Antweight help

[Max]

Hi everyone,

We are planning on making a couple of antweight robots at school, a lifter and a spinner.
I'm thinking we can use 2x botbitz 8v 50:1 motors, 2x botbitz 10a escs, one 2s 350mah 20c lipo (http://www.hobbyking.com/mobile/view...=&idparentcat=).

Then we just need RC gear.

Does that all sound alright?

Also what kind of size servo do we need for a decent lifter?

Cheers

[razerdave]

Sounds good to me, but 10A is rather excessive. In ants you can get away with 3A easy (been running my 4WD one on 3A controllers, never let me down)

Lifter servos, I would recommend a HS82-MG, metal geared, can take 7.4v and quite quick when needed (check out any video of Stewie to see what a full 90 degree sweep is like).

One battery ? Or is that a typo ?

[Max]

I was thinking just one battery per robot, is the capacity too small?
Can the receiver take 7.2v or do I have to wire the lifting servo directly to the battery?

[razerdave]

Sorry Max, I was sleepy when I wrote that . The capacity is fine, in fact for a competition one it's probably overkill. Bulletproof runs one the same size and he takes about an hour and a half of constant use to even slow down.

As for lipos to receivers, NEVER DO IT! They just can't take it. Take the positive from the servo and wire it in before the speedos. The other 2 can do in the RX. Don't forget to cut 1 wire from the botbitz ESC's because they will have a BEC each, only need 1.

[Max]

Thanks Dave,
Would this brushless motor be appropriate to run a horizontal bar spinner (directly connected so 1:1 ratio)
http://www.hobbyking.com/mobile/view...dparentcat=518

The weapon would be like this one:
http://www.fightingrobots.co.uk/thre...robotics/page3

It is 1400Kv and would run on 2s giving about 10,000 rpm which sounds way to fast to me but I'm not sure!

[razerdave]

A little heavy perhaps but perfectly useable. Just be wary of the wires, they look like they sit a bit close to the 'barrel' of the motor.

[Max]

Ok, final parts list for 2 antweights:

4x Motors http://www.technobotsonline.com/polo...gearmotor.html
2x Motor Controller http://www.technobotsonline.com/polo...a-mc33926.html
4x Wheels http://www.technobotsonline.com/polo...l-42x19mm.html


2x battery http://www.hobbyking.com/mobile/view...=&idparentcat=
1x weapon servo http://www.hobbyking.com/hobbyking/s...g_0_12sec.html
1x brushless weapon motor http://www.hobbyking.com/mobile/view...dparentcat=518
1x brushless controller http://www.hobbyking.com/mobile/view...dparentcat=186
Connectors (for battery, motors etc.) http://www.hobbyking.com/hobbyking/s...0pcs_set_.html and http://www.hobbyking.com/hobbyking/s...0pcs_set_.html
2x Transmitters/receivers could use these: http://www.hobbyking.com/hobbyking/s...x_Mode_1_.html
1x BEC http://www.hobbyking.com/hobbyking/s...BEC_3A_5v.html


Any thoughts on wheels, esc, brushless esc or brushless motors?

[harry hills]

Well, personally I'd go for cheaper motors like the botbitz, but shipping and time etc. No comments about the controller. Wheels are very heavy though, but are used.
You won't need BEC's the brushless esc has that built in.

[plargen]

you can get them cheaper from china
http://www.ebay.co.uk/itm/12mm-6V-DC...item25846a98ee

[marto]

Remember that controller will need something to drive it. Like an AVR or arduino. If you want something lower current which is relatively cheap got the Baby-O B328 which is 2A.

Steve

[Max]

Ahh, didn't realise that! I guess we'll have to make up a simple circuit to covert the ppm signal from the receiver to the pwm circuit for the motor driver. Obviously wont have room for an arduino but I guess we could design a circuit with an ATMega chip programmed on an arduino then plugged into a smaller custom circuit- that could allow us to introduce some autonomy in the future.

[marto]

Yeh or could just use our 10As as you suggested initially.

[Max]

Too late as already bought those polulu ones! May try to see if we can return them but will be a bit of a pain

[Max]

What capacity 2s lipos do most people use for competitions? One is for a flipper bot and one is a spinner. Looking at the battery we've got it takes up loads of room and weight (http://www.giantshark.co.uk/product/...c-lipo-battery) (almost 40g).
Just don't want to order something too small! The smallest I've found is 120mah which weighs 11g- would this be suitable or can anyone find a smaller one!
Thanks,
Max

[harry hills]

Sounds about right. I run 120-180mah packs in mine.