energy harvesting

[Schuyler]

I am thinking if it is possible to use a reader to read out the values through the ST25DV(Powered mcu by the Veh from ST25dv). Therefore, I bought x-nucelo-NFC7 and stm32l4, and I hope to power L4 through EH energy, but the energy obtained through NFC makes the L4 power lamp light up, but the MCU does not run successfully. What should I do?

[Rene Lenerve]

Hi Schuyler,

you need to determine how much power EH is able to provide to the MCU to know how to configure the L4. You can measure Voltage and Current.provided by the EH to help you understand what to do with the L4. Upon that you need to reduce the consumption of the L4 by reducing clock speed and using low power mode of the L4. Don't forget to deactivate IPs you are not using in your application (this could save some power). Another tips, is to set all unused GPIOs in ANALOG input mode too.

Here are documentation links to help you:

AN4913 : Energy harvesting delivery impact on ST25DV-I2C Series 

RM0432 : Reference Manual for STM32L4 

I hope this can help you.

Kind Regards.

[Schuyler]

Hi @Rene Lenerve 

I have measured the energy output of EH, and its power is only less than 10 MW, which cannot drive the L4 acquisition sensor. Then I have learned the NFC WLC function, and how does ST25 achieve wireless power supply? How is the Battery charging implemented?

Kind Regards.

[Berenice BENVEGUDA]

Hi @Schuyler ,

In NFC WLC the EH function of the ST25DV is not used.

You told us that f you get 10mW, Have you worked on your reader environment ( power, position, distance, etc) to try to get more ? 

Best Regards,

BB

[Schuyler]

Hi @Berenice BENVEGUDA 

OK! The best EH I can get from the manual is a few milliwatts, which is not enough to drive the L4 for any other purpose. However, I also need to use the energy of NFC to drive MCU, so I think the energy collected by EH cannot complete my task, so I consider the function of NFC WLC. Is there any relevant reference for the example of driving L4 through ST25DV?

Best Regards,

[Peter BENSCH]

@Schuyler 10mW can be quite sufficient if you avoid all power wasters. This includes things like @Rene Lenerve has already mentioned (unused GPIO on the STM32L4 have to be switched to analogue mode, clock speed, etc.). But this also includes externally connected circuit parts, such as the lamp you mentioned at the beginning, which alone probably takes up the entire EH energy.

If you want to operate a NUCLEO with the X-NUCLEO and EH, you have to carefully identify and meticulously minimise all power consumers, both externally and internally (stop modes, clock of HSE, switching off any unused peripherals, etc).

By the way, a connected ST-LINK on the debug port also counts.

[Schuyler]

Hi @Peter BENSCH 

My project is to use the collected energy to test the sensor, and the power consumption is 40mw, so I estimate that this function cannot be realized, and the collected energy can only be expanded through NFC WLC.Any better suggestions?

Best Regards,

[Peter BENSCH]

Hi, @Schuyler

Well, the NFC field is strong enough to power an STM32L4 and even a segment LCD connected to it, although NFC was not originally intended for this purpose. The low power consumption of ultra-low-power MCUs makes this possible in the meantime. However, the achievable power is no longer sufficient for larger consumers.

Regards
/Peter

[Schuyler]

Hi @Peter BENSCH 

Yes, but I have noticed that some related products of ST company also collect sensor signals without power supply, such as STEVAL-SMARTAGx. May I ask if this should also supply power to L0 through NFC energy?

[Peter BENSCH]

Yes, the STEVAL-SMARTAG1 is also completely powered by the NFC field, but in addition to the ultra-low power STM32L031K6, it also has only ultra-low power sensors LIS2DW12, LPS22HB and HTS221 (obsolete), which in total manage with significantly less than 1mA.

Regards
/Peter

[Schuyler]

Hi @Peter BENSCH 

Yes, if I also add a battery and use the energy obtained by NFC to charge the battery, can I achieve the effect of driving the MCU, I only need to use the energy obtained by NFC to drive the MCU to achieve the purpose of sensor acquisition. At present, the energy obtained by the EH of ST25DV cannot directly drive the MCU

[Schuyler]

Hi @Mark5_ 

I have evaluated the product, the minimum energy of the sensor is 50mw, I only tested the EH pin of ST25DV before, but the energy source is not up to the requirements, I plan to add a rechargeable battery and use the energy obtained by NFC to charge the battery, but there is no relevant reference, only know about STEVAL-SMARTAGx.

[Schuyler]

Hi @Peter BENSCH 

Yes, because I use wireless charging technology to collect sensors, and use the energy obtained by NFC to run the MCU is also to make the sensor work normally, which is required by the project, so I would like to refer to the case of how ST company designed NFC wireless charging to run the MCU