ADC value fluctuation (Noise)?


#1

Hi All,

I have hooked up an ultrasonic sensor range finder to ADC1 pin by reading the ADC value from the command “cm ADC read EXT_ADC1” the output shows a decent value and works with changes in the distance. However, sometimes the value drops suddenly without a change in the range about (200 points) for example for a distance of target 1200mm the analog value shows between 1198 to 1203, that looks accurate suddenly sometimes the analog out shows 910 and comes back to normal state quickly.

I really don’t understand where is the noise coming from? The same sensor hooked to Arduino works very well.

The sensor is powered with the 5V connector on Raspberry PI connector pin 2.

Any ideas why the ADC value is dropping and the data looks as shown below


#2

What happens if you connect a 1.2v input to the adc pin?


#3

Can you connect the one sensor to both the Arduino and the mangOH and log the results simultaneously - and see how they compare?


#4

I will try this and let you know.