AVR-Chat

Dave,

Dave Mucha wrote:
> Hi all,
> 
> I'm trying to find more data about the R/C throttle control.
> 
> as I am to understand, the control input to an
> ElectronicSpeedController (ESC) is over a repetitive 20mS frame.  and
> in that frame there is a range between 0.5 and 2.0mS that is the value.  

   Not quite.  The standard is a 1ms to 2ms pulse, with 1.5ms being the 
center, every 20ms.  Most servos or whatever are happy with .8 to 2.2, 
going further than that is problematical.

> That would make it so 0.5mS is a zero speed and 2.0mS would be 100% speed.

   1ms is full to one direction or speed, 2ms is full to the other 
direction or speed.  Zero is 1.5ms.

> am I correct on this?
> does anyone have a schematic for an ESC for a burshless motor ?

THOSE types of controllers are family jewels, you might find some open 
source stuff out there though.

> I'm looking for a 25,000 RPM motor to use on a PCB drilling machine
> and these seem small enough and high speed enough to do the job. 
> Unfortunatly, the combination of motor and ESC can run upwards of $1750 !

   I doubt that you'll want an RC controller for that kind of operation, 
they aren't all that reliable - which is OK for an RC car, not so OK for 
a precision milling operation.  Also, for a mill you'll want motor 
feedback so that the bit can keep a constant speed up under changing 
loads - An RC motor driver won't do that.

> Any comments or suggestion are welcome.

   I recommend Googling for motor controller designs with feedback that 
use PID or something close to that to control the motor speed.

DLC


> Dave
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> Yahoo! Groups Links
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-- 
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Dennis Clark          TTT Enterprises
www.techtoystoday.com
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