LED strip, turnout PCB

Long time no see, hein?

Initially we thought the LED strips would be a piece of cake, it is just a matter to weld everything together and it should work, right? NOOOOOOOOOOO, and that’s a huge no. We spent lots of time making things work. We had all sorts of problems, some with the connection itself, wires that were too fragile, strips which had tracks physically damaged. For the software, we had a problem with the SPI, which according to the LED’s datasheet was irrelevant, but it was not. For the electronics, we had two types of strips and the incompatibility between them was not documented. Nightmares, days spent to debug all the problems we had.

Consequently, our turnout PCB software PSSC had to be postponed, and worse, we had a very short deadline to code it. Well, I finished it one week ago and we have just received the PCBs, hopefully we will get them working today. The code is basic and based in an example, but I spent sometime getting familiar with the code, specially commands related to the BLE stack. Additionally, the drivers are protected from overheating by a sequential switching with a cool down sleep.


RoseOnRails – motor and LED

Hi everyone!

This morning, Gleison and I re-did the experience to measure the inductance of the motor (we had made an error in our circuit, related to the reference voltage of the ocilloscopes..). We also re-measured the internal resistance of the motor and after several measurements found an average value of 31ohms. For the inductance, we found a value of about 6mH, however the measurement seemed to be incoherent at some point, so we’ll use the inductance-meter Alexis said we would receive in the following days. We then did the Simulink simulation (with the motor controlled with the PWM and the H-bridge) and visualised di/dt with the change in PWM frequency. However, the simulation didn’t re-produce the result we were waiting for and there were several things we didn’t understand and (in spite of researches on Google for help with Matlab and Simulink) didn’t manage to perfectly control. After discussing with Alexis we decided it was just a loss of time to try and determine it so precisely. So we well just take a PWM frequency of about 20kHz.

This afternoon, Yann, Gleison, and I talked about the LED and Yann told us that according to Sam we could simply control the led strip with GPIOs (no need for SPI). While Yann was busy with the PCB, I decided to write the code to control the led strip with one GPIO and one timer (in PWM mode), on our STM32 Olimex board. Since I started this pretty late, I finished it at about 11h30.. and Télécom students know well what that means: “Bonsoir. C’est l’heure svp.” (Hello. Time to leave please.). I was a bit disappointed since I would have liked to test and do the changes until it would (finally!) work. But well, we’ll do it tomorrow then! (can’t wait 🙂 !!)

Regarding BLE, well unfortunately I didn’t have the time to work on it today. I will try to do so tomorrow though.