Monthly Archives: January 2016

Timed Audio Field Recorder with a Raspberry Pi Cirrus Logic Audio Card

The problem is still the same as it was this time last year – the birds get up before I do in the Spring and I can only be one place at a time. Automatic recording devices let me scout locations in parallel.

A timed field recorder needs to be cheap, because somebody might nick it, it needs to be weather-resistant because it’ll be stuck outside, and it needs to be low-power, because 13A mains sockets are rare outside. Oh and it needs to be standalone, and not part of some cloud, because mobile Internet is ratty and expensive.

tl;dr the hardware performance is good but software support is dire. You can make this work but it isn’t fun at all. If you can use something like a USB stereo audio in board then do it rather than use this Cirrus Logic Audio Card, particularly if you have mains power available. I like the Behringer UCA202 and it works with the Pi

A Raspberry Pi and A Wolfson audio card sort of fitted the bill, but the Wolfson Audio card is no more. I say sort of, because I’m still looking at about £70 for a Pi 1, the audio card and enough odds and sods to power it. You can buy a Zoom H1 for about £80, although there’s still a bit more cost in powering it for long times, keeping the water out and making up some gizmo to pretend to be you pressing the big rec record button early in the morning.

But with the Pi I get to drive the recorder via cron and ssh, and transfer the files via the internet or mobile data in some places. Even if I don’t get a case, though they are to be had for the Pi/CL Audio card combination…

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  1. HiFi world clock it in at £220!

Making a fake Chinese Wattsup 12V power meter less dangerous

You can buy a pukka Wattsup meter from RC Electronics for $60. That’s just too dear for me, I want to be able to apply a few of these in various places, so I go with the cheap fake Ebay version for £5.99 🙂 At the time I didn’t realise it was a cheap fake Wattsup, it was simply billed as Watt Meter

as it arrived

as it arrived

It duly arrived from some joint in Shenzhen and it wasn’t hard to see that quality control left something to be desired. But hey, whaddya expect for £6? I couldn’t source the LCD display and box for £6!

Chinese suppliers don’t actually have to deliver reliability at these low prices because the cost of sending the product back to China for a refund is higher than writing off the goods. Since I’m prepared to fix the odd part I’m happy to take the risk. It didn’t seem to be a good idea to apply a 12V car battery to this sucker as is, without some investigation. Plus having the display centred is a nice touch…

1512_DSCN2785Hmm, nothing to centre the boards. Other than that, looks okay, except for the exposed positive solder joint in the main battery 12V line Insulated from the case by the blue anodising and now’t else. At least the LCD contacts are pushed away from the metal by some foam. The LCD groundplane ends just shy of the edge of the board so it may not short on the box, but it still seems a risky business to risk having the box at +12V potential when the anodising gets scraped through. Most 12V systems assume exposed metalwork is either isolated or connected to the negative terminal. I don’t feel that lucky as to go around with a +12V exposed metal box, so I got some of that pressed card (plastic can easily melt if it gets hot) and put it in inside the box, to at least give me an extra layer. I do see the wisdom of RC electronics using a plastic case, but then an 80% discount speaks a language of its own. How do I know it’s a fake Wattsup? Continue reading