[sdiy] Tonewheel relics

[Sarah Thompson]

Would belt drives work? They have huge advantages over gears if you need
smooth transfer with no cogging or backlash.

On Mon, Oct 23, 2017 at 4:34 AM, <rburnett at richieburnett.co.uk> wrote:

> @roman and Richie: thanks! From my limited experience with bldc's I
>> feel they would be costly, especially a 12-way driver system for them.
>> Would they need hall sensor feedback to get the tuning accurate
>> enough?
>>
>
> Yes, probably not cheap.  I don't think you'd need hall sensors to detect
> the field, but you would need to ramp the frequency up at a controlled rate
> to allow the mechanical bits time to accelerate up to operating speed.
>
> The pll sounds nice and classic. I'll look into that. At present I'm
>> not sure if the pick-up  coils of the generator could handle more
>> loading, e.g. As required for closing the loop. But a high impedance
>> buffer would probably be ok.
>>
>
> Take the feedback for the PLL from the highest frequency that you can.
> The loop filter in the PLL has to filter out the ripple in the compared
> reference and positional feedback signals.  The higher you can make the
> reference and feedback signal frequencies, the larger the bandwidth of the
> loop filter can be, and the quicker the PLL speed controller will settle.
> i.e.  Don't use a reference signal that is just one pulse per revolution,
> as this can mean you end up with a very sluggish control loop!
>
> -Richie,
>
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