AnalogueSignals < AFNOG

---+ Analogue Signals

Up to now, we only treated digital signals in output mode (LED) and in input mode (pushbutton). Sensors often produce analogue signal levels, however. A thermistor, for example, returns a voltage level which corresponds to the temperature. How can we treat signals like these?

Our slider potentiometer produces a similar signal level, and we will connect it to an <b>A</b>nalogue to <b>D</b>igital <b>C</b>onverter (ADC). The ESP32 chip already supplies a 12 bit ADC. With 12 bits 4096 different numbers can be represented, and we therefore get a resolution of our measurement of 1/4096 which corresponds to ~0.025 %

<img alt="slider.png" height="384" src="%ATTACHURL%/slider.png" title="slider.png" width="467" />

The potentiometer has 3 pins: OTA (or OTB), VCC, GND which must be connected to the triple base as follows:

#PotConnection
| *Potentiometer* | *Triple Base* |
|  OTA  |  A0 (ADC) GPIO 36  |
|  VCC  |  3V3  |
|  GND  |  GND  |
Use the male/female Dupont wires to make the connections.

<img alt="slider_conn.png" height="206" src="%ATTACHURL%/slider_conn.png" title="slider_conn.png" width="470" />

You find a description of the !MicroPython driver in the [[https://docs.micropython.org/en/latest/esp32/quickref.html#adc-analog-to-digital-conversion][doc]] again. The ADC works for a range of 0..1V only while the potentiometer produces signal levels of 0..3.3V. A signal attenuator allows adapting the ranges. It must be set to ADC.ATTN_11DB for our 0..3.3V slider.

<verbatim>from machine import ADC,Pin
from time import sleep_ms

slider = ADC(Pin(36, atten=ADC.ATTN_11DB)  # use the ADC on GPIO 36 and set the attenuator to 11 dB
while True:
     print("Raw 12 bit value from slider: ",slider.read())
     sleep_ms(100)</verbatim>

The only hardware still missing is the [[rgb LED chain]]

-- %USERSIG{UliRaich - 2022-10-16}%

---++ Comments

%COMMENT%

Attachments

Topic attachments
I	Attachment	History	Action	Size	Date	Who	Comment
png	slider.png	r3 r2 r1	manage	152.9 K	2022-10-24 - 10:58	UliRaich
png	slider_conn.png	r1	manage	77.7 K	2022-10-24 - 10:59	UliRaich

This topic: AFNOG > ASP2022 > MinimalLectures > AnalogueSignals
Topic revision: r3 - 2022-10-24 - UliRaich