Monthly Archives: July 2014

PICE case and WiFi upgrade for the remote farm camera

The issues with the Raspberry Pi farm camera were of waterproofing and of iffy Wi-Fi range. Both of these are addressed in the new version. The PICE waterproof case from the guys at EdVenture marshals this motley collection of bits

Pre-PICE prototype

Pre-PICE prototype

into something a bit more organised. There’s no getting away from it, the PICE is quite expensive at about the same as the Pi itself, but it does solve a lot of the mechanical problems of trying to run a Pi outside with a camera. The landscape version is the one i needed, since the case is only water-resistant with the top horizontal – the Pi is mounted on that and even if water does get in it falls to the bottom away from the Pi. The previous version of the PICE took the picture in portrait mode with the case oriented for best water resistance, which isn’t so useful for our aims.

This is a good interim solution – it gets the cameras into a tighter configuration, and should let me pull back the main MiFi box back to a more central location to serve the rest of the cameras. As a result each camera will draw less power which is good. The Edimax EW7711 USB WiFi unit has a better performance than the USB nano-dongle – the reason is obvious when you look at the size of the aerial of the nano

size really does matter in some applications, and and aerial much less than 1/4 wavelength is going to struggle to get the signal out

size really does matter in some applications, and and aerial much less than 1/4 wavelength is going to struggle to get the signal out

although it’s 2.4GHz the wavelength is still 13cm; you still need to get enough metal in the sky to get the 300m path length to work, unless you can mesh. Continue reading

Remanufacturing a 12V power tool battery

Cordless power tools often die not because they’re worn out but because the battery fails, or only holds a charge for a short time. Every tool’s battery pack seems to be different, either from the sheer cussedness of consumerism making you buy a new tool, or because nobody has standardised battery packs, You can fight back, because though the battery packs are all sorts of sizes, the parts inside are usually drawn from standard sized parts, they’re merely packed in different ways.

I had a cordless strimmer, once advertised years ago in the Guardian, from a no-name supplier with two battery packs. Both of which are now duff – a strimmer is a fairly hard life for the battery packs with about 50-100W. Here’s how I remanufactured the battery packs. These are NiCd battery packs – the key issue to to replace like with like. You can replace NiCd with NiMh but don’t cross any other chemistries.

A possible source of raw materials

A possible source of raw materials

Continue reading

Facebook Is For The Moment Not For Ever

Ah Facebook, can’t live with it, can’t live without it. Too many people are on Facebook that I’d like to be able stay in touch with. Jennifer Golbeck has a point, however.

Social media in general should be about the moment. 1  It’s a stream of consciousness, not a diary or a novel, or even a Captain’s Log. Think about it – most social media is a ‘hey guys look at this’ There’s no need for it to become ‘evidence that may be used against you in future’ or ‘material that supports Facebook’s business model when we can work out how to monetise it’

The solution is relatively simple. Go to the Timeline and erase everything that’s older than three months. It’s not so easy to do, but it is fascinating to read the absolute banality of your Facebook status updates from years ago. There’s no reason for much of it to persist. Never mind Facebook, even I’d use it against me – every day you live is a day you won’t see again. What exactly made posting that fat cat picture such a great use of my time 🙂

As a side effect icing all that banality makes your FB timeline much tighter and cleaner. The banality is fun at the time, but the time has passed ‘ere six months are gone. I’m not so naive as to believe Facebook deletes the associated meta-data, so there’s a case to be made for reducing the dross proactively. It’s what a blog is for – so you can own your data. There’s a difference between disseminating information and giving up the rights to it – while you can’t unsay anything on the Internet, you don’t have to give it away for resale.

Notes:

  1. where a moment is about a month, maybe a year if you stretch it

Remote Farm camera – experimenting with WiFi

Clive from the Raspberry Pi Foundation very kindly let us have a Pi Model A and camera, so it’s time to take this project forward a stage. At the moment the alpha test version is in service keeping an eye on our new piglets. Although the original purpose was to keep an eye on our newly arrived cattle pigs are more enterprising, so it’s good to know where they are

Our camera on the pigs

Our camera on the pigs

Development was stalled however since it’s not easy to work on a piece of kit in service.  Ideally one MiFi box could serve a number of cameras. This would reduce the camera power drain and consolidate.

The trouble is that the site is on the edge of town, a couple of hundred metres from the nearest houses, and I want to use BT Wi-Fi

Yagi wifi antenna

Yagi wifi antenna

I acquired one of these from ebay I didn’t have much hope for the integrity of the device, and to gain height I needed to go 250m further way from any likely source of WiFi. But it worked a treat, as a WISP client, I’m amazed. I was able to see 18 access points, five of which were BT WiFi , 3 of which were 5dB or above. The TP-Link gives a decent link at more than 5 and nothing at 2. I streamed a video to confirm the stability of the link.

TP Link signal strength with yagi

TP Link signal strength with yagi

I use it with a TP-Link TL-WA5110G which has the advantage of having a sma antenna socket and a native power supply of 12V. Although the adaptor is specced at 1A I measured the power drain at about 210 mA (~2.5W @12V). Which isn’t great but not terrible

A WISP client is not a  repeater

The trouble with using the tP link as a WISP client is the signal is presented as Ethernet, and I’d then want to re-radiate the signal on a different Wi-Fi network.  I could set it as a repeater, but then every Raspberry Pi would have the hurt of logging into BT WiFi. Whereas if I use a Raspberry Pi connected via ethernet to the TP-link and a WiPi dongle to connect to the farm I can collect pictures from the cameras on the farm network and perhaps power-manage the TP Link to only update every so often.

So an unexpected win, and I can look at using a Model B as a concentrator