RMS Technologies IMC17 INTEGRATED MOTOR CONTROLLER/DRIVER - Manual (Page 22)

Old 4-Pin cable Connect
to
New 3-Pin cable
Pin # Color/function Color/function Pin #
Pin 1 Red (PWR)  No connection --
Pin 2 Green (GND)  Green (GND) Pin 2
Pin 3 Brown RS485 B (+)  Brown RS485 B (+) Pin 3
Pin 4 Black/white RS485 A (-)  Black/white RS485 A (-) Pin 1
Peak current versus Amps/Phase
Where does the 1.4 times come from? Current is continuously changing when a
motor steps. If the motor is rated for 1.0 A/Ph, it may receive 0 Amps, 1 Amp, 1.4
Amps, or anything in between if you are microstepping. For ease of explanation, we
will look at the current waveform when we half step, or set the driver/controller to 2x
microstepping.
If we take a look at both the A and B phases, and plot on an X-Y chart of when each
phase receives current, and how much it receives, it will look like the chart below.
Beginning at position 1, Phase A receives negative current, and Phase B receives
positive current. Let’s assume it is at coordinate (-1, 1).
The position versus time graph just above, plots only the A Phase, following the eight
different steps the motor will make. Current is changing with each position. Recall
that a negative in electronics simply means reverse direction of current flow.
RMS Technologies Page 22 4/3/2009
IMC17/IMCE17 User Manual Rev 1.06
1
3
7
5
1 2 3 4
100%
100%
0%
HALF- STEPPING
Current Wave Form
PHASE A
Current
POSITION
PHASE B
PHASE A
2
4
8
6
5 6 7 8
141%
141%
time
Peak current
(1.4 times Amps/Ph)
Average, or RMS
Is only 1 Amp/Ph