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An $800 robot... mlw 07-06-2005
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Posted by Brian Dean on July 9, 2005, 10:55 am
On Sat, Jul 09, 2005 at 01:24:48PM +0000, blueeyedpop wrote:

> I think that is the tank WallMart was selling some time back.

That was $150 wasn't it, not $50?

> The neat thing about the DMM is you just plug in, and go...

Sorry, I'm more inclined to use a single $99 MAVRIC-IIB for this and
control the whole 'bot, not just the drive motors :-)

Not that the DDM is not nice - it looks very nice. I'm sure it is a
fine product, just not my cup of tea.

I'm still be interested in that base for $50, though. Randy?

-Brian
--
Brian Dean
ATmega128 based MAVRIC controllers
http://www.bdmicro.com/

Posted by blueeyedpop on July 10, 2005, 9:48 am
If I understand the DMM correctly, it does GPS, and trajectry control. Don't
know if the "hood is open" for more user code though...

> On Sat, Jul 09, 2005 at 01:24:48PM +0000, blueeyedpop wrote:
> > I think that is the tank WallMart was selling some time back.
> That was $150 wasn't it, not $50?
> > The neat thing about the DMM is you just plug in, and go...
> Sorry, I'm more inclined to use a single $99 MAVRIC-IIB for this and
> control the whole 'bot, not just the drive motors :-)
> Not that the DDM is not nice - it looks very nice. I'm sure it is a
> fine product, just not my cup of tea.
> I'm still be interested in that base for $50, though. Randy?
> -Brian
> --
> Brian Dean
> ATmega128 based MAVRIC controllers
> http://www.bdmicro.com/



Posted by Randy M. Dumse on July 10, 2005, 11:24 am
> On Sat, Jul 09, 2005 at 01:24:48PM +0000, blueeyedpop wrote:
>> I think that is the tank WallMart was selling some time back.
> That was $150 wasn't it, not $50?
> ...
> I'm still be interested in that base for $50, though. Randy?

Yes these were originally $150.

W.E. Cole posted on the DPRG list that Walmart was clearing these tanks
out at $50 this spring. He got two, and I asked him to get me one also.
Many but not all the Walmarts followed suit. Also these tanks can be
found on eBay sometimes going around $50 up.

So no, NMI isn't selling the tank base. Yes it is a nice one. Watch out
for the motors. They measure around .6 ohms static at worst case, which
means startup voltage will be ~10 - 20A. They're a little hard on
H-bridges. Once rolling, they're around an Amp or two.

The DDM has two of our 5A Hbridges on it. Without heatsinks they're good
for 2A. They work here by pulsing and going into protection on start up.
The PWM rate keeps applying pulses of power until the tracks get moving.

--
Randy M. Dumse

Caution: Objects in mirror are more confused than they appear.



Posted by Brian Dean on July 10, 2005, 9:05 pm
Hi Randy,

On Sun, Jul 10, 2005 at 10:24:47AM -0500, Randy M. Dumse wrote:

> W.E. Cole posted on the DPRG list that Walmart was clearing these
> tanks out at $50 this spring.

That's a great deal.

> Watch out for the motors. They measure around .6 ohms static at
> worst case, which means startup voltage will be ~10 - 20A. They're a
> little hard on H-bridges. Once rolling, they're around an Amp or
> two.

I'm currently working on an h-bridge that sounds perfect for this.
I've tested at over 30 Amps continuous with a heat sink and they were
asking for more. I have yet to actually push the limits to determine
the upper bound. They will be for sale soon, but until then you can
see 5 of them here, bottom photo, with a variety of heat sinks:

http://www.bdmicro.com/darpa-gc

Click the photo for a larger shot.

-Brian
--
Brian Dean
ATmega128 based MAVRIC controllers
http://www.bdmicro.com/

Posted by D. Jay Newman on July 9, 2005, 3:28 pm
blueeyedpop wrote:
> I think that is the tank WallMart was selling some time back.

Yes, this definately looks like the 1/6th scale M5 Stuart
Tank (R/C) that Walmart is still selling for around
$150.

They're a nice base and will haul a heavy payload,
but the motors/treads are fairly loud and wake my wife. :(

I still have a spare for sometime later when I want
to use it. And this time I'll keep the top with the
(non-functional) gun.
--
D. Jay Newman
http://enerd.ws/robots/

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