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Analog Inputs
The Make Controller has 8 10-bit analog inputs.
A tour through the features of the Application Board.
Page
2
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7.
The Application Board provides 8 analog inputs, to read values from sensors and other input devices. Each input reads voltages from 0 - 3.3V, and converts them to digital values with 10 bits of resolution, giving values from 0 - 1023.
Analog input 7 is normally connected to the trimpot, but you can disconnect the trimpot jumper in order to connect an external input device.
Analog Input Power
Each bank of analog inputs has a voltage/ground pair (VIn and Gnd) on the connector to provide power for input devices you connect to the board. By default, the board is set to provide 3.3V at VIn, but can be easily changed by configuring the voltage select jumper. The voltage for each bank of inputs can be set independently to one of three values: 3.3V, 5V, or V+. The selected voltage will be available at the VIn connector - VIn1 for the first bank and VIn2 for the second.To change the jumper, lift it off the board and replace it facing the label of the voltage you'd like. One side of the jumper must always cover the middle pin.
For resistive sensors, this does not pose a huge problem, as you can power your sensor from the 3.3V supply on the board. For devices that explicitly output 5V however, you may need to provide some additional circuitry to arrive at the appropriate voltage.
The circuit below shows a voltage divider that will convert a 5V signal to a 3.3V signal. R1 and R2 are resistors, and must maintain a ratio of 5 to 3.3 to arrive at the correct voltage. For the most precision, R1 should be 20K and R2 should be 39K. Because these values are not so common for resistors, 10K and 15K will also work quite well.
| Set to 3V |
Set to 5V | Set to V+ |
|---|---|---|
Input Voltages
As the Controller Board runs at 3.3V, each of these inputs accept a 0-3.3V signal. Although the inputs are protected against higher voltages being applied, it's best to avoid applying voltages outside this range. The inputs are rated as 5V tolerant, so you're not likely to damage the board, but the inputs are only sensitive in the 0-3.3V range.For resistive sensors, this does not pose a huge problem, as you can power your sensor from the 3.3V supply on the board. For devices that explicitly output 5V however, you may need to provide some additional circuitry to arrive at the appropriate voltage.
The circuit below shows a voltage divider that will convert a 5V signal to a 3.3V signal. R1 and R2 are resistors, and must maintain a ratio of 5 to 3.3 to arrive at the correct voltage. For the most precision, R1 should be 20K and R2 should be 39K. Because these values are not so common for resistors, 10K and 15K will also work quite well.
| Circuit to convert a 5V signal to 3.3V |
|---|
