Tuesday, 4 November 2014

Temperature Gauge

Cheap LCD temperature gauge, another eBay purchase from China for about £3. Designed as a PC case thermometer, but it will be part of the custom heating controller now I have a working timer module.

Friday, 31 October 2014

Up-cycled Up-lighter

I bought this up-lighter almost 20 years ago in B&Q. Back then it was fitted with a 500 watt halogen lamp, which was an expensive proposition even back then, so the light wasn't used much. I finally got round to modifying it to take a state-of-the-art LED G10 lamp using a recycled lamp fitting. It is just as bright as before and now uses...  4 watts! That's  a 125th of the electricity for the same light output. The cable is a bit heavy and I want to make sure the connections are 100 percent safe and secure before bringing the light into the house, but it works.

Free-roving Lego Technic classic robot

We had a security alert nearby yesterday (aka 'bomb scare!'), which was kind of coincidental as we had just finished building our own hazardous-working grab robot. The design is from Richard Pawson's 1986 robotics book, but I beefed-up the end effector (that's mad scientist speak for 'grab') to make it more robust and we are looking at mounting a ram device on top for forcing open suspicious packages!!

Sunday, 19 October 2014

LEGO Robotic Arm 2

This arm is a hybrid derived from several designs taken from two books and a 'classic' Lego Technic website. The books are -

'Make and Program Your Own Robots' by William Clark (1985, ISBN 0-0916-2890-3)

'Robot Projects' by Richard Pawson (1985, ISBN 0-7112-0419-5)

Both feature interfacing to the Sinclair Spectrum, so using an Arduino or Raspberry Pi would be really suitable alternatives. Clarke's book provides a simple microswitch design using paper clips that we have tried out.  I want to look at building an alternative motor with PWM control and optical feedback sometime.

Monday, 25 August 2014

CBM-910 Printer

I acquired this really neat Citizen till roll printer a while back, but only got to re-inking the ribbon last year and then it started giving problems. I was about to throw it out and decided to try it one last time with a decent power supply made up using an old laptop adaptor and one of the awesome little switch mode voltage converters I got on eBay recently. With 2 amps and a nice stable 7 volts the printer is now working a treat. On the self-test you can see the gobbledygook when the printer was attached to the old linear power supply and underneath the correct print out using my DIY switch mode supply.

The printer is serial with a standard RS232 interface that should connect to a USB-to-serial adaptor. There are a few interesting 'Internet Of Things' (IOF) projects using small printers and a Raspberry Pi or an Arduino could send serial data out to be printed locally. A few experiments are in the pipeline I think!

Sunday, 20 July 2014

Mindstorms I2C Experiment

I wanted to try out the Mindstorms NXT2 with raw I2C, but this involved making a homebrew 6-pin connector because Lego use a proprietary type to avoid kids sticking them into your Ethernet wall socket. Some Minicraft cutting and epoxy sticking later and on the second attempt I had a working breakout cable.

The little board cost a couple of pounds on eBay and has an I2C analogue-to-digital converter with a light dependent resistor, thermistor and variable resistor for testing. Programming blocks for Mindstorms are easily downloaded and installed to the Lego software.

The NXT is reading ambient light and displaying an 8-bit value on-screen.

Cardboard Keyboard

This started life as a cheapo case and keyboard for a 7-inch Android tablet, but recently I really just wanted an ultra-lightweight USB keyboard. I took the case apart and then I had the idea of using art mounting card to make a new case. Two layers of this card are very stiff once they are glued together, but each layer is easily cut with a craft knife. I got an A3 sheet of the card for £4 so there is stacks left for other projects.

Monday, 26 May 2014

New Computing Set-Up

Well, I've started to come out of hibernation at last, due to the indifferent weather and everyone having a bad cold last week. I finally got around to gutting 4 old PCs and taking the carcasses to the dump, cases for recycling really, and then I upgraded the workshop PC to 2gb of RAM and added a second 160 GB hard drive. Not state-of-the-art, but I was able to install Linux Mint 15 so I can browse the web and do Arduino and PIC stuff again.  I treated myself to this Fujitsu Android tablet from Lidl of all places and with a 99p stand, a USB keyboard and the 'On-The-Go (OTG)' adaptor I bought for my 'phone I have myself a cheap transformer computer.

Wednesday, 26 March 2014

LCD Monitor LED Backlight Conversion Update

I think I have finally managed to convert an LCD monitor with a faulty backlight to LED backlighting. As is very common the cold cathode lamps or the inverter had failed so instead of a clear white light I was getting a purple sort of hue and not a very bright one at that.

This is a tricky enough job and the first 2 I tried, an old TV and a monitor,  didn't survive the surgery, but this one seems to have. I need to finish the wiring, but early tests show a good image.

UPDATE - 1st April 2014

The inverter had failed and there was a tell-tale burn mark round one of the transformers on the PCB. I got the LEDs wired to a 14v feed from the power board in the monitor. A good hack I think, but a brightness control will need to be sorted out using a cheap PWM power control module.

Wednesday, 1 January 2014

Home Brew Temperature Sensors

Bored today, so I decided to make up some remote temperature sensors. They're based on 18DS20 1-wire sensors which can be operated over just 2 wires in power parasitic mode where power is taken from the data line and held in a capacitor on the chip to allow it to make the temperature conversion. In this mode the VCC (positive) and GND (negative, ground) pins are wired together and then to ground. 

The ends are made from old bits of Biro pens and pieces of heat shrink sleeve. For anyone who tinkers or 'makes' a good supply of heat shrink sleeve is essential and makes for very neat finishes. Good for car wiring too.