Hi community,
I'm currently working on a simple Weather Station project that gather some environment measures (barometric pressure and temperature with BPM180, luminosity with TSL2561 and relative humidity with HTU21D) and broadcast them over RF using a nRF24L01+ module. I also wanted to experiment SMT and airflow soldering so I put 0805 and SMT parts on my board.
I reached a point where I feel quite confortable with the project's schematic and board I designed.
So now I'd like to to challenge what I produced with experts to reveal if I made some mistakes and correct them before producing some boards (I plan to use OSHPark).
Following schematic and board was designed on Eagle 7.2 Light Edition:
In addition to your reviews, I also have some question:
I plan to program my uC (an Atmel 328p) using SPI ISP and an AVR USB programmer, but not with a soldered connector but directly with pogo pins as mentioned here and here. Do you have any feedback on this technique?
I want to measure the VIN (battery voltage/charge), so I implemented what is described in this Arduino forum post, ie. use uC's ADC with a voltage divider. The voltage divider in the schematic was sized to decrease a 5V voltage to 1V (to be compatible with the ADC internal 1.1V voltage reference) but I now want to ensure that the VIN never goes above 5V to protect the ADC. I read here and there that I could use two Schottky diodes (eg. SS34 aka 1n5822) or a Zener diode. What is the best in your opinion?
Edit: with Schottky diodes, I have to connect one diode from line to a 5V reference but I don't have one on the board since I regulate the input to 3.3V (see the power rail on the schematic). Is there any solution?
The SMT 0805 RGB LED seems quite common part but I still have a doubts whether it's common anode or common cathode (schema shows common anode but their is no description on the part I bought). I'll probably have to test myself once I receive the parts.
Some blogpost about nRF24L01+ module mention that transmission can cause a current peak and make module behavior unstable. A solution is to put a CAP close to the 3.3 VCC and GND pins. I chose a 4.7uF one but it was an empirical choice based on reading. How can we size it correctly?
Thanks a lot for your help!
Kind regards,
Nicolas
I'm currently working on a simple Weather Station project that gather some environment measures (barometric pressure and temperature with BPM180, luminosity with TSL2561 and relative humidity with HTU21D) and broadcast them over RF using a nRF24L01+ module. I also wanted to experiment SMT and airflow soldering so I put 0805 and SMT parts on my board.
I reached a point where I feel quite confortable with the project's schematic and board I designed.
So now I'd like to to challenge what I produced with experts to reveal if I made some mistakes and correct them before producing some boards (I plan to use OSHPark).
Following schematic and board was designed on Eagle 7.2 Light Edition:
In addition to your reviews, I also have some question:
I plan to program my uC (an Atmel 328p) using SPI ISP and an AVR USB programmer, but not with a soldered connector but directly with pogo pins as mentioned here and here. Do you have any feedback on this technique?
I want to measure the VIN (battery voltage/charge), so I implemented what is described in this Arduino forum post, ie. use uC's ADC with a voltage divider. The voltage divider in the schematic was sized to decrease a 5V voltage to 1V (to be compatible with the ADC internal 1.1V voltage reference) but I now want to ensure that the VIN never goes above 5V to protect the ADC. I read here and there that I could use two Schottky diodes (eg. SS34 aka 1n5822) or a Zener diode. What is the best in your opinion?
Edit: with Schottky diodes, I have to connect one diode from line to a 5V reference but I don't have one on the board since I regulate the input to 3.3V (see the power rail on the schematic). Is there any solution?
The SMT 0805 RGB LED seems quite common part but I still have a doubts whether it's common anode or common cathode (schema shows common anode but their is no description on the part I bought). I'll probably have to test myself once I receive the parts.
Some blogpost about nRF24L01+ module mention that transmission can cause a current peak and make module behavior unstable. A solution is to put a CAP close to the 3.3 VCC and GND pins. I chose a 4.7uF one but it was an empirical choice based on reading. How can we size it correctly?
Thanks a lot for your help!
Kind regards,
Nicolas