ACRIOS Systems wiki

ACR-CV-101N-R-D with temperature probe connected

We have encountered request regarding the solution for high-temperature remote readings, that could go up to +120°C but also would measure humidity. This use-case can be found in HACCP applications, in the monitoring of warehouses or anywhere, where the information about temperature and humidity is crucial. The biggest challenge lays in the low-power nature of the solution since the LPWAN network will be used.

ACR-CV-101N-R-D

Temperature and humidity probe communicating over Modbus (RS485)

This application can be implemented using ACR-CV-101N-R-D converter and this converter is also being used in this application note. The ACR-CV-101N-R-D converter is communicating over NB-IoT, has a non-powered RS485 bus and D battery with the capacity of 17 000 mAh.
More suitable option would be using ACR-CV-101N-R12-D converter, which has powered RS485 bus by 12 volts. The temperature and humidity probe being used can hold anything between 3.3 - 24V.

-----------------------
--- CONFIGURATION -----
-----------------------
----- NB-IoT ----------
APN = "nb.m2mc"
PLMNID = "23003"
protocol = "UDP"	-- UDP or TCP
ip = "192.168.0.20"
port = 4242
receiveTimeout = 500 -- the maximum execution time in milliseconds
------ Timing ---------
-- device wakeup interval
periodHours = 0
periodMinutes = 5
-----------------------
-----------------------
-- CONFIGURATION END --
-----------------------
 
function onWake ()
 
 
    api.rs485Setup(9600, 0, 1, 8)
    dataToTransmit = ""
 
    --read temperature
    api.rs485State(1)
    api.voltageSourceState(1)
    api.delayms(500)
    req = pack.pack('<b8', 0x01, 0x03, 0x00, 0x01, 0x00, 0x01, 0xD5, 0xCA)
    api.rs485Receive(0) -- flush input buffer
    api.rs485Send(req)
    ans,len = api.rs485Receive(500) 
 
    if len == 7 then
        dataToTransmit = dataToTransmit .. 'T' .. ans:sub(4,5)
        temperature = string.byte(ans:sub(4,4))*256 + string.byte(ans:sub(5,5))
        if temperature > 0x7FFF then
            temperature = -1 * (0x10000 - temperature)
        end
        temperature = temperature/10
        print("Current temperature is: " .. tostring(temperature) .. "C")
    end
 
    -- read humidity
    req = pack.pack('<b8', 0x01, 0x03, 0x00, 0x00, 0x00, 0x01, 0x84, 0x0A)
    api.rs485Receive(0) -- flush input buffer
    api.rs485Send(req)
    ans,len = api.rs485Receive(500) 
 
    if len == 7 then
        dataToTransmit = dataToTransmit .. 'H' .. ans:sub(4,5)
        humidity = string.byte(ans:sub(4,4))*256 + string.byte(ans:sub(5,5))
        humidity = humidity/10
        print("Current RH is: " .. tostring(humidity) .. "%")
    end
 
    api.voltageSourceState(1)
    api.rs485State(0)
 
    -- send data to LoRaWAN/NB-IoT
    api.dumpArray(dataToTransmit)
 
 
    if #dataToTransmit < 1 then
        buf = "NO DATA RECEIVED"
    else
        buf = dataToTransmit
    end
 
    print("To NBIOT: ")
 
    api.dumpArray(buf)
 
    print("Sending to NB-IoT")
    api.nbSend(ip, port, buf, receiveTimeout, protocol)
 
    print("Done sending")
    print("Sleep now, wake in " .. tostring(periodHours) .. "hrs:" .. tostring(periodMinutes) .. "mins.....")
 
    api.wakeUpIn(0,periodHours,periodMinutes,0)
end
 
function onStartup()
    print("Starting up NB-IoT Abest Modbus script with APN settings")
 
    result = api.nbAT("AT*MCGDEFCONT=\"IP\",\"" .. APN .."\"", 5000, 1)
    print("APN result: " .. result)
 
    result = api.nbAT("AT+COPS=1,2,\"" .. PLMNID .."\"", 5000, 1)
    print("PLMNID result: " .. result)
 
 
end

[17:41:28:193] SYS: —- New request —-␍␊
[17:41:28:193] SYS: Battery Voltage: 3679 mV␍␊
[17:41:28:193] LUA: starting lua script version 1␍␊
[17:41:28:865] LUA: Starting onWake() script␍␊
[17:41:29:489] ~>Current temperature is: 28C␍␊
[17:41:29:601] ~>Current RH is: 40%␍␊
[17:41:29:617] ␍␊
[17:41:29:617] ⇥  00 : 54 01 1A 48 01 92 ␍␊
[17:41:29:633] ~>To NBIOT: ␍␊
[17:41:29:633] ␍␊
[17:41:29:633] ⇥  00 : 54 01 1A 48 01 92 ␍␊
[17:41:29:649] ~>Sending to NB-IoT␍␊
[17:41:30:241] NBIOT: wake the module up!␍␊
[17:41:31:089] NBIOT: wake the module up!␍␊
[17:41:31:441] NBIOT: Signal level 21.␍␊
[17:41:32:641] NBIOT: No return data␍␊
[17:41:38:672] ~>Done sending␍␊
[17:41:38:720] ~>Sleep now, wake in 0hrs:5mins.....␍␊
[17:41:38:742] SYS: date / time - 2020/10/12 / 17:41:37␍␊
[17:41:38:742] SYS: wake up at day / time - 12 / 17:46:37␍␊
[17:41:38:751] LUA: destroyed all lua objects, exiting␍␊
[17:41:38:751] SYS: entering sleep mode␍␊

Oct 12 17:34:36 challenger python[31631]: 2020-10-12 17:34:36 diff = 21:07  :  received message from:  ('46.234.125.38', 59164) in hex:  54011C4803D4

The payload captured on server side is “54011C4803D4” in hex. The first and the fourth byte stands for temperature and humidity. After we convert “54” from HEX to ASCII, we get “T”, which stands for temperature. The “48” is “H”, which stands for humidity. The “011C” and “03D4” are temperature and humidity values. After translating the whole payload, we get T284 H980. Temperature is 28.4°C and humidity 98%RH.