Total cost?

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hobojoe
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Re: Total cost?

Post by hobojoe »

Thanks guys, I get Rorys kit is the best thing to start with but putting together the electronics for me will not be an issue.
I just need to understand how motor control is achieved and I am set. Still reading to figure this out. "you cant fix what you dont understand" is something I have come to learn.
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joey_picus
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Re: Total cost?

Post by joey_picus »

From what I've seen, it's always more difficult than you think it is and you must sacrifice at least the first four or five revisions to Our Lord And Saviour George Francis in a cloud of ritual smoke until you have something that works! Good luck with it if you do though - my (non-technical) advice is to see if you can package any controller in a unit with a small 2.4ghz reciever in order to have all the electronics in one module. It makes things a lot more convenient!
Joey McConnell-Farber - Team Picus Telerobotics - http://picus.org.uk/ - @joey_picus
"These dreams go on when I close my eyes...every second of the night, I live another life"
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Shakey
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Re: Total cost?

Post by Shakey »

So rorys kit and buying your own ESC's and plugging them into an RX are basically the same. The only difference is plugging, realistically if either option breaks it's not a self repair job, it'll require swapping microchips or IC's.

Now on to how ESC work:

The Servo Signal
So the signal that comes out the receiver is known as PWM signal. Let's use seconds as they're nice and big. Imagine every 3 seconds you turn the wire on, depending on how long you turn the wire on represents a number from 1-100%. Turning the wire on for 1 second is 0%, turning it on for 2 is 100%. So your receiver changes this length of turning the wire on to send information. Only now imagine instead of every 3 seconds it does this many times per second.

The ESC
Now that bit of information can't control a motor directly, this is where the ESC steps in. The ESC reads this number from the wire to now how much power to put in the motor. So if the signal is 100% the ESC is turning the motor on fully. It does this much like the receiver. Only it wants power not information, so if we want 100% power it turns the wire on for 3 seconds every 3 seconds. This means it basically doesn't turn it off. If it wants to stay still it turns it on for 0 seconds every 3 seconds, half power is 1.5 seconds every 3 seconds and so on. This is also PWM (but a slightly different kind) and this on and off action is known as switching in ESC's.

Wiring this
All you need to do is plug the servo leads into the receiver and connect the power wires to the battery and the motor wires to the motor. There's honestly not much to learn in this section. If you have more than one speed controller (2 single channels etc.) it's a good idea to remove one of the red servo wires so only one goes to the receiver, this is because both ESC's are providing power at the exact level for the receiver. If both of them try to do this they may disagree on what is exactly the right power and this disagreement can damage the part of the ESC that provides it so only 1 should be used.

Honestly I recommend one of Rorys ESC's+Receiver as I don't think there is much to learn in this wiring step. You get one of the most robust ESC's available in a small, lightweight package already with receiver. It's also a known quantity, so many ants run them and failures are very rare. It simplifies the bot this is a good thing. The less wires to come loose or be yanked out the better. In fighting robots the name of the game is to keep it simple!
Nuts And Bots - For all your components and ready built antweights!

Alex Shakespeare - Team Shakey / Nuts And Bots / Team Nuts:
AWS 44, 45, 49, 51 & 55 Winner - Far too many robots!
hobojoe
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Re: Total cost?

Post by hobojoe »

Thanks Shakey,

I get that you cant just repair an ESC, but you can carry spares and should one pop, swap it out. But thanks for the write up, what I took from it is that looking at motor "drivers" isnt really what I should be looking for, but going out to find brushed ESC's.

I run an FrSky Taranis as my transmitter so mixing for the channels ect will be managed from the radio as there is a lot of control that can be added to it.

I have all the electronics on order, as well as some carbon fibre for the chassis (its a gamble). Looking forward to it all arriving. Sadly the motors are going to be ages.

Thanks for the help.
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Shakey
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Re: Total cost?

Post by Shakey »

My point was to go for something known and trusted to work.

I think you're falling for a common mistake of thinking there needs to be more complexity behind the machines.
Nuts And Bots - For all your components and ready built antweights!

Alex Shakespeare - Team Shakey / Nuts And Bots / Team Nuts:
AWS 44, 45, 49, 51 & 55 Winner - Far too many robots!
hobojoe
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Re: Total cost?

Post by hobojoe »

lol, I do know what everyone is getting at. But it makes it very difficult for anyone to learn how things fit together when the only response is "get Rory's kit". I'm not trying to make it more complicated, I am trying to make it fun to build and trying to make sure I know how it all works.

For me a lot of the fun is the down and dirty building, finding components that work together, the playing with settings to get things to work. Getting a "ready to roll" kit removes about 80% of the fun for me.

Every forum I have checked that has an Antweight section basically says come to RW101, and then every response is to get Rory's kit. My main hobby is drones, where I have built about 7 or 8 from components because I enjoy the build. A colleague and I are going to be starting this journey together, he has zero experience with anything like this, has never even soldered before... I made sure he got Rory's kit because that is the best thing for him to do. Because for him, the main enjoyment is putting together a bot and fighting it. He cant see any joy in messing around with channel mixers and soldering, whereas I do.

I do know that, should all else fail, I can just order the kit and know it will work. But having a go at building it first is the way I always approach things, and if I waste £40 to learn, I am happy with that.
Rapidrory
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Re: Total cost?

Post by Rapidrory »

The reason I put the kit together in the first place was cause I enjoy the building and electronics side of robots. If that's what you're interested in that aspect too then go for it! There's a lot that can be learnt; I had no idea how speed controllers worked when I started, now I build them for everyone else :P

The reason why everyone tells you to get a kit is that for most new guys are interested in the driving and design of the robot, and getting a kit saves them spending a load of money on setups that either don't work or are very outdated. But for the few of us who are interested in the electronics side of things, then buying a pre made kit rather defeats the point.

There are a few ESCs out there you can buy, although few of them are particularly suitable for the job. The ultra cheap option is using servo boards which requires adding a few components to get them to work and a bit twitchy to drive with.

Depending how into the electronics/ programming side of things you want to delve, I'd encourage you to have a go at making your own controller. Doesn't have to be tiny; could just be some through hole chips on some perf board, but you'll learn a lot from doing it!
Rory Mangles - Team Nuts

Robots: Nuts 2 and many more...

NanoTwo Motor Controllers: https://nutsandbots.co.uk/product/nanotwodualesc
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Rhys
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Re: Total cost?

Post by Rhys »

But the kit is really just a good esc and a receiver. None of the work is done for you. And good speed controllers are very limited in UK antweights. Your choices are basically:

1. Rory's esc. Cheap, reliable and designed specifically for antweights.
2. Sabretooth. Expensive, heavy and only made in the USA as far as I'm aware.
3. Servo boards. Cheap but unreliable and poor control.
4. Baby o. Good controller but takes lots of effort and extra hardware to programme.
5. Make your own. Not really an option unless you have an electronics degree, lots of free time and money.

So it's not that you'll be taking a shortcut. It just seems like a no brainer. If you can find anything better that's great, but there really is very little out there on the open market that will work in a 150g robot. It's not like drones where there's an abundance of hardware.

Nobody is trying to stop you learning, just offering the best advice for a beginner so you don't end up wasting money on tat.
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Rapidrory
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Re: Total cost?

Post by Rapidrory »

Making your own isn't THAT hard once you've learnt the basics. Anyone who likes to play around with arduinos could probably put one together once they know how. You just need a processor and a motor driver chip or two. Wiring them together is fairly straight forward (no fancy I2C protocols or anything). If you used arduino code then there's probably a load of libraries that could be plugged together to make the code work. It may not be the best or the smallest controller, but it certainly teaches you a lot more than buying something off the shelf.
Rory Mangles - Team Nuts

Robots: Nuts 2 and many more...

NanoTwo Motor Controllers: https://nutsandbots.co.uk/product/nanotwodualesc
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Rhys
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Re: Total cost?

Post by Rhys »

True. I might be underestimating hobojoes knowledge. But it does speak volumes that even amongst experienced roboteers only a tiny percentage make their own. I'm just thinking how frustrating it would be if you had all the motors, receivers, batteries but couldn't use them until your learnt enough to make your own controller. I lost patience just soldering and uploading someone else's code to a b328.
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