Problem: Need a constant 5V supply with enough capacity  for robot or Raspberry Pi. This needs to be regulated.

Consideration 1: 7.2V Ni-MH battery with at least 3000 miliAmper per hour (mAh), but if voltage is too big it will burn the Pi!

Consideration 2: 4 x 1.2V Rechargeable AA battery that will supply 4.8V, this won’t last  and won’t supply the minimum 800mA requirement of Raspberry Pi.

Solution: Build your own voltage regulator!

How?

Buy this from your local electronic supplier:

• 1 x 7.2V or higher battery
• 1 x mini breadboard or PCB if you keen to solder
• 1 x LN7805 +5V 1A voltage regulator. (For 6V you need LN7806 regulator)
• 2 x 100 nanoFarad (nF) 25V electrolytic capacitor
• 2 x 100 picoFarad (pF)  = 0.1nF ceramic capacitor
• 1 x diode 1N4004 or IN4001
• 1 x input pin (for battery)
• 1 x output pin (for connection to Raspberry Pi / robot)
• several breadboard wires

Connect them all up according to this diagram:

Source: http://reviseomatic.org/help/e-components/Voltage%20Regulator.php

Please note that to work consistently the power source needs to be at least 2 volts higher voltage then the power output.

Example usage is for the robot project.

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