AVR-Chat

Hi Dan,

Current sensing resistors are basically very low resistance, high
precision resistors, typically in the < 1 ohm range.

By measuring the voltage drop across one of these, you can determine the
current going through it.

For example, say a stepper motor is rated at 3.2V and 2.0A. You can
actually provide the stepper with a much high voltage, say 24V, and
monitor the current. When the current reaches 2.0A, then you cut the
voltage. When it drops a bit, you turn the voltage back on. So basically
you're performing PWM on the current. This is how "chopper" based
stepper drivers work.

--
Dave Hylands
Vancouver, BC, Canada
http://www.DaveHylands.com/

> -----Original Message-----
> From: dv7839 [mailto:danvernon@earthlink.net] 
> Sent: Friday, April 02, 2004 10:49 AM
> To: AVR-Chat@yahoogroups.com
> Subject: [AVR-Chat] What is a current sensing resistor
> 
> 
> I hope this isn't too far off topic.  I was doing some 
> research for an 
> AVR powered stepper motor driver design when I came across a 
> reference 
> to a current sensing resistor.  Could someone please explain 
> what this 
> is, and why one might use it?
> 
> thanks,
> dan
> 
> 
> 
>  
> Yahoo! Groups Links
> 
> 
> 
>  
> 
> 
>

Dave,

Thanks very much.  That fits with what I was looking at.  For some 
reason I was thinking it was something fancier than that.

dan
--- In AVR-Chat@yahoogroups.com, "Dave Hylands" <dhylands@b...> wrote:
> Hi Dan,
> 
> Current sensing resistors are basically very low resistance, high
> precision resistors, typically in the < 1 ohm range.
> 
> By measuring the voltage drop across one of these, you can determine 
the
> current going through it.
> 
> For example, say a stepper motor is rated at 3.2V and 2.0A. You can
> actually provide the stepper with a much high voltage, say 24V, and
> monitor the current. When the current reaches 2.0A, then you cut the
> voltage. When it drops a bit, you turn the voltage back on. So 
basically

> you're performing PWM on the current. This is how "chopper" based
> stepper drivers work.
> 
> --
> Dave Hylands
> Vancouver, BC, Canada
> http://www.DaveHylands.com/
> 
> 
> > -----Original Message-----
> > From: dv7839 [mailto:danvernon@e...] 
> > Sent: Friday, April 02, 2004 10:49 AM
> > To: AVR-Chat@yahoogroups.com
> > Subject: [AVR-Chat] What is a current sensing resistor
> > 
> > 
> > I hope this isn't too far off topic.  I was doing some 
> > research for an 
> > AVR powered stepper motor driver design when I came across a 
> > reference 
> > to a current sensing resistor.  Could someone please explain 
> > what this 
> > is, and why one might use it?
> > 
> > thanks,
> > dan
> > 
> > 
> > 
> >  
> > Yahoo! Groups Links
> > 
> > 
> > 
> >  
> > 
> > 
> >