Digimac II and IV

[leccyflyer]

Well, very nearly there with the Digimac III conversion with special thanks to Phil for all the help in providing one of his excellent encoders and providing advice on some of the other bits needed to do what I was after,

First step was to remove all the 27mhz innards, but to retain the On-Off Switch and with the intention to use Phil's encoder, plus a Lemon 2.4Ghz RF module from Stuart. I don't have any sophisticated test equipment, so it will be a simple function test and range check to ensure all is well. I've also got a plan for a wee depron Super Sixty -more like a Super 30 - to use as a test bed.

I followed the excellent document on the assignment of the different channels, paralleling up the unused channels and getting the three main function connected to the existing pots. I wanted to maintain the look of the transmitter externally, with the only addition so far being a S/C button on the front fascia, beneath the main flight control stick in Mode Two configuration. Having read on here of the benefits of flying On The Button, but with a safety net of the rudder-elevator propo stick to hand. I wasn't sure of the preferred position for the S/C button, so intended fitting another, on the top right of the case and having one sequential and the other compound.

The other thing I considered vital was a throttle cut switch, as on my existing modern transmitters - a long throw 2 position switch on the top right of the transmitter. Unfortunately the supplier sent two short throw, 3 position switches by mistake, so that remains to be fitted. Once that is in place I#ll be able to fit the second S/C button. I've made provision for rates and expo internally, using the pots recommended in response to my question the other day. I 3D printed mounts for the encoder, RF module and the rate and expo pots, plus knobs for those pots. I decided against having the rates on a switch, but that might conceivably change.

Power is provided by a 2 cell 2800mahl Li-Ion pack, which fits nicely in the space beneath the rates and expo mount. The 3D printed mount for the RF module resembles an oil production platform, supported on four nylon bolts which engage with captive nuts affixed to the case with double sided tape. That positions the aerial connection in the ideal location to accept the short antenna as it emerges from the 2,4ghz aerial housing.

Phil was a great help again in providing some Zener diodes and resistors to make the meter function as an extended range meter, compatible with the 7.2v Li=Ion pack.

I'm waiting to fit those last two switches before the grand switch on and keeping my fingers crossed that the magic smoke signals don't spoil the show. Ultimately I want to dedicate this set to operating my Outlaw and, assuming that's successful, will make the same conversion on my Digimac IV, probably to drive my forthcoming Mini Super.

Thanks to everyone on the forum, who's collective knowledge has made this first attempt at a conversion so enjoyable, but especial thanks to Phil for answering the daft questions of a complete electronics neophyte and providing such super support.

[leccyflyer]

Martin on RCM&E forum looked at my pictures and spotted a problem with my agricultural soldering, where the signal wire was just touching the telemetry pad on the module as well as the PPM tab, giving a potential shirt circuit - so I've just fixed that and hope it's kept the magic smoke inside,

Must admit it was the part of the job that did give me the heebie jeebies - those pads are awfy close together for a newbie who's previous experience has been soldering battery connectors and making up sub-C NiCd packs.

I've yet to connect power up and won't do so until I have the last couple of switches connected.

[wookman]

Nice job Leccy. Good luck with the Outlaw.

[leccyflyer]

Thanks man - slowly getting there.

Had a Road To Domestos moment this morning, but thanks to Phil, who advised again on one of my misgivings the set was saved from going down the pan. I'd just copied Wee MacGregors wiring on the stick pots like for like, but on reading again, for the hundreth time, the document which accompanies Phil's encoder suddely realised that the central tab on the pots was for the signal, not the positive. Phil confirmed that was the case and a few minutes with the soldering iron rectified the problem. I've included a replacement pcture of the amended connections to those pots.

There was no putting it off any longer I finally had to switch on and everything worked, eventually. I justtested the set with a loose spare receiver at first to check all was working before committing to a test with a model. After the stick calibration and some adjustment for reversing the controls everything checks out fine. The throttle lock works, the failsafe works, rates and expo work, the two single channel buttons work giving sequential and compound emulations. Here's how the finished set looks.

Don't know why the preview is upside down :o Just click on it.....not anymore! Cheers Tobe

Next step is a range check and flight testing. I don't really want to risk the Outlaw for the first go and, since my pal Bob has such great fun with a half sized profile depron Super 60, i thought I'd knock one up as a test bed. Fuselage halves are just curing as I write, wing is all ready to be joined later and the bare model should be done and kitted out by tomorrow evening.

[leccyflyer]

Quick test bed aeroplane for flight testing the Digimac III all ready to go - hopefully tomorrow if the weather co=operates. Thankfully all the controls worked in the same direction as on the Outlaw.

Not very traditional, but a proven design and only a few hours work, a half size 32" span profile Super 60 in laminated 6mm depron, with 20g pole and stator outrunner, 10amp esc, 2s1p 800mah pack and 8x6" prop. That set up works well with my <250g SEMFF funfighters and also with my pal Bob's identical model. AUW is 260g - I could have got it withing the 250g limit with a lighter undercarriage, or by not having a dihedral brace, but I don't mind the extra 10g too much.

[leccyflyer]

Successful maiden flight of the Digimac III and Super 30 combo this morning. Not the best conditions as it was completely overcast with plenty of moisture in the air, so much so that when it turned into proper mizzle later on it stopped the flying. With a reduced power range check and failsafe check successfully circumnavigated did have an initial problem with the motor cutting out when powering up. Cured by swapping in an identical motor from one of my SEMFF fighters - just two grub screws undone and redone to accomplish the motor swap.

The wee Super 30 flew really nicely, following a hand launch, though with a tendency to head to the right a bit, cured with a few clicks of left trim - I'd copied the right thrust from the Schoolboy and the Super 30 doesn't need that much. I'll cure that more permanently with a couple of washers behind the cruciform mount. Once trimmed on the sticks the model flew well and encouraged me to try flying on the button for the first time. That was great fun. I found that I preferred the compound button on the top of the TX and even managed to get my timing right for a three pushes for an up elevator command. Pootled around for most of the flight on the button, getting the feel for it - however I did have to correct a couple of less comfortable positions by reverting to the sticks. For the landing I turned the model into the very minor touch of wind and landed on the sticks. Very pleased with how the wee test bed performed. Before I could get a second flight the mist turned into proper mizzle - the sort that soaks you through -and stopped play.