REVISED ENGINE SOUND SIMULATOR
Overview
The original sound unit, first posted in these pages in Autumn 2008, and
available as a 'hobbyist' self assembly kit, is now available
ready-made in a more compact and professional form. This has been
achieved by omitting the chip re-programming and auxiliary audio out
sockets which were, it seems, rarely used and by designing a printed
circuit board (PCB) for the remaining circuitry. The PCB did away
with the 27 track cuts and 15 wire links on the stripboard layout, as
well as allowing more dense component placement. At the same time the
lead terminations have been improved and the whole unit now fits in a
neat 80mm x 40mm flanged ABS box.
Just to recap, this is
a universal engine sound module that can produce a variety of
different engine sounds. In
all cases the hardware module remains the same and the type of engine
sound and its character are varied by firmware (i.e. the fitted
software) alone.
The three software
builds currently available implement multi-cylinder “petrol”,
“diesel” or “steam” engines, the number of
cylinders being a user selectable option by the use of a jumper link.
In all cases the engine sound varies smoothly and proportionally with
the throttle demand in both forward and reverse. The petrol and
diesel engine variants have an idling time-out of around 20 seconds
after which they run down and stop. Opening the throttle again causes
the engine to re-start following a short “cranking”
sound. The steam engine variant starts and stops immediately on
throttle opening or closure.
The
unit can be used with any radio system, including PCM, that
utilises the industry standard 1 to 2mSec servo signal. In other words all commonly used R/C transmitters and receivers. 'Neutral' (i.e.
joystick at centre position) is assumed to be set at 1.5mSec and this
condition is indicated by a case mounted LED which assists in
setting the transmitter throttle trim.
The
unit is easily installed by removing the Electronic Speed Controller
(ESC) lead from your receiver and plugging in a lead from the sound
unit in its place. The ESC lead then plugs into the sound unit,
thereby obviating the need for a Y lead.
The
unit's electronics takes its power from the receiver, but the
loudspeaker derives
its power from either the model's main propulsion battery or a
separate battery pack. Connections for speaker power and the
loudspeaker itself are made using screw terminal blocks and the wires
exit through milled slots in the side of the case.
The following videos show the unit in action:
- Video of the steam version in action in the North Sea drifter "Peggy"
- Video of the petrol version in action in the tug "Phoenix"
- Video of the diesel version in action in the fishing vessel "Marignon"
Units
are available from Technobots and include a 12 page colour booklet covering installation, set-up and
advice on loudspeaker selection and mounting.
Specifications
speed
demand sensing method -
receiver throttle channel (unit has pass-through to ESC)
neutral
(idling) signal condition –
1.5mSec
receiver
voltage
- (which
powers the unit's electronics) 4.8v min to 6v max (this is usually
supplied by a BEC which is often incorporated in the ESC)
speaker
impedance - 8
ohm minimum (Technobots part no. 2400-015 recommended)
speaker
supply voltage - from
zero to 12v (governs the volume of the unit)
power
output - approx 4W RMS @ 12v into 8 ohms (equates to 160W PMPO
in today's modern hi-fi advertising terms!)
engine
types - 'petrol', 'diesel', 'steam'
number
of cylinders - petrol & diesel 2, 3, 4, 5 or 6 and steam
1, 2, 3, 4, 5, or 6 (link selection procedures)
engine
stop / start - automatic, determined by throttle demand and
idling period
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