Doable?!

I am just getting into the Raspberry Pi scene so forgive my ignorance - how difficult would it be to write code that could take a distance measure (maxSonar) in mm and convert it to volume (ounces remaining). I have this hairbrained idea to try and monitor fluid levels in my beer keg or hot liquor tank. Yes I am aware of flow meters - just have the sonar on hand from a friend that I can use. Any suggestions would be greatly appreciated.

-Tad

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xever over 10 years ago +1

It appears your range finder has a 4-20mA output, in which case you will require an ADC input to measure the distance and then eventually resolve that into volumetric measurement. The rPi does not have…
dougw over 10 years ago +1

RaspberryPi may be a bit of overkill for this application - perhaps an arduino would be simpler... Using a MaxSonar With an Arduino Arduino Playground - MaxSonar

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dougw over 10 years ago

RaspberryPi may be a bit of overkill for this application - perhaps an arduino would be simpler...
Using a MaxSonar With an Arduino
Arduino Playground - MaxSonar
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Former Member over 10 years ago in reply to dougw

Yeah I didn't get the Rpi specifically for this application but when my buddy offered a sensor and challenged me to make it work... I managed to get it wired up by following the tutorial at Maxbotix. I was rather surprised I got it working. That being said, will it damage my Rpi due to the 4-20mA output? Would I be better off getting the TI Launchpad (CC3200) offered by Christever or one of arduino boards?
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dougw over 10 years ago in reply to Former Member

The 4-20 mA signal can be converted to a voltage using a resistor between the signal and ground.
The MB7389 operates from power supplies between 2.7 and 5.5 volts.
If you are running from 3.3V to be compatible with the RPi, the 4-20 mA output cannot exceed the power supply voltage, so it wouldn't hurt the RPi inputs. If you are running from a supply larger than the internal RPi supply you may need to choose a resistor that limits the voltage. It is the same resistor in either case since you always want 3.3 v max. V=IR .... 3.3 = .02 * 165
So any resistor smaller than 165 ohms should work if my math is right. 150 ohms is the nearest common value. This value will generate 3v at full scale from the sensor.
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Former Member over 10 years ago in reply to dougw

Douglas,

Thank you for the info, new to all this so I get a bit nervous around voltage, resistors, etc. I was able to get the sonar operational, now to find/write code to convert mm to ounces from the sonar. Appreciate all the info/help.
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Former Member over 10 years ago in reply to dougw

Douglas,

Thank you for the info, new to all this so I get a bit nervous around voltage, resistors, etc. I was able to get the sonar operational, now to find/write code to convert mm to ounces from the sonar. Appreciate all the info/help.
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