SILICON CHIP
Publisher & Editor-In-Chief
Leo Simpson, B.Bus.
Editor
Greg Swain, B.Sc.(Hons.)
Technical Staff
John Clarke, B.E.(Elec.)
Robert Flynn
Regular Contributors
Neville Williams, FIREE, VK2XV
Bryan Maher, M.E. B.Sc.
Jim Yalden, VK2YGY
Garry Cratt, VK2YBX
Jim Lawler, MTETIA
David Whitby
Photography
Bob Donaldson
Editorial Advisory Panel
Philip Watson, MIREE, VK2ZPW
Norman Marks
Steve Payor, B.Sc., B.E.
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2
SILICON CHIP
PUBLISHER'S LE'l-l'ER
Those wonder£ul
op amps;
they're so versatile
As you will have gathered by now, if you have been reading SILICON
CHIP for a few issues, one of our major aims each month is to present
electronic projects which appeal to enthusiasts with wide-ranging interests. And so it is this month, with projects aimed specifically at enthusiasts who have interests in railway modelling, photogi'aphy, high
fidelity and chemistry. The latter refers to the pH meter which will be
of use to people who have to maintain a swimming pool or fish tanks,
or perhaps are keen gardeners.
While we trust that the projects we present each month will hit the
spot with readers who have specific interests, we hope that all the
projects will be of general interest to a majority of our readers, merely
because the circuits are interesting in themselves.
·
We get quite a kick out of developing these projects and consider it a
challenge to get the best circuit performance for the minimum cost.
For the last few weeks for example, we have been delving closely into
the specifications of a number of "state-of-the-art" operational
amplifiers as we develop a number of hifi-related projects. You will
see the results of these endeavours over the next few months. While
we were doing this research we also had occasion to review the performance of that relatively common quad op amp, the LM324.
When you really look at it, this is a remarkable op amp; not
necessarily state-of-the-art but remarkable nonetheless. Just consider:
it can operate from single or dual supplies; it is directly compatible
with logic circuitry; it has very low current drain, typically less than
800 microamps at 5V DC; and best of all, it is dirt cheap. "So what!"
· you might say. Well have a look at the train controller and pH meter
circuits described in this issue. By coincidence, they both depend
heavily on the LM324.
The pH meter uses all four op amps in one package in the same way,
to obtain a circuit which compensates cleverly for the tricky
parameters of a pH probe. And in the train controller circuit we use
the eight op amps in two LM324 packages in four different configurations: three voltage followers, an oscillator, an amplifier and two comparators, with one interfaced directly to logic circuitry.
We find it fascinating that it is possible to use such a common and
cheap device (it only costs about $1.40) in such a variety of useful
ways. The design of such circuitry might be way over your head but if
you carefully follow the circuit description in these project articles
you should eventually gain a good insight into how they work.
For many people, this analysis of how circuits work is the real
"buzz" of electronics; they don't wish to build 'em, just analyse 'em.
Well that's great. You can enjoy electronics in a practical way by
building projects; or by just reading the articles and analysing the circuits. There are few pastimes more satisfying.
Leo Simpson
