User manual

TMCM-1180 and PD86-1180 Hardware Manual (V1.03 / 2011-DEC-02) 21
Copyright © 2011, TRINAMIC Motion Control GmbH & Co. KG
The coolStep™ current regulator allows to control the reaction of the driver to increasing or decreasing
load. The internal regulator uses two thresholds to determine the minimum and the maximum load angle
for optimum motor operation. The current increment speed and the current decrement speed can be
adapted to the application. Additionally, the lower current limit can be set in relation to the upper current
limit set by the current scale parameter CS.
Please refer to the TMC262 Datasheet (www.trinamic.com) for more information.
7.1.5 sensOstep™ encoder
The sensOstep™ encoder used in this unit is based on a magnetic angular position encoder system with
low resolution. It consists of a small magnet positioned at the back end of a stepper motor axis and a Hall-
sensor IC with integrated digital signal processing (e.g. for automatic gain control, temperature
compensation etc.) placed above the magnet on the back side of a motor mounted printed circuit board.
The encoder offers a resolutions of 8 bit (256 steps) per revolution which is completely sufficient for
detecting step losses with a standard 1.8° stepper motors.
8 TMCM-1180 operational description
8.1 Calculation: Velocity and acceleration vs. microstep and
fullstep frequency
The values of the parameters sent to the TMC428 do not have typical motor values like rotations per second
as velocity. But these values can be calculated from the TMC428-parameters as shown in this section.
The parameters for the TMC428 are:
Signal
Description
Range
f
CLK
clock-frequency
16 MHz
velocity
-
0… 2047
a_max
maximum acceleration
0… 2047
pulse_div
divider for the velocity. The higher the value is, the less
is the maximum velocity
default value = 0
0… 13
ramp_div
divider for the acceleration. The higher the value is, the
less is the maximum acceleration
default value = 0
0… 13
Usrs
microstep-resolution (microsteps per fullstep = 2
usrs
)
0… 7 (a value of 7 is
internally mapped to
6 by the
TMC428/TMC429)
Table 8.1: TMC428 velocity parameters
The microstep-frequency of the stepper motor is calculated with
3220482
velocity]Hz[f
]Hz[usf
div_pulse
CLK



with usf: microstep-frequency
To calculate the fullstep-frequency from the microstep-frequency, the microstep-frequency must be divided
by the number of microsteps per fullstep.