Laser based projector

This is again a final year project by Melissa and her team, who all are students at Cornell University. The electrical part of the project consists of Galvanometer and the microcontroller which acts as an input to the position detector sensor and also are responsible for control loops which have been implemented using proportionate derivative controller. The mechanical part consists of a combination of different devices which makes up the laser projector. A part of the software runs on a Linux based PC which handles file parsing, point scanning, frame display, and serial transmission to the control board.

For this laser projector, the moving and still parts of the galvo are switched around. The current running through the coils causes the rotary motion of the magnet, and subsequently, both the position detector electrode and the mirror attached to the ends. The project have been designed keeping in mind that further research and development should take place on a similar concept. The project schematics needs a little bit of improvement as accessing the board is a challenging task. A different project but still a long way to go before we see something like this in the market.

Water softener level detector

In places where water contains higher concentration of dissolved minerals is considered to be hard ware. It does not affect human health, but teapots, washing machines and dishwashers suffer from calcification. To avoid this problem, there are water softeners used where special salt is used to soften water. Of course this salt also dissolves and needs to be refilled time to time. David always forget to refill the tank because there is no visual indicator of it. So what you don’t see – you don’t care. To avoid future conflicts with his wife, he decided to add visual indicator to water softener.


On front panel he mounted LED bar graph where salt level is displayed. Also he added photocell to detect room light. It simply detect if someone is in the room or passes by by dropping a shadow. Other time bar graph is turned off. This hopefully prolongs life of LEDs and saves a bit of electricity. Another part is measuring salt level. Since salt is hard material, he used Sharp GP2D12 Infrared Distance sensor. It is able to measure distance from salt from 10cm to 80cm.

AVR based Stepper Motor Controller

I know many of you have faced a numerous number of issues in controlling even the simple stepper motor and try to get the basic code to work.  This was also the case with the designer of this project. With his project you just have to plug in your stepper motor and whatever power supply you have and you are ready to go without any need for breadboard or any driver. The motor is controlled by using a potentiometer and also features a set of buttons to fast forward or fast reverse.

The input to the driver can be anywhere between 8V and 24V and is built around a Attiny10 controller by Atmega running at a variable frequency in between 8MHz and 12MHz. Also, the driver can be programmed according to your needs with the help of the programmer port attached to the backside of the driver.  As per the current revision, if by chance you have plug the step stick the wrong way, it will zapp the attiny as well as the step stick. So you have to be really careful while using it. Overall, an excellent driver for those who are just started learn to the stepper motor but provided you use the step stick carefully.

MobileECG may be next great open hardware project

There isn’t much open hardware medical instrumentation projects that can be considered completed and reliable. MobilECG project could pretend to be one that could compete with medical grade devices. Actually Péter, the founder of project, intended to collect decent amount of funding to get medical certification. But campaign didn’t went as planned, so he decided to make project open. Since the most of work is already done it would be sad to see project die. The decision to make it open is plausible and maybe it will completed with help of community.

MobilECG is very compact device that can measure ECG using 12 leads. The ECG signal is digitized using TI’s ADS1278 eight channel ADC. For interfacing and communication to host there are two AVR micros used – Attiny24 and ATU64. Schematic is developed using KiCAD software. Firmware isn’t complete – only minor functionality with several known bugs. Anyone with biomedical engineering knowledge will definitely see the potential of this device that can be attached to any device like PC, android or other and explore own ECG signals.