May 2011

The µCurrent Precision Multimeter Adaptor

Just as a classic moving-coil multimeter can ‘load’ a circuit and affect the accuracy of its readings, did you know that your digital multimeter can’t measure currently accurately because of its inherent ‘burden voltage’? The meter’s current shunt resistor drops as the circuit’s current passes through it. Display resolution and accuracy can be lost due to the need to use a higher range than necessary, in order to minimise the effects of the meter’s ‘burden voltage’.

This constructional project overcomes this problem – it’s a precision adaptor for multimeters that gives up to a 100-fold reduction in burden voltage for a given range. The very comprehensive article fully describes the benefits and principles of operation – recommended for all electronics hobbyists!

Please Take Note: µCurrent Multimeter Adaptor

[May 2020] Kits of components (as advertised) are no longer available from the designer.

Digital Audio Oscillator

Are you involved in testing audio equipment such as amplifiers or speakers? This compact and inexpensive digital audio oscillator could be ideal for many testing and troubleshooting purposes.  It can produce sine, square, triangle and sawtooth waveforms from 10Hz to 30kHz ±4% . It features digital up/ down frequency pushbuttons and an LCD digital display and is bound to be a boon to audio construction enthusiasts.

This professional design is copyright in its entirety. [May 2020] A full kit including pre-programmed Atmel microcontroller is no longer available from Altronics.

Build a 6-Digit GPS Clock (Part 1)

This 6-digit LED clock displays time super-accurately thanks to the data received via the Global Positioning System. With big, bright 58mm high digits for hours and minutes, you can’t fail to ‘clock’ this magnificent digital masterpiece! Permanently locked to the GPS time signal, our project shows UTC or local time as desired, and can be adjusted for any time zone. Part 2 next month explains the add-on GPS module.

Simple Voltage Switch for Car Sensors

This project can be used anywhere you want a relay to switch when a signal voltage reaches a particular preset level. Originally designed with automotive applications in mind, it has many applications in other 12V circuitry. Adjustable hysteresis and switching level. Relay output.

Teach-In 2011 (Part 7)

The latest instalment of our highly popular educational series investigates timers, including the ubiquitous 555 timer that’s been universally popular for decades. PC-based circuit simulation ideas are also included.

Air Movement Sensor

Recycle-It describes a super-sensitive air movement detector using a scrap airflow meter from a car.

Also in this issue:

• Ingenuity Unlimited (readers’ own circuits)
• Techno Talk on the progress with LED lighting
• Circuit Surgery continues its analysis of the principles of feedback
• Practically Speaking offers more electronics workshop assembly basics.