Quick update on the power transmission

Yesterday we put the flexible plastic tube to isolate the inner metallic tube from the axis on our power transmission (see this post ). With the help of Karim, Sibille and me devised a way to test if power gets across our ball bearings using some large resistors. We were able to see that we can transmit 30 amps, but the resistors’s resistance was too low for proper testing, so we could not test the voltage drop.

It is crucial for us to test the voltage drop, since right now we are transmitting 5V through the ball bearings and powering devices that function on 5V on the rotating part.… Read more

Some tests before the prototype: Let’s PCB

A Test PCB

Before making our first device, we aimed at having a smaller one to test some components we do not have time to test: h-bridge, multiplexer, etc.

So, I had to complete a Test PCB that Alexis began. We already have chosen the components, and he chose the step-down converter, which we would use for our circuit.

I spend two days for placing and routing this PCB. We had two constraints: to put our coils at a precise place and the hall sensor just under them and to add the other component where there was still someplace. We choose to try to not add a battery since a phone charger can give us a 5V voltage with 1,5A current.… Read more

A few bits about motors and ESCs


Last Friday we received new motors : the EP4108 320KV with built-in ESC.

We’re particularly interested in those because they have a reflashable integrated BLHeli ESC. It turns out that, starting with BLHeli_S v16.5, which is an open source ESC firmware, a new protocol is supported to replace the old PWM control method : DShot. It’s a serial protocol where speed information is encoded in 16-bit frames, instead of analogically in the duty cycle of a PWM signal.

There are three generations of BLHeli firwmare : BLHeli, BLHeli_S, and BLHeli32 (wich is no longer open source), each with several versions.… Read more

Final LED tests

Since we started doing research on which LEDs to choose for our project, there three different LEDs / type of LEDs we considered:

  • The LE RTDUW S2WP , requiring 1.4 A
  • The ASMG-PT00-00001, requiring 200mA
  • Four similar SMD PLCC 2 (the package compatible with the flexible waveguides we were considering) LEDs: ASMB-MTB1-0A3A2, HSMA-A431-Z50M1, CLM2D-GCC-CC0F0783 and ASMB-BTE1-0B332, all requiring around 20mA

The LEDs for the PCB petals (see our latest architecture post) were to be either the LE RTDUW or the ASMG-PT00, and the LEDs for the top PCB were to be the ASMG-PT00 or one of the four SMD PLCC2 LEDs.… Read more

Cause every time they flip, I get this feeling

Time for more tests with marbles

In my last post, I was a little sad. We were about to abandon the heart of our project: marbles because they were too powerful. Alexis gives us some hope by saying that we may have better result with some iron. So we try the configuration on the right (there is an iron plate between the two marbles), but it gives bad results. The iron does not constrain the magnetic field. It just attracts more the two marbles. We were about to try with some steel when the miracle came…

The miracle came from coils

In fact, the coils already have some iron on them.… Read more

Can you feel it ? Yes we can !

In the components familly, it was time for the Hall effect sensors to be tested.

The sensor:

We used the SS39ET from HonneyWell. This sensor has 3 pins. One is GND, one is Vcc and the last is the output. The output is a voltage proportional to the magnetic field. We choose for Vcc a value of 3.3V.

First tests, let’s use a voltmeter.

To do the first tests we measure the output voltage with a voltmeter. To power the device we used a DC power supply. We also added an ampermeter to measure the current going to the Hall effect sensor.… Read more

Marbles: “I can’t let you go, I want you in my life”

Designing our grid

Have you ever played with some neodymium balls? These are potent magnets, so we had to find a way to use them in our device without making them dependent on the magnetic field of another marble. Because if we had to manage this field, we would have always to power our coils, and they would have burnt. That’s why we choose to buy many different balls to try to find the best compromise between the distance and the diameter of the marbles.

With a plank of beech, we cut with a laser engraver. We made many different holes of many diameters with various distance to know which one is the best.… Read more

LED’s do some tests

Yesterday I set out to test the LEDs we received : ASMG-PT00-00001 and LE RTDUW S2WP. The first is a powerful RGB LED, while the second is an even more powerful RGBW LED. They need to be quite powerful because in order to avoid a blurry image due to the motor rotation the duration of the flashes must very brief, and since the LEDs are flashed only once every 137.5 degrees of rotation that means they are off most of the time.

The goal here is to test under conditions similar to those the LEDs will actually be used in : once every 1/30 seconds, they will be turned on for 100µs using high frequency PWM modulation for the colors, and then switched off again.… Read more

I have a coil. I have a current => I have a magnetic field ! Wait, do I ?

A naive first approach

We received the coils denominated SDE1006A-681K. These are 680 µH inductance coils.

We roughly soldered two wires on each pole of the coil as you can see on the image below for very basic testing.

Next we needed to connect it to the IoT node. As a very basic montage for testing, we configured user button with polling on the IoT node to drive one of the GPIO pin we have on high when pressed.

We used a resistance to limit the current output. As we wanted a current of the ordre of the mA we used a resistance around 1 kΩ.… Read more