08/21/2014 at 18:51 •
I just finished my first test run... I glued the needle to the pickup and started a small Arduino sketch to drive the stepper...
But my "responsible parents" did'nt allow me to test this on myself :-( ... so I had to take my father's arm instead :-)
You can watch the video here:
At the end you can see the red blood inside the flexible tube... Here's a picture of it as well...
08/20/2014 at 17:54 •
What would a sensor (aka phototransistor) "see" when it looks at out skin? I wanted to know this prior to coding to know what to look for - I knew that the blue veins would absorb light differently, but how exactly?
So I took a modified webcam to take some pictures. I'll use the webcam in another project - it can only "see" IR light now. I removed the IR-blocking filter and replaced it with old analog film (developed) that blocks everything except IR. And I attached some SMD-IR-LEDs as well... somehow the autofocus is not working really good, but you can see the huge difference: the veins look very dark in IR light compared to "normal" light in the visible spectrum.
Now I know what to look for - it should be a local minimum concerning the amount of reflected light detected by the phototransistor.
When I successfully detected the vein, I'll upload the code and some pics - and a video of this device in action (puncturing my vein)
BTW: I took photos of my fathers arm, this is not mine :-)
08/19/2014 at 18:54 •
That was luck! I used the stepper shield and an Arduino to drive the motor (stepper), simulating the movement across the arm in search for the vein. Everything worked fine and I just used a 12V power supply for the (yeah, too little) motor. After a minute I reallised something smells funny - the second motor was overheating. Must try with less voltage next time :-)
Today the video of the first build attempts is ready. I will show tomorrow how veins look in infrared light...
08/19/2014 at 18:50 •
... I found out trying to de-solder the ribbon-connector and attach wires instead. It was more heat than the plastic carrying the little connectors could stand - one small connector just vanished within the molten plastic and I could not connect the motor any more .... FAIL.
08/19/2014 at 18:46 •
I started by taking apart a DVD drive and extracted the stepper motor. I took everything out of the pickup (CCD-Array, mirrors, laser-diode) to use it as a kind of transport mechanism.
You can check the video here: https://www.youtube.com/watch?v=rcEgp4auuuk