I have a question about using thermistors for input with the micro maestro.
I wired a thermistor into input 1 as if it were a switch (using the diagram on page 53 of the user guide), and it works great.
However, when I enable another input, the second input reading appears to be dependent on the first. On the 0-255 scale, input 2 stays about 20 points away from input 1 as it changes.
I’d like to know why the second input is dependent upon the first. Or is there a better way of doing this?
Hello,
Did you actually connect a second thermistor, or do you just have a floating input? A floating input will have a voltage close to the value of the previous port (because of residual voltage left in the ADC as the microcontroller switches between inputs) but once you connect something to it, it should work fine.
If you do have something connected, can you tell me what resistor value you used?
-Paul
Paul,
Thanks for the quick reply. I didn’t respond immediately because I found a problem in my system - I had been using a faulty connector between the board and the thermistors. This has been corrected, and here is the setup and problem:
Maestro servo connections: servo (0) thermistor (1) thermistor (2)
Both thermistors are wired as if they are switches (using the diagram on page 53 of the user guide). The thermistors have a resistance value of around 240 kilohm at 70 degrees fahrenheit, and around 5 kilohm at 275 degrees fahrenheit (the max temperature I would like to record).
The separate resistor I have wired in is a 22 kilohm resistor.
Readings
70 degrees fahrenheit at thermistor1, with only thermistor1 plugged in:
input1: 230
input2:255
70 degrees fahrenheit at thermistor1, with thermistor1 and thermistor2 plugged in:
input1:215
input2:215
85 degrees fahrenheit at thermistor1 and 70 degrees fahrenheit at thermistor2:
input1: 195
input2: 195
Major problem: Both input values move with each other as only one real value is changed (the resistance of input1)
Minor problem: All else the same, the presence of a second input changes the value of the first input. I assume that this is an inherent restriction of the platform
Thanks again for the help
Hello,
Do you have two separate resistors, or are your two thermistors connected to the same resistor somehow? Can you post a picture of your setup?
-Paul
