15
Figure 21. 4 to 20 mA HCNR200 receiver circuit.
Figure 22. 4 to 20 mA HCNR200 transmitter circuit.
-
+
V
-
+
V
CC
5.5 V
R1
10 kΩ
+ILOOP
HCNR200
PD1
-ILOOP
R2
10 kΩ
R4
100 Ω
2N3906
Z1
5.1 V
0.1 µF
R3
25 Ω
0.001 µF
R5
80 kΩ
LM158
HCNR200
PD2
2
HCNR200
LED
LM158
Design Equations:
VOUT / ILOOP = K3 (R5 R3) / R1 + R3)
K3 = K2 / K1 = Constant = 1
Note:
The two OP‑AMPS shown are two separate LM158, and not two channels in a single dual package,
otherwise the loop side and output side will not be properly isolated.
Design Equations:
(ILOOP/Vin)=K3(R5+R3)/(R5R1)
K3 = K2/K1 = Constant ≈ 1
Note:
The two OP‑AMPS shown are two separate LM158 IC’s, and NOT dual channels in a
single package, otherwise, the LOOP side and input side will not be properly isolated;
The 5V1 Zener should be properly selected to ensure that it conducts at 187µA;
-
+
80k Ω
PD1/IC1
LM158
IC2
LED/IC1
HCNR200
1nF
150 Ω
Q1
2N3906
R1
R2
Vcc
5.5V
Vin
0.8V~4V
C1
-
+
LM158
IC3
PD2/IC1
1nF
10k Ω
25 Ω
10k Ω
3k2Ω
5V1
100nF
100kΩ
150 Ω
Q2
Q3
Q4
2N3904
2N3904
2N3904
R3
R4
R5
R6
R7
R8
C2
C3
+I
LOOP
- I
LOOP
12V~40V
4 ~ 20mA
4mA (Vin=0.8V)
20mA(Vin=4V)
“0” @ 2200Hz
“1” @ 1200Hz
