AN863 Datasheet, PDF (9/22 Pages) STMicroelectronics – Improved sensorless control with the ST62 MCU for universal motor

IMPROVED SENSORLESS CONTROL WITH THE ST62 MCU FOR UNIVERSAL MOTOR
Figure 5. A low cost 8-bit micro-controller ST6220, a rail-to-rail operational
amplifier TS912, a triac and a small value sense resistor make the
heart of this sensorless speed regulated drive
RS232
R1
0.22 / 3 W
BTB 08 600 CW
C2
470 uF
10v
VDD
5.6V
0.1uF
C3
2x33pF
VDD
TIMER
OSCIN
220 V
1N4148
8 MHz
OSCOUT
NMI
TEST
NRESET
R8
PB7
PB6
C1 _{470 nF}
PB5
400V
VSS
2.7 k
R10
68 n
PA0
C4
PA1
100
VDD
R9
MOTOR
PA2
R11
R7
PA3
22 k
PB0 zero cross.
6
PB1
R6
8
7
1k
5
PB2
0.22u
4
C5
TS912AI
PB3
750
PB4
R5
390
R2 ^0.5W
ST6220
R4
1nF
HWD
R3
C6
The triac is controlled by pins PA0/PA1/PA2 of the micro. They are in parallel in order
to get enough current to trigger the triac. The 100 ohm resistor R11 limits the current
in the triac gate.
Two push-buttons are provided on pins PB5 and PB6 of the micro for the user inter-
face. Pushing one speeds up the motor, pushing the other slows it down. Alterna-
tively, it is possible to replace this push-button interface by a potentiometer R8, which
could be measured by the internal ADC. Both are shown on Figure 5, buttons and po-
tentiometer, but the attached software only implements the push-buttons.
Finally, Figure 5 shows an output of the micro-controller labeled RS232 (together with
the VDD supply). In the attached software, some routines are provided to help in the
application development and motor characterization. They allow to connect the motor
control board to the serial port COM1 of a personal computer. While the motor is run-
ning, the personal computer displays in a graphical form motor data such as meas-
ured current and firing delay, allowing easy interpretation and measurement. Of
course, it is necessary to use opto-isolated components to connect the computer to
the motor drive. This connection to a personal computer is described in annex 3.
9/22