LINEAR MAGNETIC FIELD SENSORS
Simple Circuit Application
strong (200 gauss) and have one of its magnetic poles
The circuit in Figure 16 shows a simple application of a
magnetic sensor. This circuit acts as a proximity sensor
and will turn on the LED when a magnet is brought within
0.25 to 0.5 inch of the sensor. The amplifier acts as a
simple comparator and switches low when the HMC1001
bridge output exceeds 30mV. The magnet must be
point along the sensitive direction of the sensor. This
circuit can be used to detect a door open/closed status or
the presence or absence of an item. Figures 17, 18, 19,
20 and 21 show other circuit examples.
Magnetic
Sensor
Magnetic
Sensor
+5V
+5V
V+
650
7
CS5509
7
+5V
1.5nF#
100
16 bit A/D
0.15µF#
1
R1*
R2*
6,11,13
2
V+
+5V
magnet
movement
7
8
5
2
3
8
Vout
Vref
-
+
7
8
1
6
CONV
SCLK
SDATA
NDRDY
XIN
Ain+
Ain-
LED
8
8
14
15
V+
V-
3
2
400
+
-
AMP04
V+
6
4
5
5
AMP04
Vout
16
4
5
4
25K
R1*
1.6Ω
9
Gain=1000, BW=10Hz
* R1 is used to trim switchpoint
# provides 10Hz rolloff
Ref+
4
10
12
3
1
LM440
2.5V
Ref-
Gnd
CAL
3
1
NCS
Calibrate:
1. Trim R1 for (+V) - (-V) < 30mV
2. Apply signal < 30mV, LED should be off.
3. Apply signal > 30mV, LED should be on.
* R1 or R2 used to trim offest
# provides 1KHz rolloff
S/R
Pulse
Figure 17—One-Axis Sensor With Digital Interface
Figure 16—Magnetic Proximity Switch
+6-15V
Magnetic
100K
Sensor
V+
650
7
CS5509
16 bit A/D
1.5nF#
0.01
1
R1*
6,11,13
2
V+
+5V
1
8
5
8
2
3
Vref
22.1K
R3**
LMC7101
+
-
+
Vout
Vref
6
7
8
CONV
SCLK
SDATA
NDRDY
XIN
Ain+
Ain-
-
14
AMP04
R2*
4
3
4
5
15
16
V+
10
5 mA
25K
1.6Ω
9
4
3
Ref+
10
12
LM440
2.5V
Ref-
Gnd
CAL
3
1
1
NCS
* R1 or R2 used to trim offest
**R3 = 451Ω for 1 axis, 921Ω for 2 axis, or 1411Ω for 3 axis
# provides 1KHz rolloff
S/R
Pulse
Figure 18—One-Axis Sensor With Constant Bridge Current and Digital Interface
+5V
+5V
V+
200
OUT-1
10K
SW1
V
BRIDGE
2
6
Sensitive
Direction
S/R+3
GND4
S/R-5
-
Vout
AMP623
+
4.7uF
tantalum
+5V
1M
O
O
FFSET+
FFSET-
7
25K
OUT+8
2.5V
HMC1021S
Z
LM404-2.5
Gnd
(1) Momentarily close switch SW1. This creates a SET pulse. (2) Measure bridge output (OUT+) - (OUT-) NOTE: Bridge
output signal will be 5mV/gauss (3) Measure Vout after AD623 amplifier (G~500) NOTE: Vout signal will be 2.5V/gauss
Figure 19—One-Axis Low Cost Sensor
12
HONEYWELL [ Honeywell ]
