The intelligent mailbox

Close up of the IR \"beam break\" circuitFor some time I have been looking to create an intelligent mailbox and security entry interface; something that has several functions, and interfaces back to a PC, which will send messages and log data. Now amongst all of this is sitting my Arduino Decimellia microprocessor, which leads me to the electronics that play with these ideas; while this may not be the perfect unit for this, it is an easy start to playing with microprocessors.

Let me start with a dream list of functions to happen at/in/near my mailbox:

  • Detect the presence of snail-mail in the mailbox: give a visual indication on the outside that I should stop and empty the mailbox, and send an alert to the network of the arrival of mail (and an alert when the mailbox is emptied).
  • Optionally count the number of deliveries of mail I have waiting, keeping count until I empty the mailbox
  • Read an RFID card to authenticate someone at the gate, and present this serial number to the network
  • Optionally read a fingerprint scan from someone at the gate, and present this as a unique serial number to the network, just like for the RFID card above
  • Read an RFID card from the vehicle in the driveway, and present this to the network
  • Detect if the gate is fully open or fully closed
  • Close the circuit to activate the gate to move (just like pressing the remote control button)
  • Detect via PIR any movement near the mailbox, and report that to the network

The next bit gets a little tricky to do with a microprocessor, so probably involves putting components in/on the mailbox, but taking the feed back to a PC for processing:

  • Have a microphone, speaker, and video camera capture the audio and video of the person, and essentially hook them up to a SIP phone that will call a SIP destination if the person is not authenticated (ie, they are a visitor pressing a traditional “doorbell”).

In theory, someone who fails authentication or presses a traditional doorbell would be connected (as in, a SIP call with the camera/mic/speaker to a call group that starts with video phones and displays in the house, and then (depending on rules such as time-of-day, etc) cascade to a 3G video cell-phone, potentially. Thus if I am home, I can see who is at the gate, and then give a response to the control system to tell the Intelligent Mailbox to throw the circuit on the gate to open it (if it is not open already), and furthermore, close the gate again.

Indeed, let’s go one better:

  • Detect the presence of an object in the path of the gate, so we know if it can be safely opened/closed
  • Detect any PIR movement inside the gate so it can send an alert to the network

I’m ignoring the “one better” bits for a “phase 2” while I concentrate on the “easier” bits for “phase 1”. So what have I got thus far:

  • An IR transmitter and receiver pair from Maplin; CH10L and CH10M
  • A pair of LEDs to visually debug if the send signal is being sent and the receive path is activating
  • A transistor, a few resistors, and voilà…

… it flashes the IR LED, reads the high values from the IR receiver and averages them a bunch of times, then goes low, reads the low values a few times and averages those, and then looks for significant deviations during the “on” cycle; a simple “beam break detection” circuit; aside from the obvious GND and +5V connections, we have one PIN of the Decimillia being used to turn the IR LED on and off, and one analogue pin used to read the IR receive circuit.

In ignoring the “count” of the mail deliveries, and just opting for “there is mail” or “there is no mail”, I can place the IR emitter no the base of the mailbox (inside, of course) and the IR receiver on the roof (inside, obviously), and any letters that are sitting in the mailbox should obscure the light path. When that happens, the Arduino does a serial write, with an API I am yet to think through, basically saying “You’ve got snail mail”.

The Arduino could live in the mailbox, and have a long, long USB or serial cable going from the mailbox, under the ground, and up the driveway (in conduit), to the house, up to the roof, and across the crawlspace to a silent low power PC (Eee box, Mini ITX, etc). Hence when the driveway comes up for replacement (its sinking all over the place, I am thinking of some heavy duty conduit runs under it (as Anand, one of my mates, has previously done). Perhaps a concrete pipe with multiple plastic conduit runs? Only needs to be around 25 metres long…

What’s next; well, I have just purchased a 555 timer and a 339 voltage comparator IC. Now, this seems geeky, even for me, but it may be possible to make the 555 and the 339 do all the logic of the timing of the flashes and the detection of the beam break, and reduce this down to just one DIGITAL pin on the Microprocessor; if the voltage is high, then the beam is broken. That reduces down the amount of code I will have loaded into the Arduino, which is a bit limited anyway, especially if I want to cram a whole bunch of other functions (see above) on the other pins.

And through all this, while I (and my family) have been having a terrible cold, all over Christmas. Oh well, only human.

Another year ends

So as 2008 winds down, whats been happening in my Tech world?

Well, Open Source electronics got a kick along with the Arduino Decimelia – both the spec of this little microcontroller. With some very easy tutorials, its sure to kick-start a whole generation of hardware hackers. It’s got me re-invigorated in circuitry. 3.0 came out, with support for some of the more recent MS Office file formats. Firefox 3 arrived, but not Thunderbird 3 (though Alpha’s of the Firefox 3.1 and Thunderbird are pretty useful already). MySQL 5.1 arrived (after being sold-out to Sun), but not without some controversy over its suitability as a stable and finished release! Python 3000 arrived, and Perl 6 did not as did not Debian Lenny, but there are no surprises there.

The Netbook made a big splash – low budget, but reasonably capable ultra-portable workstations, often powered by Linux, but still with WinXP support — notably not MS Vista support. Vista SP1 turned up, but didn’t fix the Win32 landscape enough to cause businesses to rush to it; indeed, most still stick to WInXP and Office 2003. While a Vista-like episode from any other vendor would have sunk them, MS appears o be riding this out, using their war chest to coast through until Windows 7 later in 2009.

So, what are the hot Open Source projects now, and will make the big impacts for 2009? Well, Asterisk PBX continues to survive well against the incumbent vendors, who all overcharge for their products. With SIP products starting to get more advanced, such as my new Seimens Gigaset SIP and PSTN handsets, we’ll likely continue to see evolution of telephony to reduce costs.Skype continues to be the main video calling solution for the moment, but as Asterisk development continues along the SIP video road, this may slowly change — a SIP to Skype bridge will be a useful step.

Mobile data networks continue to offer more speed, at more reasonable prices. Many domestic tariffs now include unlimited* (obligatory fair usage applies) data plans, but continue to charge like wounded bulls when roaming. In Europe, the European Commission continues to make a level playing field across the region by enforcing fairer charges. On the fixed line, in the UK Virgin Media started to offer Fibre to the home, but at highly restricted speeds (for fibre) of just 50 MB/s. On the WiFi front, 802.11n finally saw the light of day, and several commercial connectivity providers started to offer solutions for business around this — a Disaster Recovery like secondary circuit that does not rely on local cable connectivity.

Solid State hard drives started to enter the mainstream with Apple releasing their MacBook Air with an SSD option. While the pricing was high, it was a start. SSD disks promise to improve throughput greatly, but require a re-think of the IO subsystem as suddenly the disk can do multiple reads and writes simultaneously (whereas spinning disks can only fetch or write one operation at a time). Capacities of SSDs are starting to scale up, and hopefully they will be available in large SAN enclosures so the option of massive-and-blindingly-fast storage can become a reality.

Hard drives in general started to hit 1.5 TB, but with the same MTBF for reads, are starting to show their age. A report showed that in a RAID 5 configuration using 1.5 TB disks, you’re likely to see a secondary failure (read failure) while trying to rebuild a RAID 5 array. If drives continue to grow in size but not reliability, then the time will come that RAID1 will be virtually gauranteed to fail in this way when rebuilding.

HD video from set-top boxes is on the agenda! Via announced its Mini ITX 2.0 spec back in June, but its difficult to see what vendors are meeting this spec. Either this, or the upcoming Asus Eeebox 204/206 units, HDMI will start to be common place on set top boxes. Couple this with a web cam and we start to have almost commercial like video conferencing in the home, and high def video playback. Link it to the arrival of high(er) speed broadband, and we’ll see more iPlayer and downloadable content. This probably spells the end of the DVD, and possibly Blueray (which is struggling to go mainstream in the UK). HD TV is slowly starting to take off with FreeSat in the UK, while Freeview (terrestrial DVB) is struggling to get the bandwidth for HD broadcast.

As the economy worldwide tries to recover, more pressure is put on implementing cost-effective IT solutions. Hence the economics demand Open Source, even if the people who are in control of some of this organisations have pre-conceived ideas of the value or reliability of it (my award for Plonker Of The Month goes to the person who said “Open Source is shit”, and doesn’t realise that over 50% of his organisation’s IT equipment runs Linux). While the Linux desktop still is not as common as speculated last year by many, its making inroads from the bottom end of the market (via the aforementioned Netbooks).

Lastly, to bring back a blunt point, a current campaign for one OS vendor says “Life without Walls“. For over a decade Linux people have been saying “In a world without walls, who needs Windows“. Lets stop paying to reinvent the wheel every 24 months (Vista’s visual improvements have changed nothing in the world), and start moving on to new problems. Cancer, AIDS, Alzheimer’s, space exploration, better education, basic water supplies for the third world, energy efficient transport (electric cars?), the decline of terrorism and war; surely these are more worthy goals for our funds than “buying Larry a new yacht”.

Keep scratching your own itch.

On the variance of price

I want to play with an RFID reader. I found a nice one from Parallax here. So, how much does this cost? Well, the Parallax web site says $39.99. Shipping and tax are all extras, but lets look at base price.

So a UK supplier quotes £37.50 for the unit. Using today’s FX conversion rate, which will vary wildly, the US$ equivalent is US$54.83. That represents a markup of almost 40% compared to the US listed price. Now taxes and delivery included, it looks like I’d be around the same percentage better off if I order in the US and pick it up next time i am there, than get it her in the UK.