Servos as speed controllers and cheapo 9g gear motors!

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daliad100
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Re: Servos as speed controllers and cheapo 9g gear motors!

Post by daliad100 » Wed Jan 02, 2013 6:27 pm

Replace the potentiometer with a trimpot or a pair of resistors. should get you close enough to deal with any wandering using radio trims.
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PJ-27
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Re: Servos as speed controllers and cheapo 9g gear motors!

Post by PJ-27 » Thu Jan 03, 2013 9:06 am

Sorry should have said, I did the hack with the resistors. A pair of 2.2Kohm ones. Initially I had no jittering and decent full proportional control fwd and rev but it just kept wondering until it was beyond the trims.

An issue with the Rx maybe?

haz
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Re: Servos as speed controllers and cheapo 9g gear motors!

Post by haz » Thu Jan 03, 2013 12:20 pm

issue with the servo boards, not the RX or trims. (the issue is that they are rubbish :P )

PJ-27
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Re: Servos as speed controllers and cheapo 9g gear motors!

Post by PJ-27 » Thu Jan 03, 2013 3:04 pm

Hahaha.

So whats the cheapest AW ESC option, BotBitz?

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Rhys
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Re: Servos as speed controllers and cheapo 9g gear motors!

Post by Rhys » Thu Jan 03, 2013 4:39 pm

Nah, I'd say the b328 (baby orangutan). It has 3A per channel, built in mixing, 5v reg, and is only 17 quid. I'm surprised people still bother with servo boards.
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peterwaller
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Re: Servos as speed controllers and cheapo 9g gear motors!

Post by peterwaller » Thu Jan 03, 2013 7:43 pm

The B328 is definitely a better bet than two servo boards but you should note that the motor drive is only 1A continuous and the regulator 100ma or less depending on the battery voltage.
So it is fine for most motors except a stalled HP type but is unlikely to provide enough 5v for a servo weapon.
At £17 they are remarkable value but you will need a programmer to load code code into them although I believe you can download the code for free.
The amount you can learn doing this for yourself is likely to increase your robotic knowledge greatly.
I havent played with one of these myself so it would probably useful if one of those who have could do a how to for any one considering using them.

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BeligerAnt
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Re: Servos as speed controllers and cheapo 9g gear motors!

Post by BeligerAnt » Thu Jan 03, 2013 8:04 pm

The Baby-O is a good solution if you put the effort into learning how to program the microcontroller. It's not that hard and there are plenty of guides available. Some good info and demo code on the Pololu website.
For a slightly gentler introduction, it is possible to use the Baby-O with the Arduino development system. Sadly, getting Arduino and Baby-O to play nicely together might actually be more difficult than just programming the Baby-O using Eclipse, WinAVR or the Atmel AVR Studio tools...

One thing to be aware of is that the motor drive chip will not survive more than a 2-cell LiPo with 12mm gearmotors. Any more than 8V will see them off without necessarily stalling the motors - needless to say, I found this out the hard way!
Gary, Team BeligerAnt

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Rhys
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Re: Servos as speed controllers and cheapo 9g gear motors!

Post by Rhys » Thu Jan 03, 2013 11:26 pm

Good point about the regulator Pete. I should have said that this will only be any good for running the rx. I usually give the weapon servo the full 7.4v for a bit more oomph, but i guess thats not for everyone as it greatly reduces their lifespan. I've tried some 7.4v rated servos, but they seem a bit limp.

As for putting the effort into programming, I have to admit I've never tried as I can't see me improving on the code marto has released on the RoboWars forum. That's written in Arduino and seems to work very well on the controller.

As for the current handling capability, I've only ever run them on 7.4v, but I believe Andy has run them successfully on 3s with HP motors, but I'm guessing a few of his controllers may have gone pop over the years. I'm currently running 4 in various ants, and they've survived the odd stall (grit in gearboxes). The only one I've blown was when I (stupidly) shorted the motor connections.
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PJ-27
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Re: Servos as speed controllers and cheapo 9g gear motors!

Post by PJ-27 » Fri Jan 04, 2013 8:52 am

Thanks for the info guys!

I have a bit of Arduino knowledge that I'll have to dust off. So the Baby-O's don't come with any firmware pre-installed? Where can I buy them in the UK or with good international delivery?

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Rhys
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Re: Servos as speed controllers and cheapo 9g gear motors!

Post by Rhys » Fri Jan 04, 2013 12:48 pm

Hobbytronics and Proto-pic stock them and are both UK based.

As for arduino knowledge, its not really necessary unless you want the challenge of writing your own code. There's a really simple guide on the RoboWars forum if you just want the boards up and running quickly.
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