TMC2041 DATASHEET (Rev. 1.02 / 2017-MAY-16)
41
10 stallGuard2 Load Measurement
stallGuard2 provides an accurate measurement of the load on the motor. It can be used for stall
detection as well as other uses at loads below those which stall the motor, such as coolStep load-
adaptive current reduction. The stallGuard2 measurement value changes linearly over a wide range of
load, velocity, and current settings, as shown in Figure 10.1. At maximum motor load, the value goes
to zero or near to zero. This corresponds to a load angle of 90° between the magnetic field of the
coils and magnets in the rotor. This also is the most energy-efficient point of operation for the motor.
1000
900
stallGuard2
Start value depends
on motor and
operating conditions
800
700
600
500
400
300
200
100
0
reading
stallGuard value reaches zero
and indicates danger of stall.
This point is set by stallGuard
threshold value SGT.
Motor stalls above this point.
Load angle exceeds 90° and
available torque sinks.
10
20
30
40
50
60
70
80
90 100
motor load
(% max. torque)
Figure 10.1 Function principle of stallGuard2
Parameter
Description
Setting Comment
SGT
This signed value controls the stallGuard2 0
threshold level for stall detection and sets the
optimum measurement range for readout. A lower
value gives a higher sensitivity. Zero is the
starting value working with most motors. A higher
value makes stallGuard2 less sensitive and
requires more torque to indicate a stall.
indifferent value
+1… +63 less sensitivity
-1… -64 higher sensitivity
sfilt
Enables the stallGuard2 filter for more precision of 0
standard mode
the measurement. If set, reduces the measurement
frequency to one measurement per electrical
period of the motor (4 fullsteps). Filtering
shouldbe switched off for pure stall detection.
1
filtered mode
Status
word
Description
Range
Comment
SG
This is the stallGuard2 result. A higher reading 0… 1023 0: highest load
indicates less mechanical load. A lower reading
indicates a higher load and thus a higher load
angle. Tune the SGT setting to show a SG reading
of roughly 0 to 100 at maximum load before
motor stall. To safely detect a stall, poll this value
at least once per fullstep!
low value: high load
high value: less load
Attention
In order to use stallGuard2 and coolStep, the stallGuard2 sensitivity should first be tuned using the
SGT setting!
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