This post describes a recent project I completed to display caller id information for incoming calls on my computers. The project uses a BT Caller Display 50 connected via an optoisolating bridge to an arduino with an ethernet shield. When an incoming call is received the telephone number is transmitted via MQTT to a python client on any computer I happen to be using at the time. This project is a great example of someone putting great effort into being lazy, the caller id data is alredy displayed on my phone but the phone generally resides in the next room so this avoids me needing to run for stupid cold callers. Initially I’d wanted to do this project just using the arduino, which may have been possible but using the CD50 makes it a huge amount easier.
When prototyping circuits I often use a breadboard and an FTDI cable which usually leaves some kind of hacky looking unstable connection using wires stuck into the FTDI cable female header connector. This arrangement often leads to failiure as the wires fall out. After much searching I’ve managed to locate a solution to allow neat connection of a female header to the breadboard.
See below for details:
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After I had problems with my sheevaplug power supply I had lost faith in the device and didn’t trust it to survive being on 24/7 without exploding/setting on fire etc… so after NewIT kindly fixed it I sold it. This left me with no server to mess with so I decided to try and build a new one – the two primary requirements being that it used as little power as possible (ideally around 10W – the same as my sheevaplug with hd and usb hub) and was totally silent. In this post I’ll describe what I came up with.
In my previous post Sheevaplug – An ideal home server I described why I loved the sheevaplug, now in this post I’m going to discuss why I now have fallen out of love with it. The main reason is shown in the following photo:
For the past six months I’ve been using the unit for 24/7 IRC using irssi, running an MQTT server and broadcasting to pachube, along with allowing me to ssh tunnel into a secure internet connection when using public wifi. So far so good. However during the middle of last week I noticed my pachube feeds had frozen, I tried to ssh into the device and that failed so being at work at the time I was miffed and couldn’t wait to go home to find out what was wrong.
This is a mod that has been covered elsewhere but I feel it’s so good it’s worth me covering here. I have to thank Dave at the eevblog for bringing it to my attention and the other people on the forums who actually did the hard work in finding this. Basically the mod makes your Rigol DS1052E think it’s a DS1102E by changing the model number in the firmware thus changing the bandwidth from 50Mhz to 100Mhz with only 3 or 4 serial commands.
To perform this you’ll need a computer with a serial communication program (here we’ll be using ubuntu and cutecom), a straight through serial cable, not a null modem cable and obviously your Rigol DS1052E.
Yesterday I spent a very tiring but entertaining day back in my home from home, Newcastle. The reason being to attend the 2nd UK Maker Faire organised by Make Magazine. My legs have just about recovered from all the standing up and walking I did so I thought I’d do a post about some of the more interesting things I saw.
Around Newcastle for the past few days knitting has been appearing attached to railings and signs, this was organised as part of the Newcastle Science week and really does look pretty cool, I especially liked this example above outside the Discovery Museum and the one below in the Centre for Life. This seems to be part of a larger movement, known as Guerilla Knitting which aims to bring a smile to peoples faces by placing art in somewhere unusual (from here – the most sensible explanation I can find).
I have mentioned in previous posts that I use various scripts and sensors to feed data into the open source MQTT broker mosquitto. Currently all data is posted to pachube, rather than everything being online I decided I wanted some physical feedback. Having made an impulse buy of two vintage Ferranti ammeters using these to display some of my data seemed like obvious answer! The code on the arduino basically just displays a number passed by MQTT on the meter and therefore could be applied to any measurement one cared to choose.
The basic idea of this system is to monitor the current internet speed usage and display it on the ammeter. The system is based around an arduino with ethernet shield which acts as an MQTT client, this subscribes to the downstream bandwidth topic on my MQTT broker, receives the messages and changes the level of a PWM output pin on the arduino which causes the meter to show the appropriate level. The meter displays the current through a resistor which is varied by the PWM signal from the arduino. The reading on the meter corresponds to the current internet speed usage as a percentage of the overall theoretical available bandwidth.
Often when I buy an electronics book, or more recently a physical computing book, there is a section detailing where to purchase components, however they’re almost exclusively in the US and details of UK electronics retailers are difficult to come by for beginners and even more experienced people. In this post I intend to detail some of the electronics component retails who I like which sell a range of components from basic resistors and wire to expensive test equipment and embedded computers.
General Component Retailers
These are the retailers I most commonly order parts from and like, there are many others who may also be good but these are my favourites, as they stock the basics they’re used more than any other category here.
Bitsbox is a small retailer with a large following, it sells mainly simple components: capacitors, resistors, basic connectors, basic tools all for very reasonable prices when ordering in small quantities, something which is not common among many bigger suppliers. Also standard postage is only 1.50 on any order. I’ve bought here many times and always had a great experience, quick dispatch and good communication.
Farnell is about the most furthest away from Bitsbox it’s possible to get in size and product selection, it stocks hundreds of thousands, maybe millions of products from the mundane basics to the high end exotica and offers free next day delivery on any order. If you need something, almost anything in electronics quickly this is where to go. They are also the only retailer I’ve found in the UK which stock Texas Instruments components. Service is another area in which farnell is great. Prices can be high on some items but not unreasonable, my recent Agilent multimeter was 20% cheaper than any other UK retailer. Beware of items marked in stock in US which attract a 15 pound postage fee.
A point worthy of note is that if you want you can pick up orders from the trade counter at their international distribution centre in Leeds, West Yorkshire, something I’ve done a few times. You have to phone to order this way but the order can be collected after 2hrs and is within walking distance of Leeds Station and also is easy to drive to/park at. This makes them my 2nd favourite retailer on this list after NewIT (below).
The sheevaplug, a marvel development platform based on a 1.2GHz has risen out of obscurity in recent times as a silent, very low power computer. It’s uses have been stretched way beyond the intended use into cars and even as a full on desktop computer, despite it’s lack of connectivity.
The basic hardware consists of:
- Marvell Kirkwood 6281 CPU at 1.2 GHz with 256 KB L2 cache
- 512 MB RAM
- 512 MB flash
- Gigabit Ethernet
- 1x USB and 1x SD
- mini-USB with serial console and JTAG
The system is fanless and there are no moving parts, so it is silent apart from a strange extremely high pitched ringing sound which is on the edge of being audible.
In this post I’m going to describe what made me choose the sheevaplug, what I have added to default system and why I love the sheevaplug.
Without a doubt TI have produced a cult product in the chronos watch and it seems to be marketed to both get people using their msp430 chips and on a smaller scale produce cool projects with the watch. They have done well in providing the code for the watch and the the included hardware works well (albeit lacking much Linux compatibility). However I feel they’ve been slightly too clever in the hardware design and thus prevented some cool uses of the product. This post comes in response to some views recently posted on hackaday.
A recent hackaday post suggested using the supplied receiver could be modified to be used with an MCU, however this is unlikely unless the MCU acts as a USB host for a CDC device. Also the currently available watches use 868MHz which is a band in which cheap transceivers are not available (or at least that I can find), when the 433Mhz version is released in march interfacing the watch with an MCU may become a trivial task with cheap hardware.
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