Team Antiquarian build diary

All things antweight

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MySolderIsOlder
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Re: Team Antiquarian build diary

Post by MySolderIsOlder » Fri Dec 07, 2018 2:31 pm

Not sure this will work - and it's a lousy video (iPhone clamped in a PCB holder!) but this might show Ffythiana being test driven and doing her self-righty thing on my workbench. Incidentally, said workbench is VERY dusty, hence the wheelspin. Really need to wash the tyres and give everything a blast with dust-off...

https://www.youtube.com/embed/c7PAHPMY088
Stuart (Anthony's dad)

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Poor-man's NanoTwo alternatives

Post by MySolderIsOlder » Mon Dec 10, 2018 9:20 am

To cheer myself up after missing out on Saturday's NanoTwo lottery (I hit the site 2 hours after Rory's posting but was already too late!) I decided to try wiring some of my little stock of "2/3S 5A Dual-Way Brushed ESCs" (https://s.click.aliexpress.com/e/sdCep9e) directly into receivers, in the hope of losing some bulky wires and servo connectors. I had previously tried something similar with the DasMikro ESCs but since those are now firmly off my list I needed to try it with their much larger replacements.
Started off with my one remaining Orange R614 Rx (below left). These tiny boards have very small holes, so you have to be careful to keep tinned wire ends really neat - but apart from that it was pretty straightforward and I'll certainly try this again when Hobbyking next have these in stock locally. With the wires folded back carefully and all wrapped up with a bit of silicone tape, the complete package is barely any larger/heavier than the ESC on its own.
The only other receivers I had handy were the cheap Redcon 4-ch DSM2 Rx's (CM421), which have a bulky 5x3-pin header at one end for servo connectors. I had previously experimented with desoldering one of these headers and it took ages to remove all 15 pins and clean out the solder holes. This time though, I twigged that I only really needed to use 6 connections (shared Vcc & ground rails, plus the signal pins for 2 motors, weapon servo and bind). The other pins could just be snipped back to the board surface and ignored. Still a chore clearing the old solder from the holes and end result was a little bulkier than with the R614 - but since the Redcons are less than a fiver each and I have a few spares lying around, it was certainly worth the effort.

End result is a receiver/controller package weighing around 12g or less (depending on how short you trim the leads), measuring 25x45mm and costing around £15. Still gargantuan compared to a NanoTwo but easier to get one's hands on.

Image
Stuart (Anthony's dad)

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Spin(d)oza

Post by MySolderIsOlder » Mon Dec 10, 2018 10:03 am

Was home-alone on Sunday so decided to see if I could make a bot from scratch in one day. Up to now I've been good at starting builds but rubbish at finishing them, so this was quite a challenge for me. End result is... "Spin(d)oza". Not the most exciting antweight in the nest but probably the only one sort-of named after a 17th century Dutch philosopher. Took about 5 hours from start to finish, not counting the time I spent on Saturday soldering up the ESC/Receiver combo.

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The 'Spin' part of the name comes from the fact that the front bulldozer scoop can swivel around the central axis, where it's securely but loosely mounted on an M3 bolt. Objective there is two-fold; it means that even if the wheel-mounting axis is slightly out of true with the front (a perennial problem with my bodgy builds), it can swivel to sit flat on the arena. Added bonus is that if it takes a hit from a spinner or flipper that isn't dead-centre, then some of the kinetic energy will be wasted spinning the scoop, rather than damaging it. Leastways, that's the theory.
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Rather than using acetate I plan to sharpen the edges of the scoop so it hugs the deck.

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Base/side are cut and bent from 2mm polycarb, as is the scoop. Front plate, to which the scoop is attached, is 4mm, top is 1mm. Reinforcing/mounting strips along the edge were cut from a bit of 6mm. Everything held together with pre-tapped M2 machine screws.

Incidentally, the single biggest improvement in my efforts to bend polycarbonate came after spending £7 on a pair of these wide-mouthed mole grips;
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Heck of a lot easier to line up accurately than a vice, and you can push things beyond 90 degrees while setting the bend. Bending the 2mm polycarb with these took some effort but worked well in the end.


Those chunky tyres were the initial motivation for this build, though TBH at the moment they seem pretty lacking in grip. Will have to see whether that improves when I clean off all the workshop dust. Otherwise might try with the Pololu moon buggy tyres, for which there is just enough room.

Here's the view from beneath. Wanted a bot that worked either way up so we could get some practice driving with the controls reversed;
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Here are the innards, with the 2s/3s 5A dual brushed ESC / Redcon 4-ch RX combo mentioned in previous post...
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...and the inevitable switch/charge/bind port assembly at the back. The switch itself is just flush with the surface - so easy enough to use with a fingernail but hopefully safe from accidental activation in combat.
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Package just fits into the 10cm cube. Total weight is 156g with the 230mah NiMH battery but there's plenty of scope for weight reductions and it would be well under the limit if I switch to a 2s Nanotech LiPo.


So that's three bots totally finished, one almost there and a couple half-started. Just possible I might complete two teams of three by Christmas as per the original plan...

Stuart
Stuart (Anthony's dad)

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MarkR
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Re: Team Antiquarian build diary

Post by MarkR » Mon Dec 10, 2018 9:14 pm

It looks great, but I wonder, what is the purpose of the large electrolytic capacitor? Is it really required, or can you maybe use a smaller one?

Mark
Robots: Betsie - RaspberryPi controlled flipper bot with gyro stablisation - too clever for her own good?
Stacie - tidy flipper; 4wd driven by hair bands

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Re: Team Antiquarian build diary

Post by MySolderIsOlder » Tue Dec 11, 2018 8:53 am

Hi Mark,

Good question - Paul suggested on another thread that it's just there to absorb voltage spikes and avoid overheating, so could probably be removed. Certainly makes sense, though TBH I've not yet needed to use one in a build where space was a real issue. If you took it off and were a bit more stingy with the heatshrink, you'd be looking at a slightly smaller package of about 33x25mm. And if you sandwiched in the receiver and maybe re-soldered the power leads to face the other way, so all wires left from the same end of the package, it could be a lot neater. Might have to give that a try.
The capacitor, which is just soldered across the two battery connections, is 470 mF and rated at 25v. Probably overkill for a 2S-powered antweight, though these boards claim to be "2S/3S 5A" so maybe they're playing safe or compensating for cheap components elsewhere?
Talking of which, in case anyone's interested in the internal organs, there's two TA6586 motor drivers, a 7805 voltage regulator and a 15W204S microcontroller. Here's what it looks like with the shrink removed - the slide switch bottom right is the mix mode. Any ideas what the two unused solder-through holes next to it might be for?
Image
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Stuart (Anthony's dad)

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Re: Team Antiquarian build diary

Post by MarkR » Tue Dec 11, 2018 10:25 am

That looks like a robust ESC, it's a shame the holes are too small for your wires. (I hate wires soldered to pads, it probably wrecked my Dasmikro and many others' too)

The TA6586 seems literally exactly the same part as the RZ7899 I'm using, except it is a pin-through-hole DIP version. I use the surface mount rz7899 and it seems good (time will tell) - it hasn't been seen any battle action yet :)
Robots: Betsie - RaspberryPi controlled flipper bot with gyro stablisation - too clever for her own good?
Stacie - tidy flipper; 4wd driven by hair bands

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Re: Team Antiquarian build diary

Post by MarkR » Tue Dec 11, 2018 10:28 am

Yes the datasheet does specify a 470uF electrolytic, so technically there should be two (one for each channel) but in my design I just used a surface mount 47uF and it seems to do the job - at least, it smooths the spikes enough so it doesn't cause the processor to reset every time I trigger the flip motor.
Robots: Betsie - RaspberryPi controlled flipper bot with gyro stablisation - too clever for her own good?
Stacie - tidy flipper; 4wd driven by hair bands

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Re: Team Antiquarian build diary

Post by Andrew_Hibberd » Tue Dec 11, 2018 3:35 pm

Hi Stuart

I really like the tapped 4mm polycarbonate, defiantly a robust method for making an antweight.

It looks like the two holes are for a jumper/switch for the receiver BEC. If you were to cut the trace between the holes and solder a 2 pin jumper you could use this jumper to select if you want to power the RX using the 5V regulator (or not).
TEAM GEEK!

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LiPO Bargain

Post by MySolderIsOlder » Tue Dec 18, 2018 12:19 pm

I realise this will be out of date very soon - but if anyone needs some more LiPOs, HobbyKing currently have both the 2S and the 3S Turnigy Nanotech 180mah in the 'bargains bin' at £3.96 for a pack of five (less than a quarter the normal price).

I went on there just now, planning to buy a single 3S (to see if those 2S/3S ESCs could handle it) so it was a pleasant surprise!
Stuart (Anthony's dad)

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Re: Team Antiquarian build diary - Conclusion of Vol. 1

Post by MySolderIsOlder » Mon Jan 14, 2019 5:09 pm

Sorry - never got round to finishing this thread...
FWIW, I did just manage to finish four antweights (ok, three, plus one over-weight) ready for Christmas, complete with an integrated storage box / arena. Latter is built out of 12mm birch ply, plus some 6mm for the internal separators, an old sheet of white-coated hardboard for the top and 1.5mm self adhesive neoprene for the linings. The arena is a measly 30", so only just big enough to be valid but still small enough to fit under the sofa. The side barriers are just softwood battens with dowels to hold them in place and you can add or remove sections depending on how easy you want to make things for enthusiastic but inexperienced young drivers. Not an ideal edging system as the acetate on the flippers tends to get wedged under the sides - but it will do for now.

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View of the inside, ready to be packed away;
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There's room inside for 2 transmitters, a charger, all the arena edge pieces - and up to 15 antweights... So only 11 more to make :D

Initial reaction from my 8-year old and a few of his friends has been very positive. I was amazed at how quickly they learned how to switch the spektrums between different models - and at how quickly he learned to out-drive me in combat. After several hours of battles, 'Flipping Ugly' (now with an upgraded servo and the obligatory switch/charge/bind port) has emerged as a very clear winner, despite its unpromising start. 'Traxx' is a distant second, slightly hampered by an inability to self-right when on it's side - though in that mode it can still flap it's way across the arena like a deranged scallop. Ffythiana has potential but is very difficult to steer - haven't decided yet whether that's because the wheels are closer together, or whether it's something to do with the ESC mixing (will have to try it with the on-board mixing switched off when I can remember how to set up mixing on the DX6i). Spindoza is currently the runt of the litter, partly because those big chunky tyres are too hard to grip well and partly because of a loose connection which means it loses the signal every few seconds. Will have to do something about that.

Anyway, it's all been a great introduction to antweightery and the time pressure of getting everything ready for Christmas definitely helped focus my ideas. Now going to crack on in a more leisurely way with some new designs (for which I will start a new diary in due course) and hoping that we'll get a chance to enter a team at AWS one day, should the event venture a little nearer the south-east.

Cheers to everyone for all the helpful advise thus far!
Stuart (Anthony's dad)

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