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Journey to a first antweight


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louis



Joined: 28 May 2018
Posts: 7
Location: Brisbane/Singapore


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Journey to a first antweight

Hi!

I have been googling around the past few days to try to start a first
antweight robot. But I'm not so confident in what I'm doing, so I'll
try to summarize here before I start to buy parts. My idea is to start
buy building a simple 2 wheels pusher and once this is all working
properly add some pieces to get a flipper or hammer.

My background is in IT, so I don't know anything about
electronics. Please excuse if my questions are stupid or have already
been answered Smile

From what I gathered online the first thing to look at is the
ESC.

People at http://www.robotwars101.org/forum/index.php advertise the
nanotwo. But nutsandbots doesn't deliver to this side of the world and
the product is out of stock. The local alternative for a kit seems to
be from botbitz http://botbitz.com/product/antweight-starter-kit/

There is not as much documentation for it as for the nanotwo. So I
have some questions:

- does it work with DSM2/DSMX or only AFHDS?
- can I plug an additionnal servo to it or I will need another ESC?
- Is it the most recommended transmitter/receiver to go with the kit?
http://botbitz.com/product/hobbyking-t6a-radio-transmitter-receiver/
- Do I need a soldering kit to link the drive motors and the ESC?

I have been told "ESCs are by far the hardest to find as you need to
find brushed ones with no brakes".

Does it correspond to the botbitz kit?

Botbitz provides motors with different voltages. But it seems that
most bots are using a 2s lipo battery which give 7.4v. Why would I need
the high voltage one then?

For the batteries,
https://hobbyking.com/en_us/turnigy-nano-tech-180mah-2s-25-40c-lipo-pack-5pcs.html
should be ok? With a lipo safe bag and a charger.

Regarding the transmitter, I found on one forum someone talking about
this one https://hobbyking.com/en_us/fs-i4x-4ch-radio-mode-1.html
which is AFHDS too so maybe compatible with the botbitz kit. Is it
really compatible? Is 4 channels too little? Does it worth spending a
bit more on a better transmitter?

If I go with
http://botbitz.com/product/hobbyking-t6a-radio-transmitter-receiver/,
is it the V1 or V2? What is the mode 1 part of the description here?
It looks like there is a mode 2 also.
https://hobbyking.com/en_us/hobby-king-2-4ghz-6ch-tx-rx-v2-mode-1.html

Where can I buy the pieces to make the frame of the robot? It seems
that many people are using 3D printing now. But at the beginning I'd
prefer not to spend time on learning CAD and finding a printer.

Everything is out of stock on hobbykind, is it normal and I just have
to monitor the products I'm interested by? Like
https://hobbyking.com/en_us/hobby-king-2-4ghz-6ch-tx-usb-cable.html
for the transmitter

What tooling should I buy except a screwdriver?

What good wiring guide should I read?

For the servos for a flipper (or a hammer), I see there are different
possibilities like the number of degrees it can move. But I don't
understand how to read the other specification. For example, how to
know if it's powerful enough to move 200g?

Are the components in this guide still up to date?
https://docs.google.com/document/d/1rr6J9y0drXSMtq43ufzqF6T0cRsWHRRYho5HKS9aEkg/edit#heading=h.fgtjtjo9fwfm

Sorry for the long post. It also helps to summarize and organize what
I have in mind.

List of required parts:

- Drive Motors
- Wheels and Hubs
- Drive Speed Controller
- RC Radio / Receiver
- Batteries
- Power Switch / Link
- Weapon Motor (If Design Requires)
- Weapon Speed Controller(If Design Requires)
- Wire
- Connectors

Vocabulary (because I didn't understand half of the words at first):

- 2WD/4WD: 2/4 wheel drive
- ESC: ESC stands for Electronic Speed Controller. It converts the PWM
signal from the flight controller or radio receiver, and drives the
brushless motor by providing the appropriate level of electrical
power.
- BEC: BEC stands for Battery Elimination Circuit. It’s just a fancy
name for voltage regulator, which converts main LiPo battery pack
voltage to a lower voltage (e.g. 2S 7.4V, 3S 11.1V or 4S 14.8V to
5V). BEC is usually built into ESC, and as the name suggests, it
eliminates the need for a separate battery to power the 5V
electronic devices.
- UBEC: UBEC stands for universal BEC or sometimes ultimate BEC. It’s
used when ESC doesn’t have built-in BEC, or standalone power system
is required. They generally are more efficient, more reliable and
able to provide more current than BEC. The UBEC is connected
directly to the main battery of the multicopter, the same way as an
ESC.
- TX/RX: transmitter/receiver
- ...

Links:

- ESC, BEC, UBEC
https://oscarliang.com/what-is-esc-ubec-bec-quadcopter/
https://en.wikipedia.org/wiki/Electronic_speed_control
- ...

Post Tue May 29, 2018 4:55 am 
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Knightrous
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Joined: 15 Jun 2004
Posts: 8492
Location: NSW


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Re: Journey to a first antweight

quote:
Originally posted by louis:

Botbitz provides motors with different voltages. But it seems that
most bots are using a 2s lipo battery which give 7.4v. Why would I need
the high voltage one then?


My antweight spinner runs 3S on the weapon, so I use the higher voltage motors. The low voltage motors die pretty fast on 3S.
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Post Tue May 29, 2018 10:04 am 
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Ondray



Joined: 06 Jul 2015
Posts: 138
Location: Newcastle


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Trying to answer what I can in order.

The ant-weight starter kit is a really good start for motors and ESC's - I wouldn't worry about the nanotwos. If you want to go real cheap and nasty there are 10A brushed ESC's on ebay that work.

The ESC's themselves don't care which transmitter protocol you're using, the ESC gets a signal from the receiver which needs the same protocol as the transmitter.

The BEC in the ESC powers the transmitter and then any small servo's plug into and are powered/controlled by the transmitter. The nanotwo is an 'all in one' system, the two ESCs and the receiver are all integrated. But you need a DSM2 transmitter, which are expensive.

This video series explains it for featherweights, but it's the same for ants just with smaller motors/ESCs. This should also cover the wiring guide and which tools you can start with.
https://www.youtube.com/watch?v=7A8aBaHi234

As for servo strength, it's listed in kg/cm - so a 10 kg/cm servo with a 1cm arm will lift 10kg, but with a 10cm long arm only 1kg. They also list the degree of motion and the speed.

Post Tue May 29, 2018 6:48 pm 
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louis



Joined: 28 May 2018
Posts: 7
Location: Brisbane/Singapore


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quote:
Originally posted by Ondray:

The ant-weight starter kit is a really good start for motors and ESC's - I wouldn't worry about the nanotwos. If you want to go real cheap and nasty there are 10A brushed ESC's on ebay that work.



Ok. Not trying to save money here. I was talking about the nanotwo because this is what appears the most often when I did some research.

quote:
Originally posted by Ondray:

The ESC's themselves don't care which transmitter protocol you're using, the ESC gets a signal from the receiver which needs the same protocol as the transmitter.

The BEC in the ESC powers the transmitter and then any small servo's plug into and are powered/controlled by the transmitter. The nanotwo is an 'all in one' system, the two ESCs and the receiver are all integrated. But you need a DSM2 transmitter, which are expensive.



Clearest explanation I read so far, thanks!

So if I go with the hobbykind t6a for now, I can later change the receiver and use a Devo 7e for example?

quote:
Originally posted by Ondray:

This video series explains it for featherweights, but it's the same for ants just with smaller motors/ESCs. This should also cover the wiring guide and which tools you can start with.
https://www.youtube.com/watch?v=7A8aBaHi234

As for servo strength, it's listed in kg/cm - so a 10 kg/cm servo with a 1cm arm will lift 10kg, but with a 10cm long arm only 1kg. They also list the degree of motion and the speed.


Thank you very much for your help! Thank you Knightrous too Smile

Post Tue May 29, 2018 9:30 pm 
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Ondray



Joined: 06 Jul 2015
Posts: 138
Location: Newcastle


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Yeah swapping receivers\transmitters later is just unplug old receiver and plug in new one.

Post Fri Jun 01, 2018 1:46 pm 
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louis



Joined: 28 May 2018
Posts: 7
Location: Brisbane/Singapore


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The botbitz starter kit has been order with the Hobbyking T6A Radio Transmitter & Receiver. Now I am looking at all the other pieces I need. I have absolutely nothing except a screwdriver. So if you see I'm missing something useful, please raise your hand Smile Same if some things don't look good or compatible.

It's seems that hobbykind is the main place to order RC related components. And here is my current shopping cart, with everything coming from the Australian warehouse:

- Polyester Velcro Peel-n-stick (Black) (1 Meter)
- Turnigy nano-tech 180mAh 2S 25C LiPoly Pack (Compatible LOSB0863) (5pcs)
- 3 x Lithium Polymer Charge Pack 18x22cm Sack
- Turnigy 870E Digital Multimeter w/Backlit Display
- Side Cutters w/plastic molded handle 90mm

At least 2 pieces are missing:

- Soldering iron.
- The battery charger (with a power supply).

I'm thinking to get 40 Watt 240V Soldering Iron from jaycar. But I don't know if 40W is good or if I should better go with something like this kit .

At first I was going with this very simple charger . But it seems to output 800mah which means 4.4C with my 180mah batteries. 4.4C is too much if I understand correctly. So I have been told to look at the imax b6 ( genuine or copy ?). Currently not available from Australia. Doesn't come with a power supply. So two questions:

1. What charger should I buy? I can wait for the copy of the imax b6 to be available. Or maybe there are stores in brisbane that sell good chargers? There are a lot of imax b6 on ebay too .
2. What power supply to get? it seems that most chargers expect 12V. This one from hobbyking? Another one from kmart? A power supply on which I can plug croc clips?

A cordless drill will probably be required at some point too.

Post Sat Jun 02, 2018 12:22 am 
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Philip
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Joined: 18 Jun 2004
Posts: 3842
Location: Queensland near Brisbane


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I have used the "very simple charger" linked above for many years on smaller batteries. It is a good option. I believe you need a switch mode power supply, but others may have more understanding than I have.

The kit is a great place to start. I bought a kit to get into ants.
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Post Sat Jun 02, 2018 4:10 am 
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Valen
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Joined: 07 Jul 2004
Posts: 4433
Location: Sydney


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I got one of these recently
https://hobbyking.com/en_us/turnigy-p403-lipoly-life-ac-dc-battery-charger-au-plug.html

It's mains powered (as well as DC) which is super handy (less crap to carry around) and you can program the current you want. Just plug the balance lead in and it starts charging. I really like it.
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Post Sat Jun 02, 2018 11:33 am 
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louis



Joined: 28 May 2018
Posts: 7
Location: Brisbane/Singapore


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quote:
Originally posted by Valen:
I got one of these recently
https://hobbyking.com/en_us/turnigy-p403-lipoly-life-ac-dc-battery-charger-au-plug.html

It's mains powered (as well as DC) which is super handy (less crap to carry around) and you can program the current you want. Just plug the balance lead in and it starts charging. I really like it.


With this kind of charger, what is the precision? I mean, if the lowest possible value is 0.1A, what is the next level of power available? 0.2? 0.5? 1?

Another question: are all chargers able to charge through the balance connector only?

Post Sun Jun 03, 2018 6:57 pm 
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louis



Joined: 28 May 2018
Posts: 7
Location: Brisbane/Singapore


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I read more about the different solutions and I came to a conclusion. It seems that the best is to get a DC charger and a power supply. Because most of the higher end chargers are DC chargers. So using an external power supply allows to change to another charger without buying a new power supply. The problem is to find a good power supply at a reasonable price and to carry/stock one more thing.

So probably starting with those is not a bad idea:
- Turnigy Accucel-6 (the 80W is almost the same price as the 50W) https://hobbyking.com/en_us/turnigy-accucel-6-80w-10a-balancer-charger-lihv-capable.html
- power supply from https://www.ebay.co.uk/itm/AC100-240V-to-DC-12V-2A-3A-5A-6A-8A-10A-Power-Supply-Adapter-For-Led-Light-Strip-/172227993858 or https://hobbyking.com/en_us/12v-8a-power-supply-au-plug.html
The one from hobbyking is only 8A though, limiting the charger.

For people building bots that are (way) bigger, it seems that the Turnigy Reaktor are interesting. And not much more expensive.

BUT at this point I'm lazy. I spent so much time trying to find what is the good choice that I was about to give up building anything. So I'm going to buy the imax B6 AC V2. Because it is A$10 cheaper, it comes with more cables and I don't have to worry about the power supply. It's less powerful, some people have bad experience with it, it doesn't handle LiHV. But at some point I need to buy something and it should be way enough for small batteries that are used in ants.

It could have been the Turnigy P403, but unfortunately hobbyking is out of stock for the australia warehouse.

Post Tue Jun 05, 2018 11:03 pm 
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