Adding a data port to a Spectrophotometer 721

So as you all know I have recently purchased a cheap spectrophotometer , I thought it could be useful in the lab for some biology projects I've been working on. But as most things in my workshop and probably yours, upgrades are always on my mind and I like to see how far I can modify. In this case I wanted to see if it was possible to connect the spectrophotometer to my computer, that way I can visually see the curvatures in data and get a better idea of what is going on. 

ISP PINS

    Now I dont have any electronic testing equipment other than a multimeter so my investigation will be basic, mostly to see if there is any change in voltage levels while changing the wavelength. My initial investigation started with the pins I found during my tear down they as you can see in the photo are labeled as ISP . 

    The five pins being in this case GND, DTA,+5V and RST. Just to knock it out I tested the 5v line and as expected it was just as it said. From there I wanted to see if there was any significant voltage coming off the data line and from my surprise there was 5v. Now this might be common I honestly dont know but it really wasn't helping my on my voyage to a interface. The journey must continue so I decided to look at other possible areas of connection. (Really need to buy an oscilloscope)

SILICONE PHOTODIODE CONNECTOR

    The only other connection on the board, is the silicone photodiode as you can see from the above photo. The photodiode connects with a +15v ,-15v , GND , AGND ,Signal (believe it was misspelled) and 5v. 

I tested the Signal and AGND pins and they showed a relation between wavelength change and voltage levels. The voltage peaked at about 6.60v ±.05 at roughly 660 nm and 548nm and bottomed at .41v at 350 nm.  When I brought it to the highest wavelength (1020 nm) voltage came down to 3.5v .

So now that I have narrowed down the data/voltage line, the plan is to use an Arduino Nano Knock off (I'm cheap) and a Cheap Arduino Voltage Monitor ($4) to bring this data to the Serial Plotter.

Current wiring plan is the following :

Now the next part is how to organize all of this on the inside of the spectrophotometer. I like having things clean and tidy , so I put a little time into designing a nice holder for the electronics.

3D Printing

Epoxy went a little crazy, ohh well it works I guess

And for all those that love 3d printing info, PLA at 100% infill because I just wanted it to be strong. Also designed in Tinkercad because I enjoy using it.

Mounting

Positioning it was difficult, the biggest issue was determining where I had the greatest amount of clearance. Getting it as close as possible to the circuit board just makes life easier. So I decided to mount it just below the circuit board.

Need to clean up the wiring and probably trim a few wires.

I didn't like how my cut came out , so I hid my rough cut with a 3d print. Just a simple border so all you can see is the micro USB.

Data

With time I'm going to write more code to handle the data but for now here is some data from the Arduino Serial Plotter .

The voltage is all over the place but when sitting at a specific wavelength as you would when using the spectrophotometer , you can monitor the change in voltage , which is directly related to the amount of light passing through the sample and hitting the sensor. The photo below is 660 nm light passing though a sample of water with a drop of Blue food coloring.

Almost 100% of the light was absorbed by the blue food coloring.

Thoughts

This will become more useful when I get a chance to write some code. Overall I really enjoyed this project , and hopefully I get to use this modification in my lab.

I hope you enjoyed the read , if you have any advice or ideas on improving this idea. Feel free to contact me .