Live wire

Yesterday evening, the whole groupe work together to test the power transmission through the ball bearings. Those tests are significant to determine if we need to add a 5V-regulator on the main board, and which regulator we choose for the bottom PCB  to account for the tension drop.

Electrical setup

We had ordered the resistors (two 0.5Ohms/25W resistors and one 0.1Ohm, 30W)  described in this article and used them to build the following electrical setup:

The generator supplies 5V because we plan to use a 5V regulator on the bottom PCB and send 5V to the main board through the ball bearings. … Read more

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

Uncrossing wires

Today Sibille and I made great strides on the bare-metal code for the led-driving processors.

Debugging

Yesterday we left off unable to see the PWM outputs on the processor pins. Today we started by remedying an oversight: we set about configuring the clocks. 

On top of that, it turns out that yesterday we didn’t pay enough attention when reading the documentation for the board: the documentation includes pinout information for other boards with other processors, and we were looking at the wrong processor…

We were then able to use a Saleae Logic analyser to observe the PWM output. At first, the frequency was off, and we spent much time looking at our clock configuration before realising that the timer prescaler didn’t behave in the way we expected (it turns out that frequency division ration if the prescaler value plus one, which is a neat way of avoiding a “division by zero” type of situation). … Read more

Update on mechanical architecture

This past few days, Vlaya, Xavier and I also worked on the mechanical architecture of our Phyllo. We’ve already made several posts on this subject, but we still have doubts and questions. Your opinions and experiences are much welcome.

General architecture

The Phyllo (the printed shell of the petals) rests on a circular PVC plate of 25cm in diameter. The main PCB is attached on the top of this PVC plate. The PVC plate is fixed to the axis by a metal piece that the school mechanic will machine for us.

Then, going down, we find the two ball bearings carrying VCC.… Read more