Bench supply with current limiting

This is a bench power supply with adjustable voltage and current limiting. [Sylvain's] creation can regulate 0-25 volts while sourcing 0-5 amps. Current limiting is a nice feature as it will allow you to test your prototypes to ensure the power regulator you choose will not be over or underpowered.

This supply is really a two-in-one. The case has two separate circuits so that you can have different power rails going at the same time. There is a microcontroller involved, but the ATmega32 doesn’t do anything more than measure the voltage and amperage and drive the graphic LCD screen. Two potentiometers are responsible for setting the voltage and limiting the current.

[Thanks Sargonout]

Build your own RFID reader

We asked for it and our readers delivered. [Klulukasz] left a comment pointing to this diy RFID reader that was a final project in 2006 for a class at Cornell University. It is well documented and includes not only a schematic and code, but an explanation of the design considerations used during the build. The project uses an ATmega32 and the parts list priced out at about $50 at the time. There were plenty of responses to the RFID spoofer post pointing out that there are readers available for $40, but we want the fun of building our own.

A bit more vague with the details but no less interesting is this other simple RFID reader design. Thanks to [Chuck] for his comment which pointed to that link.

Building the yellow submarine

Submarine builds are always fun but frequently produce headaches when it comes to keeping the water out. [Jason Rollette] built this ROV to explore a shipwreck in Lake Michigan. The main structure is PVC and various bilge pumps are used for propulsion. An AVR ATmega32 controls the on board electronics with an Ethernet tether to the surface. He’s even got a visual basic program that displays system information and a video feed. It may not be as stylish as the last submarine we saw but it’s amazingly well thought out and well built.

[Thanks Daphreak]