Getting started with electrics

[FAT MAN]

Hello to everyone,
Ryan, my Autistic son, has been a fighting robots fan for a long, long time. We made a simple rambot with spikes 3 years ago and were ready to take part in battles but he couldn't handle the prospect of his bot getting bashed so we postponed everything.
However, he might just be able to now, so we are going to upgrade it and hopefully get to RoboChallenge in Yeovil 2015.
I need some ideas regarding the layout of the circuit board needed and details of failsafes (I really don't know much about them). Do I need a separate battery for each motor drive? What to use for a removeable link, I was thinking of a 30A flat car fuse - would that work?
The components that I think we need - 5 cell LiPo battery for 18 volt
2 X drive motors
Speed controller
Removeable Link + LED
Receiver + battery
We've enjoyed reading many of your build diaries and we hope to post one when we get started in earnest.
We're looking forward to all your ideas with great anticipation.
Ta Ta for now from Ryan and Colin.

[leorcc]

Hi Ryan and Colin,

Do I need a separate battery for each motor drive?

No, you can use 1 battery and have both speed controllers feed off that. The motors get their power from the speed controllers.

What to use for a removeable link, I was thinking of a 30A flat car fuse - would that work?

Provided to motors don't draw as much current yes, but I would use a fuse more suited to the battery you intend to use. I normally do not use a fuse as a link, but a RC connector in a loop between the battery plug and the ESC's. A EC3 or EC5 connector or Deans Ultra are very good for those.

The components that I think we need - 5 cell LiPo battery for 18 volt

That is not a bad choice provided your motors and speed controllers can handle it.

2 X drive motors

18V Drillmotors or Banebots gearmotors are very usable.

Speed controller

1 or 2, depending on the type. Two of the Botbitz TZ85a ESC's are very nice for featherweight drives, and not a big assault on the wallet.

Removeable Link + LED

Correct

Receiver + battery

The receiver can get its power from the TZ85a, so it does not need its own battery.

I'd say your shopping list is pretty much complete apart from a frame and armour of course.

Good luck and happy building.

Attached a wiring diagram for a 2 ESC layout wit link and fuse (mandatory for Lipo).

dual esc setup diagram.jpg

[daveimi]

Hiya, my 5 yr old has mild autism and the loud noises and hectic routine / meal times etc were a struggle. The other big thing is that the Robochallenge champs is full combat with the spinners etc. The live events are a lot more laid back with minimal damage so dunno if you'd be better getting to some of those first to see how he is. I haven't managed the champs yet because of the same reasons.

Edit - I will go against what everyone says and say that from my own experience the easiest way to get in the arena is a pair of Gimson motors, Sabertooth controller and a cheap radio Rx/Tx set. Get a cheap 12v nihm battery for £15 and £7 charger from Component Shop Website, and use Deans connectors to solder up a removable link. Drill some wheels to 13.5mm and hammer in 3/8unf brake pipe connectors so they screw straight on to the Gimsons. Job done. There are a million ways to build a robot but have found this to be extremely simple and easy to fix at the events.

Edit 2 - You can buy Antweight Kits and Feather Kits with everything in that go together like lego. Also worth considering, can provide you info if you need it.

[leorcc]

Gimson has supply issues with the GR02 that is why I did not recommend them.

[daveimi]

Oh ok. Been a few months since I bought any feather bits. I didn't mean it to sound bad, erm just meant if you can get them it saves locking clutches up etc.

[FAT MAN]

Hi,
Thanks very much guys for the very useful info. Ryan is very excited that you're out there willing to help him.
Do we have to use 2 ESC's because I was thinking of using 1 via a mixer. If we can use 1 ESC how do we wire it to 2 motors?
And can someone explain failsafes, What are they? Do we need one? How does it fit into the circuit?
Thanks again guys,
Colin & Ryan

[harry hills]

Hi Colin, Hi Ryan.

If you have a dual channel esc (one like the sabertooth, scorpion or ragebridge) that has two outputs then you only need the one. The Botbitz are single channel, each one only controls a single motor so you will need two.

Failsafe is not really an additional component (although it can be) It just means that when your transmitter is turned off your robot stops moving. In order to enter a competition you will have to pass a tech check where among other things you will have to put your robot into full forward and switch off your transmitter, if the robot's motors stop turning you pass and if not then you haven't failsafed and will fail the tech check. You can normally set this by getting decent radio gear and rebinding the transmitter and receiver with your settings and trims in neutral.

Harry.