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Optically Isolated Analog Input Module for Arduino
This isolated analog input module is useful for interfacing Analog signals of various types originating from analog sensors and field devices. The module is beneficial for in-process controls, factory automation, industrial applications, etc. Interfacing an analog voltage, an analog sensor to Arduino or other various microcontrollers with optical isolation is very easy with this module. The circuit requires two power supplies for the input and output sides. The module takes 0 to 5V analog input and provides optically isolated 0-3.3V as output. The circuit can also be interfaced with a 10V sensor, for 0 to 10V input, change the resistor R3 to 1.8K and the output will be the same 0 to 3.3V. The operating power supply input side and output side is 5V DC. Hook up the sensor or analog voltage to the input of this module and connect the output to the Analog Pin of Arduino or ADC of any microcontroller. The circuit is based on an optically isolated linear optocoupler. The isolation voltage between input and output is 3750V. IC1 LM358 is used as a closed-loop servomechanism to sense the photodiode current and drive the LED of the optocoupler. IC2 is a linear optocoupler and IC3 LM358 is a signal conditioner for the phototransistor. D1 is the power LED for the input side supply.
The LOC110 Single Linear Optocoupler features an infrared LED optically coupled with two photodiodes. One feedback (input) photodiode is used to generate a control signal that provides a servomechanism to the LED drive current, thus compensating for the LED’s nonlinear time and temperature characteristics. The other (output) photodiode provides an output signal that is linear to the servo LED current. The IC features wide bandwidth, high input-to-output isolation, and excellent servo linearity.
Features
- Operating power supply for the input side and output side is 5V DC
- Current consumption 10mA
- Analog Signal Input Range 0 to 5V
- For Analog Sensor 0 to 10V, Change R3 to 1.8K Ohms
- Output 0 to 3.3V/ 10mA
- PCB dimensions: 45.56 x 13.97 mm
Schematic
Parts List
| SR. | QNTY. | REF | DESC | DIGIKEY/MOUSER |
|---|---|---|---|---|
| 1 | 1 | CN1 | 5 PIN MALE HEADER 2.54MM | DIGIKEY 732-5321-ND |
| 2 | 1 | CN2 | 3 PIN MALE HEADER 2.54MM | DIGIKEY 732-5321-ND |
| 3 | 2 | C1,C4 | 10uF/10V SMD SIZE 1206 | YAGEO |
| 4 | 2 | C2,C3 | 0.1uF/50V SMD 0805 | YAGEO |
| 5 | 1 | C5 | 100PF/50V SMD SIZE 0805 | YAGEO |
| 6 | 1 | D1 | LED RED SMD SIZE 0805 | OSRAM |
| 7 | 1 | R1 | 10K SMD SIZE 0805 | YAGEO |
| 8 | 2 | R2,R8 | 499E 1% SMD SIZE 0805 | YAGEO |
| 9 | 1 | R3 | 4K7 1% SMD SIZE 0805 | YAGEO |
| 10 | 2 | R4,R5 | 100K SMD SIZE 0805 | YAGEO |
| 11 | 2 | R6,R7 | 20K 1% SMD SIZE 0805 | YAGEO |
| 12 | 2 | U1,U3 | LM358 SMD SO8 | DIGIKEY LM358DR2GOSCT-ND |
| 13 | 1 | U2 | LOC110 DIP8 | DIGIKEY CLA113-ND |
Connections
Gerber View
Photos
Video
LOC110 Datasheet
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PCB
Hi, What changes are needed to use the above circuit for measure 4-20ma analog sensors?
Very detailled and explained article.
Where to buy this module ?
We can produce this board on order, just use the quote button to request a quote.