Rover Test Video #31 – Getting Closer!!

Rover Test Video #32  – Success!!

As you can see, RoverLORD nailed it!

Test # 29 – SONAR Sweeping Bench Test

Test #30 – SONAR Sweeping Floor Test

Here we are getting closer to good collision avoidance.  Bob the Dreaded Conduit Pipe looks like he may be close to defeat.

Links to all the Articles with Rover Videos:

• Article with Rover Test video #1
• Article with Rover Test videos #2, #3, and #4
• Rover Test video #5

Jimmy Buffer steps up to the Microphone

We have 8 digital outputs from the Rabbit’s parallel port A that we need to shift from 0-3 volts up to 0-5 volts and we have determined experimentally that we are too lazy to solder 8 Op-Amps.

First, the buffer is a digital device so it will either output 0 volts or 5 volts (Vcc).  According to the buffer chip’s datasheet, it will read anything above 2 volts as a logical 1.  The Rabbit’s output at 3.3 volts will get bumped up to 5 volts by the buffer and that means “bye-bye” to the operational amplifiers.

Swapping out the Op-Amps with an 8-pin buffer

Adding Features

With the circuit already drawn up in DipTrace, it wasn’t tough to update it and add a few new features.

• Add some 50-pin headers so we can plug directly into the RCM5600W’s demonstration board
• Replace the 8 Op-Amps with a single bus driver chip
• Add one more voltage regulator so we have access to 12 volt, 5 volt, and 3.3 volt supplies
• Add a socket for an XBee ZigBee modem

Check out Larry’s blog entry for more details and the files used to create the circuit board.

The New Schematic

Schematic Version 1.1

The last item is a big feature addition.  The Rabbit already has 802.11g Wi-Fi built into the RCM5600W and we’re planning on using the embedded server to deliver web pages for controls and other functionality.  However, Wi-Fi is short range and if we were to hypothetically toss the Rover out of a plane at 30,000 feet his odds of finding a Wi-Fi connection aren’t great as he plummets to the earth.  It might be useful to have a long range wireless connection for commands like “deploy parachute“.

Some of the ZigBee modems like the XBee can have much higher range because they operate at lower frequency.   A high gain ZigBee device operating at 900 Mhz with good line of sight can reach a range of up to 6 miles.  We won’t be sending data quickly, but remote operation becomes a real possibility.

The New Fangled Custom Printed Circuit Board (PCB)

The Rover PCB

The Joy of Lazy

While it might seem like a bad thing to be too lazy to solder down 8 Op-Amps, we have actually reduced the complexity of the design and the overall production cost.  In embedded engineering a simpler design is generally better and a little laziness up front will save us plenty of work later if we decide to build an army of Rovers to conquer the earth.

Puck traveling in Europe to deliver seminars on embedded web servers.

My name is Puck Curtis and I am an electrical and computer engineer working for Digi International with their family of Rabbit embedded computers.  This blog will be an informal narrative of the design, development, and prototyping process which will guide the reader through the project.

As a working engineer, I want the reader to understand that nothing really works on the first try.  Part of being an engineer is solving the problems that always crop up in the design cycle.  With this in mind, I will intentionally include some discussion of things that didn’t work out.

The companion to this blog is Larry Cicchinelli’s blog which will provide the other side of the conversation.  Larry is an old school engineer with plenty of analog and digital hardware experience while I spend much of my time working digitally and incorporating networking technolgies like TCP/IP, Wi-FI, and web development JavaScript and AJAX for our embedded computers.

Click Here for Larry’s Blog