# 3pi Expansion Kit with Cutouts - Black

 Pololu item #: 979 41 in stock Brand: Pololu Status: Active Free shipping in USA over $60 Price break Unit price (US$)
1 11.95
10 10.76

 Quantity: backorders allowed

This kit gives you everything you need to add a second level to your 3pi robot. The black printed circuit board matches the color of the 3pi and has cutouts that let you view the LCD below and make it easier to reach the power button, reset button, and programming header.

Can I augment/customize my 3pi by adding my own electronics/sensors?

Yes. The easiest way to augment your 3pi is through an expansion kit, which can comes either with cutouts that let you see the LCD below or without cutouts. The version without cutouts replaces the LCD, giving you access to more I/O lines and more prototyping space. An expansion kit is not required for addition of your own electronics, however.

The 3pi robot has a limited number of free I/O lines that can be used as inputs for additional sensors or to control additional electronics such as LEDs or servos. Please see section 10.c of the 3pi user’s guide for more information.

I’m adding peripherals to the 3pi that require 5 V. How much current can the 5 V (Vcc) power bus supply?

Because the 5 V goes through two power stages, the answer is not completely clear-cut. The 5 V regulator itself has a 900 mW power dissipation limit, so with a 4.3 V drop from the 9.3 V boost voltage to 5 V, we get just over 200 mA. The stock electronics on the 3pi typically use under 50 mA (however, this depends on what your program is doing, if you are making high-frequency noise with the buzzer, and so on), so you could figure an absolute max of 150 mA, with 100 mA being a more comfortable guideline.

However, the boost voltage has a limit of its own of around 1 A, which is dependent on your battery voltage. The motors and IR LEDs also use this supply, so using a lot for your 5 V will affect what is available for the motors. You can almost stall the motors and still have the full boost voltage on the motors in the stock configuration; if you’re also drawing an extra 200 mA for other electronics, the boost voltage will start dropping as the motors approach stall, though this is not necessarily a bad thing since it will limit the stress on the motors and lower the voltage drop on the linear regulator.

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 Prototyping PCBs Original 3pi Robot 3pi Robots and Accessories Premium Jumper Wires Connectors LEDs
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