Silicon Chip – April 2019

96 Silicon chip Australia’s electronics magazine siliconchip.com.au

Coming up in Silicon chip

AD584-based precision voltage references

Jim Rowe looks at three low-cost but very precise voltage references, all based

on the Analog Devices AD584 IC. They can provide very stable 2.5V, 5V, 7.5V

or 10V reference outputs, which can be trimmed to within a fraction of a milli-

volt of the ideal reading.

Australian International Airshow 2019

Dr David Maddison attended the biennial Avalon airshow and will describe all

the latest technology (military and civilian) presented at this world-class avia-

tion showcase.

Bathymetry through the ages

Dr David Maddison describes how the use of knotted ropes and timber poles

to measure water depth gave way to sonar. But modern sonar is about more

than just water depth measurement. It can be used to map the seafloor, for

discovering and imaging wrecks and other submerged objects.

High-current linear bench supply

This power supply has low ripple and noise due to the use of linear regulation.

But it can still deliver plenty of current (more than 5A) with an output of up to 50V.

Using 3.5-inch touchscreens with Arduino & Micromite

We’ve used 2.8-inch touchscreens extensively over the last few years but larger

displays with a significantly higher resolution are now available with reason-

able price tags. They use the same SPI interface and so can easily be hooked

up to and controlled by an Arduino or Micromite board.

UHF repeater

Based on reader requests, this device extends the range for devices such as

our 2015 Driveway Monitor which use UHF transmissions to send data from

a remote unit to a base station. It can both extend the usable range and also

solves line-of-sight problems caused by hills or obstacles that are in the way

of the signal.

Note: these features are planned or are in preparation and should appear

within the next few issues of Silicon chip.

The May 2019 issue is due on sale in newsagents by Thursday, April 25th.

Expect postal delivery of subscription copies in Australia between April 23rd

and May 10th.

Notes & Errata

DAB+/FM/AM radio, February 2019: in the parts list on page 85, we wrongly described the BC817 transistors as PNP and

BC807 as NPN. BC817s are NPN and BC807s are PNP. The type numbers and part designators given are otherwise correct.

Also, note that the 5.5 turn side of T1 is terminated on the CON6 side, as described in the text; this is not clear from Fig.2.

Four-channel sound system using a single woofer, Circuit Notebook, February 2019: the circuit diagram does not show

the part type for ICs3-9. The author recommends LM833 although NE5532 should also be suitable.

Low Voltage DC Motor and Pump Controller, October & December 2018: for PWM frequencies above 1kHz, a 30V+ schott-

ky diode must be connected across the fan/pump, cathode to positive, with a current rating at least half the load’s maximum.

Solder it across the unit’s outputs or the fan/pump terminals. This prevents the Mosfets from overheating when they absorb the

back-EMF pulses. We also suggest that you solder 10μF 25V X5R capacitors on top of the 100nF bypass capacitors for IC2

and IC3 and add a 2200μF 25V low-ESR electrolytic between the +12VF and 0V (fan power input) terminals on the board. Note

that the loads may run briefly when power is first applied; disconnect all loads before making a connection to CON2 (ICSP).

USB Port Protector, May 2018: TVS2 has a metal tab under its body which is not mentioned in the article, and depending on

how you fit it, it could become shorted out. Make sure that this tab only makes contact with one of the two pads before solder-

ing it in place.

Advertising Index

Altronics...............................66-69

Ampec Technologies .................. 9

Cypher Research Labs............. 10

Dave Thompson ....................... 95

Digi-Key Electronics ................... 3

Emona ....................................IBC

Hare & Forbes ......................OBC

Jaycar ...........................IFC,45-52

Keith Rippon Kit Assembly ....... 95

LD Electronics .......................... 95

LEACH Co Ltd .......................... 79

LEDsales .................................. 95

METCASE Enclosures ............... 6

Microchip Technology ..........11,75

Mouser Electronics ..................... 5

Ocean Controls ........................ 13

Philips ......................................... 8

Rayming PCB & Assembly ......... 4

Rohde & Schwarz ....................... 7

SC Vintage Radio DVD ............. 93

Silicon chip Shop...............88-89

The Loudspeaker Kit.com ........ 55

Tronixlabs ................................. 95

Vintage Radio Repairs ............. 95

Wagner Electronics .................. 12