11 May 2009

Stepper Motor Speed Profile
AVR Application Note AVR446
AVR446 Source Code

4 May 2009

i0.3.out.88.web.v4.asm
i0.3.serial.88.packet.asm

27 April 2009

Power supply, motor and wiring ready to test the new bipolar stepper driver Internet Zero node.

Selection of sense resistors and reference voltage

Note: maximum rating (0.5 V) on the SENSE1 and SENSE2 pins is not exceeded.

The maximum value of current limiting is set by the selection of Rsx and the voltage at the VREF pin. The transconductance function is approximated by the maximum value of current limiting, ITripMAX (A), which is set by

ITripMAX = Vref / ( 8 %D7 Rs )

where Rs is the resistance of the sense resistor (Ω) and Vref is the input voltage on the REF pin (V).

We assume that the maximum current we need is 0.5 amp per phase.

V = IR %A0=> V = 0.5*Rs for each phase.

Assuming Rs is 0.5 Ω, V = 0.25 V < 0.5 (less than maximum rating on the SENSE1 and SENSE2 pins).

Since Rs = 0.5 Ω and ITripMAX = 0.5 amps,

0.5 = Vref / (8 x 0.5)

=:> Vref = 0.5 * 4 = 2V

We can make a voltage divider with Rtop 10K and Rbottom 7K.

13 April 2009