July 2013

Soft Starter for Power Tools

Some electric saws,  routers and other large electric hand-tools can deliver a nasty kick when they power up, causing you to misalign the cut or miss the target altogether. In extreme cases some power tools can deliver such a nasty torque kick that the operator loses grip altogether, risking injury from the power tool.

Our Soft Starter project is ideal for plunge saws, routers, angle grinders and many more power tools that have strong power-up torque surges. It restricts the initial inrush to provide a controllable ramp-up of speed.  Minimum load power required: 100 watts, max load current 10A (2400W), limits to < 20A inrush. Also see our Soft Starter (April 2013) suitable for use with equipment containing SMPSUs.

MIXED VOLTAGE P.C.B. FOR EXPERIENCED, COMPETENT CONSTRUCTORS ONLY. ALL COMPONENTS AND WIRING MAY BE AT MAINS VOLTAGE.

6-Decade Capacitance Substitution Box

When breadboarding or developing new projects, sometimes you need to experiment with various capacitance values to find the optimum one. This decade box makes it easy to find the right value empirically, and it offers hundreds of thousands of values from 30pF to 6µF.

Now you can fine-tune oscillators, timers,  networks, filters and feedback circuits and more at the turn of a switch. Single PCB simplifies construction.

High-power brushless motors – Recycle It!

Many thrown-away bits of kit contain useful brushless motors that can be re-engineered into high-powered ones by upgrading their wiring and magnets. This very interesting feature shows how a typical brushless motor from an old CD drive or similar, can be upgraded to a higher power sufficient to power a model airplane! A great project idea for experimenters to dabble with.

High-current Adaptor for ‘Scopes and DMMs.

If you want to measure and monitor mains current of up to 25A or more using your oscilloscope or digital multimeter then this adaptor was designed with you in mind! It works just as well with DC and it has significantly better resolution and bandwidth than most clamp meters. Modifications to increase the current capacity are included.

MIXED VOLTAGE P.C.B. FOR EXPERIENCED, COMPETENT CONSTRUCTORS ONLY. SOME HIGH POWER COMPONENTS AND WIRING MAY BE AT MAINS VOLTAGE.

Jump Start – Temperature Alarm

The last in our regular electronics educational series describes the design and construction of a temperature alarm. Its thermostatic action can be useful for controlling cooling fans or generating an ‘overheat’ alarm. Adaptable for fridge freezers, food temperature controls, baby bath water checker or many other applications needing a simple temperature warning. Analysis of the circuit using Circuit Wizard software is also described.

This concludes our introduction to electronics using Circuit Wizard software. Richard and Mike Tooley will be back in the September 2013 issue, with Teach-In 2014, dedicated to the popular Raspberry Pi single board computer.

Also in this month’s EPE:

• Techno Talk – are the effects of the sun’s activity and solar radiation overstated?
• Circuit Surgery – our in-house surgeon examines the principles of flip-flop triggering
• Practically Speaking – some practical workshop encouragement for constructors
• Max’s Cool Beans – Max turns his attention to the basics of electromagnetic radiation. As one does.
• Net Work – the Internet column introduces IE10, remembers Mosaic’s 20th birthday and emphasises the problems that Java can bring.