Alt-BEAM Archive
Message #05702
To: "'beam@sgiblab.sgi.com'" beam@sgiblab.sgi.com
From: Wilf Rigter Wilf.Rigter@powertech.bc.ca
Date: Fri, 13 Aug 1999 12:30:10 -0700
Subject: [alt-beam] Re: 245 reverser
Hi Richard,
Don't forget that this is meant to be an effective solution only
under certain circumstances ie if you only have 245s. For example for
independently reversing 2 branched Bicores I would use one 74HC86. There are
lot's of solutions looking for problems. If you can precisely describe the
problem (ie This is what I am using now, I would like to do the same thing
using the same parts (don't tell me to use a PIC or something) but I would
like to do it using half the parts or do twice as much with the existing
parts), no doubt we would find the best solution for that problem. To put
it another way, unless there are compelling reasons, you don't want to have
to start from scratch, and like to continue along the same learning curve.
>Ah, but this is a stand alone reverser that will do two motors, and
can
>be used with a microcore... I think.
Yes, yes, yes
>Will the 245 drive BG Micro motors, or do i need to stack
One 74AC245 or two 74HC245s
>Do both motors reverse???
No only M1 reverses, M2 does not but G controls both during PNC
active high.
>I'll have to have at least 2 motors able to reverse, but they have
to work separately.
If you use h-bridge outputs then use two HC245s : PNC disable for 2
h-bridges and for reversing one h-bridge and one motors.
Only one direction control so up to 4 "simultaneous" output
reversals (but not separate independently controlled reversals)
>I've actualy NEVER built a 245 motor driver, though I have used 2
or 3 arrangements of >H-Bridges and a darlington controled switch.
The 245 is really used as a mux not a controlled invert/noninvert
function. Since most applications of the "reverser" effectively swap sets of
2 complementary inputs and 2 complimentary outputs, the application of a
mux or a controlled inverter has the same results.
regards
Wilf Rigter mailto:wilf.rigter@powertech.bc.ca
tel: (604)590-7493
fax: (604)590-3411
> -----Original Message-----
> From: Richard Piotter [SMTP:richfile@rconnect.com]
> Sent: Thursday, August 12, 1999 9:14 PM
> To: beam@sgiblab.sgi.com
> Subject: 245 reverser
>
>
5703 Fri, 13 Aug 1999 12:37:05 -0700 [alt-beam] Re: something weird with caterpillarBot "'beam@sgiblab.sgi.com'" Wilf Rigter Problem probably is the resistance of the "reverser" circuit which drives
the h-bridges. Try changing the green resistors in the Complete Walker
circuit to 2K. That should be low enough in most cases unless your motors
use high current near the limit of the h-bridges.
regards
Wilf Rigter mailto:wilf.rigter@powertech.bc.ca
tel: (604)590-7493
fax: (604)590-3411
> -----Original Message-----
> From: david perry [SMTP:davidperry@kmail.com.au]
> Sent: Friday, August 13, 1999 2:50 AM
> To: beam@sgiblab.sgi.com
> Subject: something weird with caterpillarBot
>
> okay then,
> now, as you may know my robot has been a flop ever since i found that i'd
> have to add huge batteries to get very weak movement from the motors. But
> for the hell of it i decided to trip the reverser (this is with a lantern
> battery and one motor connected) and vroom! off it went, even with one
> motor it could propel itself along with no troubles. so whats going on?
> the 74hc240 is suppose to be a switch not an amp. I don't care much about
> reversing, how can i utelise this? The extra power only lasts for about 10
> seconds, can i permantatly close the switch? Please help, need help,
> quick, *please help*!!!!!!
>
> David Perry
>
>
> __________________________________________________________________
> Get your free Australian email account at http://www.kmail.com.au/
5704 Wed, 11 Aug 1999 19:48:18 -0500 [alt-beam] Re: Contest entry beam@sgiblab.sgi.com SG wow Ian! looks good! very impressive... and sturdy too!
Hey! do i recognize those batteries?
i didn't know Chiu was gonna count for coolness and asthetics, or i would
tried faster to werk out the bugs on Lotus! i'm kickin myself now! o
well, theres always Lotus II...
-Sparky
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