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Thread: Journey to my first antweight

  1. #1
    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 Also I'm based in Australia/Singapore.

    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...tter-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-...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-4...io-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...tter-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-ki...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-ki...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?

    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
    - 10:1, 30:1, 50:1:
    - 1s, 2s, 3s: Batteries with 1, 2 and 3 cells

    Links:

    - ESC, BEC, UBEC
    https://oscarliang.com/what-is-esc-ubec-bec-quadcopter/
    https://en.wikipedia.org/wiki/Electronic_speed_control
    http://www.fightingrobots.co.uk/thre...ense-of-it-all
    - ...

  2. #2
    Ocracoke's Avatar
    Team Kaizen

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    Hey there, welcome to the forum!

    To answer your questions directly:

    - 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...tter-receiver/
    - Do I need a soldering kit to link the drive motors and the ESC?
    It will only with AFHDS but since that transmitter comes with a matching receiver, that shouldn't be an issue. Yes, if using the receiver supplied, then you'll be able to plug a servo straight into it. I suspect you will need a soldering iron to connect the motors to the drive ESCs. As for wherever the transmitter is recommended or not - the Devo 7e is normally favoured at the AW level (over in the UK at any rate) but that shouldn't stop you from using something else. My first AW doesn't use a Devo 7e, uses a completely different transmitter/receiver combination.

    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?
    I am not sure I've ever heard that before but I don't see braking mention mentioned on the page for the ESC (http://botbitz.com/product/botbitz-1...ed-controller/) so I can only presume they aren't braked?

    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?
    You wouldn't. The "low voltage" motors page on the site say the motors will support 8v so 7.4v LiPo's won't stress them at all.

    For the batteries,
    https://hobbyking.com/en_us/turnigy-...pack-5pcs.html
    should be ok? With a lipo safe bag and a charger.
    Looks good to me.

    Regarding the transmitter, I found on one forum someone talking about
    this one https://hobbyking.com/en_us/fs-i4x-4...io-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?
    I couldn't say if it was compatible or not, presumably it is because of the matching frequency specifications but don't hold me to it. As for the number of channels, that is entirely down to wherever your design needs it. Your drive will need two channels (forwards+backwards and left+right) and for a weapon, I know some folks use the rudder channel to control it (I do on my Beetleweight).

    If I go with
    http://botbitz.com/product/hobbyking...tter-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-ki...v2-mode-1.html
    Both transmitters linked appear to be V2s. The mode 1/mode 2 part defines on which side the non-sprung throttle channel is on. Typically over here, we use Mode 2 where the throttle stick is on the left, Mode 1 is where the Throttle is on the right.

    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.
    I can't answer this one. I don't use a CAD printer myself for my AWs, I craft my frames with nothing more than a sheet of plastic and a Dremel. Fiddly but satisfying.

    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-ki...usb-cable.html
    for the transmitter
    Yeah, you'll just need to keep an eye out for when it comes back into stock or find a alternate supplier.

    What tooling should I buy except a screwdriver?
    As hinted previously, I find a Dremel with a selection of drill attachments works well. If you don't fancy that, hand tools to cut plastic/metal would also work here, so a hacksaw would probably be in that list.

    What good wiring guide should I read?
    There are one or two "how to build a combat robot" threads around here that have wiriing diagrams with them, I'd go and find one of those.

    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?
    Do you have an example of this specification? Also, unless the weight limit in Austrilia/Singapore is different for the Antweights, 200g is overweight (here, it is 150g).

    Hope this helps.
    Team Kaizen

    AW: Osu, Ikari, Ramu
    BW: Shu! (Build Thread)
    FW: The Honey Badger (Build Thread)
    MW: Kaizen (Build Thread)

  3. #3
    Quote Originally Posted by Ocracoke View Post
    Hey there, welcome to the forum!
    Thank you!

    Quote Originally Posted by Ocracoke View Post
    It will only with AFHDS but since that transmitter comes with a matching receiver, that shouldn't be an issue. Yes, if using the receiver supplied, then you'll be able to plug a servo straight into it. I suspect you will need a soldering iron to connect the motors to the drive ESCs. As for wherever the transmitter is recommended or not - the Devo 7e is normally favoured at the AW level (over in the UK at any rate) but that shouldn't stop you from using something else. My first AW doesn't use a Devo 7e, uses a completely different transmitter/receiver combination.
    So with the botbitz kit, I could use any receiver I want as it doesn't come with a receiver included (unlike the nanotwo) if I understand correctly? And I could even change the receiver later if I get a new transmitter.

    What are the differences between the devo 7e and the hobbyking t6a except AFHDS/DSMX and the memory for 30 robots in the devo?

    I think I will go with the T6A first, because it's half the price of the devo 7e and I don't do anything fancy yet. But I'm curious to understand what it changes.

    Quote Originally Posted by Ocracoke View Post
    I am not sure I've ever heard that before but I don't see braking mention mentioned on the page for the ESC (http://botbitz.com/product/botbitz-1...ed-controller/) so I can only presume they aren't braked?
    What is the difference between braked and non braked?

    Quote Originally Posted by Ocracoke View Post
    Do you have an example of this specification? Also, unless the weight limit in Austrilia/Singapore is different for the Antweights, 200g is overweight (here, it is 150g).
    https://hobbyking.com/en_us/turnigyt...-08sec-9g.html
    200g was just a random number. I think the limit is 150g here too.

    Quote Originally Posted by Ocracoke View Post
    Hope this helps.
    It does! Thank you very much.

  4. #4
    Ocracoke's Avatar
    Team Kaizen

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    Indeed, you can use any receiver you like so long as it accepts the standard JR wiring to plug the servo/ESCs into.

    The Devo 7e has more channels for a start (6 I think) and is much more programmable than the T6A I believe. I use a OrangeTX transmitter that works nicely for my purposes.

    I believe the difference between braked and unbraked is that when you go from 100% to 0% (for example), the braked ESCs will slow the motor down quite vigorously to make it stop quicker. ( ).

    The servo linked looks OK, it is the torque reading that will tell you how powerful it is, which is important for a flipper. However, for an axe, speed is more important.
    Team Kaizen

    AW: Osu, Ikari, Ramu
    BW: Shu! (Build Thread)
    FW: The Honey Badger (Build Thread)
    MW: Kaizen (Build Thread)

  5. #5
    Ok, thanks for you help. I will try start to buy the pieces then.

  6. #6
    I was looking at chargers for those 2s 180mah batteries: https://hobbyking.com/en_us/turnigy-...0863-5pcs.html

    For now I have been recommended different models. But after some googling I wonder if those advice were good.

    - https://hobbyking.com/en_us/turnigy-...e-charger.html
    This is a 800mah charger. Which means 4.4C. Unless the charger is actually smart enough to use less power when charging small batteries. But for this price it would be surprising. And it actually needs an external power supply, so it's not that cheap.
    - Imax b6. Genuine or not? It's not even sure that the genuine is genuine. Some people on rcgroups.com seems to dislike this charger.
    - Turnigy P403 which has a bad review on rcgroups.com too but has the advantage of inbuilt power supply.

    For chargers that can be configured such as the Imax B6 and the P403, what is the granularity of the power? If minimum is 0.1A, next possible value is 0.2A? 0.5A? 1A?
    Is rcgroups.com forum a legitimate source?
    Are all chargers able to charge through the balance connector only?
    Last edited by louis; 3rd June 2018 at 09:37.

  7. #7
    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-...v-capable.html
    - power supply from https://www.ebay.co.uk/itm/AC100-240...-/172227993858 or https://hobbyking.com/en_us/12v-8a-p...y-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.

  8. #8
    Ocracoke's Avatar
    Team Kaizen

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    I seem to recall seeing a few Imax chargers at the last ant event I was at. I use a Accucel-6 which works fine for all of my robots, ranging from Ants to the Middleweight category though I probably want a second one at this rate.
    Team Kaizen

    AW: Osu, Ikari, Ramu
    BW: Shu! (Build Thread)
    FW: The Honey Badger (Build Thread)
    MW: Kaizen (Build Thread)

  9. #9
    Deathly Hallows's Avatar
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    I bought an IMAX B6 on eBay only to discover I needed a power adapter, so watch for that. I think the A6 version takes a kettle lead. For me it seems perfectly capable, came with leads for lots of different connectors, handles 1-6 cells, and charges at up to 6A I think. Will do a little ant battery at a lower current quick enough. You'll get one for £20 delivered

  10. #10
    Member

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    The imax b6 ac version has built in mains. So just uses kettle lead.
    I like the seperate PSU as it doesn’t heat up as much the actual controller as PSU is seperate. Plus less heavy if I wanted to take it away and not bring the ac adapter but use a PSU at the location I’m going to

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