next topic »

[on:]

Hi everyone,

My mission is to build an Arduino Uno on a breadboard/protoboard, powered by batteries. Currently "my shopping list" is:
- ATMEGA 328 with Arduino UNO bootloader
  and 2 x 22pf load capacitors
  and 16Mhz through hole crystal for "stock" Arduino speed
- 3V regulator MCP1700
  and 3 x 1uf capacitors
  Output Voltage Fixed: 3.3V
  Input Voltage Max: 6V, Input Voltage Min: 3.5V
- 4 rechargeable AA batteries in box (4 x 1.2v = 4.8v)

The Arduino should drive:
- Roving Networks RN-XV wifi module
  Input power between 3.0V and 3.7V (3.3V + or - 10%)
  Uses 40mA when connected and 180mA when transmitting data
- DS18B20 digital thermometer (sensor)
  Input power between 3.0V and 5.5V

I have some doubts/uncertainties about the following:
- Is a good idea to run the Arduino on 3.3V? (I thought so since my wifi module also runs on 3.3V)
- When running the Arduino on 3.3V, can I run it on 16Mhz? (I hope so, otherwise I'll need another crystal and change the bootloader)
- Is the MCP1700 a good choice as a regulator? (the Arduino should be "low power" and sleeping most of the time, so I don't want to waste battery life on the regulator)
- Am I missing something? Would you advice another approach?

Thanks a lot!
J

[Reply #1 on:]

Hi,

- Is a good idea to run the Arduino on 3.3V? (I thought so since my wifi module also runs on 3.3V)

Won't hurt anything.

- When running the Arduino on 3.3V, can I run it on 16Mhz? (I hope so, otherwise I'll need another crystal and change the bootloader)

Technically, no.  Practically, probably.

3.3V / 16MHz is outside the processor's specifications.  However, many people run the processor at that point without problems.  There are Arduino compatible boards available that run at that point.

If you're building something that has to be guaranteed reliable, pick a different point (higher voltage or lower clock frequency).  Otherwise you'll be fine.


Someone else will have to help with the rest.