May 2015

Low-cost Precision 10V Reference

Digital multimeters can gradually drift over the years but seldom are they checked for accuracy. This project offers a 10.000V DC reference voltage accurate to within ±5mV or ±0.05%, and is ideal for checking the calibration of your DMM.

At its heart is a high-accuracy AD587 reference chip that is perfect for this application. It can be trimmed or accuracy, built into a diecast box and is entirely self-contained.

Deluxe fan speed controller

Designed specially for ceiling or pedestal fans, this unusual non-switching controller offers continuous speed control from zero to maximum without generating any RFI or motor noise.

It’s suitable for 230V shaded pole and capacitor-run motors, and has built-in over-current limiting and over-temperature cutout. The controller allows you to set a running speed that’s just right for your needs. It can also be used as a dimmer for desk and reading lamps up to 60W.

WARNING MAINS VOLTAGE

 All parts are at mains potential. Never operate the unit unless the lid is in place.This design is suitable for skilled and experienced constructors only.

RGB LED Strip Light Driver

RGB LED strips are increasingly popular and can produce many colourful displays using a suitable controller.

Most of them consist of a continuous, flexible adhesive strip of surface mounted RGB LEDs and are easy to buy via the Internet.

This constructional project drives up to six RGB strips, up to 5A each, to produce a rainbow of colours in up to ten different eye-catching patterns plus auto-cycle mode which changes the pattern periodically.  Use it to decorate a Christmas tree, shop windows, an exhibition float or anywhere where you want a bright, pulsating and flashing light show. Includes reverse polarity protection and constant brightness control.

 Surface mount design needs good soldering skills

Teach-In 2015 (Part 4)

Our Teach-In tutorial series continues with an investigation into noise and distortion in linear circuits. If ever you wondered about harmonics or the meaning of total harmonic distortion, then this is the series for you! The practical section of Teach-In 2015 describes the testing of the simple headphone amplifier using modern software to produce useful on-screen displays.

PIC n’ MIX

Our in-house PIC microcontroller expert wanders lonely as a Cloud – in the Internet of Things, that is. Under the microscope is the very appealing Byvac BV508 PIC32 processor on a tiny ESP8266-based wi-fi transceiver board, suitable for embedding in IoT appliances and offered to users at an irresistible price.  The Byvac IoT Wi-Fi Discovery Kit is taken for a test run this month.

Also in this issue:

• Circuit Surgery – constant current sources (Part 3) –   CORRECTIONS/ OMISSIONS See July 2015 issue .
• Practically Speaking – sourcing electronic components and storing them
• Audio Out – Ge-Mania – Germanium transistors revisited (Part 2)
• Max’s Cool Beans Blog – Mastering Meters – some vintage moving coil meters restored
• Techno Talk – NFC-based tags with tamperproof technology
• Net Work – dual WAN routers and adding extra Ethernet ports to your router; POP3 mailbox spam filtering.

Next month: Burp-charge Your Batteries; Touch-screen Digital Audio Recorder; 50 Years of the 2N3055 Power Transistor; Teach-In 2015 Part 5.