In this post I try to make my Arduino based TTN Nodes more power efficient.
Try to save energy
An Arduino Pro Mini with 3.3V consumes power. However, many do not know that you can already save a lot of electricity here!
Today I try to drastically reduce power consumption.
How to basically reduce power consumption, can be found under “Arduino Pro Mini 3.3V Low Power” at Google. I have already done everything. So unsolder LED and Regulator.
From 5mA normal you can reduce a lot:
- 1mA through the LED
- 0.5mA through the power regulator
Now we still have 3.5mA. This is too much.
Through the LowPower library we can put the Arduino into deep sleep, which is really impressive!
Theoretically we come down to 5uA, so 0.005mA!
Measurements
Today my new multimeter arrived 🙂
UNI-T UT61E, really nice!
So let me take the first measurement.
First I tried to use the built-in measurement with uAmA. However, it only show me errors and I quickly dodged on the already more accurate shunt method. For this one, take a resistance between battery and consumer.
So that the consumer still gets enough electricity, take as small as possible. If one takes too small, however, the voltage drop is too low and the multimeter gets only fractions of mV, which are then also inaccurate.
I first tried 10 ohms. However, the node was then in a permanent reset.
I then turned four 10 ohm resistors together so that I get to 2.5 ohms, in my case 2.6 ohms. Now it works fine!
If we measure 100mV, we divide it by 2.6 ohms. So 38mA.
Without LowPower-Mode
Without the LowPower library, the result is not so good:
9.88mV / 2.6 Ohm = 3.8mA
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case EV_TXCOMPLETE: Serial.println(F("EV_TXCOMPLETE (includes waiting for RX windows)")); if (LMIC.txrxFlags & TXRX_ACK) Serial.println(F("Received ack")); if (LMIC.dataLen) { Serial.println(F("Received ")); Serial.print(LMIC.dataLen); Serial.println(F(" bytes of payload")); } // Schedule next transmission os_setTimedCallback(&sendjob, os_getTime() + sec2osticks(TX_INTERVAL), do_send); break; |
With LowPower-Mode
0.1mV / 2.6 Ohm = 0.038mA = 38uA
We saved 100 times alone with this step:
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case EV_TXCOMPLETE: Serial.println(F("EV_TXCOMPLETE (includes waiting for RX windows)")); if (LMIC.txrxFlags & TXRX_ACK) Serial.println(F("Received ack")); if (LMIC.dataLen) { Serial.println(F("Received ")); Serial.print(LMIC.dataLen); Serial.println(F(" bytes of payload")); } // Schedule next transmission //os_setTimedCallback(&sendjob, os_getTime() + sec2osticks(TX_INTERVAL), do_send); for (int i=0; i<int(TX_INTERVAL/8); i++) { // Use library from https://github.com/rocketscream/Low-Power LowPower.powerDown(SLEEP_8S, ADC_OFF, BOD_OFF); } do_send(&sendjob); break; |
As you can see in the code, the LowPower function was used with 8s deep sleep. Very easy, very successful!
But are 38uA good? As you can read here, I expected 10uA and thought that would be generous.
So, what’s the problem? Or do we have a problem at all?
3200mA / 0.01mAh = 320.000h = 36 years!!
That was the original calculation for deep sleep without sending and without self-discharge. Let’s adjust the value:
3200mA / 0.038mAh = 84.210h = 9.6 years!
Before using the LowPower library:
3200mA / 3.8mAh = 35 days!
Conclusion:
I would say we have no problem. We learned in the already linked article that 5% self-discharge is a bigger problem.
So all right!
Very satisfied 🙂
So all right!
Very satisfied 🙂
LowPower Test Node Code:
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/******************************************************************************* Copyright (c) 2015 Thomas Telkamp and Matthijs Kooijman Permission is hereby granted, free of charge, to anyone obtaining a copy of this document and accompanying files, to do whatever they want with them without any restriction, including, but not limited to, copying, modification and redistribution. NO WARRANTY OF ANY KIND IS PROVIDED. This example sends a valid LoRaWAN packet with payload "Hello, world!", using frequency and encryption settings matching those of the The Things Network. This uses ABP (Activation-by-personalisation), where a DevAddr and Session keys are preconfigured (unlike OTAA, where a DevEUI and application key is configured, while the DevAddr and session keys are assigned/generated in the over-the-air-activation procedure). Note: LoRaWAN per sub-band duty-cycle limitation is enforced (1% in g1, 0.1% in g2), but not the TTN fair usage policy (which is probably violated by this sketch when left running for longer)! To use this sketch, first register your application and device with the things network, to set or generate a DevAddr, NwkSKey and AppSKey. Each device should have their own unique values for these fields. Do not forget to define the radio type correctly in config.h. *******************************************************************************/ #include <Arduino.h> #include <lmic.h> #include <hal/hal.h> #include <SPI.h> #include <Wire.h> #include <LowPower.h> // Enable debug prints to serial monitor #define MY_DEBUG int BATTERY_SENSE_PIN = A0; int BATTERY_FULL = 4.2; // LoRaWAN NwkSKey, network session key // This is the default Semtech key, which is used by the early prototype TTN // network. // DEVEUI und AppEUI LSB static const PROGMEM u1_t NWKSKEY[16] = { }; // LoRaWAN AppSKey, application session key // This is the default Semtech key, which is used by the early prototype TTN // network. // MSB static const u1_t PROGMEM APPSKEY[16] = { }; // LoRaWAN end-device address (DevAddr) static const u4_t DEVADDR = 0x00 // These callbacks are only used in over-the-air activation, so they are // left empty here (we cannot leave them out completely unless // DISABLE_JOIN is set in config.h, otherwise the linker will complain). void os_getArtEui (u1_t* buf) { } void os_getDevEui (u1_t* buf) { } void os_getDevKey (u1_t* buf) { } static uint8_t mydata[] = "Hello, world!"; static osjob_t sendjob; // Schedule TX every this many seconds (might become longer due to duty // cycle limitations). const unsigned TX_INTERVAL_MINUTES = 1; const unsigned TX_INTERVAL = 60 * TX_INTERVAL_MINUTES; // Pin mapping const lmic_pinmap lmic_pins = { .nss = 10, .rxtx = LMIC_UNUSED_PIN, .rst = 9, .dio = {4, 5, 7}, //DIO0, DIO1 and DIO2 connected }; void onEvent (ev_t ev) { Serial.print(os_getTime()); Serial.print(": "); switch (ev) { case EV_SCAN_TIMEOUT: Serial.println(F("EV_SCAN_TIMEOUT")); break; case EV_BEACON_FOUND: Serial.println(F("EV_BEACON_FOUND")); break; case EV_BEACON_MISSED: Serial.println(F("EV_BEACON_MISSED")); break; case EV_BEACON_TRACKED: Serial.println(F("EV_BEACON_TRACKED")); break; case EV_JOINING: Serial.println(F("EV_JOINING")); break; case EV_JOINED: Serial.println(F("EV_JOINED")); break; case EV_RFU1: Serial.println(F("EV_RFU1")); break; case EV_JOIN_FAILED: Serial.println(F("EV_JOIN_FAILED")); break; case EV_REJOIN_FAILED: Serial.println(F("EV_REJOIN_FAILED")); break; case EV_TXCOMPLETE: Serial.println(F("EV_TXCOMPLETE (includes waiting for RX windows)")); if (LMIC.txrxFlags & TXRX_ACK) Serial.println(F("Received ack")); if (LMIC.dataLen) { Serial.println(F("Received ")); Serial.print(LMIC.dataLen); Serial.println(F(" bytes of payload")); } // Schedule next transmission //os_setTimedCallback(&sendjob, os_getTime() + sec2osticks(TX_INTERVAL), do_send); for (int i=0; i<int(TX_INTERVAL/8); i++) { // Use library from https://github.com/rocketscream/Low-Power LowPower.powerDown(SLEEP_8S, ADC_OFF, BOD_OFF); } do_send(&sendjob); break; case EV_LOST_TSYNC: Serial.println(F("EV_LOST_TSYNC")); break; case EV_RESET: Serial.println(F("EV_RESET")); break; case EV_RXCOMPLETE: // data received in ping slot Serial.println(F("EV_RXCOMPLETE")); break; case EV_LINK_DEAD: Serial.println(F("EV_LINK_DEAD")); break; case EV_LINK_ALIVE: Serial.println(F("EV_LINK_ALIVE")); break; default: Serial.println(F("Unknown event")); break; } } void do_send(osjob_t* j) { // Read sensor values and multiply by 100 to effectively keep 2 decimals // Signed 16 bits integer, -32767 up to +32767 int16_t t = 0; // Unsigned 16 bits integer, 0 up to 65535 uint16_t h = 0; // Unsigned 16 bits integer, 0 up to 65535 uint16_t b = readBat() * 100; byte buffer[6]; buffer[0] = t >> 8; buffer[1] = t; buffer[2] = h >> 8; buffer[3] = h; buffer[4] = b >> 8; buffer[5] = b; LMIC_setTxData2(1, buffer, sizeof(buffer), 0); Serial.println(""); Serial.print("Sending - temperature: "); Serial.print(t); Serial.print(", humidity: "); Serial.print(h); Serial.print(", battery: "); Serial.print(b); Serial.println(""); // Check if there is not a current TX/RX job running if (LMIC.opmode & OP_TXRXPEND) { Serial.println(F("OP_TXRXPEND, not sending")); } else { // Prepare upstream data transmission at the next possible time. LMIC_setTxData2(1, buffer, sizeof(buffer), 0); Serial.println(F("Packet queued")); } // Next TX is scheduled after TX_COMPLETE event. } void setup() { Serial.begin(115200); Serial.println(F("Starting")); // Fuer A0 Battery: analogReference(INTERNAL); #ifdef VCC_ENABLE // For Pinoccio Scout boards pinMode(VCC_ENABLE, OUTPUT); digitalWrite(VCC_ENABLE, HIGH); delay(1000); #endif // LMIC init os_init(); // Reset the MAC state. Session and pending data transfers will be discarded. LMIC_reset(); // Set static session parameters. Instead of dynamically establishing a session // by joining the network, precomputed session parameters are be provided. #ifdef PROGMEM // On AVR, these values are stored in flash and only copied to RAM // once. Copy them to a temporary buffer here, LMIC_setSession will // copy them into a buffer of its own again. uint8_t appskey[sizeof(APPSKEY)]; uint8_t nwkskey[sizeof(NWKSKEY)]; memcpy_P(appskey, APPSKEY, sizeof(APPSKEY)); memcpy_P(nwkskey, NWKSKEY, sizeof(NWKSKEY)); LMIC_setSession (0x1, DEVADDR, nwkskey, appskey); #else // If not running an AVR with PROGMEM, just use the arrays directly LMIC_setSession (0x1, DEVADDR, NWKSKEY, APPSKEY); #endif #if defined(CFG_eu868) // Set up the channels used by the Things Network, which corresponds // to the defaults of most gateways. Without this, only three base // channels from the LoRaWAN specification are used, which certainly // works, so it is good for debugging, but can overload those // frequencies, so be sure to configure the full frequency range of // your network here (unless your network autoconfigures them). // Setting up channels should happen after LMIC_setSession, as that // configures the minimal channel set. // NA-US channels 0-71 are configured automatically // LMIC_setupChannel(0, 868100000, DR_RANGE_MAP(DR_SF12, DR_SF7), BAND_CENTI); // g-band // LMIC_setupChannel(1, 868300000, DR_RANGE_MAP(DR_SF12, DR_SF7B), BAND_CENTI); // g-band // LMIC_setupChannel(2, 868500000, DR_RANGE_MAP(DR_SF12, DR_SF7), BAND_CENTI); // g-band // LMIC_setupChannel(3, 867100000, DR_RANGE_MAP(DR_SF12, DR_SF7), BAND_CENTI); // g-band // LMIC_setupChannel(4, 867300000, DR_RANGE_MAP(DR_SF12, DR_SF7), BAND_CENTI); // g-band // LMIC_setupChannel(5, 867500000, DR_RANGE_MAP(DR_SF12, DR_SF7), BAND_CENTI); // g-band // LMIC_setupChannel(6, 867700000, DR_RANGE_MAP(DR_SF12, DR_SF7), BAND_CENTI); // g-band // LMIC_setupChannel(7, 867900000, DR_RANGE_MAP(DR_SF12, DR_SF7), BAND_CENTI); // g-band // LMIC_setupChannel(8, 868800000, DR_RANGE_MAP(DR_FSK, DR_FSK), BAND_MILLI); // g2-band LMIC_setupChannel(0, 868100000, DR_RANGE_MAP(DR_SF12, DR_SF7), BAND_CENTI); // g-band LMIC_setupChannel(1, 868100000, DR_RANGE_MAP(DR_SF12, DR_SF7B), BAND_CENTI); // g-band LMIC_setupChannel(2, 868100000, DR_RANGE_MAP(DR_SF12, DR_SF7), BAND_CENTI); // g-band LMIC_setupChannel(3, 868100000, DR_RANGE_MAP(DR_SF12, DR_SF7), BAND_CENTI); // g-band LMIC_setupChannel(4, 868100000, DR_RANGE_MAP(DR_SF12, DR_SF7), BAND_CENTI); // g-band LMIC_setupChannel(5, 868100000, DR_RANGE_MAP(DR_SF12, DR_SF7), BAND_CENTI); // g-band LMIC_setupChannel(6, 868100000, DR_RANGE_MAP(DR_SF12, DR_SF7), BAND_CENTI); // g-band LMIC_setupChannel(7, 868100000, DR_RANGE_MAP(DR_SF12, DR_SF7), BAND_CENTI); // g-band LMIC_setupChannel(8, 868100000, DR_RANGE_MAP(DR_FSK, DR_FSK), BAND_MILLI); // g2- // TTN defines an additional channel at 869.525Mhz using SF9 for class B // devices' ping slots. LMIC does not have an easy way to define set this // frequency and support for class B is spotty and untested, so this // frequency is not configured here. #elif defined(CFG_us915) // NA-US channels 0-71 are configured automatically // but only one group of 8 should (a subband) should be active // TTN recommends the second sub band, 1 in a zero based count. // https://github.com/TheThingsNetwork/gateway-conf/blob/master/US-global_conf.json LMIC_selectSubBand(1); #endif // Disable link check validation LMIC_setLinkCheckMode(0); // TTN uses SF9 for its RX2 window. LMIC.dn2Dr = DR_SF9; // Set data rate and transmit power for uplink (note: txpow seems to be ignored by the library) LMIC_setDrTxpow(DR_SF7, 14); // Start job do_send(&sendjob); } float readBat() { int sensorValue = analogRead(BATTERY_SENSE_PIN); #ifdef MY_DEBUG Serial.println(sensorValue); #endif // 1M, 470K divider across battery and using internal ADC ref of 1.1V // Sense point is bypassed with 0.1 uF cap to reduce noise at that point // ((1e6+470e3)/470e3)*1.1 = Vmax = 3.44 Volts // 3.44/1023 = Volts per bit = 0.003363075 // 2M, 470K 1.1V ref => 5,78V Max! // 5,78/1023 = 0.00565 float batteryV = sensorValue * 0.00565; #ifdef MY_DEBUG Serial.print("Battery Voltage: "); Serial.print(batteryV); Serial.println(" V"); #endif return batteryV; } void loop() { os_runloop_once(); } |
Hi Mario, this is great stuff! Thanks for posting. A lot of people are going to be really happy with this.
BTW: I love your 2.5 Ohm resistor 😉
Thx 🙂
Hi Mario, great article!
How did you connect the battery to the Arduino Pro mini 3.3v?
The battery, full charge, has 4.6V, removing the regulator
do you risk damaging the RFM95 module?
Thanks
I hava a LDO (MCP1700-330) between BAT out of Protection Circuit and Arduino, so i have perfect 3.3V. This LDO has only 1 uA Current instead of the Original Converter from the Arduino RAW Pin!
Nice day!
Thanks for the reply
but I still have a doubt …
also in your article “My first own TTN node with self designed PCB”,
in the components list there is “MCP1700-330 LDO (1.6uA, 250mAh max, 2.3-6V input)”, but in the “Affiliate links” it does not appear
sorry, but I do not know the component well
looking on the internet, I find the component in the TO-92-3 format
use the component individually, have you bought a small card that contains it?
do you have a reference link?
Sorry for the late reply. Here is the link to the product:
http://s.click.aliexpress.com/e/Zr33nAI
I also wrote it in the article on the PCB. Thank you 😉