Alt-BEAM Archive
Message #12579
To: beam@sgiblab.sgi.com
From: Ben Hitchcock beh01@uow.edu.au
Date: Mon, 27 Mar 2000 12:51:14 +1000 (EST)
Subject: [alt-beam] Re: JOEL HIRTLE
You can find Joel's ICQ number (34721998) and other ICQ numbers at:
http://wollongong.apana.org.au/~ben/icq.html
You can even add your own number to the page!
Ben
> Hey I had to format my PC and lost all my ICQ names and other BEAMish info. Joel can you please e-mail me your UIN (use jester96@iname.com, not this address)? Thanks. Also anyone else I had on my list.
>
> PLEASE no one reply to this on the list as it's not really BEAM related (well only sorta)
>
> Chris
>
> ---------------------------------------------------
> Get free personalized email at http://www.iname.com
--
Nothing is foolproof to a sufficiently talented fool.
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>
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>
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>
> Timothy...
>
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>
>
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> ______________________________________________________
>
12581 Sun, 26 Mar 2000 19:57:11 PST [alt-beam] Re: Cap across the motor leads?? beam@sgiblab.sgi.com "Timothy Flytch" Toy companies are notorious for using what every they have, or can get
cheap... They(motors) may have been some R/C rejects...
Timothy...
>
>Thats partly the reason we (RC modelers) put caps across our motors.
>However voltage spikes aren't that big a deal alone. The problem we have
>is
>with RF noise from the brushes in the motors. The caps relive some of the
>voltage spikes, which remove alot of the sparking from the armature.
>
>
>James Taylor
>"Edgar The Hate Bug"
>URL: http://fly.to/springmeadows
>ICQ 14888587
>----- Original Message -----
>From: Evan Dudzik
>To:
>Sent: Sunday, March 26, 2000 10:54 AM
>Subject: Re: Cap across the motor leads??
>
>
> > okay, this is a common thing especially among r/c cars
> > and planes and boats... they are for leveling out the
> > voltage spikes, etc. to the motor, they keep the
> > motor running off a smoother voltage/current...
> >
> > --- Meabadboy@aol.com wrote:
> > > In a message dated 3/26/2000 12:14:32 AM Eastern
> > > Standard Time,
> > > sparkyg@seark.net writes:
> > >
> > > << remember to tell him to put a .01uf cap across
> > > his motor leads. >>
> > >
> > > Hi,
> > >
> > > I know partially why you do this, noise, ect. ~ but
> > > the other day I tore
> > > apart a small toy airplane that the kids hve long
> > > sence quit playing with for
> > > parts ~ the plane was in the shape of a f-15 and had
> > > a small gearbox with a
> > > front and rear flashing lights ~
> > >
> > > Anyway the motor had a Resistor sodered to each post
> > > on the motor (22 ohm) ~
> > > but there was 3 caps sodered to the motor as
> > > follows:
> > >
> > > 1 cap was sodered between the posts of the motor had
> > > a #102 (small disk cap).
> > > 2 caps were sodered with one of the leads to the
> > > case at a common point of
> > > the motor and one to each of the posts so that each
> > > post went to a common
> > > point of the metal case of the motor thru a #102
> > > disk cap
> > >
> > > why did they do that? ~ is there a purpose to
> > > this???
> > >
> > > Steve
> > >
> > >
> >
> > =====
> > +------------------------+
> > |http://surf.to/photovore|
> > |Photovores online! |
> > |Evandude Dudzik |
> > +------------------------+
> >
> > __________________________________________________
> > Do You Yahoo!?
> > Talk to your friends online with Yahoo! Messenger.
> > http://im.yahoo.com
> >
>
______________________________________________________
12582 Mon, 27 Mar 2000 14:19:48 +1000 TO MUX OR XOR ,THAT IS THE QUESTION was : Reverser circuit drawn "Wilf Rigter"
> The "reversed" reverser is one of many little conundrums people run into
> when learning about these circuits.
>
> The reverser layout drawing on Ian's site, is of a 240 chip laying on its
> back with pins mirror image compared to the data sheet. The layout drawing
> contains TWO reverser circuits on one 240 chip. This is useful for "three
or
> more" motor walkers and other applications. In case of 2 motor walkers
you
> will only need one of those reversers and the remaining 4 inverters can be
> used for other things like the master/slave bicore or motor drivers. So
when
> experimenting with this reverser on a breadboard, use just one half of the
> 240 chip wired up as one reverser. As always GROUND UNUSED INPUT PINS to
> avoid unexplained problems.
>
> The reverser circuit works by letting the control pin determine if input
> signals are to be inverted or not at the ouputs and this function makes
this
> design a XOR reverser as distinct from a MUX reverser.
>
> <>
>
> The first figure shows a small part of Ian's XOR reverser with the
> resistor connected across an 240 inverter between pin 2 (input) and pin 18
> (output). This is one of four inverters controlled by tristate enable pin
1.
> When pin 1 is 0V, the inverter "inverts" signals from input to output ie
a
> 0V signal at the input pin produces a +V signal at the output pin and
> conversely a 0V signal produces a +V output.
>
> When pin 1 is positive (+V) , then the inverter output is an open circuit
or
> floating pin. A signal connected to the input pin 2 passes through the 47K
> resistor unchanged to the output pin 18 when the inverter output is open
> circuit ie V input = V output. Unlike the inverter output, in the
> noninvering mode, the 47K resistor can only drive very small loads. This
> restricts the use of this reverser to driving output loads like a slave
> bicore or a HC139 type h-bridge but NOT a 4 or 6 transistor h-bridge
input!
> Ian's almost complete walker is an example of this XOR reverser used
between
> the master bicore outputs and the slave bicore inputs.
>
> The reverser works by inverting or not inverting 2 inputs connected to
> bicore or microcore outputs. For a bicore whose output signals are always
> complementary polarities, this inverting or non-inverting of signals is
> equal to swapping outputs. When used with a microcore the result is the
same
> although not strictly speaking by swapping microcore outputs but rather by
> changing the polarity of the rest state at motor driver inputs (motor not
> running) and using an inverted polarity for the active state motor state.
>
> In fact, this type of XOR reverser can be much more easily made with a
> 74AC86 XOR gate, in which small motors can be driven directly from the
> output pins without additional buffers or h-bridges and which I posted
many
> moons ago.
>
> The other type of reverser is a MUX or multiplexer which consists of a set
> of switches that are controlled to connect outputs to different inputs.
The
> 4016/4066 and HC4066 are the simplest of this type. There are many beam
> designs by Mark and others that used the 4016 or 4066 quad bilateral
> (analog) switch which the equivalent to four switch or relay contacts that
> can be individually switched on or off.
>
> These older designs used a whole 4016 chip and an extra inverter for one
MUX
> reverser which made this design less popular than the XOR reverser. But a
> new 4066 MUX WALKER design is much more efficient and in addition provides
> left/right turning circuit as well as small motor drivers in this simple 2
> chip circuit.
>
> <>
> Each of the 4016/4066 sections is not actually a mux with only 1 input to
1
> output selection (1 to 1) but several sections can be wired in different
> configurations to make up a N input to 1 output mux . The 4051, 4052 and
> 4053 chips are other versions offering single 8 to 1, quad 2 to 1 and
> triple 3 to 1 mux decoding respectively. Just to show you how versatile
> these chips are check out Steven Bolt's designs or my own 4053 voltage
> doubler design.
>
> A relay with Double Pole Double Throw (DPDT) contacts is a good example of
> an electromechanical MUX reverser is capable of switching amps of motor
> current and is very popular with other robotics groups. The same relay is
> also used as an H-bridge. However there is a penalty for using relays:
power
> and size. Relays are bigger than equivalent semiconductor h-bridges and
the
> coil of a relay may require 50 ma of wasted power to turn on. Lastly rated
> minimum coil voltage is 5V and many beam project run at 2-3V On the plus
> side, the motor is efficiently connected, with very low losses through
> metallic contacts, to the power source and you are less likely to smoke a
> relay compared to an h-bridge.
>
>
> enjoy
>
> wilf
>
> > -----Original Message-----
> > From: Ken Hill [SMTP:hardlock@internetcds.com]
> > Sent: Saturday, March 25, 2000 11:43 PM
> > To: beam@corp.sgi.com
> > Subject: 2nd post - Anyone please? - Reverser circuit drawn wrong??
> >
> > Regarding the 240 reverser circuit from the beam online site, If appears
> > that from the data sheet of the chip that the number 2 inputs and
outputs
> > should actually be reversed on the drawing? Those two bottom buffers
run
> >
> > the other direction across the chip don't they? Or does it matter? Or
> > should they just be moved up one pin on the chip?
> >
> > I assume that the IN's are enable + and - from the core or whatever
brain
> > circuit, and the OUT's go to + and - motor bridge IN's. When it
reverses,
> >
> > these switch polarities at the reversers output? Using 2 opposite
facing
> > LEDs across each of the outputs, I can't get it to work that way on the
> > breadboard. (either as drawn, or reversed). I can verify that the
buffers
> >
> > are turning on with a low to the enables, but no reverse. (And they said
> > this was a "very easy" circuit..... :)
> >
> > Also, I found the circuit for the 245 H bridge and the 139 reverser / H
> > bridge circuit. If I use the 139 I can eliminate both the 240 reverser
> > and
> > the 245 H bridge, correct? (I understand the current limits and the need
> > to
> > stack them).
> >
> > Thanks, Ken
>
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