This blog is about Simon, a young gifted mathematician and programmer, who had to move from Amsterdam to Antwerp to be able to study at the level that fits his talent, i.e. homeschool. Visit https://simontiger.com
As some of you may know, Simon is working on building a real-life 8-bit computer from scratch, guided by Ben Eater’s tutorials (it’s a huge project that may takes months). He has also been enchanted by the idea to build the computer in a simulator as well, researching all virtual environments possible. The best simulator Simon has tried so far has been Circuitverse.org, although he did stumble upon a stack overflow error once, approximately half-way through (maybe the memory wasn’t big enough for such an elaborate circuit, Simon said). You can view Simon’s projects on Circuitverse here: https://circuitverse.org/users/7241
Simon has also tried building an 8-bit computer in Simulator.io, but it was really difficult and time consuming:
The next hopeful candidate was the Virtual Breadboard desktop app for pc. Simon downloaded it about ten times from the Microsoft store but it somehow never arrived, most probably because our Windows version was slightly outdated but who knows.
And finally, Simon has also discovered Fritzing.org, an environment for creating your own pcbs with a real-life look. He may attempt actually making a hardcopy SAP-1 via Fritzing after he’s done with the Ben Eater project. Conclusion: sticking with Circuitverse for the time being.
Simon has been mesmerised by this book for a couple of days by now, the Digital Computer Electronics eBook (third edition). He has downloaded it online and has been reading about the so called “simple as possible” processors or the sap’s (he loves the name) one of which is like the 8-bit computer he is currently trying to build from scratch.
Simon gave me a whole lecture on the differences between Sequential and Combinational Logic: in the former, there’s a presence of a feedback loop (the output actually goes back to somewhere else in the circuit), and the latter has everything going in one direction (the inputs come in and the outputs go out).
It’s a little bit like the difference between a Feed Forward neural network where the output only depends on the input and a recurrent neural network where the output also depends on what the output was previously,
Here’s a problem with sequential logic circuits: they go crazy like this very often (confused NOR gate). That’s why most sequential logic circuits have a clock in them. A clock acts like a delay so that it won’t go crazy.
That’s the power of sequential logic: you can have the same input but a different output. This is useful for storing data: I release the input, but the data is stored. It can only be archived in sequential logic.
The delay comes in error detection (on the rising edge of the square wave).
We did two more experiments a couple days ago: Liquid Wires (creating a simple circuit using graphite and liquid glass, a sodium silicate solution) and making our own Zinc-Carbon Battery, a chemical source of electric current that relies on an oxidation-reduction (redox) reaction between manganese dioxide (MnO2) and zinc (Zn).
A redox reaction involves the transfer of electrons from one element (the reducer) to another element (the oxidizer).
Our battery is divided into two sections, separated by wadding: one section holds the oxidizer MnO2 and the other contains the reductant Zn. When the crocodile clips are connected to a diode, the circuit is closed and the reaction can begin: electrons start migrating from the zinc section to the manganese section (manganese dioxide mixed with graphite o make it a better conductor). We used ammonium chloride NH4Cl as the electrolyte.
Last week Simon suddenly unpacked his old electronics sets and completed several projects with Arduino, his old single-board friend that got him into coding a little over a year ago. Back then it was the most difficult stuff he had ever tried, his first “setups”and “draws”, his first dive into serious circuits. Now Arduino (and iCircuit) is something he does while taking breaks from the real studying/ coding. Amazing how skillful he has become in assembling the circuits, too. All those little wires. Especially considering he still isn’t an expert at tying his shoelaces.
Yesterday Simon asked me to buy new electronics software he found on the internet. It’s a realtime circuit simulator and editor called iCircuit. Simon has already built several circuits in it last night and there is so much more to discover. He was following Derek Banas’ tutorials on electronics.
After he tried it during a Digisnacks group session last month Simon really wanted to have his own Lego WeDo set. The waiting seemed endless, Sinterklaas lost the parcel once and worried if it would reach Simon on time, but in the end everything worked out magically well. And even though the drag and drop programming seems to be too easy for Simon, we enjoy watching him complete the laborious projects all by himself. He didn’t use to be this dexterous with the tiny Lego pieces just a few months ago, his fine motor skills are improving by the day. In fact his piano teacher just told me exactly the same thing about his piano fingers yesterday.
This is how we made it. We taped a stencil to a large sheet of white paper and applied the conductive paint, then waited for the paint to dry.
While waiting, we loaded several mp3 files on to the MicroSD card that came with the touch board. Simon made sure the files were named in the right order, to correspond to the correct electrodes on the touch board. We found the sound files at FreeSound.org:
Simon placed the MiscroSD back into the touch board:
We carefully removed the stencil, this was the result:
We attached the touch board and the speaker to the poster, then cold soldered the holes in the electrodes with conductive paint.