[GreenKeys] Baud rate change

[Harold Hallikainen]

On Tue, August 31, 2021 10:09 pm, Joe Duszyński wrote:
> I have a European machine that runs on 220v 50hz and the motor speed is
> 2000 rpm.
> Of course on 60hz 220v it runs faster than 2000 rpm  I'm looking to change
> the motor to a DC motor but would also like to change the baud rate in the
> process to 45.5 vs the 50 it "was set at" the gear ratio appears to be 5
> to
> 1  five revolutions of the motor to 1 rev of the transmitter/receiver
> shaft.
> Can this be accomplished by using an 1800 RPM motor vs 2000 RPM??
>
> This is the calculation I used to come up with 1800 RPM
> 22ms * 7.5 bits = 165ms
> 60000ms(in 1 minute)/165ms = 363.6363 RPM
> 363 RPM X 5(1:5gear ratio) =1818 RPM

Interesting! Is this a synchronous motor? I'm used to 60 Hz synchronous
motors running at 1800 RPM.

On the main shaft, doesn't it use a 1 bit time stop bit? That is, the
shaft would stop after 22 ms even though the stop bit is 31 ms. That
allows for speed variation between transmit and receive. In software UARTs
I've written, I start looking for the start bit of the next character at
the middle of the stop bit.

Has anyone used variable frequency drives to adjust a teletype speed? My
brother has a machine shop and VFDs are amazingly cheap. He does a few
horsepower single phase to three phase for each machine.

Harold



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