Ultra low power transmitting for short distance

Thread Starter

Answerzzz

Joined May 11, 2022
4
Hi,

I am using a small battery to power both a sensor and a transceiver to send a signal for ~500 meters. I am looking for the lowest power-consuming method. I don't really care about how low my transfer rate. 1 sample per 1 is good enough

For my sensor, I was thinking of using a Thermistor with a load resistor because it is low power.

However, I was not sure what to use for a transmitter:

BLE, LORA, SIGFOX. Also, I probably need something to read my analog to digital too like a processor.
As a whole system:

What is the lowest power approach? Can you recommend a chip?
 

Yaakov

Joined Jan 27, 2019
5,495
Welcome to AAC.

Take a look at the ESP32-S3. It is designed for ultra low power operation and has a ULP coprocessor that can do IO even when the CPU Is in deep sleep, and wake it up if needed. Also, ESP Direct is a good way to transfer the data, it is lower overhead than WIFi and can be made very low power.

It also has 2 12-bit ADCs that the coprocessor can access in low power mode, and a realtime clock.
 

MrSalts

Joined Apr 2, 2020
1,532
Hi,

I am using a small battery to power both a sensor and a transceiver to send a signal for ~500 meters. I am looking for the lowest power-consuming method. I don't really care about how low my transfer rate. 1 sample per 1 is good enough

For my sensor, I was thinking of using a Thermistor with a load resistor because it is low power.

However, I was not sure what to use for a transmitter:

BLE, LORA, SIGFOX. Also, I probably need something to read my analog to digital too like a processor.
As a whole system:

What is the lowest power approach? Can you recommend a chip?
The lowest power approach is a Nordic ultra low power Bluetooth.
the problem with ESP32 is that people rarely buy bare microcontroller chips that Allow you to control everything including low power. Most people buy an ESP32 module that includes a eeprom, possibly a voltage regulator and even USB to Serial chip and LED and antenna. All this is usually some dozens of micro amps to hundreds of microamps in the "low power mode" which is a sleep mode and the processor cannot do anything. Then, when you power it up at regular intervals, it will draw about 250mA which is quite a bit to power the radio (wifi or Bluetooth).

the Nordic chips are very efficient and the technique is used in AirPods and many other low power applications. Power is very low when not actively transmitting and even pretty low while transmitting vs an esp products.

cypress also has options...
https://www.infineon.com/dgdl/Infin...ampaign=202110_globe_en_all_integration-files
 

BobTPH

Joined Jun 5, 2013
4,749
The lowest power approach is a Nordic ultra low power Bluetooth.
the problem with ESP32 is that people rarely buy bare microcontroller chips that Allow you to control everything including low power. Most people buy an ESP32 module that includes a eeprom, possibly a voltage regulator and even USB to Serial chip and LED and antenna. All this is usually some dozens of micro amps to hundreds of microamps in the "low power mode" which is a sleep mode and the processor cannot do anything. Then, when you power it up at regular intervals, it will draw about 250mA which is quite a bit to power the radio (wifi or Bluetooth).

the Nordic chips are very efficient and the technique is used in AirPods and many other low power applications. Power is very low when not actively transmitting and even pretty low while transmitting vs an esp products.

cypress also has options...
https://www.infineon.com/dgdl/Infin...ampaign=202110_globe_en_all_integration-files
With a range of 500 meters?

Bob
 

Yaakov

Joined Jan 27, 2019
5,495
I actually looked the range for Bluetooth, and it was, surprisingly 100 m. I am sure my Bluetooth devices don’t have that range.

Bob
Bluetooth 5 has a maximum range of 1000m, but outdoors and free field without intervening absorptive and reflective barriers. In practice, it is less, though I have been surprised by the effective range of BLE devices in my house. We have a large house and I can hear the exercise equipment in the basement and people's Apple Watches from other floors.
 

LowQCab

Joined Nov 6, 2012
1,915
You won't get 500-Meters without proper "real" Antennas on each end,
especially in Low-Power-Output-Mode.
Preferably, highly directional Antennas with some serious-Gain.
You must also have a completely clear, "line-of-sight", path between the Antennas,
no trees, no bushes, no nothing but Air, between the Antennas.
.
.
.
 
Hi,

I am using a small battery to power both a sensor and a transceiver to send a signal for ~500 meters. I am looking for the lowest power-consuming method. I don't really care about how low my transfer rate. 1 sample per 1 is good enough

For my sensor, I was thinking of using a Thermistor with a load resistor because it is low power.

However, I was not sure what to use for a transmitter:

BLE, LORA, SIGFOX. Also, I probably need something to read my analog to digital too like a processor.
As a whole system:

What is the lowest power approach? Can you recommend a chip?
Have a look at the Tinymesh / Radiocrafts products. They have a point-to-point module with analogue input or a mesh product with serial / UART input. There are though minimum order quantities. For the sensor look at the TSIC TO92 sensors (some are accurate to 0.1C and draw very low currents). Wake the whole thing with a TI nanopower timer and mosfet, transmit and go back to sleep.

Regards, Ralph
 

MrSalts

Joined Apr 2, 2020
1,532
I am trying to do something like this too. A few years back someone recomended the HC12 modules but those are a bit outdated now. So recently someone told me about the Nordic nRF24L01 which operates on 2.4 GHz and draws only 11.3 mA when transmitting at full power (0 dBm). These are available on eBay.
I've seen these around but had no idea how cheap (inexpensive) they are.
have you used them? Can you point us to some good tutorials?
 
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