Kerry Wong built a DIY constant current/constant power electronic load. It can sink more than 200W of power:
A while back I built a simple constant current electronic load using an aluminum HDD cooler case as the heatsink. While it was sufficient for a few amps’ load under low voltages, it could not handle load much higher than a few dozen watts at least not for a prolonged period of time. So this time around, I decided to build a much beefier electronic load so it could be used in more demanding situations.
One of the features a lot of commercial electronic loads has in common is the ability to sink constant power. Constant power would come in handy when measuring battery capacities (Wh) or testing power supplies for instance. To accommodate this, I decided to use an Arduino (ATmega328p) microcontroller.
Building a constant current/constant power electronic load - [Link]
Zak Kemble build a digital wristwatch with a 1.3″ 128×64 OLED display & AVR ATmega328P microcontroller:
The main incentive behind this project was to see how much I could cram, in terms of both hardware and software, into a wristwatch-like device that is no larger than the display itself. An OLED display was chosen for being only 1.5mm thick and not requiring a backlight (each pixel produces its own light), but mostly because they look cool. The watch was originally going to have a 0.96″ display, but this proved too difficult to get all the things I wanted underneath it. Going up a size to 1.3″ was perfect.
DIY OLED digital wristwatch - [Link]
Niek designed this BareDuino micro, that is available at github:
For some Arduino projects, you don’t actually need that many IO pins. That’s exactly the case when I tried to build a simple RGB throwie that would cycle through colours. I was looking for a cheaper alternative to the Arduino UNO’s ATmega328P when I stumbled across this post by MIT’s High-Low Tech lab. They developed a library for programming the 8-pins ATtiny45/85 from the Arduino IDE. It’s a very smart solution to use permanently in some low pin-usage projects, but you still need to hook up individual wires from your programmer to the ATtiny to be able to program it. That’s when I came up with the idea of the BareDuino Micro.
BareDuino micro - [Link]
Harrymatic @ instructables.com writes:
I am in the process of designing a function generator and I needed a frequency counter to check it against. This project uses a minimal number of components for a very economical and compact design. A bare-bones Arduino clone is at the heart of this project and the measured frequency is shown on an LCD display. The maximum frequency that this can measure is about 8 MHz (at a 50% duty cycle). Despite the fact that this counts the frequency on one of the digital pins, I have found that it will quite happily measure sine and triangle waves providing that they have a suitable amplitude.
8MHz Frequency Counter - [Link]
Unit is based on Arduino Atmega328P MCU, with over 430 UV LEDs. The PCB board is made using Toner transfer method and isn’t perfect. It was just too big and I was too lazy to do it again. However, marker here, scratch it there and it it good enough.
The unit itself is on single sided copper clad board, no additional cables, no narrow paths (except for one for power on the MCU). Design is straight forward. It’s designed to be powered from 12V source (computer) and take around 2,7Amps @ full power which means around 30Watts.
DIY UV Exposure Unit with LED and Arduino - [Link]
An Arduino-based clock with 180 RGB LEDs. The LEDs are driven via 12 TLC5925 1- channel constant-current addressable drivers – [via]
Its built on doublesided copper clad board using Toner transfer method. The routes aren’t smaller than 0.44mm and all vias are made for 0.8mm drilling (truly DIY). Just around 5 vias are under a component and 7 segment displays have singnals only from bottom side (for easy soldering)
- 180 RGB LEDs driven by TLC5925 constant current LED drivers
- each LED addressed separately (12x TLC5925 with 16 outputs each)
- each colour adressed individually
- 4x 7 segment LED display
- Atmega328P as MCU
- DS1307 real time clock
- Photoresistor (for adjusting brightness)
- And DHT11 for temperature and humidity
- Backup battery for clock
- 5V DC (eg USB)
Clock with 180 RGB LEDs on home-etched circuit board - [Link]
This is a low-cost prototype electrooculography (EOG) system, based on the ATmega328P, that allows people with motor disabilities to write text on a screen using only eye movements. Luis explains: [via]
The human eye is polarized, with the front of the eye being positive and the back of the eye being negative. This is caused by a concentration of negatively charged nerves in the retina on the back of the eye. As the eye moves the negative pole moves relative to the face and this change in the dipole potential can be measured on the skin in micro volts. To translate this voltage into a position, two sets of electrodes are used to measure the differential voltage in the vertical and horizontal direction, on this project, however, just horizontal movements are recorded.
Honduran High Schooler’s Low-Cost Eye-Controlled Interface – [Link]
JeeLabs has a product known as the JeeNode v5, which is essentially a miniature Arduino (Atmega328p) board with an onboard RFM12B wireless module. Boards are available with the serial interface (shown above) as well as USB.
While it’s not an Xbee compatible RF unit, the RFM12B has its own RF12 library of functions which should help you accomplish many control and data transfer tasks.
JeeLabs JeeNode combines Arduino, RF – [Link]
Arduino based POV globe capable of displaying monocolour bitmaps upto 72 pixels high and x width. (uses 72 LEDs, and one input to get rotation speed)
Arduino byte array for images are generated using the c# program included in this project
Image displayed is synch’d to speed of motor using a reed switch, this allows image to display around hole globe correctly, and maintain a constant position.
Code has been added to move the image slowly (so globe rotates nicely)
POV Globe using arduino (atmega328P) and 72 SMD Leds – [Link]