A Quick Hello

[Spaceman]

Just ordered my TX (someone in china has literally sold me a lemon).

At the moment I am budget constrained (Between jobs) so will probably play around with some servos I have. However, once the money starts pouring in again I think the gear motor/ speed controller sounds the way to go.

Keeping it simple (stupid) and not wishing to run before I can walk, My first thoughts are for a simple pusher, maybe with a moving lifter. I appreciate that there are some fantastic kits about but I feel the need to have a go myself.

[EpicentrE]

Good decision; you'll learn a lot more by putting it together yourself than you would through assembling a kit.

Although most servos will make for quite a slow robot, there's a few things you can do to help; The easiest one is to just have bigger wheels, but if this doesn't fit in your design or is still too slow, you could look at speed modifying the servos. You do this by removing some gears from the gear chain and gluing/pinning some others together in order to reduce the overall gear reduction. If you want some more advice on this, take a picture of the gear train inside your servo and we should be able to advise on how best to modify it.

You'll of course also need to modify the servos for 360 degree rotation, but there are guides on how to do this all over the web.

[Rapidrory]

See, I'd agree it's better to build it all yourself; you learn more that way (and hopefully costs less )

If you have any experience with electronics, hacking servos for drive isn't too hard; just remove the sensor potentiometer and replace it with a pair of 2k ohm resistors (or there abouts), then just remove any stops that prevent the output from turning through 360 degrees. A compromise you can do if you want to try gear motors is to remove the servo boards from the servos, and wire them to drive the gear motors. This only works if the servo motors were of a similar size to the gear motor, otherwise you end up burning out you servo board.

One thing you do need to check is that most servos run off 6v, and a 2 cell Lipo will give out around 8v. When i was first playing around with servo board drive, i just dropped the voltage through a couple of heavy duty diodes (~0.7v drop per diode), but a heavy duty voltage reg may be better.

You'll also need to mix the control channels; other wise the throttle stick drives one wheel, and the steering stick drives the other, which is very hard to control Either you can modify your transmitter to do it with some resistors (I posted a thread on how to do this a little while ago http://robotwars101.org/forum/viewtopic.php?f=1&t=2114) or you can buy a channel mixer for a few £. (EDIT: My Blade just arrived; the sticks are all PCB mounted, so you'd need to do some pretty tricky PCB hacks, reprogram the transmitter's ATMEL controller, oor just buy a mixer :L)

[Spaceman]

Hello

Literally just as I posted last I was offered a job. So decided to order some gear motors and wheels.

So all I need to order now is battery and charger and a speed controller. Also will prob get a servo mixer.

My blade has arrived. Seams a nice enough tx., cheep and cheerfull.

Any particular reccomendations for a speed controller? Motors are 6v and 1.5 amp on stall I believe.

Also. I assume v tail mixers will function as a mixer?

Rich

[Rapidrory]

Congratulations on getting a job; try not to spend it aall on robots (It's surprisingly easy )

Both Peter Waller and I make and sell speed controllers for the antweight community, but there are a few commercial options as well (though I don't have much experience with the commercial ones as I've only used my own, and everyone I fight with regularly uses either mine or Peter's controllers)

Most speed controllers have mixing built in (or at least as an option), so you won't need the servo mixer for that. If they're the pololu HP motors, both mine and Peter's can handle them fine, as they're what most antweigts use.

The boards for my speed controllers should be back from china next week, and I plan to start shipping them in early to mid June (after exams :L)

[EpicentrE]

Congratulations on your job! Good to see you're spending the new income wisely .

There are a few different options for speed controllers. The best of the best are the Fingertech TinyESCs, but shipping them from Canada is annoying and can be expensive if you get caught by customs. There's also the Sabertooth 2x5, which is far more powerful than what you require, and big and heavy because of it. Botbitz do a couple of good ones, but they're both showing as "out of stock" at the moment.

The other option, if you're only running at ~6v, is to use a couple of servo boards from mid-size servos. Just remove these boards from the servo, modify them like you would if you were making a continuous rotation servo (so gluing the pot or replacing it with resistors), and then wire them to your motor.

Regarding mixing, if you use a two-motor controller (such as the Sabertooth 2x5) they have them built in, but if you use 2 single motor controllers (like the TinyESCs) you'll need an onboard mixer.

I'm sure someone will let me know if I've forgotten any ^^.

Edit: I'm sure Rory's boards will also be brilliant if you want to wait for one of those .

[Rapidrory]

Yeah, wouldn't advise the sabertooth, They're pretty big and expensive compared to everything else; to give you an idea, this is one of mine next to a sabertooth (It's a dead sabertooth that I'm raiding for parts :L)



The FingerTec ones are about the same size as mine, but they only drive one wheel each, so as was said before you'll need two.

The downside of mine is that they're new so although they look very promising in preliminary tests (https://www.youtube.com/watch?v=7wW33Ph ... e=youtu.be), I can't say how reliable they are in the long term. Hopefully they'll run indefinitely, but I can't say until people have been running them for a while. I do plan on offering a warranty though.

[EpicentrE]

I hate to move away from Fingertech since I love them, but Rory's boards, if they turn out to be as reliable as hoped (and if the HP one is going to be available ), are looking unbeatable in almost every way.

[Rapidrory]

Hehe, well that's the plan anyway

(Just so you know, a few HP boards were ordered alongside the regular ones, having been entirely redesigned with a much better layout to take up to 20V reliably, so they should be available for order soon too )

[Spaceman]

For now ive ordered a sabertooth to get me going. I am sure that down the line I will change to smaller controllers and probberly become a customer for your boards.

Also got a battery and charger on order so once stuff arrives i should have all the core bits to make my first ant. I will try to set up some kind of build diary one here as i enjoy those others have done.

Rch