Alt-BEAM Archive

Message #06237



To: "'beam@sgiblab.sgi.com'" beam@sgiblab.sgi.com
From: Wilf Rigter Wilf.Rigter@powertech.bc.ca
Date: Wed, 29 Sep 1999 14:45:05 -0700
Subject: [alt-beam] Re: master/slave bicore


As Wouter says:

74AC logic outputs used for a motor driver can source and sink more current
which really means more voltage developed across the motor = more power =
more RPM = bigger steps. Hey! that all makes sense doesn't it?

I have used 74HCT and 74AC logic up to Vcc=8V but warning! that is pushing
it well beyond the spec'd limits of 6V to 7V max (depending on
manufacturer), and likely to fail catastrophically if the outputs are
shorted or if the motor is stalled.

regards

Wilf Rigter mailto:wilf.rigter@powertech.bc.ca
tel: (604)590-7493
fax: (604)590-3411

> -----Original Message-----
> From: Wouter Brok [SMTP:w.j.m.brok@stud.tue.nl]
> Sent: Wednesday, September 29, 1999 9:38 AM
> To: beam@sgiblab.sgi.com
> Subject: Re: master/slave bicore
>
> Hi,
>
> >Now, this is my very first walker, so I'm experimenting with how to
> change
> >it's walking. The front legs don't lift quite as high as I've seen on
> the
> >others. Looking through some of the old messages, I found one that
> seemed
> >to imply that using HCT's could be a problem that way. He said he went
> with
> >AC's and got more leg movement. Anyone know what I'm talking about?
>
> Possible. One reason I could think of is that for example your motors ask
> so much current that the voltage on the outputs of the HCT drops. This
> will
> give you motor less 'power' so to say. AC's are able to output more
> current
> then HCT's so the voltagedrop at a certain output-current of the inverters
> is less for an AC, thus more 'power' to the motors (sorry for the crappy
> way of phrasing it, hope you get what I mean).
>
> I didn't read the previous messages on the subject very well, so actually
> this answer might make little sense. If you use the 240's to drive the
> motor it might be the case though.
>
> I did read though that you connected your circuit to a 6 V powersupply. I
> hope you are aware of the fact that most of those logic-series chips are
> said to operate from 2 to 6 volts. This is true for the HC's I use, maybe
> not for your chips (have a look at the datasheets), but what jumped to
> mind
> when I read your message was 'wow, 6 volts that's on the edge .... of
> course they can take a bit more, but be carefull with it'
>
> Well, hope you can use my comments.
>
> Wouter Brok.
>
>



6238 Wed, 29 Sep 1999 16:55:28 -0500 [alt-beam] Re: master/slave bicore "Richard Caudle"
content-transfer-encoding: quoted-printable


---------------------------------------------------------------------------=
-----

Par wrote:

> Well, I kinda worried about using the full 6V, but it seems to be ok. =
I
> haven't noticed any heat or anything. The main reason I went there is =
that
> that at 4.5 it's quite sluggish. I guess it might help if I use anothe=
r 245
> to bump up the signal.


I frequently use 9VDC with my HC's. They seem to work just fine. I realiz=
e that the datasheets say differently, but isn't that one of the basic BEAM=
philosophies? No cooking happens until about 15VDC. (I've done it!)

Don't believe everything you read!

Richard Caudle
richard@cqc.com
Home ICQ - Frankendaddy

---------------------------------------------------------------------------=
-----

Guardians of the sacred words: Nee, Ptang, and NeeWhon! =




content-transfer-encoding: quoted-printable



>
Par wrote:
 


> Well, I kinda worried abo=
ut using =

the full 6V, but it seems to be ok.  I
> haven't noticed any h=
eat =

or anything.  The main reason I went there is that
> that at 4=
.5 =

it's quite sluggish.  I guess it might help if I use another 245
=
> =

to bump up the signal.


I frequently use 9VDC with my HC=
's.  =

They seem to work just fine.  I realize that the datasheets say =

differently, but isn't that one of the basic BEAM philosophies?  No co=
oking =

happens until about 15VDC.  (I've done it!)

 

Don't believe everything you =

read!

 

Richard Caudle

href=3D"mailto:richard@cqc.com">richard@cqc.com
Home ICQ - =

Frankendaddy




Guardians of the sacred words: N=
ee, =

Ptang, and NeeWhon!         =






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