# RF Energy Harvesting Project Help

#### hawkril504

Joined Dec 5, 2019
12
Hello, this is my first post here. Hope you guys are doing extremely well.

Anyways, I'll cut to the chase. In order to graduate, me and my friends took upon ourselves a wireless RF energy harvester project. Here's a brief about the topic.

Our objective is to receive RF energy and then turn it into useable DC energy. This energy will then be deposited in a li-on battery. We also have to monitor the current and the voltage with sensors. Finally, an app will be deployed in order to check the battery charge level.

This pretty much sums up what will we be doing. Circuitry-wise, our EE engineers are confident enough. I will be handling the application part but herein lies our problem, how can we send the data which we gathered with sensors to our phone application? How can we overcome this? Please bare in mind that we have to use wi-fi, it's written in the specs..

Any help will be appreciated! Thanks alot, have a great day

#### Papabravo

Joined Feb 24, 2006
19,346
I certainly hope that your graduation does not depend on achieving spectacular results. Let us look at the problem in terms of available power. At any given location on the surface of the Earth the amount of RF energy available is between -80 dBm and -130 dBm. If you are not familiar with those ways of measuring power let me explain. The designation "dBm" means decibels with respect to 1 milliwatt. So -80 dBm is eight orders of magnitude smaller than a milliwatt. That would be 10 picowatts. That amount of power can produce a large combination of voltage and current, but the product of your harvesting efforts will always be 10 picowatts or less, if the process is not 100% efficient. So have at it guys.

Maybe you could improve your results if you did your experiment underneath a 50,000 watt clear channel AM transmitter antenna.

#### MrAl

Joined Jun 17, 2014
9,565
Measure the voltage and current with two digital meters.
Use a WiFi camera aimed at the meters to send the data to the phone as a video.

#### hawkril504

Joined Dec 5, 2019
12
The good part is that my graduation doesn't depend on really good results. It just needs to work, thats it. If we can build this project in a not so professional and basic way, that's just fine.

#### hawkril504

Joined Dec 5, 2019
12
Measure the voltage and current with two digital meters.
Use a WiFi camera aimed at the meters to send the data to the phone as a video.
I liked this idea but my instructors won't accept it Sounds clever tho

#### djsfantasi

Joined Apr 11, 2010
8,587
What (if any) microprocessor are you using? There are many Wi-Fi add-on solutions available for different platforms and some even have it built-in (ESP01 and family ).

Does anyone on your team know how to code?

#### hawkril504

Joined Dec 5, 2019
12
What (if any) microprocessor are you using? There are many Wi-Fi add-on solutions available for different platforms and some even have it built-in (ESP01 and family ).

Does anyone on your team know how to code?
Yes, I suppose I can code what's needed. I know Java and the app will be exclusively on Android. Can you elaborate on this Wi-Fi add-ons? Will we add these to our circuit?

#### Lo_volt

Joined Apr 3, 2014
276
Do a search for "smart phone data acquisition". This will bring up a range of possibilities. There are finished Data Acquisition systems that are available. As well there are components and development platforms for designing your own, possibly on an Arduino or Raspberry PI based system or the like.

#### LesJones

Joined Jan 8, 2017
3,818
If you phone is a smart phone using the android operating system and has Bluetooth it should be easy. You can use a microcontroller to format the data and send it via a Bluetooth serial data module to the phone. You would not even need to write an application to run on the phone. You could use a terminal emulator program such as Blueterm running on the phone. I do a similar thing monitoring battery charging. I use an INA219 voltage and current sensor with a PIC12F1840 to format the data as ASCII text which is sent via a wireless link (Using HC-12 modules.) to either a PC or Android tablet. To request data I just send out a couple of characters that are recognised by the PIC and it returns the data as an ASCII text string to be displayed.

Les.

#### pmd34

Joined Feb 22, 2014
520
I think as djsfantasi touched on, the way to go would be to use something like an esp32 module, which could use on board ADCs to measure your variables and then transmit them to your phone app. I have not played much with them yet myself.. though I bought the book.. and module!
https://www.elektor.com/the-official-esp32-book (also from amazon)
There is also lots of info on the web about how to make Apps and do the programming for exactly that kind of thing with the ESP32 (besides the book itself).

#### hawkril504

Joined Dec 5, 2019
12
Do a search for "smart phone data acquisition". This will bring up a range of possibilities. There are finished Data Acquisition systems that are available. As well there are components and development platforms for designing your own, possibly on an Arduino or Raspberry PI based system or the like.
Thanks for the tip, I'll be searching it.

#### Papabravo

Joined Feb 24, 2006
19,346
All of which will take more power than you can ever harvest. Don't know why this project appears so popular, it's about as worthless as a screen door in a submarine.

#### hawkril504

Joined Dec 5, 2019
12
If you phone is a smart phone using the android operating system and has Bluetooth it should be easy. You can use a microcontroller to format the data and send it via a Bluetooth serial data module to the phone. You would not even need to write an application to run on the phone. You could use a terminal emulator program such as Blueterm running on the phone. I do a similar thing monitoring battery charging. I use an INA219 voltage and current sensor with a PIC12F1840 to format the data as ASCII text which is sent via a wireless link (Using HC-12 modules.) to either a PC or Android tablet. To request data I just send out a couple of characters that are recognised by the PIC and it returns the data as an ASCII text string to be displayed.

Les.
Thanks for the info, I will show this to my EE partner. I need to ask about Bluetooth and see if we can use it.

#### hawkril504

Joined Dec 5, 2019
12
I think as djsfantasi touched on, the way to go would be to use something like an esp32 module, which could use on board ADCs to measure your variables and then transmit them to your phone app. I have not played much with them yet myself.. though I bought the book.. and module!
https://www.elektor.com/the-official-esp32-book (also from amazon)
There is also lots of info on the web about how to make Apps and do the programming for exactly that kind of thing with the ESP32 (besides the book itself).
Thanks for the module name, I will look into it and see if it helps or not. I need to confer with my teammates about this module because I really don't know about electronics at all.

#### hawkril504

Joined Dec 5, 2019
12
All of which will take more power than you can ever harvest. Don't know why this project appears so popular, it's about as worthless as a screen door in a submarine.
You are right, I totally agree with you. No point in doing this yet I have to do it...

#### MrAl

Joined Jun 17, 2014
9,565
What (if any) microprocessor are you using? There are many Wi-Fi add-on solutions available for different platforms and some even have it built-in (ESP01 and family ).

Does anyone on your team know how to code?
How hard is it to program a WiFi enabled app on an Adroid cell phone?

#### MrAl

Joined Jun 17, 2014
9,565
I liked this idea but my instructors won't accept it Sounds clever tho
Yeah i didnt think they would ha ha.
But it would work and there's be virtually no work to it.

#### hawkril504

Joined Dec 5, 2019
12
How hard is it to program a WiFi enabled app on an Adroid cell phone?
Since the complexity of the app is low, I don't think that it will be hard. All we have to do is somehow get the data from our RF energy harvester circuit and then send it to the Android app. The app will show the battery charge level.

#### djsfantasi

Joined Apr 11, 2010
8,587
So... that’s why I asked if you knew what microprocessor you were using. I couldn’t do this without a microprocessor.

I am most familiar with the Arduino family. It also has onboard ADCs. I’d use an HC12 module for Bluetooth communications, or an Ethernet shield for the Arduino.

The Ethernet/Ethernet2 add-on or “shield” can be programmed to be a web server. Then, with any browser on the network, you can read the values that you have read from your sensors. Of course, you need to put them their by your microprocessor. I think the ESP32 can be a web server as well.

You should also browse SparkFun.com They have modules as well.

But if you expect to power sensors and a wireless connection with harvested energy, forget about it.

If this is a purely academic exercise, perhaps to show the folly or limitations of RF Energy harvesting, go at it.

#### MrAl

Joined Jun 17, 2014
9,565
Since the complexity of the app is low, I don't think that it will be hard. All we have to do is somehow get the data from our RF energy harvester circuit and then send it to the Android app. The app will show the battery charge level.
What i really meant was how does the Android app 'read' the WiFi port?