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Roomba iCreate is an excellent low-cost mobile robot for teaching or research purposes. Their vacuum cleaner versions are very popular and can be purchased in many countries.

The Beagle Board is an inexpensive board based on a OMAP3530 platform (a powerful System on Chip) designed specifically to address the Open Source Community. It has been equipped with a minimum set of features to allow the user to experience the power of the OMAP3530 and is not intended as a full development platform as many of the features and interfaces supplied by the OMAP3530 are not accessible from the BeagleBoard. By utilizing standard interfaces, the BeagleBoard is highly extensible to add many features and interfaces. It is only for “ENGINEERING DEVELOPMENT, DEMONSTRATION, OR EVALUATION PURPOSES ONLY”, so no commercial use is allowed without permission.

This tutorial is based on guides appearing in “Hacking Roomba” book (Wiley-2006). Here it describes how to make a voltage regulator to connect a 5V device to the 16V iCreate batteries. However, it only shows how to do it through the mini-din conncector that every roomba robot has. In this tutorial this connection is made through the DB-25 'Cargo Bay Connector' that iCreate robots have.

The cargo bay connector is a DB25 connector. Here is also a description of the mini-din pin-out that can be found in every roomba:

CIRCUIT DESIGN

First it must be made a DB-25 connector with pin 10, 11 or 12 soldered to a +V (red) cable and pin 14, 16, 21 or 25 to a GND (black) cable. It is better if this connector is put in a DB-25 box enclosure. Here is this final connector used:

There must be made also the barrel jack cable to connect. The barrel jack must a 5.5mm connector. It is easy to solder to wires (positive and negative). Other jack barrel connectors can be soldered if for example you want to connect an extra 5V USB hub to the iCreate Roomba.

The second step consists in making the regulator circuit itself. It can be based on a typical 7805 5V voltage regulator but this is extremely inefficient. It must take into account that this circuit must transform 16V from the roomba batteries to 5V. If for example the BeagleBoard and the periphericals have 500mA of battery consumption the power dissipation (P=V*I) is P = 11V * 500 mA = 5,5 Watts. That's a lot power lose in form of dissipated heat!

An alternative is to use a switching regulator like the Traco TSR 1-2450 (see reference at the bottom). This regulators do not almost dissipate heat are very efficient. This design decission is important because it will provide more battery autonomy to the robot.

Here is the circuit scheme used with both regulators alternative.

Note that an status LED and a switch have been added. There is also a diode to prevent from connecting V+ and GND lines in the wrong order (and also to prevent from a reverse charge/current that could damage the BeagleBoard).

Here there are showed the two alternatives to the voltage regulator circuit:

1) With the 7805 voltage regulator:

2) With the TSR 1-2450 switching regulator:

See that both green terminal block connectors have been added to input (16V) and output voltage (5V) terminals on the circuit in order to make it easier (and modular) to connect the Beagle Board (and other 5V periphericals).

And finally all together mounted on the iCreate Roomba:

Beagle Board: http://beagleboard.org

Roomba iCreate: www.irobot.com/create

Traco switching regulators http://www.tracopower.com/fileadmin/medien/dokumente/pdf/datasheets/tsr1.pdf