DIY
CIRCUITS
REMOTE VOLUME KNOB
Turn the knob without leaving the couch.
By Paulo Rebordão
There’s nothing like hard work to get your mind
running. Having to get up from the couch to adjust
the volume on my old stereo amp several times
each night got me thinking. I didn’t want to buy
a new stereo, so I came up with a plug-in remote
volume controller that you can easily adapt to
anything with a reasonable-sized volume knob.
Photography by Paulo Rebordão
My circuit uses a Picaxe-08M microcontroller,
which is programmable in BASIC, and a TSOP2238
infrared receiver, which sees signals from any
Sony (or compatible) TV remote. The removable
device hangs off the volume knob, attached with
velcro.
At the top, an R/C servomotor turns the knob
through about 180° of travel, which should be
enough range for most environments. At the
bottom, 3 AA batteries act as a “keel,” weighing
that end down so that the knob is forced to turn.
Design and Program
Before actually building, I conceptualized the circuit,
drew a schematic, and wrote a draft version of the
software. You can download my schematic and final
program at
makezine.com/16/diycircuits_volume.
I prototyped the circuit on a solderless breadboard, adding the extra circuitry required to
program the Picaxe-08M (as described on page
22 of the online Picaxe Manual), including a Picaxe
download cable connected to my PC’s serial port.
From this setup I tested and tuned the software
until everything worked right. I downloaded each
revision to the chip by pressing F5 in the Picaxe
Programming Editor.
From your remote, the software recognizes the
Up/Down volume buttons as well as Mute. Pressing
Mute again will restore the previous volume level.
There’s no auto power off, although standby
Make: 149
