Subject:
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Re: Motors & handyboard
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Newsgroups:
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lugnet.robotics.handyboard
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Date:
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Tue, 18 Feb 1997 19:29:07 GMT
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Original-From:
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Chuck McManis <cmcmanis@freegate.netAVOIDSPAM>
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Reply-To:
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CMCMANIS@FREEGATE.NETavoidspam
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Viewed:
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1312 times
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Adam wrote:
> Guys,
> I caught the mail on motors (3V etc.) and wasn't impressed.
> I just bought one of those Bulldozer Kits from Tamiya and I
> believe it contains 3V motors. Is there NO possible way of
> using these motors??? I did notice the HB motor driver chip
> getting quite hot with little load on the motors.
It has been my experience that it is easier to change the drive
circuitry than it is to change the motors. The circuitry is just
solder and chips, the motors are mechanical tooling.
Driving the Tamiya BullDozer from the HB is certainly possible
but if you do this I highly recomend an optically isolated external
H-bridge. The easiest way to do this is to take a four channel
optoisolator (available from Digikey (1-800-digikey)) to drive
an integrated H-bridge like the UDN2998W (the L293's really big
brother) I just finished building a really versatile bridge using
a MAX622 and some MOSFETs. If someone would care to lay it out
for me I'd be happy to fax them the handrawn schematic.
The h-bridge I designed connects to the motor out of any of the
handyboard, miniboard, rugwarrior, or 6.270 board and provides
(depending on the MOSFETs you pick) 15 - 50 amps of isolated
switching. It consists of the following parts:
U1 - NECP2504-4 Quad opto-isolator
U2 - MAX622 High side charge pump
RP1 - 100K x 4 resistor pack
RP2 - 330 x 4 (Miniboard, 6.270), 680 x 4 (HBoard) resistor pack
R1, R2 - 4.7K 1/8 watt resistors
Z1, Z2 - 12v Zener diodes
C1, C2 - .01uF Mylar capacitor
C3 - 1uF Tantalum capacitor
Q1, Q2
Q3, Q4 - Enhancement mode N-channel MOSFET (any MOSFET with
a full enhancement Vgs of 10v, which is nearly all
of them)
J1, J2 - Two port screw attached power connector
I'm willing to give away the design for free if someone will help
with the layout and also allow their layout to be given away for
free. My hope is to put together a gerber file in the format that
AP Circuits in Canada accepts and put that on ftp server, then
people could simply fill in their Credit card info, ftp the
file to AP and get boards back the next day. My guess is that the
'build your own' price on this will be about $30 per h-bridge
plus the cost of the board.
Now I realize that this sounds expensive, and it is compared to
fully integrated chips, however it has several advantages:
1) It optically isolates your motor power suppy and noise. This
greatly enhances system reliability in high current situations.
2) The bridge works on motors from 3volts through 12volts. This
covers a lot of motors!
3) The current capacity and cost can be tailored to meet the need.
15A MOSFETS go for about $1.75 each (you need four), 75A MOSFETS
go for abour $8.00 each.
4) It requires zero change to your computer hardware, can be easily
driven by non-Martin designs, and supports dynamic braking if you
choose (my Speed Controller PIC chip could plug right into it.)
5) Its reusable, it plugs into the board, and the motors plug into
it, you can share a pair among several robots if you choose.
Its disadvantages are:
1) Its cost, without a group purchase it will probably cost close to
$100 to outfit two of these into a robot.
2) Its size, with a double sided PC it will still be about 2 square
inches (1" x 2")
3) It uses a part (MAX622) that isn't available through most
distributors.
Anyway, inquiries to me please. Thanks,
--Chuck
--
cmcmanis@netcom.com http://www.professionals.com/~cmcmanis
All opinions in the non-included text above are the sole opinions of
the author.
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Message has 1 Reply:
 | | Re: Motors & handyboard
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| (...) Why not use the H-bridge that is already on the bulldozer? If you work backwards throught the motor driver circuitry, or use the RF controller to send commands to the dozer and see what voltages change you can figure out where the inputs to (...) (27 years ago, 19-Feb-97, to lugnet.robotics.handyboard)
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Message is in Reply To:
| | Re: Motors & handyboard
|
| Guys, I caught the mail on motors (3V etc.) and wasn't impressed. I just bought one of those Bulldozer Kits from Tamiya and I believe it contains 3V motors. Is there NO possible way of using these motors??? I did notice the HB motor driver chip (...) (27 years ago, 15-Feb-97, to lugnet.robotics.handyboard)
|
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