January 19, 2015 10:12 PM CET
in the topic
Technical questions in the forum
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Tamás Fábián said:
This alsomeans that SBrick might turn on the motors more quickly than the IR recever, and therefore the noise might me louder.
Moreover, the IR receiver only applies PWM duty cycles other than 0 and 100% (where there's no noise, but this is the case with SBrick too) if you use it with a 8879 remote.
Additionally, SBrick can utilize 255 PWM levels. The first 20-30 levels are not really useful with PF motors, since they won't even start. At these levels, there is no motor noise to cover the beeping. Once the motors are running at a reasonable rate, their noise usually masks the tweeting.
If you're really annoyed by the noise, I can do a few experiments to either lower the PWM frequency (lower sounds are harder to radiate, and are masked better by the motors), or increase it (with a bit of luck, above the ~20 KHz limit of the human ear). Since this can affect power efficiency (higher the frequency, higher the switching loss, there's more heat), such parameter should be allow tweaking (let the user to override it).
(Hm, I've looked at the code, and the lowest frequency is about 490Hz, the highest is well above 100KHz. DRV8833's rise and fall time is 160 & 180ns, so it might be able to work at that frequency.)
Hi
If a silent sBrick is possible I'd be happy. It is somewhat annoying tho hear all the current noise. Especially when multiple engines run at the same time. Just done my Excavator and when it drives an turns upper part and crane arm it sounds more like a space thing rather than an excavator.
However I like the idea of sound control. That would be a great next product: a controlable LEGO loke loudspeaker giving the "s" a whole new meaning.
