Author Archives: geoff

Space antenna!

Late in 2019 I heard of an upcoming project by SpaceAustralia to home brew your own radio-telescope, with the objective of peering at the Milky Way. Previously only the domain of scientists with very nice radio dishes, the reducing cost of entry has now put it in range of the hobbyist so it seemed like a cool thing to try.

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Saving the planet 3 batteries at a time

Sometimes little wins give you disproportionate satisfaction.

I bought a battery-powered LED light from a local hardware store. It cost 10 bucks and is surprisingly decent quality, using 3 x AAAs. Pushing the front bezel turns it on, pushing it again turns it off. I bought it for the enclave under the stairs where the wine lives. Problem is, I was confident that at some stage we’d would forget to turn it off again and come back to a non-functional light. That happened ahead of schedule, the first batteries lasted about a week. Righto then, we’ll fix that.

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The Mongrel

What has USB, a Delta-Sigma oversampling DAC, integrated circuits, an old school tube, and MOSFET output drive?

I call it a Mongrel, because it’s got a bit of everything in it.

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Don’t buy garbage

I often hear expectations on what electronics “should” cost being set based on the cheapest price available on Ebay, Aliexpress et al.  Everybody loves a bargain, but the old saying “you get what you pay for” is just as true as ever.  What worries me is that by paying for junk, rather than quality, consumers are voting with their wallets for an inferior technological future.

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Taming the rPi Touchscreen PCB

After my last article‘s mission of discovery I set about trying to stop the rPi Official 7″ Touchscreen from interfering with my 2-way radio.  It looked like the LCD ribbon cable was broadcasting spurs every ~1MHz or so right through the VHF range.  I acquired some adhesive copper tape thinking I could shield the cable to prevent the noise from escaping.

The copper tape arrived, and despite wrapping the LCD ribbon cable and grounding the copper tape it failed to provide any shielding benefit.  Nuts.  So what else can I try?

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Raspberry Pi Car Shield

Raspberry Pi 2 + Power supply PCB + 7″ TFT

I’ve had an aftermarket ECU (Adaptronic) in my car for a little while now, and I wanted some extra dash gauges.  My car (Nissan R34 GTT) has a spot on the dashboard perfect for a 7″ TFT.  Raspberry Pi is the obvious choice, However, you can’t just run a Pi directly off the accessory power in a car.  Aside from voltage conversion, graceful shutdown is also mandatory!

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Raspberry Pi Webcam (Fishcam)

One day I was looking at my fishtank and thought it would be nice to see my fish behaving naturally.  The problem with sitting in front of the tank is they recognise someone is there and go into their “feeding” pattern – rising to the top of the tank in expectation of food.

If I added a webcam, I could push my  RPi temperature display into service.  As a bonus, I could measure the temperature of the tank at the same time.

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RPi SD Card corruption, a new kernel, device trees and a lesson learned

I recently fell victim to the perils of my own laziness.  Rather than gracefully shut down my Raspberry Pi in order to move it, I pulled the power cord.   I had done this dozens of times in the past with no ill-effects but today was my unlucky day.  The Pi did not come back!

Unfortunately, this snowballed from a simple file corruption issue into a full reinstall, which ended up using a different kernel version that broke my custom 1-wire bus setup.  Great.

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