Month: March 2012

Boombox follow up

Written by Fergal Hainey

Just saw this on the Maplin website http://www.maplin.co.uk/low-noise-stereo-preamp-kit-220053 . A lot cheaper than a CMoy and has the right impedances. I could split my 1/8″ jack to DIN cable and put this in the middle with a 9V battery and it could work maybe.

My friend with the tapes also gave me an old stereo audio transformer from RS he said could work. Sounds like some sort of magic bullet, a passive one component solution to clean boosting. I may give it a go but am a bit worried about the arcane stuff about impedance matching and also that I may blow something in the boombox if I’m mistaken about it’s power output.

SD to HDD copier for video recorders

Written by Fergal Hainey

When on long kayaking holidays with friends with video recorders like GoPros, we either have to stop videoing because the SD cards fill up, or bring a laptop to empty them onto. Neither is ideal, especially as the laptop can run out of battery fairly early on.

It seems there used to be a market for portable SD card backer uppers, but they were priced for professional photographers, as they were the only ones who’d take so many photos that it would be more economical than buying another SD card. It’s hard to fill up a couple of modern SDHC cards with photos, so these backer uppers seem to have faded out. Now there is a new problem that video files take up a lot more space than photos, and for best results video recorders need to be left running so you don’t miss any of the action.

My first thought was that maybe this is something you could achieve with a microcontroller, like an Arduino. Low memory and data throughput makes this not very feasible. Although the task is simple, unfortunately it looks like this one of those things you do need more power for. This spurred me to think of the Raspberry Pi, the new development board that has been on the news as it intends to be an education platform. The specs make it look perfectly capable, and it should have a similar price and footprint to an Arduino. Sounds perfect!

Although I can’t get hold of one yet, I got to thinking about how it would work. It already has USB connectors, and can run a sort of Linux. Making scripts to copy things when there’s an SD card and a USB HDD plugged in will be easy with a Linux OS already on there. Thinking about the USB, I realised it may not be able to handle the current required of a HDD, even a portable 2.5″ one. From the specs it looks like running a disk from the USB ports would not provide enough power. Well, a lot of top end USB HDDs take mains power, so it’s possible to have a different power source. How about a USB hub which provides power, and plugs into the Raspberry Pi to provide data. A quick read over USB specs shows supplying a separate 5V power line to any device should be fine. And the Raspberry Pi and can take its power from USB, so the hub could power the Pi too, perfect. The addition of a voltage regulator could make the hub able to be powered by batteries, perfect for travelling.

So a Raspberry Pi, a USB hub, and a battery compartment. Should take up a lot less space in your bag, won’t run out of batteries, should be a lot cheaper than the old photo backer uppers, and you can supply your own HDDs. Considering the Pi has HDMI out, it could be plugged in to review videos too! The Pi runs its OS off an SD card, so it should be easily upgradable with new features. It does sound like a very feasible solution.

All this makes me wonder, could there be in the future a whole range of cheaply available gadgets, and you simply plug in your Pi and save the cost of all its components with each one. Simply add to the SD card  the data you need to run each gadget you have, do some hardware detection, and easily do updates and feature additions! This would be a great boon too consumers, not just people interested in tinkering with things.