Problems using the LM358 Amplifier Module

Other Hardware Sensors
1

Hello! I am currently using the TCRT5000 Reflective Optical Sensor for my project. The sensor outputs data in a range of about 0-1000. I was hoping to connect the LM358 Amplifier Module (Adjustable Gain up to 100x) to my sensor in order to increase the output signal.

The wiring of the op amp module seems very simple. However, when I connected everything the output changed to a range of around 450-550. I am confused as to why this is happening, and quite stuck.

To test it out, I used a different Arduino board and the KY-038 Sound Sensor with a different LM358 Amplifier Module. To my surprise, I got the same result of a a range of around 450-550.

Clearly, I am doing something very wrong. Any help would be greatly appreciated!

2

I'm fairly sure most of us don't have a crystal ball.

If you want serious help, then post a link to the sensor, a diagram with parts values showing how you did get that 0-1000, a diagram how you did connect it to the LM358, and the code (with code tags!).
The type of Arduino might also be important.
Read the 'how to post' guidelines first.
Leo..

3

In normal operation, the output of the TCRT5000 sensor is already in the range of 0-5V (with a 5V Arduino), so it cannot be amplified.

Please post a schematic diagram showing how everything is connected, with pin numbers and part labels.

4

Attached are wiring diagram of the sensor (with and without the module).

It working properly without the LM358 amp module, and not working properly once I add the module.

http://tinkbox.ph/sites/mytinkbox.com/files/downloads/LM358_100_GAIN_OPERATIONAL_AMPLIFIER_MODULE.pdf

^Link to the module description

The module only has 4 pins (IN, OUT, VCC, GND).

OBS_withAmp.jpg
OBS_withAmp.jpg1094×1410 149 KB

OBS_withoutAmp.jpg
OBS_withoutAmp.jpg1092×1184 131 KB

5

That LM358 module is apparently ac-coupled so probably no use at all to you. Its also not rail-to-rail anyway.

Your sensor output is already full-scale to the Arduino analog pins.

Are you wanting to zoom in on some part of its range? For that you need a DC amp with settable gain and offset.

And where's the datasheet for the TCRT5000?

6

This is your sensor data sheet. I haven't a clue what you are trying to do? The sensor has an Open Collector transistor output suitable for Digital Input pin of an Arduino. It uses a phototransistor. Why are you trying to amplify the output? Here is an overview using the part already on a module board with an Arduino. If using a module board keep in mind:

Features:

  • Supply Voltage: 3.3V~5V

  • Detect distance: 1mm-8mm

  • Digital Outputs LOW when objects detected

  • On-board indicator LED to show the results

  • On-board potentiometer to adjust the sensitivity

  • On-board LM393 chip

The output is digital high or low. If you are using only the part tie 10K resistor to the collector out and the other end of resistor to 5.0V or 3.3V and the collector resistor junction to your digital input.

Ron

7

Fritzing diagrams are worse than useless.