Voltage reading difference between web browser and iOS app

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  • Device & model you are using (Ex: Pi 2 Model B or Arduino Uno with W5100 ethernet shield)

Rpi 2 mod B

  • What dashboard are you using? (Web, iOS, Android)

Web and iOS

  • Please describe the bug / issue as detailed as possible. Attaching the code and any relevant screenshots would be very helpful!

I have 2 widget setup up to read voltage using the mcp3008.

The web browser shows volt and correct voltage but the iOS app shows lower voltage and float. No matter how many times I hit save float dos not change to volt. This has been an issue with other widgets where saving the sensor several times eventually solves the problem. I usually wait a minute to allow the server to catch up but this voltage widget refuses to change and read the correct voltage after 2 days old trying.

Also as a suggestion I would like a scale on that generic sensor that allows scaling so it will read true voltage resolution that’s been reduced from 26vdc down to 3.3vdc. 0-26v to 0-3.3v.

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@bestes addendum to this issue, the readings won’t go over value of 1 on iOS or web.

-does it display correct values when using a Python test script directly on the Pi?
It sounds…broken.

Looks easily reproducible, let us look into this and push out a fix for next iOS update. Thank you for letting us know! Seriously, really helps when we try and fix these things! I’ll update this thread when we can push a fix.


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Um… maybe I broke it with 5v on the mcp3008. Script?, not a clue, research time, Ill figure how to write a script in python. I’m still an Rpi toddler.

Here’s a Python test script that runs on a Pi:

I deleted the widgets and added new and now web browser is showing 3.3v and varies with the pot when changed. Still the iOS app only shows Iv . Hmmm. I think there’s a bug.

Also the widgets showed on the web first then five minutes later they show up on the iOS app even tho I added from iOS.

I will try the script and see what happens.

-the engineers shall make it their highest priority,
getting that widget to work correctly.

They have been informed that they are not allowed home
until it’s fixed.

I have the exact same issue and just saw this thread when I was about to create a new issue (I didn’t after seeing this).

I am using a Raspberry Pi 2 and have just configured it with Cayenne. I’ve also been using the latest iOS app (running on iPhone 7 with iOS 10.1.1).

I currently have a number of modules connected, some using Cayenne, some not:

  • DHT11 Temperature & Humidity sensor (this is relaying info to a dashboard on Beebotte (Beebotte) and wired up to GPIO18 on the Pi

  • DS18B20 1-wire temperature sensor (wired up to GPIO4 on the Pi using a 4.7K resistor as recommended)

  • MCP3008 Analogue converter (wired up as per the tutorial on here) and finally,

  • LDR photoresistor (wired up as per the tutorial on here)

I managed to get the sensors working (with the exception of the DHT11 as I understand this is still being developed by myDevices Cayenne) and I was able to set the widgets up on the web dashboard, as well as within the iOS app. However, the photoresistor always defaults back to “Float” on the iOS app when I want it to be “Volt”. I set it as Volt in the settings on the web dashboard, but it seems to default back to Float whenever I open the iOS app.

The idea is that I can see the voltage of the photoresistor in the app when I’m away from home (my Pi is monitoring the conditions in my spare room where I have two batches of homebrew beer fermenting away, so it would be great to see the environmental conditions), but not being able to see this properly in the iOS app is a little frustrating.

Not sure if this is a bug, but it would be great if this could be fixed ASAP as my beer will be ready soon! :smiley:

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@bestes any word on this? Also setting a conversion scale to display voltage range as needed. Say a full 3.3v from the mcp3208, my dial would read 36v solar panels.

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Hi @wmontg5988,

Yikes I am late to the party here. Sorry for the late reply.

So for voltage scaling, is this what you would expect:

Multiply the value coming into Cayenne (say, 3.3v) by this number (some variable), and display the final number for this sensor/widget (in your case, it would be 36v).

Just want to be clear before I pass this along to the team :slight_smile:


Hi @raspberrycoulis,

sorry for the late reply here. This should actually be fixed now :slight_smile:

Let me know if it is not fixed please. Thanks!


Thanks @bestes and yes the widget should have a scale field to enter a variable/multiplier to upscale the reading to suit application (iOS)

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