the Frequency Meter with Non-contact Mains Reading (Software, 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)
Items relevant to "Simple Linear MIDI Keyboard":
  • 64-Key Arduino MIDI Shield PCB [23101211] (AUD $5.00)
  • 8x8 Tactile Pushbutton Switch Matrix PCB [23101212] (AUD $10.00)
  • Simple Linear MIDI Keyboard PCB [23101213] (AUD $5.00)
  • Firmware for the 64-Key Arduino MIDI Matrix (Software, Free)
  • Software for the Arduino MIDI Shield & 8x8 Key Matrix plus 3D keycap model (Free)
  • 64-Key Arduino MIDI Shield PCB pattern (PDF download) [23101211] (Free)
  • 8x8 Tactile Pushbutton Switch Matrix PCB pattern (PDF download) [23101212] (Free)
  • Simple Linear MIDI Keyboard PCB pattern (PDF download) [23101213] (Free)
  • Simple Linear MIDI Keyboard Joiner PCB [23101214] (AUD $1.00)
Articles in this series:
  • Arduino-based MIDI Soundboard - Part 1 (April 2021)
  • Arduino-based MIDI Soundboard – Part 2 (May 2021)
  • Simple Linear MIDI Keyboard (August 2021)

Purchase a printed copy of this issue for $10.00.

CIRCUIT NOTEBOOK Interesting circuit ideas which we have checked but not built and tested. Contributions will be paid for at standard rates. All submissions should include full name, address & phone number. Portable amplifier built from modules One of the things I like about Silicon Chip is that some of the articles published give me ideas for future applications. A good example of this is the El Cheapo article on Class D amplifier modules (May 2019; siliconchip.com. au/Article/11614). Several problems about the particular amplifier described were identified in that article. I searched online for a better unit, and found a TPA3116D2-based 2x50W + 1x100W power amplifier for less than $20, including delivery. The layout of the components on the board was different from the one shown in the article; I suspect it is an improved version. It seems to have none of the problems described in the article. The specifications for this amp quote a working voltage of 12-24V, but the data sheet for the TPA3116D2 IC shows that it will work down to 4.5V. I could 80  Silicon Chip not find a voltage regulator chip on the board, so I tested the amplifier at lower voltages and found that it worked without any apparent problems. With that in mind, I used this amplifier board, in conjunction with two other modules, to make up a radio, Bluetooth and MP3 player that is powered from a nominally 11.1V Li-ion battery pack. The pack I used contains nine 18650 cells arranged in a 3S3P configuration (three sets of three paralleled cells connected in series). I bought this second-hand, and it has built-in cell protection and equalisation modules. It can be charged using a standard 12V DC, 1A regulated plugpack. That charges each cell to 4.0V, which is close enough to full charge voltage (4.2V) for my needs. Australia’s electronics magazine The other two modules I used are a 12V-powered MP3 decoder board with Bluetooth, USB, SD card and FM radio support. It also came with a remote control, and cost just $6. The remote control allows for input selection and volume control. Earlier versions of these MP3 decoder boards were sold as running from 5V, so would need a regulator in my circuit. But later ones are rated to run from a voltage as high as 12V, and still work well at lower voltages. I also bought an 18650/26650 Li-ion battery tester, which shows the battery voltage and load current, for just $10. I decided to incorporate it in my unit to make checking the status of the battery pack easy. I mounted all these components (battery, amplifier, MP3/Bluetooth/FM module and voltage display) inside a large ABS plastic box I bought from Jaycar. I added speaker connectors stripped from a dead amplifier so that external speakers could be easily connected. I sourced some speakers from my local op shop for $2 each, and the sound isn’t too bad. With the battery between 9-11V most of the time, it can be wound up far too loud for an average room. Larger (and better) speakers can be connected to improve the sound quality, making it into a portable outdoor unit with a lot of grunt. I sourced the on/off switch and 5.5mm DC charging socket from Jaycar. The internal wiring is quite straightforward, as you can see from the circuit diagram. I used hot-melt glue and a mixture of nuts and machine screws for a quick and straightforward build. I gave the finished device to my granddaughter as a Christmas present in 2019. It has worked flawlessly for the last eight months, and she has only had to charge the battery four times! She tells me she charges the battery when it stops working. She usually connects her mobile phone using Bluetooth, but occasionally uses other input methods. Sid Lonsdale, Whitfield, Qld. ($100) siliconchip.com.au The MP3 decoder/FM module ► incorporates the display. While most current versions of this module are powered from 12V, earlier versions used 5V and so a separate regulator is needed. The amplifier controls (below the display) are from left-right: left/right channel volume; subwoofer adjustment; total volume control. The amplifier is the smaller device sitting below the twin JVC speakers. Larger speakers (up to 50W) can easily be used if needed. ► A close-up of the display of the ► 18650/26650 Li-ion battery tester module. It displays the battery voltage and load current. The internals of the portable amplifier are shown above at larger than actual size. The power amplifier module measures approximately 100 x 85mm and is sold for about $20 including postage online. Note that this TPA3116D2-based module has a power-on artifact which induces a pop noise on all speakers even when muted. siliconchip.com.au Australia’s electronics magazine August 2021  81