Hardware Installation

Analog Inputs ADC

Analog inputs read sensors that give a voltage instead of on/off — level, humidity or pressure transmitters and the like. boneIO Black has 7 of them, ADC 1–ADC 7. How they are wired depends on the controller version: controllers from 1.0 have a SERVICE port next to POWER, older ones do not.

Controllers from version 1.0 (with a SERVICE port)

• Every input has its own protected, buffered input stage, so it takes 0–13.8 V on the terminal — a 0–10 V transmitter connects without an external divider.
• The terminal marked X next to ADC 1 is AGND, the analog ground. Connect the sensor's ground there.
• These controllers have no ADC PWR terminal.
• The default filter (multiply by 1.8) shows the voltage after the input stage, about 0.13 of the voltage on the terminal. To read the voltage on the terminal itself, set multiply to 13.8. See ADC.

Examples:

• 0–10 V transmitter (humidity, pressure, level…): +24V from the POWER terminal to the transmitter's supply, its output to an ADC terminal, its ground to X (AGND). With multiply set to 13.8 the panel shows 0–10 V.
• NTC 10 kΩ thermometer: from +3.3V (the I²C terminal) through the NTC to an ADC terminal, and a 10 kΩ resistor from that terminal to X (AGND). The terminal never sees more than 3.3 V. The panel shows a voltage, not a temperature — the app has no thermistor curve, so convert it in Home Assistant. With multiply at 13.8, the NTC's resistance is R = 9.2 kΩ × (3.3 − U) / U, where U is the reading in volts and 9.2 kΩ is the 10 kΩ resistor in parallel with the input's own 115 kΩ. The temperature follows from the NTC's B value in its datasheet.
• The same thermometer from +5V: the NTC takes +5V from the 1-WIRE block instead, the 10 kΩ resistor stays. A higher supply gives a larger swing per degree, so a finer reading. The terminal never sees more than 5 V, and the resistance is R = 9.2 kΩ × (5 − U) / U. That +5V also powers the 1-Wire sensors; the NTC draws about 0.3 mA.

Ground the sensor on X (AGND) rather than on any GND terminal: it is the same ground, but on its own path, so the current of the relays and the processor does not flow through the wire the voltage is measured against.