Driveway Sentry

 

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!

 

VOX Circuit

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.

 

EPE is the No. 1 UK hobby electronics magazine. You can subscribe to EPE and have a printed copy delivered to your door (worldwide), or download a special version for mobile or tablet users on the Pocketmags platform, or (coming soon) a new PDF downloadable version for Windows users.

 

 

Milliohmeter artwork 0813.zip

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From the August 2013 issue, artwork (PDF) for published designs is now available free to EPE subscribers only. Non-subscribers may purchase the artwork file direct from us for a nominal sum. Please contact our Orders Dept for information or to place an order.

 

PLEASE NOTE -

EPE PRINTED CIRCUIT BOARDS

 

As from the July 2013 issue, we can supply ready-made printed circuit boards ( 8-digit order codes) to the original design specification via mail order or from our Online Shop