saving power using MOSFET

Other Hardware General Electronics
1

I am creating an embedded application that will be using one of the arduino minis (Still experimenting with which one). Most likely, i will be using the 3v Pro Mini in the final version - i'm just waiting for them to come in. Currently i am using a 5v Pro Mini and Adafruit Pro Trinket 5v.

In a previous thread on this subject ( saving power for battery operated Arduinos - #15 by newneo_phyte - General Electronics - Arduino Forum ) it was suggested to try and use the I/O pins to power the sensor and nRF24, but this isn't proving to work.

My plan now is to use a MOSFET or two to switch the power on and off for the sensor and nRF24.

The circuit uses a USB Micro breakout for power.

I don't have a clue as to the starting point for the MOSFET to use. The sensors I am using are either the MAxBotix ultrasonic sensors or Sharp IR sensors

Sharp: Pololu Carrier with Sharp GP2Y0A60SZLF Analog Distance Sensor 10-150cm, 3V ---- datasheet: https://www.pololu.com/file/0J812/gp2y0a60szxf_e.pdf

MaxBotics: MB1014 LV-ProxSonar-EZ1 – MaxBotix --- datasheet: LV-ProxSonar-EZ Datasheet – MaxBotix

So which through-hole MOSFET should i use, or, what data am i trying to garner? I know i want a P-channel, but beyond that...

I started here but then didn't know where to go:

http://www.mouser.com/Semiconductors/Discrete-Semiconductors/Transistors/MOSFET/_/N-ax1sf?

IP=1z0z63xZ1z0y3dt

Thanks for any help!

2

How are you powering your project.

Maybe you could use a Pololu 3.3volt DC/DC converter with enable pin (shutdown) for the sensors.
e.g. https://www.pololu.com/product/2842

Using a 5volt cellphone battery pack, as mentioned in the other post, might be a bad idea.
Because there are no 5volt batteries....

I think your last thread failed, because you're not showing us the whole picture.
Leo..

3

Im planning, at least for now, to just deploy with the cell phone backup battery packs since they are easy to come by and easy to recharge (as opposed to a dedicated lipo/li-ion battery which may have a better form factor, but will be more difficult to recharge in the field).

As far as the whole picture, the plan is to give these to customers for real time tracking for both them and us. The easier it is for them to get things charged the better, i think.