Fuelino Proto3 first assembly

This morning, before going to work, I finally had some time to assemble the first Fuelino Proto3 board. Since this board is only for testing purpose, in order to save some time I did not mount filter capacitors, I mounted a cheap electrolytic capacitor that I had quickly available, and put some cheap 12V Zener diodes (500mW) since I still have to receive the 1W ones (they will arrive today from Akizukidenshi, hopefully). I am very happy because the components fit very well, without any space overlapping (not like Fuelino Proto2).

However, I found out that in the electrical design, I made some small mistakes (damn it), which fortunately do not have a big impact on the functionality. I wrongly decided to use the pins A6 and A7 of the Arduino Nano (Atmel ATmega328p), erroneously thinking that they could be used also as digital input/output, with pull-up features. I was wrong. These pins only have analog digital conversion functionality.

Unfortunately, as shown in the schematics (fuelino_p3_schematic) and in the board layout (fuelino_p3_board):

1. On A6, I connected the Enable/Interrupt pin (not the Slave Select pin, fortunately!) for the second SPI port, which corresponds to the 7th pin, from left, on the SPI port on the low left side of the board. In case this pin is not used, there is no impact on functionality.
2. On A7, I connected the "battery voltage" reading. It corresponds to the output of a comparator (LM339) which changes status depending on the battery input voltage, so that the microcontroller can understand when IG switch (ignition key) is turned OFF by the driver. I wanted to use this info in order to stop SD memory writing in case battery voltage drops. Unfortunately, since A7 input does not have pull-up function, it is not possible to read the status, but I think that the problem can be bypassed by connecting an external resistor (1.5kOhm, in the picture below) between 5V pin supply and A7. In case this info is not necessary, there is no need to perform this modification (soldering on the back side).

The next step will be to test the board and the software "on the desk" (with the Pico DrDaq signals simulation and acquisition environment). Once the board is working properly on the desk, I will test it on my motorcycle.

Author: Davide Cavaliere

I am an Italian Electrical Engineer graduated at Politecnico di Milano. My interests are motorcycles and cars, electronics, programming, Internet of Things, and Japanese culture. View all posts by Davide Cavaliere