Wireless Power Design Kit - Medium Power - Review

Table of contents

RoadTest: Wireless Power Design Kit - Medium Power

Author: chwast

Creation date: 12 Nov 2017

Evaluation Type: Development Boards & Tools

Did you receive all parts the manufacturer stated would be included in the package?: True

What other parts do you consider comparable to this product?: null

What were the biggest problems encountered?: My general comment is: This kit from my perspective was designed more to address marketing needs rather than engineering. Yes you can find some data about kit ( http://www.rohm.com/web/eu/wireless_power ) however you cannot find i.e software or some guidelines how to connect with Microcontroler using UART and read for example efficiency etc... I need to admit that I didn't tried to obtain this data via query form. Maybe in this way I could get more data.

Detailed Review:

Detailed Review:

Firstly I want to thank Element14 for allowing me the chance to review this  product. Also I need to apologize in advance if my description will contain some mistakes but it is a first time when I am writing a review of the product like this.

Unboxing:

Wurth Electronik ( WE ) always deliver the dev kits in the great packages. It is a pleasure to receive the kit from them. Great quality, clean and professional solution.  The Design kit compose of

- Transmitter board

- Receiver Board

- LED module Board

- power supply with exchangeable plugs ( US/EU etc )

Final setup for testing:

Testing  Goals:

I wanted to check how the wireless system could be useful in the situation where we wanted to mix the fluids which are stored in the plastic or glass containers and we don't want to make opening in the canisters or use the magnetic field to rotate the blade inside the container ( laboratories using this method right now ).My thought is the following if you we can place in the canister the DC motor with blades which allow to push the fluids and we can wireless supply it we could potentially have a nice alternative for existing methods. In order to verified it I wanted to check few points:

- Check how much power the wireless system can deliver

- Transient response of the wireless system depends of the load

- Possibility to supply DC motor what is needed

- What will happen if between TX coil and RX coil water layer exist

In order be able to verified it I build the Test setup see below:

Fig.1 Test Setup ( on top 3 load resistors )

Fig.2 Lead connected get Vout and GND

Fig.3 How I get out the output for testing.

Fig.4 Oscilloscope with current probe which I have used for testing

Fig.5 Mode which I was using for testing ( Transmitter board )

Fig.6 Switches setup on the LED Module

Results:

Fig.7 CH1 output voltage , CH2 output current

If we calculate Current mean value x Voltage mean value = 11.12W Poutput

Fig8. Transient response to switch full load ( rise )

As we can see system response within 1us and drop in voltage is around ~1V

Fig9. Transient response offload ( fall )

As we see response withing 1us and overshoot in voltage occurred around ~15V

After this tests I know that

a) system is able to deliver around 10W

b) load need to be able to withstand 15V over voltage conditions at least for 1us

First application of the DC motor shows that the system was shout down. I was not sure why until I measured the current demands. Due to the in-rush current demands system simply shout down. In order to restart I have to remove the receiver coil from transmitter and restart everything.

Fig.10 CH1 output voltage , CH2 inrush current on the DC motor.

I resolve this problem by adding low resistance in series with DC motor (for the final application the best could the PTC resistor ) , after this modification I was able to supply the DC motor from system

Fig.11 CH1 output voltage , CH2 current consumption by DC motor

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Last point was to check how the system will behave if between TX coil and RX coil liquid is present.

Fig.12 Plastic container with water

Fig.13 Receiver coil protected by scotch tape

Results shows that liquid between RX and TX coils affect the communication and the power transfer is not occurring. Even if the water is very shallow

Additional tests with some drops on the TX coils show that whenever the coil is not completely covered by water then the power transfer is possible:

Fig.14 This condition power transfer is possible

Fig.15 This condition power transfer is possible

Fig.16 This condition power transfer is not possible

Summary:

Above quick testing confirm that the power output is stable and reliable to supply the loads. Transient response also allow us to understand how quickly system adopt to new conditions which is great in terms of defining the how to use the charger in the proper way. The liquid between TX and RX coils shows the limitation of the application in the original thought ( it is an air transformer ). However it also help to understand how to mount the RX module in the canister in order to have the right and correct power transfer. If the design of the canister allow to keep the air gap between RX and TX the solution will work ideally.

What is also important is that pushing the power to the device inside the liquid which we are steering , open a huge use cases like i.e transfer information about temperature,, density, viscosity etc via communication link between RX and TX. This kind of solution also open a possibilities to mix the substances which are flammable , since the motor will be sealed and no "sparking" parts are exposed.

Generally: Great modern technology, I am very greatful Wurth Elektronik and Rohm Semicoductors to allow me test this dev kit