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Using an QTR-A Reflectance Sensor at 3.3V

#1

Hi,

I am using an QTR-MD-04A Reflectance Sensor Array at 3.3V to detect a line for a small line following robot. Unfortunately I am only getting a 2% variation (of the 0V - 3.3V range) in output value with line compared to without.

For these tests the sensor was 3-4mm above a piece of white printer paper with a black area created using a sharpie.

I have used both a microcontroller and multimeter to read the output, though on the microcontroller the noise outweighs the variation to a large degree.

The product is listed at operating between 2.9-5V, so I assume I have overlooked something…

Any ideas?

#2

Hi.

That sensor should work with 3.3V. Are you using one of our Arduino examples? Can you post a sample of the output you are seeing? Can you also post pictures that show how everything is connected and the paper you are using to test?

-Claire

#3

Hi Claire,

Thanks for your response!

I switched to a 5V Arduino Uno to (hopefully) make things simpler:

I tried the sample code, but did not get any meaningful calibration readings, so only got readings of 0. Because of this, I reverted to using the analog in serial out example code on the arduino app.

This is the plot from the arduino:

image
A19C9209-A963-45BF-9326-0377443F410B.jpeg1536×1039 272 KB

This is my current set up:

image
17192E2E-4817-4D0C-B701-B20FC182991E.jpeg3264×2448 1.73 MB

I get the same sort of readings on a multimeter as before, with readings of 2.55 - 2.58V with and without line.

What am I missing?

#4

It is hard to see what pins on the sensor you are connecting to in that picture. Could you post a diagram of your connections or list the connections between the sensor and Arduino? Could you also post a picture of the component side of your board?

-Claire

#5

Hi again Claire,

Late night soldering… never a good idea. I had the CTRL pin hooked to Vcc, and no Vcc.

In case anyone is looking do use 3V and wondering if it works - it does.
I have been able to get a good reading at 10-12mm from a surface, with an output between 0.24V - 0.86V w/ and w/o line, a very usable range.

Thanks you Claire, and sorry to wast your time!