Скачать или смотреть Engine Sound Unit for Model Boats

Prototype unit demonstrating proof of of concept, prior to commercial availability later this year (2015). Originally developed using an Arduino, the microcontroller hardware was then reduced to just the bare minimum to support this application. Sound samples ('start', 'run' & 'stop') are stored in the chip's program memory and are used to audio modulate the mark/space ratio of a high frequency PWM stream from one of the chip's counter/timer outputs. A two pole low pass active filter then filters out the PWM frequency to recover the original audio. This technique avoids the expense of a D to A converter. The 'run' sample is looped and clocked out at a rate proportional to the throttle demand to get the varying speed. A short press of the push button allows neutral (stop) to be set within the range 1.4 to 1.6mSec. A longer press enters a routine to set the span of the throttle joystick. Holding the button pressed at power up and counting the 'beeps' allows the user to set the idle timeout period (in units of 10 seconds). A pot allows the user to set the top speed of the engine (and thereby its overall speed range), the tickover being fixed. The PCB fits onto a commercial 20W class D stereo amp to form a small compact module. The sound unit output is mono but is fed to both channels in case two speakers can be used. The amplifier's volume pot is wired through to the sound unit PCB for ease of access. Note: when adjusted in the video, little effect can be heard as the video camera's AGC (automatic gain control) compensates for the changes in volume. The commercial amp was used for expediency, and an own design mono amplifier may be substituted later to reduce the cost even further. As the chip's program memory is only 32K this limits the total sound sample storage to just a few seconds, but as the video illustrates this can be sufficient. Currently I'm sourcing sound samples to create a range of engine variants as options for the final product. I welcome your feedback to influence the final design before going to market. Note I've already been down the route of using an SD card to allow the user to install their own sound samples but feel the system I've arrived at is a simpler, cheaper unit to allow 'plug and play' functionality for those whose skills lie in modelling rather than electronics.