Mass Spectrophotometer

It’s Sunday. I had planned on getting the next part of my shed done (laying the concrete and bricks for the foundation), but forgot that shops don’t open Sundays. Damn.

The next time I’ll be free to work on this will be Wednesday, so I’m stuck here with nothing much to do but imagine.

I was trying to figure out which tools I need to build first once the lab is completed.

The end goal is to produce my own medicines/drugs, so I will need to develop a protein synthesis machine. I said yesterday that I thought it would be possible to do with home-built equipment. After reading up on it further, I am certain of that now.

But, there is no point starting off with that, yet. Even if I built a machine which could build proteins (using “solid state protein synthesis” – very simplified explanation here), I would have no way of being sure that it worked.

So, I need to build a measurement device first that can identify proteins.

The most common method used in a lab is by using a mass spectrometer. Those are quite expensive, even if you build them yourself.


Mass spectrophotometers, though, are cheap to build. The idea is simple – dissolve your sample in a solution, shine light of various colours through the solution, and measure the strength of the light that gets through the sample by using a light-dependent resistor. Here’s a video showing one in action. The diffraction grate is rotated a little at a time to change the frequency of light being inspected, and the voltage change is shown on screen.

The diffraction grate, by the way, is made from a piece of CD or DVD! If you shine light onto a DVD and look at the reflection, the light is broken apart into its various colours. This happens because of quantum mechanics. I thought I understood the mechanism (as described in Brian Cox’s book “The Quantum Universe”), but Wikipedia’s description is confusing.

Even while I’m building the protein synthesis machine, this will still be useful – I can use it to analyse the content of my garden’s soil to figure out the best crops to grow in it 😉

So, I now have a small shopping list of things to buy to build this spectrophotometer.

In fact, I might already have all the ingredients! I think I’m missing a light dependent resistor, but might not be…

Gauss gun – part 1

At the end of the last semester of Monaghan Coder Dojo, I promised the students we’d do something cool for the next series of classes. We’re going to build a Gauss gun.

A Gauss gun is a rail, which a metal projectile travels along. It has a series of electro-magnets on it. As the projectile approaches each magnet, the magnet turns on, accelerating the projectile in towards the center of the magnet.

As the projectile reaches the center, the magnet turns off, so the projectile travels through it, and on towards the next magnet.

The same trick is done a few times, accelerating the projectile more and more each time, until it finally reaches the end of the track.

The first thing I had to do was design a circuit which you can turn on electronically that will stay on, and which you can then turn off electronically. I mean, the circuit should not involve a switch that requires physical effort to turn on and off, as that may slow down the projectile.

So, the solution I came up with was:
1. a circuit which uses a transistor to turn on. This way it can be enabled by shoving a little bit of power through the transistor’s base.
2. the circuit, once completed, will feed a little bit of its output electricity back into the transistor’s base by using a capacitor to give a smooth and continuous power line.
3. to turn it off, we will short-circuit the capacitor.

I did a quick “proof of concept” with an LED.

In the next article, I’ll show how to adapt this so that the “switches” are photoelectric cells, so you can turn the circuit on by disrupting one light beam, and turn it off by disrupting the next.