5. ADJUSTING THE MOTOR DRIVER
5.1 Dierent resistors
Please note that the motor drivers of the CNC kit must rst be adapted to
the motors to be operated before they can be used. The adaptation must
be carried out in order not to cause any damage to the motors or the motor
drivers themselves in the long run.
For this you have to pay attention to certain resistors on the motor driver
boards, as you will see in the following picture, because these are needed to
determine to which value the rotary potentiometer has to be set.
5.2 Calculation of the value to be set
In order to be able to calculate to which mV value the rotary potentiometer
must be set, we calculate:
V
REF
(reference voltage) is the value that must be set on the rotary
potentiometer.
rotary potentiometer.
I
MAX
(rated current) can be found in the data sheets of the motors you want to
use.
R
CS
(Current Sense Resistor) is the value of the resistors marked in the picture
above.
V
REF
= 8 * I
MAX
* R
CS
There are dierent variants of the A4988 motor drivers, so there are also
dierent resistors with dierent values. The most common variants use the
resistors R050
(0.05 Ohm)
, R100
(0.1 Ohm)
and R200
(0.2 Ohm)
.
5.3 Measuring the value to be set
To now be able to set the rotary potentiometer correctly, you will need a
multimeter, a cable with crocodile clips and a conductive screwdriver.
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