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The finished prototype

17 Dec

Here are some pictures of the finished prototype:


Hardware schematic

12 Dec

Here below is a brief schematic over the hardware parts in the prototype bracelet. Most of the components are visualized with only their pins. However, the schematic will give a good overview of what’s put together.

Brief explanation: The YellowJacket module works almost like an Arduino, but has an onboard WiFi-device. The YellowJacket is connected to an OLED display (using serial communication), a push button and a vibrating DC motor. The circuit is powered with a 1-cell Li-Po battery (~4V, 600mAh) but since most components need 5V to work properly, a voltage booster device is connected between the battery and all other components (providing a steady 5V supply).


“Bracelet” components together and working

8 Dec

Now all components seem to work together! The picture below shows everything for the “bracelet” thing, except a missing push button. A Li-Po battery gives power to the circuit, but since it only provides about 4V and both the display and the YellowJacket needs 5V, a voltage booster is used. Out of the voltage booster, a stable 5V supply is fed into the YellowJacket and the OLED Display. The vibrator runs at about 3V (with help of a resistor). The FTDI programmer will not be attached to the “bracelet”, but is needed when programming the YellowJacket device.

Next, a push button will be added and then everything should be put together in a more compact way…

An overview of all components  of the “bracelet” (except for a missing push button).

YellowJacket has Internet (and runs a webserver)

8 Dec

The YellowJacket runs a webserver where one can (in the example picture shown below) turn on and off pictures on the OLED Display. The YellowJacket also enables a vibrator when a picture is showed, to provide feedback to the user that a pictures is being displayed. It was easy to connect the YellowJacket to a locally created wireless network connection, but in that case it had no Internet access (which is necessary to be reached from anywhere). The problem was that in school, the WLAN’s require special login information, which the YellowJacket can’t handle. The problem was solved by bringing a router which could share the school’s Internet connection. Still though, the YellowJacket supports encryption, so WPA2 encryption was used to avoid intruders in the network.

Now, with a working Internet connection, the YellowJacket can be reached from everywhere in the world (where an Internet connection exists, of course).

An example of  a connection made with the YellowJacket’s webserver. The red circle shows that picture 3 is turned on.

OLED Display testing

23 Nov

Late yesterday I finally got the OLED display to work properly. Two things made it annoying and difficult:

1. To put pictures on the uSD card (to be inserted into the display unit) one needed a specific program (Graphics Composer), otherwise the display can’t show them. No matter what I did it refused to upload the pictures. After a lot of searching I found out that the company responsible for that program had a lot of trouble with it to work on newer OS’s (Vista, Windows 7, independently if 32 or 64 bits). Fortunately, I had another computer with Windows XP where it worked perfectly… ANNOYING!

2. An Arduino library for the display existed, but unfortunately wasn’t completely finished. The specific function I needed was to display stored images from a uSD card, and this function was implemented wrong…

Later on I got everything to work!

The Arduino Nano controls what to display (in this case which picture, for how long, etc) through serial communication to the display device. Pins connected are Voltage (3-6V), GND, RESET, TX and RX.

Since the resolution is quite low, 128×128 pixels, it’s of course not perfect in any meanings. However, the picture is clear and will work pretty well in this project.