Early 2014 we
sold a pre-built version of the well-known Forrest Mims III Atari punk console
(APC) that incorporated some modifications and extras of our own devising. We
discontinued this product in 2016 after making available an add-on LFO and a
sequencer. We are now offering this new
version of the APC. It incorporates the original 556 dual
oscillator set up with an option to bring a Light Dependent Resistor (LDR) into
circuit to produce a simple optical ‘Theremin style’ effect.
We have
discarded the external control voltage circuitry, so further expansion by us is
not envisaged, however, some notes are included at the end of this document on
how to build onto and expand the basic design.
This version
includes some features that we wish we had used in our previous design, for
example the audio out connector is a full size ¼” jack. We learned the hard way
that a 3.5mm jack does not have the stamina to work long term in this design.
Power for the unit is provided by a 9 volt battery that is fixed to the PCB
using a battery holder. Previous designs relied on the user providing power to
a screw terminal jack that again was not an ideal solution. An on/off switch is
included to allow the unit to be self-contained and reduces the chance of
discharging the battery.
The APC
design is simplicity itself, but the range of sound effects possible are wide
and the scope for expansion of the design equally large.
The 556 timer
chip is a dual 555 timer package, which means it has 2 x 555 timers built in to
one package. This very versatile chip has many (many) applications and in this
design the two timers are configured with one as an Astable multivibrator and
the other as a Monostable multivibrator. The Astable unit is the main
oscillator or noise maker, its output is used to trigger the monostable and the
monostable acts as a pulse duration control or divider of the oscillator that
means the resulting sounds are chopped or extended depending on the setting of
the divider potentiometer, while the oscillator potentiometer defines the
frequency of the Astable.
Whats included in the Sale?
1. A built working APC
2. The comprehensive user guide
Please Note : No battery is included in this sale, in the photos this is for illustration only