Mind/Iron Blog Articles

The Joy of Prototyping

There's nothing like prototyping to get the creative juices flowing. Sure, you can work out a robot design on paper or in a 3D CAD program, but there's something missing. Perhaps it's the tactile feedback, the ability to instantly and instinctively unplug one component and substitute another. Or, the ability to perform 'illegal' operations, such as mangling a connector to make it mate with a device not made to spec. It's hard to innovate — that is, create something new — if it has to first be defined in a software package. For example, I have yet to see the equivalent of gaffer's tape in a robot simulator or CAD program.

Sometimes, a little bubblegum and string can work wonders. As shown in the accompanying photo to the right, I'm developing a prototype of a sound tracking robot, based on both amplitude differences and time delay. What looks like a tangled mess is actually an orderly mess, centered on an Arduino Uno with Grove shield. The shield is inexpensive and accepts a variety of Grove cables with servo, power, or four-pin connectors. The cables are a joy to work with — as soon as you cut off the locking mechanism on the four-pin connectors that makes them impossible to dislodge.

At the end of one cable is a 567-based phase locked loop (PLL) board from Ramsey Electronics. I modified the board with the addition of a signal diode and bypass capacitor so that it would drive a digital pin on the Arduino. Then there's the artificial ear — the inverted red silicone cup with a modified Grove microphone sensor mounted on the back. I replaced the original Grove omni-directional microphone element with an inexpensive directional electret element from Digi-Key. Then, there are the jumpers between cables made with Futaba-compatible servo extender connectors.

You might also notice the black gaffer's tape holding down the LED indicator buttons and the lead to the servo. In the case of the LEDs, the tape keeps the fingernail-sized LED boards pointed upwards where I can see them. As far as the servo lead goes, the tape is an ounce of prevention. For some reason the folks at Grove decided to bring power to the servo through a male connector — meaning the Arduino's 5 VDC and GND connections are exposed. With all those cables and end connections, exposed power sources aren't a good thing.

This is just one of many possible prototyping environments. It happens to be my favorite for working with Arduinos, but when I have an analog circuit based on a few chips, I use a standard breadboard environment. If it's a super-simple circuit, I might even pull out the wire wrap tool and wire components together in a few minutes.

Rarely do I heat up the soldering iron for a prototype. Soldering irons are for production, when I know I won't be changing a component or connection every 10 minutes — with one exception: Tubes.

Tubes are in a world of their own. Because of the high voltages involved, I don't use breadboards. What I do use is an old guitar amplifier chassis with clean sockets, rows of solder posts, and a hefty high voltage and filament power supply. The other major feature is a set of circuit breakers on all the supply leads.

What's your prototyping environment of choice? Do you have something that you've built that’s worth sharing with readers? If so, please drop me a line. SV

Posted by Michael Kaudze on 01/23 at 10:42 AM

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