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hpr4058 :: Radio Thermometer

Stache talks about building a thing to solve an issue at work

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Hosted by Stache_AF on 2024-02-21 is flagged as Clean and is released under a CC-BY-SA license.
Hobby electronics, circuit python. (Be the first).
The show is available on the Internet Archive at: https://archive.org/details/hpr4058

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Duration: 00:05:21

Hobby Electronics.

Building electronic devices and kits, repairing electronics and learning about components and their uses.


# If you ever want to make this code better, please do
# but for the love of God, please save this code first.
# It is written in circuitpython to prevent the need
# to compile code, and the RFM69 does not work with
# micropython.

import board
import analogio
import digitalio
from time import sleep
import math
import adafruit_rfm69
import busio

RoomNum = 10 # What room number is this in
SenderRoom = 10 # What room number reports to the receiver
RoomQuant = 12 # How many rooms are there
RecAddr = 254 # What's the address of the receiver
Radio_Freq_Mhz = 915.0 # What's the frequency of the radio
RetryAmount = 3 # How many times to retry sending the packet
min_okay = 12493 # Approx 20 deg C
max_okay = 9571 # Approx 26 deg C
led = digitalio.DigitalInOut(board.GP25) # Onboard LED
led.direction = digitalio.Direction.OUTPUT
CS = digitalio.DigitalInOut(board.GP13) # Pin 17
CS.direction = digitalio.Direction.OUTPUT
RESET = digitalio.DigitalInOut(board.GP6) # Pin 9
RESET.direction = digitalio.Direction.OUTPUT
SCK = board.GP10 # Pin 14
MOSI = board.GP11 # Pin 15
MISO = board.GP12 # Pin 16
spi = busio.SPI(SCK, MOSI, MISO)
rfm69 = adafruit_rfm69.RFM69(spi, CS, RESET, Radio_Freq_Mhz, baudrate=1000000)
#rfm69.reset()
rfm69.xmit_timeout = 10.0
#rfm69.freq_mhz = Radio_Freq_Mhz
rfm69.tx_power = 20
rfm69.node = RoomNum
rfm69.destination = RecAddr
#rfm69.encryption_key = (b'\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00')

adcpin = board.GP26 # Pin 31
thermistor = analogio.AnalogIn(adcpin)

resend_time = 1

def ask_all(radio):
    send_packet = ''
    temp_list = []
    room_packet = ''
    for a in range(RoomQuant):
        temp_list.append('')
    for b in range(RoomQuant):
        digitnum = str(b + 1)
        if len(digitnum) == 1:
            digitnum = '0' + str(b + 1)
        if not int(digitnum) == RoomNum:
            radio.send(bytes('query','utf-8'), destination = int(digitnum))
            sleep(.5)
            room_packet = radio.receive(timeout = 1.0)
            if room_packet == None:
                room_packet = str('0')
        else:
            room_packet = temp_retrieve()
        temp_list[b] = digitnum+room_packet
    for c in range(RoomQuant):
        send_packet = send_packet + temp_list[c]
    return send_packet

def temp_retrieve():
    #Voltage dividor
    Vin = 3.3 # Pin 35
    Ro = 7500 # 10k resistor 10000 was initial setting, changed for calibration

    #Steinhart constants
    A = 0.00110683
    B = 0.000238464
    C = 0.00000006507394

    # Get voltage value from ADC
    adc = thermistor.value
    print(adc)
    Vout = (Vin/65535)*adc

    # Calculate resistance
    Rt = round((Vout * Ro) / (Vin - Vout),0)
    # Rt = 10000 # Used for testing. Setting Rt to 10k equates approx 25C

    # Steinhart - Hart equation
    TempK = 1 / (A + (B * math.log(Rt)) + C * math.pow(math.log(Rt), 3))

    # Convert from K to C
    TempC = TempK - 273.15
    TempF = (TempC * (9/5)) + 32
    print(Rt, TempC, TempF)
    return temp_check(Rt)

def temp_check(digis):
    if digis < max_okay:
        return '1'
    elif digis >= max_okay and digis < min_okay:
        return '2'
    elif digis >= min_okay:
        return '3'

temp_retrieve()
while True:
    led.value = True
    if SenderRoom == RoomNum:
        tx_packet = ask_all(rfm69)
        print(tx_packet)
        for x in range(RetryAmount):
            rfm69.send(bytes(tx_packet, 'utf-8'))
            sleep(5)
    else:
        rx_packet = rfm69.receive(timeout = 10, keep_listening = False)
        if not rx_packet == None:
            tx_packet = temp_retrieve()
            print(tx_packet)
    sleep(.2)
    led.value = False

Schematic
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PCB Layout

PCB 3D Rendering


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