Repost: OS Pixie 2.4g Conversion (from 2014)

[Phil_G]

Reposted at Rons request, from 2014: (can you believe its almost 4 years?)

OS Pixie 2.4g Conversion

My Dad started me flying R/C at about 10 years old, and after varying success with his home-brew Single-Channel radios, a second-hand OS Pixie was our first ever commercial R/C set. It was supremely reliable and I've many happy memories of single-channel slope soaring back in the late 1960s, with the first of what would be many Veron Impalas. It had a relay receiver driving a 'Climax Unimite' motorized actuator which was incredibly noisy. It could be heard plainly at 200 feet above, but was very handy when finding a glider buried in deep bracken! When the lift was good, we'd confidently stay up for ages whereas with a rubber-escapement you were having to land through lack of turns... of course with a superregenerative receiver, flying involved strictly taking your turn, and not being an air-hog



Owning an OS Pixie again had been a nostalgic 'must' for some time, when Doug kindly gave me an original boxed Pixie, with the receiver connectors still unsoldered - probably unused. Now I love this set and I'm very very grateful - but its immaculate and so not really an ideal conversion candidate. The aim was always to fly a Pixie again - and so the hunt for a suitable donor continued. Eventually at this year's Nats swapmeet, Shaun spotted an old, tatty Mk1 Pixie and I crossed the sellers palm with silver. I was really chuffed to find a Pixie tx in any condition and happily paid £15 for it. Its far from mint, has cracks and chips but its just like the one we had. I'm looking forward to flying a Pixie again!

At the time it was one of the smallest Single-Channel sets ever, if not the smallest full range transmitter. I thought it would be a real challenge to fit everything in, others have done the larger Mk2 (the later model was still small but bigger than the first one) but as far as I know this is the first Mk1 conversion [this is reposted from 2014] and it looks really tiny. There are examples of Pixie Mk2 conversions on the S/C website. Here's the disassembly and a trial run fitting all the bits:

Space being at a premium, I cut down an encoder board by lopping off the Futaba connector end, and mounted all the components flat without socketing the pic, tried various layouts and in the end it all fitted in easily. The biggest problem is all the heavy wiring - quite why Frsky use mains 'twin & earth' to connect everything is beyond me - so I removed it all, ditched the bind board, rewired it again with the thinnest servo cable which I think was 28swg. Its all hard wired, no plugs & sockets, to save space. The V8HT module has the original heatshrink removed then after rewiring re-shrunk with a piece that fits properly without overlaps.

As per the trend, the bind board is ditched in favour of a separate LED and a new SMT pushbutton, again to save space. Details here. The module led fits nicely in the Pixie aerial-tuning hole, with a bit of filing the aerial fitted exactly into the original hole, with the encoder leds just under the on/off switch.

The new bind button is a minute smt button mounted inside next to the battery (PP3 as per original). One shortcoming of the original Pixie was the tone button - it was horrible, spongy and with no real feel, so I found a microswitch that matched the original but with a nice click and good tactile feedback. To make it look authentic, I had to spray a button black as I could only find a red one!

Power comes from an EBL 2S lithium battery which is physically identical to the original PP3, but of course rechargeable and at 600mAH (measured) it lasts forever. The EBL's are from ebay, I bought a set of 4 with a charger - they're suberb batteries for RC work, or smoke alarms, remotes, radios...
At the moment the batteries are listed on ebay but not the chargers - but a 2S lipo setting on your conventional charger is fine, 600mA, just a straight charge as balancing is done internally.

Anyway here's a video rundown of the completed Pixie, all good to go (sorry it somehow ran to 7 minutes!):



The Pixie's first flight was IIRC at Marske-by-the-sea with Ron... but there was no video so obviously that didnt happen (ITNVIDH™). But some months later, a flight at Callow Bank, with video!





To bring the topic up-to-date, Neil & Mike have been working on a brand-new, 3D-printed OS Pixie case - which looks fabulous - watch this space!

Pixie review from 1964:

And from an interesting Russian site the pixie schematic:

Cheers
Phil