When a piece of artwork is displayed in a gallery, those special instructions on how to shut down a computer are not always transferred to the person closing the gallery each night. My expectation is that the mains plug will just be pulled out. Now, …
To design the front panel, a 2D drawing package was needed, I tried a few of the free ones, but couldn’t get on with them. I eventually settled on QCAD which is a paid for program, but not hugely expensive. To design the front panel, …
The Akiniscope has a swingy meter. The meter is an old meter from Ebay, that looks about right, but I have no idea what it was originally used for. It’s an ac meter, going up to 1V max. After playing with it for a bit, I’m guessing that’s 1V RMS. I’ve found it doesn’t really care what frequency is input, having tried 1kHz, and 50Hz sine waves.
The Raspberry Pi doesn’t have a digital to analogue converter (DAC), but one can be attached via I2C, but it would take quite a bit of processing power to generate a waveform, and control it’s amplitude. So, I decided to ofload the processing to something else, which was a Adafruit QT Py – SAMD21. This little device has a 10 bit DAC, and is small and cheap, so is ideal. The code generated a triangular wave, and alters the amplitude randomly. Added in is a digital input from the Raspberry Pi, which goes high when the camera is operating, when that happens, the meter bounces round at the full range.
All the sound is generated by the Raspberry Pi, unless Akiniscope falls off the wall and smashes. From the Raspberry Pi it goes into a generic USB audio dongle. The sound is then amplified by a Stereo 20W Class D Audio Amplifier. I tried various …
Building a new project, I tend to start with a big mess of wires on the bench. Although it looks like a big mess, I make sure there’s no bare wires, and boards can’t short out on anything. To speed up wiring and testing, I …
My favourite sound on Akiniscope, mainly because it comes from such an unexpected source, is the camera warning sound. It sounds like this:
It is a soap dispenser in the Nottingham Playhouse toilets. Luckily I was working there when I discovered it, so had the equipment to record it. Although I did get some odd looks.
I was doing some welding for someone, and, after a couple of weeks, I realised the sound of welding may work for Akiniscope. So, I recorded it, chopped it up into start middle and end sounds, and used those as the sounds of the camera …
I’ve found a nice PIR proximity sensor to detect when people walk in front of the Akiniscope, and take their picture. Most PIRs are deliberately made to be seen. This one, although more expensive, is small and discrete, and you can even mount it behind …
The computer I’ve used to run Akiniscope is a Raspberry Pi Zero W. This has most of the facilities I need, and is small, cheap, and uses little power, which could reduce the size of the power supply I use.
I went for one without headers for connecting the digital inputs and outputs, the GPIO, so I could solder wires on to it, which takes up less room, and involves less parts.
It has a header for a camera, which I defiantly need. It doesn’t have an audio out, like some of the larger models, I could add some electronics to create an audio output on one of the GPIO pins, but decided to use a USB audio dongle.
The W in the name means it has WiFi. I was unsure whether to use this or not. Once installed though, how would I communicate with Akiniscope? WiFi seemed the easiest answer. What would I need these communications for? Updating the software, in the early stages, retrieving logs, for fault finding, and archiving, or deleting, the pictures taken by Akiniscope. One can never guarantee network connection at a random location, so I’ll make Akiniscope it’s own WiFi node, and not name the node as Akiniscope, but something uninteresting.
So, has the Zero W got anything missing? A Real time clock. If you have an internet connection, then computers can synchronise time via NTP. Desktop computers have a bit of electronics and battery, which is called a Real Time Clock (RTC), but to save space and complexity, the Raspberry Pi doesn’t have one of these. So, why do I need the correct time within Akiniscope? The one thing that needs it is logging. I’m still debating with myself whether to add a RTC, or not.
Nov 2021 Update
Raspberry Pi Zero 2 W is available. Am I going to swap to that? Of course I am. Everything runs really swiftly now. What a wonderful little device.
When I upgraded, I also changed how I connected all the GPIO. I used a RasPiO Breadboard Pi Bridge. To connect to the Raspberry Pi Zero 2 W, rather use the 40 pin socket header that comes with it, I used a 40 pin boxed header, this enabled me to attach via a ribbon cable, helping me with space on installation.
Having written most of my early programs using a DEC VT100 terminal, I knew I wanted some of the feel of that type of equipment involved: The green glow of a CRT display, and the lined characters of the font embedded within the terminal. So …