[d.c.~daylight ltd.]


~ PROJECTS ~

Since leaving the BBC in 1995 after 14 years and starting d.c. ~ daylight ltd. we have designed electronic products and successfully completed complex projects for ~ London Weekend TV ~ SEGA ~ SICK AG ~ Sunkist ~ Marconi ~ Contraves Space AG ~ General Dynamics ~ Global Laser ~ DEKA air care ~ TATE Liverpool ~ Vector Technology ~ Optos ~ Test Technologies ~ Polamco ~ Richmond Defence ~ LJMU and others

Despite being educated in the "digital age" most of my work has been discrete analogue design ~ Problems with track layouts on PCBs for GHz digital modulation of diode lasers were solved using traditional analogue and RF transmission line techniques ~ A power amplifiers for space application could not use commercial IC building blocks so was designed around discrete devices with traditional lumped matching to greatly reduce the size and weight

One of the main challenges of analogue design is wide temperature operation ~ In the past it was tuned circuits or sensitive d.c. amplifiers that drifted ~ Nowadays extremely sensitive MEMS sensors and ADC references or components like diode lasers that heat to 100s of degrees in a fraction of a second and thermally self destruct if the control circuit is not carefully considered and well designed

Whatever challenges or problems you may be experiencing with your electronic project or product I am sure we can help you solve them ~ If we cannot help directly I will say so and not waste your time ~ Where we can help we will provide documentation and training for your staff so that you know exactly what was done and why ~ Please email or call Keith Snook on 02920 657 149 if you think d.c. ~ daylight can help you

Some past projects are shown below ~ Some smaller problems solved were not recorded with pictures and some larger commercial confidential projects are still subject to NDA so these are not listed


Kanji Wood [Afan Forest] Sound Sculpture

A sound installation art project in the trees of Kanji Wood ~ Afan forest South Wales

Up a tree ~ Fitting a bespoke PV regulator designed to efficiently solar power and control the 3 sound pods pictured below

Each pod has a 12V lead acid battery and these were to be charged from a single solar panel ~ A traditional PV shunt regulator with all 3 batteries connected in parallel would be wasteful so a regulator that switched the panel current to each battery as needed was designed and proved to be more efficient as the panel current was always being directed to charge the battery that needed it most

The sound pods are triggered by movement and could be set off by animals or gust of wind during the night so the solar panel voltage is used to turn off the pods when the batteries would become run down ensuring they are able to accept a charge when the sun next shines
Suspended between a triangle of pine trees ~ 3 stereo sound pods hang like nuts ready to emit sounds of the forest and its history to people passing under them

The control system and amplifiers for the pods had to be be very efficient so Class D (Modified Tripath) amplifiers were used and to further increase efficiency the "H" bridge supply was envelope modulated using information from a custom modified MP3 player sent ahead of the audio signal output


As part of the celebrations for "Liverpool 08 European Capital of Culture" We provided design and installation consultancy to the artist Peter Appleton for a laser optical communication link between the two Liverpool Cathedrals and the magneto acoustic drive for the stringed instruments used within the Cathedrals

The original intent of the project was to transmit audio between the two cathedrals using analogue modulated green lasers that I had designed when working for Vector Technology but the fast modulation required was not possible with laser powers higher than about 50mW and the visibility of these was considered low

It was also considered that 2 parallel visible lasers would look awkward so we installed a separate infra red digital communications link which interfaced to both cathedrals sound systems easier and then installed a parallel 2W visible laser shinning from the stable platform of the Anglican tower to the glass tower of Catholic cathedral

November 2007 testing the Visibility of the Vector Technology 50mW Analogue Modulated green laser module shinning from the Anglican to the Catholic Cathedral along Hope Street Liverpool

Summer 2008 the 2 churches were connected with beams of low power infrared light transmitting digital audio signals between their sound systems ~ The intent of the project was "highlighted" in September 2008 with a 2W green laser along the same route ~ see BBC News ~ programme

One advantage of working on such an interesting project is that you get to go places and see things that as a member of the public you would not normally have access to

The picture on the right was taken from a balcony high up inside the Anglican cathedral while we were investigating cable runs between the laser optical communication link equipment placed higher on the side of the tower and the sound booth at ground level

Even more remote ~ Inside the tower of the Catholic cathedral can only be reached by climbing the outside of the building and then climbing through a door in one of the glass panels ~ To fix our equipment to the tower it was a long climb with safety harness and often a lot of tools but the view both inside and outside was well worth the effort

This large area of coloured glass made an ideal termination for the high power green laser which along with other safety precautions I put in place at the Anglican cathedral ensured the system could not cause harm to anybody


September 1998 ~ I contracted to Contraves Space AG in Zurich on a European Space Agency project to design a small very efficient VHF power amplifier for an atomic frequency reference which would be mounted on the International Space Station ~ The size and efficiency requirement was extremely tight not to mention the limitations on component choice I would later find due to the aerospace qualification required

After many emails and a few visits to Switzerland and reading through my old BBC engineering notes and text books I realised the efficiency was not such a problem and the small size could be met but not using PCB stripline matching as other contractors had tried ~ I modelled several sample designs using lumped component matching and quoted for the first stage of the project to produce a design that functioned as a SPICE model

My input was a very small part of a larger project known as ACES and it was not until April 2004 that I got to actually build the first prototypes (left) and supply 2 working devices for testing on the rest of the atomic clock at the Neuchatel Observatory

The very small prototypes looked a bit messy but the size and performance more than made up for the appearance ~ The only problem making the final article would be finding non plastic inductors and no variable components and making a PCB with copper filled via heatsink that would pass a vacuum and temperature test

This VHF amplifier provides power to a coil antenna whose RF field dissociates hydrogen molecules at low pressure into a "plasma" stream of H atoms which provide the frequency reference of a Hydrogen Maser at 1420405751Hz to create the reference for an accurate Atomic clock

The amplifier was to be used in space and driven from a VHF oscillator whose output level and frequency would be carefully controlled to provide a specific level of hydrogen plasma and its full title was Space Hydrogen Maser Hydrogen Dissociation Oscillator Power Amplifier or SHM HDO-PA

February 2008 ~ I finally get go ahead to build and deliver 3 Space Qualified Engineering Models of my SHM HDO-PA for the European Space Agency ~ Atomic Clock Ensemble in Space

Many of the inductors (now fixed value) were available as expensive space qualified parts and to overcome the need to tweak the lumped matching I was allowed to make open frame coils using silver plated copper wire and this further improved the efficiency over the prototypes

How do you test a SHM HDO-PA in Wales UK without having access to the rest of the Space Hydrogen Maser Physics Package in Neuchatel Switzerland ?

Apart from the usual tests like linearity – gain – frequency response and power made with RF analysers the final test is can it power a loop antenna to induce a plasma in a low pressure gas vessel

The answer as you can see is yes it can and it does this with much higher efficiency and in a smaller space than the tight specification

During the 10 year period (not my time scale) it took to produce the engineering model of the SHM HDO–PA I did other design and verification work for the Swiss company under a framework contract ~ Specifically of interest to me was a problem with apparent noise affecting the purity of a 20405751Hz oscillator used to offset the "odd" part of the hydrogen frequency and 2 other similar oscillators used to verify and change the cavity tuning which I solved

The frequency required to get exactly 1,400,000,000Hz which divided by 14 gives 100MHz (the main clock output) and two other frequencies to automatically tune the narrow band sapphire loaded cavity (ACT) were generated by an FPGA using direct digital synthesis (DDS) with the 100MHz output as the FPGA clock ~ The 2 ACT signals either side of the hydrogen frequency get detected and measured and when equal amplitude the cavity is assumed centred

The discrete digital nature of the DDS signals and the fact that the final detection of the 2 ACT signals was done in software also meant that there would always be errors in cavity tuning and the ACT signal could never be independent of the hydrogen frequency which is "pulled" by the cavity tuning ~ The problem was solved using mathematics and software changes and relied on the fact that the complete atomic clock in space also had a cesium part (PHARAO) available as an independent external reference

I proposed a simpler analogue solution using homodyne detectors for the ACT frequencies that greatly reduced the complexity of the ACT circuit and in addition separated the ACT signal path from the hydrogen frequency signal path which could then be made with limiting amplifiers further reducing the design complexity and improving noise performance which for an atomic clock equates to improved accuracy

The microwave cavity was buried deep in several layers of heat insulation with several heaters in between each layer to maintain its temperature accurately as the clock orbited the earth about every 90 minutes ~ The temperature stable cavity was then "tuned" by an electrical signal from the ACT circuit which controlled a varactor diode connected to a wire loop inside the cavity

The time constant for the ACT signal needs to be long and this was achieved using traditional op–amp integrators which combined with other filtering required to keep the varactor control signal "quiet" meant that the ACT signal was affected by temperature changes in the signal electronics before it reached the varactor

I suggested that the cavity heater control circuit could be used to tune the cavity ~ simplifying the ACT and giving it a naturally long well damped time constant and eliminating the varactor and its noise ~ The cavity would then determine its own operating temperature within set limits and would be more accurate ~ This principle could also be applied to the ovens of most crystal oscillators so no external noise gets in but will this ever happen?

Due to many changes of companies undertaking this project I doubt my design will now become a flight model and orbit the earth on the international space station but I would like to thank Phil Smith at SemeLab especially for the open top transistors to prove my thermal analysis and Sam Samarasinghe at Express Circuits for help with the space qualified PCB with copper filled via heatsink area



Laser Diode Modules and Driver Circuits
In 1997 I moved away from Broadcasting and London and joined Vector Technology ltd. in South Wales to help them complete a contract with Marconi to design and build a trackside to moving train optical data and video link for the new Chek Lap Kok Airport in Hong Kong
Toward the end of the contract Marconi (then GPT) were withholding final payment until ALL documentation was presented in "electronic format" as their contract clearly stated ~ It appeared that Vector would have to provide not only drawings but also their source code and supporting bespoke software and thus some intellectual property

I had used Adobe Acrobat to create my handbooks for LWT and BBC projects and suggested converting all the documents including calculations and PCB layouts into pdf format which then led to hyperlinking them together to form a single document for each section of the system ~ GPT had to agree that pdf was "in electronic format" and their customer MTR in HK eventually got a comprehensive system manual when it was finally handed it over to them many years later by Vector Technology following the closure of Marconi communications

From 1999 rather than move to another job I contracted to Vector Technology to develop and improve their laser optical communication products based on the robust analogue modulation method I had developed for Marconi ~ this became of interest for covert optical communication between ships at sea and for real time images from UAVs or drones as we now know them ~ The detectors were so sensitive and wide band and could detect low level optical emanations from similar equipment used by others

Analogue video modulation with a genuine real time response was of interest for security cameras in lift shafts where cabled solutions were both expensive and had to be replaced regularly ~ The LiftMaster system from Vector Technology was well received but some customers felt they needed digital cameras and monitors so we extended the system to include some standard protocol interfaces and become bi–directional if required

The bread and butter products of Vector were OEM laser diode modules ~ initially to replace HeNe lasers and later lasers capable of being directly modulated with various signals like coded words ~ To provide a more accurate relationship between the analogue input and light output I introduced a novel closed loop modulation and a range of complimentary optical detectors capable of accurately detecting the linear modulated signals in the presence of interfering ambient light

As senior engineer at Global Laser I further developed the Vector Technology technique for controlling and linear modulation of DPSS lasers which despite their severe natural non linear characteristics can have better than 1% linearity up to 100% modulation using my control circuits

Click here for the old LiD3010 data from Vector Technology

Many lasers in the RS catalogue and from Farnell and Edmund optics use my designs and concepts based on discrete component analogue electronics and thermally balanced PCBs ~ The OptoElectronics company produce custom lasers based on new designs and together we have further improved the stability and linear modulation of green and blue laser diode modules ~ If you need assistance with Diode Laser or electro optical–detector design or applications please contact me or Ken Owen at RGB Uniwave ltd.