I am having a problem trying to get the Hackster thermistor demo working that is outlined here (
https://www.hackster.io/mc-Things/iot-ntc-thermistor-temps-using-thethings-io-7f6934)
I ordered the same USP10972 thermistor and believe i have the wiring correct but the values I'm getting out fluctuate a lot and are never anywhere near valid. I also get a lot of not a number errors so there's obviously something wrong! The hackster description calls for a 100 ohm resistor but the one used in the image is a 10k...I've tried both but neither solves the issue.
Ultimately I want to get it working on the 120 and then port it to the 205 so that I can read water temp's outside under the ice.
Here's the code I'm using to push the data to Losant. I also have the onboard temp and battery being pushed as well but I've remove that from the code below to keep it on topic.
Class Thermistor
Const USP10972_BETA As Integer = 3892
Const USP10972_R25 As Integer = 10000 '10kOhm
Const USP10972_DIVIDER_R1 As Integer = 10000 '10kOhm
Shared USP10972 As NTCTermistor
Shared Event Boot()
USP10972_DIVIDER_ENABLE = False
USP10972 = New NTCTermistor(USP10972_BETA, USP10972_R25)
End Event
Shared Event measureTemperature() RaiseEvent Every 10 Seconds
Dim LosantTopic As String = "losant/deviceID/state"
Dim losantPayload As Json = New Json
USP10972_DIVIDER_ENABLE = True
Device.EnableOpamp()
Thread.Sleep(10000)
Dim thermistorResistance As Float = USP10972_DIVIDER_R1 * (1 / ((Device.BatteryVoltage().ToFloat/ USP10972_VOLTAGE.ToFloat) - 1))
USP10972_DIVIDER_ENABLE = False
Device.DisableOpamp()
Dim tempPstring As String = USP10972.TemperatureCFromResistance(thermistorResistance).ToString
Dim tempPJson As Json = New Json
tempPJson.Add("probeTemp", tempPstring)
losantPayload.Add("data", tempPJson)
Lplan.Publish(LosantTopic, losantPayload.ToListOfByte)
End Event
End Class