Independent Buzzer Type CO Alarm HT45F43

Independent Buzzer Type CO Alarm
HT45F43
Characteristics
 MCU characteristics : internal 2x OPAs & 2x comparators, EEPROM,
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HIRC 4MHz + 32K LIRC reduces external component count
Sensor : electro-chemical sensor (ME2-CO)
Power supply : 9V alkaline battery
High volume buzzer : > 85DB
Standby current : typ. 21A, max. 27A
Low voltage detect : 7.5V
Self test / calibrate function
LEDs : red, yellow, green
Voice functions for : CO level, battery low etc.
Internal oscillator and reset circuitry for reduced external components
Internal OPA for sensor signal amplification -- no need for external amplifier
Watchdog wakes up MCU every 32 seconds -- checks CO level and battery
Operating Procedure
 Preheat description
One min.preheat time required at power on. Other operations implemented during
this time generate a double Beep sounds.
 CO level measurement function
WDT wake-up every 32 sec -- implements CO level check. > 30PPM alarm sounds
for 30 sec and LED1 flashes. Alarm cancelled by pressing switch.
 Switch activated auto test function
Short Press: Battery test, 1.65V voltage ref. test, CO Sensor open circuit test
 For battery low -- single Beep sound and the green LED2 flashes once
 For CO open circuit -- double Beep sounds and the green LED2 flashes twice
 For 1.65V ref. out of range -- three Beep sounds and the green LED2 flashes
three times
 For no malfunctions -- four Beep sounds and the red LED1 flashes four times.
 Calibration function
Hold the switch down and apply power to execute. Implements a 30PPM / 50PPM /
100PPM / 300PPM calibration -- yellow LED3 will flash. Flash 3 times with 0.5 sec
stop indicates 30PPM calibration and so on. The switch can be used to change the
calibration level. After the calibration has completed the system enters the normal
operating mode.
Application Circuit
CO Sensor Fixed Voltage
and Amplifier Circuit
LED
Indicators
U1
6
Q1
1.65V
R5
3V3
9
1K
C8050
100K
1M
R8
PA2/A1P
15
R7
PC1/AN5/OSC2
PA0/CNP/COM0
PA2/A1P/C2OUT
PC3/OSC4
OPA1
PC2/OSC3
PA3/A1N/INT0
R6
1M
10uF
ME2-CO
13
C
J270
W
3V3
1K
PA0
R1
1K
PB3/AN0/SCS
14
C1
3
4 LED2
LED1
RED
LED2
GREEN
LED3
YELLO
PA2/A1P
3V3
VSS
LOW_BAT/RESET
PA0
R2
1K
5 LED3
R3
PA4/A1E/TMR1
ICP
Interface
TEST
R9
33K
3V3
12
JP1
1
2
3
4
5
PA5/A2P/PFD
PA1/C1OUT/TMR0
2
OPA2
11 PA6/A2N/BZ
51K
Test and
Calibration Switch
10 PA7/A2E/BZB
R10
C7
104
C2
10U/16V
16
P1
HT7133
1N4148
D2
2
12V
R13
C3
2 2 U/3 5 V
1
9V
750K
Vin Vout
GND
3
3V3
C4
22U/16V
1
128R
12V
6R
C6
104
R16
1K
VDD
C8
104
7
R15
1K
BUZZER1
122R
1
R17
10K
R18
2K
PC0/AN4/OSC1
65MH
L1
Q2
2N3906
VSS
Q4
2
C8050
3
Q3
104
C5
C8050
+
R14
-
390K
LOW_BAT/RESET
Battery
Power Supply
8
PB6/AN3/RES
Buzzer Driver
Circuit
HT45F43
Related Data Report
Item
ESD Test Report
Operating Current
Type
Result
CONTACT type
10kV no reset or system crash
AIR type
16kV no reset or system crash
Typ. standby current
21A
Max. standby current
27A
Alarm operating current
Less than 50mA
M
F
G