Go Down

Topic: Nano Power specs (Read 1 time) previous topic - next topic

calcoast

I am trying to find out if anyone knows how much power the 5vdc pin on the nano board can source.  For my project I have a regulated 12vdc power supply to connect to the Vin pin.  I would like to power a 20 x 4 LCD and three variable pot's (voltage dividers) to the analog inputs from the 5vdc pin on the nano, but can't find any documentation on how much power that pin can source.  Any help would be appreicted.
Thanks!

CrossRoads

The regulalor is good for aboout 500mA I believe.
Will shut itself down if gets too hot - it has to dissipate 7V x 800mA of power to put out 5V x 800mA of power.
The documentation is looking up the datasheet for the regulator called for on the schematic.

UA78M05, the little 4-pin regulator on the bottom of the board
http://www.ti.com/lit/ds/symlink/ua78m05.pdf
350mA looks like a more realistic number from page 5 of the data sheet.
500mA possible, but regulated output may vary some.

If you have 10K pots (5V, wiper to arduino, ground) thats' only 0.5mA, so the pots are  not the concern.
The ATMega and FTDI chip will need 30-40mA depending on what you have them doing.
How much do the LCDs need?
A part like this
http://www.newhavendisplay.com/specs/NHD-0420DZ-FL-YBW.pdf
only needs 3.5mA - the backlight is what gets you, 150mA. I would use an seperate regulator for that, not the Nano's.
You could wire 4 of these in parallel with seperate Enable pins so that only 1 at a time is responding.

For a couple dollars more , they are available with Serial interface too:
Serial Interface: I2C, SPI or RS232
http://www.newhavendisplay.com/specs/NHD-0420D3Z-NSW-BBW.pdf

Open Short SPI 100KHz max clock
Short Open I2C 100KHz max clock
Open Open RS232 5V, TTL signal, 115.2Kmax

Power draw is higher, 65mA, while backlight is less, just 20mA
I2C has selectable addresses, SPI needs seperate SS line,  RS232 need outside hardware to multiplex the hardware UART out to the displays?
Maybe 4 instances of Software Serial?
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

Go Up