HMC10XX FAMILY
Simple Circuit Application
12
The circuit in Figure 15 shows a simple 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
* R1 or R2 used to trim offest
# provides 1KHz rolloff
Vref
Magnetic
Sensor
1.5nF#
650
R1*
R2*
-
+
25K
LM440
2.5V
V+
AMP04
H
Vout
1
8
6
5
2
3
Ain+
Ain-
Ref+
Ref-
Gnd
CONV
SCLK
SDATA
NDRDY
XIN
CAL
NCS
1.6
V+
7
4
8
5
1
3
7
8
9
10
2
14
15
16
4
3
1
CS5509
16 bit A/D
12
V+
6,11,13
+5V
S
I
+5V
S/R
Pulse
Figure 16—One-Axis Sensor With Digital Interface
* R1 or R2 used to trim offest
**R3 = 451
for 1 axis, 921
for 2 axis, or 1411
for 3 axis
# provides 1KHz rolloff
Vref
Magnetic
Sensor
1.5nF#
650
R1*
R2*
-
+
25K
LM440
2.5V
V+
AMP04
H
Vout
1
8
6
5
2
3
Ain+
Ain-
Ref+
Ref-
Gnd
CONV
SCLK
SDATA
NDRDY
XIN
CAL
NCS
1.6
V+
7
4
8
5
1
3
7
8
9
10
2
14
15
16
4
3
1
CS5509
16 bit A/D
12
V+
6,11,13
+5V
S
I
+6-15V
S/R
Pulse
10
-
+
Vref
22.1K
R3**
B
100K
LMC7101
5 mA
0.01
1
3
4
Figure 17—One-Axis Sensor With Constant Bridge Current and Digital Interface
30mV. The magnet must be strong (200 gauss) and have
one of its magnetic poles 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
16, 17 and 18 show other circuit examples.
4
Gain=1000, BW=10Hz
* R1 is used to trim switchpoint
# provides 10Hz rolloff
Magnetic
Sensor
0.15μF#
100
R1*
+
-
AMP04
H
1
8
6
5
3
2
7
4
8
5
+5V
7
400
+5V
Calibrate:
1. Trim R1 for (+V) - (-V) < 30mV
2. Apply signal < 30mV, LED should be off.
3. Apply signal > 30mV, LED should be on.
V-
V+
Vout
LED
magnet
Figure 15—Magnetic Proximity Switch