This month’s highlights
This interesting project detects vehicles moving (or being moved) by utilising the earth’s magnetic field. Use it to protect property, farm machinery moving through a driveway or gateway for example. False alarms caused by e.g. animals are therefore avoided.
When movement is detected by a buried sensor loop, it switches on a mains or battery-powered lighting system and activates an optional piezo buzzer alarm for a preset period of 2-25 seconds. 555/ SPST relay output is adaptable for many other applications. All constructional details are described with full colour photography showing every aspect of assembly. A unique way of safeguarding your property!
Voice-operated switches find their uses in radio transmitters to control the microphone but the same principles can be adapted to switch a light, an amplifier or even unlock a door. This sound switch uses an electret or dynamic microphone and has adjustable sensitivity and a DPDT low voltage relay output.
Milliohm Adaptor for DMMs
This low-cost adaptor will let you use almost any digital multimeter (DMM) to make accurate low-resistance measurements.
Based around an instrumentation amplifier, this design lets resistance values be read out on the DMM in millivolts. It offers a 0-0.1 ohm scale and 0-10 ohm range.
Superb Four-Channel Amplifier – on the cheap!
This high-quality home amplifier consists of a mixture of salvaged parts and pre-built modules. It follows on from the home loudspeaker project of Feb. 2013 and is not a conventional project but rather a collection of recommendations to help you build your own.
Amplifier modules can be sourced on auction websites and the author gives some useful advice on purchasing them.
Computer Error: reliable digital processing (Part 1)
Short series on high-reliability computing. Part 1 covers the start of computing’s early days, using thermionic valves (vacuum tubes).
Also in this issue:
- Techno Talk – how the EU could shut down domestic appliances remotely; LED street lamps.
- Max’s Cool Beans – more on radiation, particles and cosmic rays
- Interface – introducing the Raspberry Pi SBC and how to interface with it.
- Circuit Surgery – an in-depth analysis of dataslicing and Manchester coding.
- Net Work – various Do Not Track implications and options discussed, for Internet users.