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Part 4 – Developing the LED lighting kit

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This first part of my progress blog is a catch-up from day one, so grab a cup of tea and some digestives – here we go!

It all started when Neil contacted me to ask if I was interested in designing some simple (his words!) electronics to be installed in a new kit.

Being naive I said – why not?  A question that still haunts me now!!

After initial discussions at which Neil revealed his idea for the founding of a new kit manufacturing collective – I was well and truly onboard for the ride, and we juggled around a few ideas as to how the first kit – the Stasis Pod would be lit.

Very soon, we had decided that a ring of LEDs in the top of the actual tube area would be the best idea, with perhaps a rotating effect achieved by individually controlling each led.  That immediately determined that a microprocessor controlled circuit would have to be used. We also decided at this point that external lights, both above and below the access door would need to be illuminated.  These were to be arranged such that they appear to be fluorescent type tubes, and to that effect a couple of the kit parts were designated to be clear, allowing the lights to be mounted behind them.

I commenced by setting up static rig of 6 LEDs and a microprocessor and developed a rotating effect.  Well, I say developed – I just set up a simple sequential “Knight Rider” or “Cylon” type effect to start with.  Hmmm, looked ok but a bit, well bland to be honest.  Engaged brain and thought for a while (do you know just how difficult that is?!).  What if I add a bit of fading up and down to produce a smoother comet tail like effect type effect as the light rotates around.  Aha!  That looks better, but tail was too long.  Quick bit of code bashing and I shortened the fade down time – now that looks better.

But, I’d forgotten to disengage my brain, so another thought arrived out of the blue…..I wonder if it would look better if I had all the light off to start with and gradually built up the rotational speed? So, yet more code mangling and I had a rotating ring of LEDs that gradually built in acceleration until the blue rotation becomes so fast that it in all effect becomes a continuous ring of light.

Something about it dissatisfied me though, so I built in the ability to change acceleration rate – just in case.  You never know – it may look totally different once its installed in the model, so better keep my options open.

It was about this time I thought it was about time I let Neil in on what I had been doing.  He, like I, liked the effect but we thought it could be built on.  We had a microprocessor in the design, so lets use some of its capabilities!  Discussions followed, and both Neil and I want to be able to have a “Whoop Whoop, something’s gone wrong, danger, danger Will Robinsons” indication.  OK, so why don’t we add a red flashing beacon – well,that idea was kicked into touch quite quickly, it was too simple.  More thought followed and I came up with an idea.  I quickly discounted it and instead suggested that we could switch off the blue led ring and make it flash red.  So, did we have room for two sets of LEDs?  Not a chance – tell you what let’s make it more difficult for ourselves and have bicolour  red/blue LEDs.  Hmmmmm, ooookay – I set to to see what I could do.

Prototype Electronics rig on the bench

The Infamous Rig – and yes, that is a Jack Daniels shot glass standing in for the stasis tube!

I then revised the rig (remember, right near the beginning?  Its still there!), no blue/red bicolour LEDs had come to light yet (!) so I used standard LEDs.  The rig is now getting very, very crowded!  A bit more (!!) programming and we can now switch modes between the standard blue and flashing red effect.  It was at this stage I decided that we’d use a Hall effect switch (thats simply a switch that is switched on and off with a magnet) to switch between the blue and red modes.

ProMini Controller Board
A Pro-Mini Board and Hall Switch showing scale

Now, just a minute – all this is all very well and good, but that rig is, well, a bit big – how to fit it in the available space?  No problem says I, all blase like – we use a Pro-mini.  A Pro-mini is a very small commercially available micro-processor board that comes with all its “life-support” system on a very small PCB, but – that raises its own set of problems. For instance,  whereas a Pro-Mini is nice and small, it doesn’t have the current handling capacity to control all the red LEDs flashing at the same time.  After considering re-writing the code (again!) to flash all the red LEDs individually, a short interval apart, it became obvious that that approach would not work as it would use up use too many processor channels.

I then remembered I’d switched my brain out of the loop a few paragraphs ago, so I booted it back up again and lo and behold – it came up with the solution.  We’ll kill 2 birds with one stone and design an adapter board to carry the Pro-Mini, piggy-back fashion, whilst also providing a switching stage for the red LEDs.  It got a little complicated and technical there in that we didn’t want yet another 6 wires to add to the cable linking the electronics in the base of the model with the led ring at the top, so I had to control the ground return from the red LEDs not the positive supplies so had to use a couple of transistors.  Ok, ok I promise – thats the first and last techno mumble jumble you’ll get from me all right?

The new adapter board is bottle shaped to fit the base (some say a whisky bottle was the inspiration for that choice – I’m saying nothing!!).  The board also has a USB socket to bring in 5 volts of electrical power and three spare pins in the connector will be used to carry the hall switch signal and two spare channels from the processor – as yet un-programmed but available for future expansion by reprogramming as required.  That means that something else might be able to connect to that USB connector – but I’m sworn to secrecy at the moment!

Time passed, as it has a propensity to do, and eventually I did find a supplier of some blue/red LEDs in Germany and purchased a batch of 600.  I manufactured a prototype LED ring circuit board and populated it with 6 of the newly acquired blue/red LEDs.  I then substituted the bi-colour LEDs for the standard LEDs in the rig.

Prototype LED Ring

Prototype Led Ring

Well, it all worked on the rig, the LED ring board had been prototyped and proved with a Pro-Mini, so now was the time to finalise the circuit boards design and then find a PCB manufacturer that could not only produce the boards but assemble them as well.  Also the quality of them was paramount.

I spent many an email conversation with prospective board manufacturers and there was a very wide range of pricing.  Whilst we were looking for the best value we could, it was also important that the final quality lived up to the price as well.

One of the problems I kept running up against involved those hard sought for bicolour LEDs.  You see, the German supplier had sent me the LEDs as 60 strips of 10 LEDs, whereas board manufacturers require the LEDs to be supplied in reels of a couple of thousand!  My plan to supply the LEDs ourselves was rapidly unravelling in front of my eyes!!  The manufacturers I contacted all said they were prepared to use the LEDs I could supply to them, but I’d have to pay for hand assembly – and believe me – that ain’t cheap!  A rethink was required, now where did I put that brain?

To cut a very long and painful story short,after much more research and midnight oil I did find a led manufacturer that the board manufacturers could get reels of LEDs from.  Each led worked out marginally more expensive than the ones I had bought, but it worked out cheaper than having to pay for hand assembly.  The new LEDs are teensy weensy as well, which is great as it gives more room on the led ring.  So, the only question surrounding the red/blue LEDs now is……anyone want 600 blue/red LEDs – cheap?!

Meanwhile, I had also managed to track down a supplier of very thin magnets for use in switching the lighting modes between normal and emergency effects.  We’ve decided to mount the magnet within an ID card to operate the switch by card swipe – cool eh?

So what’s left to do?  Well, I’m now reprogramming (again? Yup, again!), because I have a few more ideas to try out involving the white lights flickering as if the power or fluorescent tubes are faulty during emergency mode, and having a third mode for static display purposes.

Future development also comes to mind – but lets just now wait for the first boards to arrive so I can put the electronics and first issue kits together in the hope that they will actually fit.

If this enormous expanse of text hasn’t put you to sleep already – watch this space for developments!

Next Article…

 

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