Projecta IM2000 Instructions d'exploitation télécharger pdf (Page 19)

with low inductance motors. On the downward cycle of the sine/cosine waveform,

the PWM operates in a two part cycle. In the first part of its cycle, the PWM is in a

non-recirculating mode to pull current from the motor windings. In the second part

of the cycle the PWM reverts back to recirculating mode to increase efficiency and

reduce current ripple.

The IM2000 will automatically change the non-recirculating pulse widths to

compensate for changes in supply voltage and accommodate a wide variety of

motor inductances. This method also allows for the use of very low inductance

motors with your IM483 driver, while utilizing a 20kHz chopping rate which

reduces motor heating but maintains high efficiency and low current ripple.

Fullstep Output Signal

The fullstep output signal from the IM483 is an active high output at connector

P1:8. This output will be TRUE for the duration of the full step. A full step occurs

when either Phase A or Phase B crosses through zero (i.e. full current in one motor

winding and zero current in the other winding). This fullstep position is a common

position regardless of the microstep resolution selected.

The fullstep output can be used to count the number of mechanical fullsteps that

the motor has traveled without the need to count the number of microsteps in

between. A controller that utilizes this output can greatly reduce its position

tracking overhead, thus substantially increasing its throughput.

Interface guidelines and a sample application for the fullstep output are located in

Section 7 of this document,

Interfacing and Controlling the IM483.

Timing

The direction and microstep resolution select inputs are synchronized with the

positive going edge of the step clock input. When the step clock input goes HIGH,

the direction and microstep resolution select inputs are latched. Further changes to

these inputs are ignored until the next rising edge of the step clock input.

After these signals are latched, the IM483 looks to see if any changes have occurred

to the direction and microstep resolution select inputs. If a change has occurred,

the IM483 will execute the change before taking the next step. Only AFTER the

change has been executed will the step be taken. If no change has occurred, the

IM483 will simply take the next step. This feature works as an automatic debounce

for the direction and microstep resolution select inputs.

The reset and enable inputs are asynchronous to any input and can be changed at any

time.

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Projecta IM2000 Instructions d'exploitation Page 19