Lupin's weblog

Here is my latest project: a simple moodlamp using a Prolight 3W RGB LED emitter. The LED itself comes on an aluminium star, but i needed to build a bigger cooler made out of an aluminium profile (usually used for rack mounting). I used two screws to fixate the LED on the aluminium sheet.

Without an additional cooler the LED will get very hot after a short while.

The electronics are very simple, an ATmega8 running at 20 MHz on breadboard. Three FETs to drive the emitters and three current limiting resistors. I first used a voltage regulator, but then i figured that the switch mode power outlet would already deliver enough current… but at a very poorly regulated voltage: I set it to 4,5 Volts and measured 5,6 Volts at the output, even under full load. Good thing i added a diode there to limit the voltage a bit so it doesn’t go higher than 5,5 Volt.

The source code is quite simple, it’s running through the HSV color space (not using V though, it’s always 1). You can adjust the speed the hue is increasing and you can adjust saturation using the two potentiometers.

The last months i was partly working on a nixie clock design. The hardware itself is nothing special, but I think it’s a very fine piece of work (at least the electronics). The mechanics aren’t that good… but I guess that’s not possible to see from my crappy pictures.  I still want to get a new cam

The name of the clock somehow shows my lack of creativity… :-/

Some infos about the clock:

- 6x IN-14 Nixie tube
- 2x Standard neon bulb
- ATmega16 microcontroller – the only “intelligent” IC on the board, all other ICs are discrete transistors and a linear regulator
- Completely built with SMD technology parts (just a few parts are through hole)
- DCF77 receiver module (the clock has no controls for setting the time)

Problems with the clock is the aluminium casing. It looks very nice, but it reduces the quality of reception… Maybe it’s a good idea to put the receiver outside of the clock in a plastic casing – but I want the clock to be 1 unit.

I will set up a seperate site for the clock once I have better pictures and the firmware is in a state that’s worth to be released (until now a few parts are missing, like smooth transitions between the numbers). The circuit is really simple, it’s an extremely cheap and simple design, but building the clock is a little bit complicated because of the small SMT components.

The ATmega decodes the DCF77 signal, keeps track of the time, controls the multiplexing of the Nixie tubes and regulates the high voltage power supply (voltage can be trimmed with an SMT trimmer pot).

Here is the finished clock in operation:

Here again:

The clock without the casing…

Innovative beer battery extends battery life in handheld application!

It works! ZOMG!

I wired up a DS1621 digital thermometer IC to the PM. With this IC it’s possible to measure the temperature very easily.

I communicate with the sensor using the same I²C bus functions as for EEPROM access (just one small additional function). The sensor outputs the temperature as 9 bits of data.

The black IC in front is wired to the PM using magnet wire.

My cheap clock/thermometer agrees with the DS1621.

Included in the zip file are instructions to wire up the sensor to the PM, so you can add a temperature sensor to your PM too (and read the temperature if you’ve got a flashcart ).

I wrote some I²C functions for the PM, they can be used to access the savestate EEPROM. The functions should be quite easy to use. I uploaded a sample of writing a few bytes to the EEPROM and reading them back. You can find it in the PM section.

PlayerOne discovered how to read from the EEPROM, the website of the Embedded Systems Academy had some useful informations to implement the functions like it’s specified by the I²C protocol.

Download the example.