Hello! And some questions - And NEA Build Log of Sorts

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JeffSergeant
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Re: Hello! And some questions

Post by JeffSergeant »

Thanks!

I used a pair of these 10A ESC Brushed Speed Controller (WITHOUT brake is the right one!) with 50:1 geared micro DC motors.

I've actually just found another type that's 1/10th the weight that I'm going to try out. BUT it doesn't have a BEC; and I'm not 100% sure they support 'reverse'. so I either need to use one of the heavier ESCs to power both (still a weight saving, but a but clunky) or source a separate BEC. I might leave that for the next model!

Just upgraded the armor to 0.8mm aluminium, and I've got ~10g spare, so I might need to make a few weight-saving holes to be able to afford a weapon/attachment of some description.
Paulmchurd
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Re: Hello! And some questions

Post by Paulmchurd »

Is using it without a brake going to Be harder to drive? What happens if you want to not drive into the pit?

Thanks for the link.
JeffSergeant
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Re: Hello! And some questions

Post by JeffSergeant »

Paulmchurd wrote: Wed Jan 10, 2018 4:07 pm Is using it without a brake going to Be harder to drive? What happens if you want to not drive into the pit?

Thanks for the link.
Both options have reverse, whacking it into reverse seems to be a pretty effective stopping mechanism and even with 'no brake' it doesn't coast at zero throttle, it's just not actively resisting turning. And being able to from straight from reverse to forwards means I can pull wheelies.. everyone loves wheelies.

With brake means that getting into reverse is awkward (You reverse the throttle to activate the brake, then return it to neutral, then reverse it again after a short pause to actually start going backwards) all of which means a couple of seconds being a sitting duck. Then you add mixing into the mix, and you never quite know when a wheel is going to be reversed, so it's all a bit hit and miss. Not completely undriveable; but unpredictable.

I gather this is normally configurable with the more expensive ESCs; but because these are the cheapest off-brands ESCs on Amazon they're not reprogrammable.
JeffSergeant
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Re: Hello! And some questions

Post by JeffSergeant »

:lol: Accidental Torque and Aerodynamics test

Aluminium Armour looking good; and I've saved myself enough to mount a lightweight flipper/lifter on the 'back';

I found it spins much too readily in reverse, but I managed to get my transmitter to reduce the steering input when it's going backwards, now it turns consistently in both directions.

I'm a bit worried it's not as nippy as some others, but it seems to pull pretty well!

Next step- shorten the ESC/RX connectors to get rid of some rats nest; and add the external power switch while I'm at it. Then work on the flipper. Last job will be finding some way to keep the armour attached to the base that's a little more substantial than electrical tape. Don't seem to have any sufficiently small nuts&bolts.
JeffSergeant
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Re: Hello! And some questions

Post by JeffSergeant »

Managed to install a flipper of sorts; it's mostly designed for self-righting, which is does swimmingly.

Currently at 150g exactly, but there's quite a lot of servo wire to come out, which should give me some wiggle-room for optional extras like screws to hold the Armour on!
Paulmchurd
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Re: Hello! And some questions

Post by Paulmchurd »

I wouldn't worry about the speed.

I'm using 600rpm and some times they are so quick when I turn a corner I just spin on the spot.

Looks good. How have you secured your wheels? A spinner robot could knock them off.
JeffSergeant
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Re: Hello! And some questions

Post by JeffSergeant »

How have you secured your wheels?
So far, friction and prayer! Once I've stopped fiddling I might just add copious amounts of glue.

Annoyingly, it appears that even the teeny tiny flipper is overwhelming the ESC and causing it to cut out as soon as the servo encounters any resistance
putting the robot into a tizzy (technical turn) and making on the wheels spin when I try and move the servo...; annoying because it wasn't doing this earlier!

The servo had a short earlier, things have been screwy ever since I fixed that; so I think it might have affected the BEC on the ESC before I worked out what was going on.

Luckily, I have two ESCs, one per motor! So I'm swapping the servo from drawing power from the Receiver (powered by ESC1), to drawing it from ESC2; I don't pretend to know exactly what's happening but it seems to be stable (and more powerful) this way around.
JeffSergeant
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Re: Hello! And some questions - And NEA Build Log of Sorts

Post by JeffSergeant »

So, NEA is nearly finished.. one more glob of hot-snot to go.

Aluminium Chassis and Armour
Soft steel flipper with thin plastic 'wedge' powered by 9g micro servo
2 x Pololu 100:1 Micro Metal Gearmotor HP
2 x Pololu Wheel 42x19mm Pair
2x Generic Brushed ESCs
FrSky D4R-II 4 Channel 2.4ghz Receiver


Lessons learned so far.

Bad.
1. Check whether your ESC has a brake function, and whether you want an ESC with a brake function before buying two of them!
2. Check your RX has a failsafe function before you buy it.. the Frsky v5dm does not have one!
3. Teeny tiny plastic micro servos are cheap for a reason, they're not very robust.
4. Enamel spraypaint doesn't stick very well to aluminium; and is removed really well by electrical tape.
5. Real rubber tyres are heavy but they look cool.

Good
1. Custom functions on OpenTX are awesome. I've set my transmitter to dynamically change the drive/turn mix depending on whether I'm in forward or reverse (as the robot spins too readily in reverse otherwise.) In fact the whole OpenTX project as a whole is a great example of open source done right.
2. Kitchen scissors can cut everything much more cleanly than any other tool I own.. they are obviously magical.
3. Blender's UV Unwrapping tool + Inkscape (for printing at the correct scale) is awesome for making nets for folding metal.
4. To shorten servo connectors; desoldering them from the PCB, shortening, then resoldering saves having to splice wires; so it probably better in the long-run.
5. Pasta machines work quite well for producing consistent thickness sheets of Polymorph/Friendly plastic; in small sections.

Ideas
1. EITHER get a DSM module for my transmitter, or work out some way to use frsky's SBUS, otherwise I'm limited on receiver size.
2. Tyre warmers! I have real rubber so why not do it properly. (Might get laughed at...)
Belianno
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Joined: Sun Dec 03, 2017 9:33 pm

Re: Hello! And some questions - And NEA Build Log of Sorts

Post by Belianno »

Hi there. Thanks for providing the link to the ESCs you bought. I've been looking for an ESC recommendation after struggling to solder a DasMikro! (I'm very much a newbie to robot building). Do you (or anyone else) know if this ESC will work with 500rpm motors? The title on the site says "..This ESC can work with 130/180/260/280/380 Brushed Motor", which I assume refers to the rpm, so think it may not be suitable for 500 rpm motors. Thanks a lot.
Ant Ipodean
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Location: Auckland, New Zealand

Re: Hello! And some questions - And NEA Build Log of Sorts

Post by Ant Ipodean »

The numbers you are referring to are not rpm, but standard motor sizes, all bigger than the N20 motors you will likely be using in a 150 ant. The rpm should not have much affect on the capacity of ESC needed.
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