16. Wildcard Week

What I’ve done this week

  • Designed the small toy using wireless charging system

Weekly Assignment Requirement

Individual assignments
Design and produce something with a digital fabrication process (incorporating computer-aided design and manufacturing) not covered in another assignment, documenting the requirements that your assignment meets, and including everything necessary to reproduce it. Possibilities include (but are not limited to):

Description of Assignment Work

This week I tried wireless charging for knowing how it worked. I am thinking to use this system for my final project.

First Idea

Sumo wrestler figure battle toy
the figure moving by a vibration motor

Existing Kit

I used the wireless charging kit by norulab firstly.

Testing the kit with LED
it worked with 5V 3.0A AC adaptor

The kit was based on blocking oscillator circuit
I tried to create original circuit referring to this

Transmission Part

Wires coated by polyurethane for the coil
Chose the wire in the middle (0.32mm) because it was good for crafting circle shape for me

BOM for transmitter
micro USB connector 1
transistor TTC015B 1
resistor 4.7KΩ 1
capacitor 1000pF 2
capacitor 1μF 1
polyurethane line 40mm

used electronics parts same as the kit

First test with breadboard

my mentor told me the breadboard had too mach impedance so it was not suitable for the circuit which needed to be controlled its electricity like wireless charging transmitter.

Second test by wired by legs of parts

coil part seemed to have problem

Receiving Part

Referring to the kit instruction, using the motor needed to use diode for turning AC current into DC by Schottky bridge diode


BOM for receiver
capacitor 1000pF 1
capacitor 10μF 1
schottky bridge diode SDI260 1
micro motor 1
polyurethane line 40mm

picked electronics parts referring to the kit instruction

made coil

and put electronics parts on it
the object stood by itself luckily


tried to test with the board included kit


I found It has polarity

tried again after reattaching motor
still not working
but I found the electricity was coming cause the LED attached simply turned on.

The motor needs 2.0V~3.0V and 50mA(@2.0V)~75mA(@3.0V)

checking voltage

checking current

I thought it could work with this power supply but it was pointed out that my measuring method was wrong by my mentor. but it had enough electricity consequently.


It didn’t work for a while. But when I added a shock on the motor by dropping it on the board. It suddenly started moving. I set the instant enclosure not to the object pop out.

I guessed it needed more power to activate its spinning
My mentor mentioned the damage of the motor. I might give it too much heat while soldering because the point I soldered was not good.
and also he told me that the position of the motor shouldn’t be inside of the coil cause it could be interfered from its magnetic force.

Recreate the kit

I remembered its circuit design was published on the internet after non-successfully testing above. Though I couldn’t make the transmission part without the kit, I think it was good idea to recreate the PCB from it using Eagle and SRM20. I thought the actual PCB would give more stable conductivity to the circuit than what I had made only with the electronic parts connecting their legs.

the schematic of the circuit had been put above already. and I made board design from it referring to the design of actual kit.

When I observed the actual kit, I recognized the coil part was narrow. I heard the setting frequency was really important for wireless charging and the coil was one of the most important part. so I tried to make it as same as possible. and also there had to have connection using the back side because of the structure of the coil. so I used via which was a kind of hole for the line going back side through it. I drew the line on back side(blue one) but it would not cut actually by SRM20 because the PCB I used had conductivity on only front side. I would attach the polyurethane line instead of cutting traces on the back side.
and pads for USB connector needed to modify from the shape in the library. I did it by illustrator to the .png file which eagle exported.

the board was cut like this.

I found I forgot to remove extra metal part by SRM20. It might affect a lot to wireless charging so I peeled it by ultrasonic cutter.

all the parts to assemble the PCB.


LED was okay.

motor was okay too.

making a coil on PCB seemed to give the stable conductivity as I expected.

An Alternative Plan

I found it was hard to manipulate two motors on the board.
And the stuff attached a motor seemed moving restlessly. so I could not challenge it because of the time limitation but if I have time later, I would changed the plan from sumo wrestling figures to a mouse running around toy as the image below.

For Final Project

I will use the following kit for my final project
Because I found the mechanism is difficult to create (especially recreating coil part)and will need more power to charge battery for my final project then I experienced this week. And the thing to think the most carefully was about safety and seemed not suitable for beginner like me to think the power system using massive amount of electricity. So I would use existing kit especially in terms of the safety.

Description of Important Weekly Learning Outcome

I tried wireless charging this time and I could cut the PCB for it. but I couldn’t create original stuff actually. I started learning by reading document published professional organization and it was hard for me to understand it within the short term. Then I tried the kit and recreated it but it was also difficult to make a proper coil which transmitted the power. I found the coil in the system had very sensible structure. Therefore, I couldn’t say this week was really successful. But I am still interested in this technology so I keep on learning this area.

Eagle sch (.sch)
Eagle brd (.brd)
Traces cutting data (.rml)
Outline cutting data (.rml)
Holes cutting data (.rml)


Manual for making wireless charging learning kit (Japanese source)

DIY keycap making (Japanese source)

DIY keycap making testing with 3 materials (Japanese source)

Designing keycap by OpenSCAD (Japanese source)

Keycap making by the kit called “L2K ADAPTERS” (Japanese source)

Ferris® File-A-Wax® Carving & Milling Waxes