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<?xml version="1.0" encoding="us-ascii"?> <feed xmlns="http://www.w3.org/2005/Atom"><title>Duncan Bayne</title><link href="gemini://duncan.bayne.id.au/projects"/><updated>2024-01-07T18:02:01+11:00 </updated><id>gemini://duncan.bayne.id.au/projects</id><generator uri="https://metacpan.org/pod/XML::Atom::SimpleFeed" version="0.905">XML::Atom::SimpleFeed</generator><entry><title>Door Timer</title><link href="gemini://duncan.bayne.id.au/projects/door-timer.gmi"/><updated>2024-03-27T23:06:32+11:00</updated><author><name></name><email></email></author><id>gemini://duncan.bayne.id.au/projects/door-timer.gmi</id><summary type="html">One of the companies on which my family relies has a problem: people keep leaving their front door open. I've offered to make them a simple buzzer to alert them to a door that's been left open for more than a minute. I'm taking this opportunity to brush off my analog electronic skills, which have almost entirely rusted since I was a child. I could just buy an off-the-shelf item, but think it'd be more fun to build it from scratch :) I'll keep a detailed build log on this page ... ## 2014 ### Sat 28 June I've assembled the veroboard; I'm particularly pleased with my design which fits comfortably on the cut-out board, and also involves no track breaks except for those under the IC. => /.static/images/veroboard-assembled.jpg Assembled circuit on veroboard I used an hacksaw to cut the veroboard to fit the enclosure (and around the piezo buzzer). I then used a fine point on a dremel to clean between the tracks at the point of the cut, as the saw blade had torn the copper about and bridged several of them. ### Wed 25 June The enclosures arrived today. I'm very happy with the manufacturing quality for such a low-cost item. However, and this is entirely my own fault, the enclosures are too shallow for the 1000µF capacitor I selected for the circuit. So I've increased the resistance from 47kΩ to 470kΩ, and decreased the capacitance to 100µF using a lower-profile axial lead capacitor. Here is a photo demonstrating the height problems: => /.static/images/capacitors-enclosure.jpg Capacitors clearly too tall for the enclosure ... and here is the fifth prototype, featuring the new components: => /.static/images/fifth-timer-prototype.jpg Fifth prototype of the timer I'm fairly sure the replacement capacitor dates back to my Funway 1 days as a child. The leads needed some cleaning up, but the timer tests out at ~ 59 seconds so I presume they're still good. => http://web.archive.org/web/20180301075309/https://tronixstuff.com/2010/10/13/australian-electronics-nostalgia-funway-kits/ DSE Funway Into Electronics kids Some additional good news is that the reed switch magnets are very strong. This means that I can mount the reed switch entirely inside the case, and the door-frame-mounted magnet will still switch the device from more than a centimeter away. This will allow for a much cleaner and more robust assembly. ### Tue 24 June The reed switches arrived - nifty three-lead units which can be used in either NO or NC mode. Here's the fourth prototype, with the power routed through the reed switch: => /.static/images/fourth-timer-prototype.jpg Fourth prototype of the timer Once installed, this will mean that the unit draws no power at all when the door is closed. When the door opens and the magnet moves away from the reed switch, the switch will supply power to the timer which will in turn start the countdown. ### Tue 17 June I've ordered two of the enclosures pictured below. It's now a matter of waiting for the enclosures, reed switches and bezels to show up so I can determine how large my veroboard can be. That will in turn determine how I lay out the circuit. I anticipate at least a week's wait at this point. ### Mon 16 June Found a nice enclosure from plastboxuk.com (now defunct) that should work. It features a separate 9V battery compartment, which is ideal. Here is the third prototype, complete with flashing red LED to indicate that the timer is running: => /.static/images/third-timer-prototype.jpg Third prototype of the timer I've measured the current at < 6mA when the buzzer is not active, and < 20mA when it is. The readings fluctuate a fair bit due (I think) to the flashing of the LED, but running with the maximum figures I should get > 90 hours out of Duracell 9V, or 29 hours if the buzzer were operating constantly. => http://www.electro-tech-online.com/threads/what-mah-value-does-a-standard-9v-battery-have.8873/ A thread on the mAh rating of 9V batteries That's assuming that the circuit would function normally with a nearly depleted battery. I'm not sure if it would (I doubt the voltage and / or current supplied would remain high enough) but it suggests I'm on the right track by powering it from a 9V battery. I've also ordered some chrome LED bezels, to make the whole thing look nice. Finally, I've ordered some reed switches to detect whether the door is open. _Edited to clarify_: Armin has pointed out that wasn't too clear. In this design the power is routed through a magnetic reed switch, so it only draws from the battery if the door is open. So the 90 hours I mention represents 90 hours with the door in an open position, which hopefully will represent at least weeks of operation, possibly months. We'll see. => http://www.arminsadeghi.com/ Armin's blog ### Sat 14 June I've built the first prototype of the door timer, which illuminates an LED after around a minute (58 seconds, actually). => /.static/images/first-timer-prototype.jpg First prototype of the timer It's built from the monostable timer circuit on the 555 Timer Circuits site, but with the LED connected from Vcc to pin 3 (known as sourcing). => http://www.555-timer-circuits.com/operating-modes.html 555 operating modes As it turns out, that green LED was under-rated for the current flowing through it; it started to turn orange as in [this video](https://www.youtube.com/watch?v=foNi-keKGs4). I've subsequently replaced it with a blue LED that works fine. Here's the second prototype, with the actual buzzer, and an LED indicating that the unit is operating (so you know that it is, for safety reasons): => /.static/images/second-timer-prototype.jpg Second prototype of the timer ### Tue 03 June Found a handy resource full of 555 timer info. Will peruse before continuing. Also want to find out about 555 power usage; would like to power the beastie off a 9V battery but I'm concerned about battery life. </summary></entry><entry><title>90s Mixtape</title><link href="gemini://duncan.bayne.id.au/projects/90s-mixtape.gmi"/><updated>2024-03-27T23:06:32+11:00</updated><author><name></name><email></email></author><id>gemini://duncan.bayne.id.au/projects/90s-mixtape.gmi</id><summary type="html">I wanted to make a themed mixtape for my brother's third-generation Honda Prelude, called Sayaka. Given the vintage of the car, I thought I'd choose from the Top 40 hits from the 1990 music charts in New Zealand. I bought an old Sanyo RD 4055 cassette tape recorder and a cassette tape from eBay, and whipped up a label in LibreOffice. The result is a lot nicer than the mixtapes I made in my youth ... => /.static/images/mixtape-front.jpg Front cover of the mixtape => /.static/images/mixtape-rear.jpg Rear cover of the mixtape => /.static/images/sanyo-rd4055.jpg Sanyo RD4055 cassette tape recorder </summary></entry></feed>