July 2015

L-O-O-O-N-G  Gating Times for the 12-Digit High Resolution Counter

This add-on PCB module enables extended period high-resolution measurements to be made with the 12-Digit Frequency/ Period Counter described in the Jan 2014 and Feb 2014 issues of EPE. It adds an additional decade divider for the external timebase input to allow measurements using a gating time of 10,000 seconds or nearly three hours. This allows users to take extended frequency measurements with a resolution of 100 microhertz.

The add-on also includes front panel LEDs that indicate the status of the gating operation. Also provided are audio signalling features using a piezo sounder. Full details of the upgrade along with all necessary photos and diagrams are included as usual.

Threshold Voltage Switch

This is a simple but adaptable module that switches a relay when an input voltage crosses a preset threshold.  It’s perfect for handling the output of an analogue-based sensor, battery voltage or similar signal and producing a snap-action on-off operation at a predetermined level.  It has many other uses with environmental or voltage detection and can be used with 5V, 12V and 24V supplies.

A low-voltage, high current relay is incorporated, offering up to 60A SPDT or 10A DPDT switching. An application as a 12V battery charger is also shown along with various relay options and choices.

Touch-Screen Digital Audio Recorder (Part 2)

This compact, hand-held unit will record and play back audio with CD sound quality, supporting 16-bit stereo PCM-encoded files at sample rates of 8-96kHz. It records and plays standard .WAV audio and is compatible with any PC or Mac. This latest design uses a standard SD card and doubles as an SD card reader if connected to a PC using its USB interface. A 72mm TFT resistive-type touchscreen display forms the main control panel and a single USB-rechargeable AA-size Lithium-Ion cell offers constructors hours of service.

This month, full constructional details are published along with using and troubleshooting.

 Surface mount design needs good soldering skills

PIC n MIX

Our PICmicro designer suggests a simple but useful oscilloscope application for his 18F development board, this month looking at design considerations and limitations.

Audio Out

Our special vintage audio column visits RIAA equalisation.

Teach-In 2015 Discrete Linear Circuit Design
Part 6: Power and power measurement

Our flagship tutorial series proceeds with software analysis of the tone control circuit and the topic of power and its measurement are then explored.

Also in this month’s issue:

• Practically Speaking – our practical column for the hobbyist gets to grips with the basics of diode terminology and characteristics
• Techno Talk – more bio-electrical weirdness and interesting oddities from the world of eco-power
• Net Work – the Internet column – how modern networked consumer goods are hobbled when dedicated apps or services are abandoned by their suppliers
• Circuit Surgery – our in-house  specialist analyses LTSpice modulator  and other special (and sometimes undocumented) functions in this popular simulation program.
• Max’s Cool Beans Blog – LED fundamentals and multicolour musings, and introducing the WS2812B LED arrays

Next month:

Resistor-Capacitor Decade Substitution Box, ‘TempMaster’ Mk3 Thermostat, Nirvana Valve Sound Simulator, Teach-In 2015 Part 7: VU Meter, heatsink design, the differential amplifier, current mirror and more.