# Harry Rickards

Geek, student and maker

1. ## Android Oscilloscope

As a poor electronics students the only oscilloscopes I have access to are so bad they display lovely square waves like this

To that end I made an oscilloscope that uses an Android device (via Bluetooth) for my A Level (end of high school) coursework. A surprisingly small amount of duct tape was used!

2. ## Smartphone Motion Detection

Way back in March, I worked on a project for National Hack the Government Day that passively detects when a user's stopped in a restaurant and vibrates their phone to let them know the food hygiene rating. To get this to work, we had to accurately detect when the user stops walking. This was much easier than expected!

3. ## MIT Tube Hack

When you take an MIT Admissions Tube, a brushless motor, an overpowered LiPo battery and an hour or so of coffee-induced sleep-deprived madness, this is what you get:

4. ## Quantum Simulation

### The problem

Last spring I took UC Berkeley's online CS191X course into quantum computing, and the basic quantum mechanics needed for it.

Something that I felt would have helped me quite a bit early on is a simple quantum circuit simulation tool. While there are simulators out there, they aren't great for just playing around with things to build intuition.

### The solution

To this end, I built Shor's Circuits. It's a pretty straightforward quantum circuit simulator built into a web app, with the killer feature that the simulation is symbolic (thanks SymPy).

5. ## PCB Production Experiences

I recently produced my first ever PCB (for a Bluetooth oscilloscope; more details on that coming soon). There's a lot of information already out there, but I thought I'd write this blog post to sum up the process and give some details on things that I struggled to find out about elswhere. In particular, most writeups seem to be either very theoretical (e.g., spending half the time talking about how the capacitance of ground planes) or very applied (i.e., telling you which buttons to click but not why you need to click them). I hope this can bridge the gap between the two.

6. ## Frequency Modulation: Carson's Rule

In an A-Level Electronics class, I was recently taught an approximation for the bandwidth of a frequency modulated signal

$$\text{BW} \approx 2(\Delta f + f_m)$$

where $\Delta f$ is the 'frequency deviation' of the carrier signal and $f_m$ is the maximum frequency of the modulating wave. The approximation was not proved or expanded upon further, so I set to the internet to find out more.