Chip with simple program for Toy

[Active8]

On Thu, 24 Mar 2005 15:29:07 -0800, Larry Brasfield wrote:

"Active8" <reply2group@ndbbm.net> wrote in message
news:1lfq8kwtn9br2.dlg@ID-222894.news.individual.net...
On Wed, 23 Mar 2005 16:20:31 -0800, Larry Brasfield wrote:
...
For the purposes I offered my circuit, I'm not making
the claim that it trumps John's. I got the idea it was for
a student who seemed to want to learn some things.

Then what is this supposed to mean?
quote
As far as I am concerned,
your topology is/was deeply flawed.
To "fix" it, I would
simply replace it with the topology I posted earlier.
/quote

Sorry for being too cryptic. There are a few
things to be learned from John's circuits. These
may be things the OP needs to learn, or wishes to.
He may have a better chance of learning them from
John's first oscillator or his later amplifier than he
would of learning them from what I posted.

The only claim I make for this is that it can be easily
and simply compensated in a predictable way via
analytical methods accessible to most EE students.

[Duplicate of above '<quo ... te> cut.]

I don't get your point. If you are suggesting there is
a discrepency between the quotes, I do not see it.

Since there is little in the way of any performance
requirement, any "trumps" proclamation would be
very premature.

[Duplicate of above '<quo ... te> cut.]

I still don't get your point. If you have one,
please try to spell it out a little for me. Maybe
if you consider the absence of a specification
you might see less inconsistency here.

Nah. I read you as saying the same thing, i.e., denying claims that
your circuit beat John's, 3 different times, 3 different ways. So I
rebutted 3 times the same way.

I eventually stumbled across your circuit in ascii art. So you
changed it, same topology. John fixed his, same topology. See a
pattern here?

Sure, viewed superficially. I can see many
patterns that way. But to learn whether they
mean anything requires more scrutiny.

The patterns that I was referring to are that people sometimes
change their circuits or later think of something they left out
word-wise/idea-wise. We point this stuff out to each other and it's
all cool and no one is thought less of either way. Unless you've got
someone pissed off. Nothing, absof*ckinglutely nothing you can say
or do to fix it. You have to S^2 (sit down and shut the f*ck up) and
listen. Try to understand what pissed them off. Look at yourself
honestly and fix anything that may be broken.

I'm doing a long overdue release sync so viewing your circuit will
have to wait.

Well, it was your request. If you have anything
interesting to say about it, I'll attend. But let's
not mix word games and circuit discussions.
The 'OT' is hard to render in gray on Usenet.

So now I have it in ascii art and ascii for LTSpice. I sometimes
just sit on stuff like that (file it till I need it) and then spend
time on it. There's nothing obviously wrong with either circuit nor
have I found one to be better. But I'm not worried about it now,
either. I'm sitting on 'em for future reference. I can look at the
loop gains if I get bored or need an amp like that.

Same with that integrator thing. Different ways. I've seen both FET
resets and || R bleeders. AFAIK, it's part philosophy, but your || R
does make it a LPF,

R_f
------------------
R_s * R_f * Cs + 1

so Fred was right as far as perfect integrators go.

One of my favorite integrators was a phone line with a square wave
input.
--
Best Regards,
Mike

 

[Roger Johansson]

"phaeton" <blahbleh666@hotmail.com> wrote:

this, but what would be the universal *best* method to acquire 12V from
smaller batteries (not really interested in strapping a Sears DieHard
to my belt, especially since i have a nice little tube amp that weighs
less )

What power source do you use for the tube amp?
Do you do street performances?

How about 2 9V batteries with a voltage regulator circuit? Would that
be wasteful or otherwise silly?

Batteries have a certain current delivery capacity, for example a common
battery can be marked with 3000mAh.

That means it can deliver 3000mA for one hour, or 1000mA for 3 hours, or
500mA for 6 hours, etc..

You need to find out this number for the different battery alternatives.

You did not say anything about the power rating of the amp, or what
number of watts you need for your performance. You know how many hours
you want to play before you must change battery (-ies).

So you can see what kind of batteries which can be used. You should avoid
using batteries in parallell, but it is possible if necessary.

You say that you need 12V for this unit. Have you checked if it can be
run from other voltages? Many 12V amp circuits can be used with 18V or
other voltages.

Using a voltage regulator to get 18V down to 12V is not a good idea.
Most power amps can use a range of voltages and the closer you get to the
upper limit the more power you can get out of the amp.

If you use a compressor/limiter unit, or an effects box including some
soft clipping, you don't use up the batteries so fast. Such a unit cuts
down on the really high current peaks in the signal, and it still sounds
loud. It is a good way to get a maximum of power from the batteries.

With 2*9V batteries, the small common size, you could maybe play for half
an hour if you play in a common living room and the audience is 5-10
people, if the amp is suitable for 12-18Volt, and with compressor.


--
Roger J.

 

[John Fields]

On 25 Mar 2005 09:18:46 -0800, mowhoong@hotmail.com (mowhoong) wrote:

I buld some flash wanrming, just a small power ,but i don't know how
to indentify
the kind of electrolytic capacitor that is use in the xenon circuit. I
remember we have to select low ohm.....I have try a nomal capacitor it
still work but i kown this is not the correct solution to pick & try
on the circuit.Can any person help
me in this topic. Thanks .

---
Google photoflash capacitor.

--
John Fields

 

[Lord Garth]

"phaeton" <blahbleh666@hotmail.com> wrote in message
news:1111768215.841113.32360@z14g2000cwz.googlegroups.com...

I'm looking at a small (simple (beginner)) circuit that I intend to
build. It is a portable guitar amplifier, designed for use with
headphones (think Sony Walkman) or even a small speaker (think
Pignose).

In any event, the circuit calls for 12V DC, which is pretty simple to
wrest from a standard universal wall-wart, but for the sake of
portability, batteries are the key. There is such a thing as a 12V
battery i've seen (i think it's an "N" battery) but since it's just a
little larger than a AAA, i'm going to guess that it will go dead
quickly (not a lot of total mass). I also haven't been able to dig up
a holder for it anywhere...

I know that i could use 8 AAs, or 8 AAAs, or a 9V and 2 AAs, but that
all seems excessive or otherwise strange. There's a lot of ways to do
this, but what would be the universal *best* method to acquire 12V from
smaller batteries (not really interested in strapping a Sears DieHard
to my belt, especially since i have a nice little tube amp that weighs
less )

How about 2 9V batteries with a voltage regulator circuit? Would that
be wasteful or otherwise silly?

Thanks!

You should go with batteries that have a high mAH figure, that will give you
the longest run time at the required voltage. On that basis, forget the 9
volt
cells.

 

[John Fields]

On 25 Mar 2005 18:19:16 +0100, Roger Johansson <no-email@no.invalid>
wrote:

"phaeton" <blahbleh666@hotmail.com> wrote:

this, but what would be the universal *best* method to acquire 12V from
smaller batteries (not really interested in strapping a Sears DieHard
to my belt, especially since i have a nice little tube amp that weighs
less )

What power source do you use for the tube amp?
Do you do street performances?

How about 2 9V batteries with a voltage regulator circuit? Would that
be wasteful or otherwise silly?

Batteries have a certain current delivery capacity, for example a common
battery can be marked with 3000mAh.

That means it can deliver 3000mA for one hour, or 1000mA for 3 hours, or
500mA for 6 hours, etc..

---
Yes, but...

The capacity of the battery is specified at a certain rate of
discharge, usually C/10 or C/20. That means that, say, a 12V, 3AH
lead-acid battery rated at C/10 would discharge from, say, a nominal
12.6V when fully charged to 10V when fully discharged, if current was
taken from it at a rate 300mA for 10 hours. If it was dicharged at a
rate of 3A it would probably discharge to 10V in 45 minutes or so, so
the capacity would suffer. OTOH, if it was discharged at a rate of
100mA, its capacity would increase and it would still have some charge
left to give after 30 hours.
---

--
John Fields

 

[tempus fugit]

Do you have a link to the schem? Maybe it could run on 9v. As far as battery
types, if I'm picturing the type of unit you want to build correctly, I
think that you'll have to suck it up and go with a 9v, even though it may
not last that long. You'll certainly lose any portability if you need 8 AA
cells to power the thing.



"phaeton" <blahbleh666@hotmail.com> wrote in message
news:1111768215.841113.32360@z14g2000cwz.googlegroups.com...

I'm looking at a small (simple (beginner)) circuit that I intend to
build. It is a portable guitar amplifier, designed for use with
headphones (think Sony Walkman) or even a small speaker (think
Pignose).

In any event, the circuit calls for 12V DC, which is pretty simple to
wrest from a standard universal wall-wart, but for the sake of
portability, batteries are the key. There is such a thing as a 12V
battery i've seen (i think it's an "N" battery) but since it's just a
little larger than a AAA, i'm going to guess that it will go dead
quickly (not a lot of total mass). I also haven't been able to dig up
a holder for it anywhere...

I know that i could use 8 AAs, or 8 AAAs, or a 9V and 2 AAs, but that
all seems excessive or otherwise strange. There's a lot of ways to do
this, but what would be the universal *best* method to acquire 12V from
smaller batteries (not really interested in strapping a Sears DieHard
to my belt, especially since i have a nice little tube amp that weighs
less )

How about 2 9V batteries with a voltage regulator circuit? Would that
be wasteful or otherwise silly?

Thanks!

 

[Larry Brasfield]

"Active8" <reply2group@ndbbm.net> wrote in message
news:6yzq405oz7r2.dlg@ID-222894.news.individual.net...

On Wed, 23 Mar 2005 06:49:25 GMT, Fred Bloggs wrote:
Larry Brasfield wrote:
....
You're welcome. I've set followups to sci.electronics.basics
because this kind of discussion is more topical there.
[Irrelevant FB spew cut.]
I won't analyze the chronology of events in depth, but after this,
he x-posted and broke an already broken thread.

You are mistaken. My post with followups set to a
single NG was followed by the OP's who elected to
reinsert sci.electronics.design. (I see no reason for
this to be in both groups, and have not tried to make
that happen. I very rarely crosspost.)

Get's him on top at
my 20, but I'll wager google has maintained thread integrity.

All modern newsreaders have thread views, and the
threads are formed from posts based upon the content
of the 'References:' and 'Message-ID:' headers. Since I
have maintained that linkage, chatter such as "broken
thread" and "breaking thread" is really stretching things
since no continuity is broken.

Your beef appears to lie solely with my alteration
of the thread title, aka 'Subject:' header. When the
title is not scurrilous, and I see the emergence of a
distinct subthread, I may append to the title. This
keeps things somewhat separated for those who
view post summaries sorted by title while keeping
the subthreads grouped with each other. I believe
this to be a sensible practise, so if you have any
reasoned argument against it, I would like to see it.

Occasionally so far, and more often later, as a thread
goes off topic, I prepend the title with '[OT]' for the
benefit of those who view titles alone to decide whether
to open a post. This is a common practise, and I
follow it because it seems sensible.

As for "Get's him on top", I do not even know what
header organizing method would be doing that, (and
I have no such motivation.)

--
--Larry Brasfield
email: donotspam_larry_brasfield@hotmail.com
Above views may belong only to me.

 

[Active8]

You know what? I'd actually start reading more of your posts if
you'd just say "this won't work because..." instead of something
like "Clearly, if he knew the op-amp was banging around,..."

I didn't read that post. I saw all that shit and just cut that out
for illustrative purposes.

The more irrelevant bs you post, the less likely you are to be
heard. All you're achieving is to get people pissed off. Any meat is
getting buried in the noise. If you'd just shut up for a while maybe
things would change.

I haven't yet found the circuit that you call your own in all that
noise. I doubt anyone trying to learn something here would bother.
I'm interested in seeing this circuit that allegedly trumps John's.
--
Best Regards,
Mike

 

[Robert Monsen]

phaeton wrote:

I'm looking at a small (simple (beginner)) circuit that I intend to
build. It is a portable guitar amplifier, designed for use with
headphones (think Sony Walkman) or even a small speaker (think
Pignose).

A guy I used to know had one of these portable amps, that he would carry
around and practice with. They guy was a phenomenal guitarist, and used
lots of electronic effects, but it was all portable. I don't know what
sort of battery it used.

In any event, the circuit calls for 12V DC, which is pretty simple to
wrest from a standard universal wall-wart, but for the sake of
portability, batteries are the key. There is such a thing as a 12V
battery i've seen (i think it's an "N" battery) but since it's just a
little larger than a AAA, i'm going to guess that it will go dead
quickly (not a lot of total mass). I also haven't been able to dig up
a holder for it anywhere...

I know that i could use 8 AAs, or 8 AAAs, or a 9V and 2 AAs, but that
all seems excessive or otherwise strange. There's a lot of ways to do
this, but what would be the universal *best* method to acquire 12V from
smaller batteries (not really interested in strapping a Sears DieHard
to my belt, especially since i have a nice little tube amp that weighs
less )

How about 2 9V batteries with a voltage regulator circuit? Would that
be wasteful or otherwise silly?

Thanks!

Since you are only driving a headphone or tiny speaker, 9V battery would
probably drive it for a good long time. A simple amplifier circuit using
an LM386 would be easy to build. No regulator required. If you search
for the LM386 datasheet, there is a schematic for a 200 gain amplifier
that would probably work just fine at 9V, using a guitar input. I think
guitar inputs generally swing about 10mV, so a gain of 200 will give you
a voltage swing of 2V. That into a 32 ohm headset will give you 125mW. I
suspect that's louder than you need. The input pot allows you to turn it
down. Lower output will mean longer battery life too.

These are just ideas, so you can then experiment. LM386 chips are widely
available from surplus electronic mailorder places. Also, you can get
them from more traditional outlets like digikey, mouser, arrow, or
futurlec. You may even be able to get them at radio shack.

Here is plans for one:

http://www.weirdscience.us/Personal/GuitarAmp/GuitarAmp.htm

This one uses a preamp, so perhaps an LM386 isn't going to drive a
speaker from a guitar signal by itself.

--
Regards,
Robert Monsen

"Your Highness, I have no need of this hypothesis."
- Pierre Laplace (1749-1827), to Napoleon,
on why his works on celestial mechanics make no mention of God.

 

[Rich Grise]

On Fri, 25 Mar 2005 08:30:15 -0800, phaeton wrote:

I'm looking at a small (simple (beginner)) circuit that I intend to
build. It is a portable guitar amplifier, designed for use with
headphones (think Sony Walkman) or even a small speaker (think
Pignose).

In any event, the circuit calls for 12V DC, which is pretty simple to
wrest from a standard universal wall-wart, but for the sake of
portability, batteries are the key. There is such a thing as a 12V
battery i've seen (i think it's an "N" battery) but since it's just a
little larger than a AAA, i'm going to guess that it will go dead
quickly (not a lot of total mass). I also haven't been able to dig up
a holder for it anywhere...

Since no one seems to have answered your actual question yet, yes,
you can stack batteries all day to get whatever voltage you want.

But I say, just use a 9V. They used to last pretty long in portable
radios.

I wish you'd posted the schematic - but probably, if it's just an
ordinary audio amp, it should work at 9V. At worst, you'll have to
change a couple of resistor values. You haven't built the circuit
yet, right? Here's a quick google:
http://www.google.com/search?q=simple+mic+preamp+schematic

The first couple I checked used 9V.

And yes, a mic preamp and guitar preamp are the same circuit since
a dynamic mic and a guitar pickup are indistinguishable at the
input of the amp.

Have Fun!
Rich

 

[Active8]

On 24 Mar 2005 22:26:54 -0800, boki wrote:

Dear All,
I found some green blocks on my video, when I tell to an
engineer, he tell me there are "green line" error.

Is "green line" error is a proper noun?

No. A proper noun is "Boki", "Hong Kong", or "Bastille Day" - a

specific person, place, or thing.

"green line" is a noun with an adjective (adj) in front of it.
"green line error" is a recursion of an adj n - sort of. The adj n
becomes the adj of a subsequent n.

HTH
--
Best Regards,
Mike

 

[John Fields]

On Fri, 25 Mar 2005 14:39:03 -0600, Michael Noone
<mnoone.uiuc.edu@127.0.0.1> wrote:

John Fields <jfields@austininstruments.com> wrote in
news:43k341drdd6heiomm151a6cq159mvd1qnu@4ax.com:
Sure. I'd be happy too. Matter of fact, since it's just text I'll go
ahead and paste it in here:


Version 4
SHEET 1 1052 680
WIRE -192 240 -192 0
WIRE -192 432 -192 320
WIRE -192 496 -192 432
WIRE -16 0 -192 0
WIRE -16 16 -16 0
WIRE -16 112 -16 96
WIRE 48 0 -16 0
WIRE 128 112 -16 112
WIRE 128 112 128 48
WIRE 128 192 128 112
WIRE 128 432 -192 432
WIRE 128 432 128 288
WIRE 208 272 176 272
WIRE 320 272 288 272
WIRE 320 272 320 192
WIRE 352 272 320 272
WIRE 384 240 384 144
WIRE 384 432 128 432
WIRE 384 432 384 304
WIRE 416 192 320 192
WIRE 512 0 144 0
WIRE 512 32 512 0
WIRE 512 288 416 288
WIRE 512 288 512 112
WIRE 512 320 512 288
WIRE 512 432 384 432
WIRE 512 432 512 400
WIRE 560 192 480 192
WIRE 560 256 416 256
WIRE 560 256 560 192
WIRE 592 256 560 256
WIRE 880 256 672 256
WIRE 880 288 880 256
WIRE 880 432 512 432
WIRE 880 432 880 368
WIRE 992 144 384 144
WIRE 992 288 992 144
WIRE 992 432 880 432
WIRE 992 432 992 368
FLAG -192 496 0
SYMBOL voltage -192 224 R0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName V1
SYMATTR Value 300
SYMBOL res -32 0 R0
SYMATTR InstName R1
SYMATTR Value 1e6
SYMBOL res 304 256 R90
WINDOW 0 0 56 VBottom 0
WINDOW 3 32 56 VTop 0
SYMATTR InstName R2
SYMATTR Value 1000
SYMBOL Opamps\\UniversalOpamp 384 272 M0
SYMATTR InstName U1
SYMBOL res 496 16 R0
SYMATTR InstName R3
SYMATTR Value 1e6
SYMBOL res 496 304 R0
SYMATTR InstName R4
SYMATTR Value 34483
SYMBOL voltage 992 272 R0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName V2
SYMATTR Value 12
SYMBOL voltage 880 272 R0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName V3
SYMATTR Value 10
SYMBOL nmos 176 192 M0
SYMATTR InstName M1
SYMATTR Value IXFX90N30
SYMBOL nmos 48 48 R270
SYMATTR InstName M2
SYMATTR Value IXFX90N30
SYMBOL res 688 240 R90
WINDOW 0 0 56 VBottom 0
WINDOW 3 38 55 VTop 0
SYMATTR InstName R5
SYMATTR Value 10k
SYMBOL cap 480 176 R90
WINDOW 0 0 32 VBottom 0
WINDOW 3 32 32 VTop 0
SYMATTR InstName C1
SYMATTR Value .1e-6
TEXT -226 520 Left 0 !.tran 0 .1s 0s .1s

Hi again Mr. Fields - I'm afraid I'm not very sure how to interpret
this. I think this is input for spice? Could you reccomend a free
version of spice (for windows) that could interepret this? Thanks again,

---
Go to

http://www.linear-tech.com/designtools/softwareRegistration.jsp

and download their free simulator, then cut and paste the text file I
posted in its entirety into some convenient directory, rename it with
a .asc suffix and open it with the simulator.

--
John Fields

 

[John Fields]

On 25 Mar 2005 13:28:48 -0800, "rollajarhead"
<rolla_jarhead@yahoo.com> wrote:

Hi

I am having trouble working out a solution to a control problem. What I
have is four (4) inputs needing to control six (6) outputs.

The inputs are, "Zoom", "Focus", "Menu" and "Common".

The outputs are, "In", "Out", "Near", "Far", "Menu"
and "Ground".

The two inputs, "Zoom" and "Focus", have momentary switches
(normally open) "In", "Out", "Near" and "Far" in that
order, corresponding to them. Input "Menu" has a switch aptly named
"Menu" and there is no switch with "Common".

Pushing a switch determines the input combination. Example, I push
"In", input "Zoom" is 12v DC and input "Common" is ground.
All other inputs stay at 0v DC. However there is about 150mV DC on
each. Now I push the switch corresponding to "Out", input
"Zoom" is now ground and input "Common" is 12v DC, all others
are as described as before.

Inputs "Zoom", "Focus" and "Common" have three states each,
12v DC, 0v DC and ground.

I have tried using diodes, transistors (NPN, PNP) and have looked at
logic combinations until I see 1's and 0's in my sleep. So I have
turned to those of you who are more capable then I to solve this
problem

---
I'm a little confused, but ISTM that if you have five switches and
various things that you want to happen when you push the switches,
they can be described in a matrix, like this:


SWITCH OUTPUT CONDITIONS
PRESSED
ZOOM FOCUS COMMON MENU
--------+--------+--------+---------+-------+
NONE | | | | |
--------+--------+--------+---------+-------+
IN | +12 | 0V | GND | 0V |
--------+--------+--------+---------+-------+
OUT | GND | 0V | +12 | 0V |
--------+--------+--------+---------+-------+
NEAR | | | | |
--------+--------+--------+---------+-------+
FAR | | | | |
--------+--------+--------+---------+-------+
MENU | | | | |
--------+--------+--------+---------+-------+

I've filled out what I think you want for the IN and OUT button
pressed conditions, so if you could fill out the rest of the entries
that would give us an idea of what needs to happen when the other
switches are pressed.

Also, what do you want to happen if more than one switch is pressed at
the same time?


--
John Fields

 

[Fritz Schlunder]

"phaeton" <blahbleh666@hotmail.com> wrote in message
news:1111787776.848585.3330@f14g2000cwb.googlegroups.com...

Robert- That amp design looks interesting too! I actually just
ordered a bunch of TDA2002 (replacement for the LM383) and some LM386s
from Jameco. Futurlec is awesome but they take forever to ship. The
LM386 is typically 1/2W, and the LM383 amp is 8W. My tube amp is
switchable between 5W and 15W.

The TDA2002 has a quiescent current draw (current draw when powered, but
with the output unloaded) of typically 45mA. Add to that maybe say 20mA for
the required current for producing your audio output and that yields a
typical power consumption of say 65mA.

Standard 9V alkaline batteries have a rated capacity of around 600mAh, so
expect battery life of something vaguely around ten hours. Although the
TDA2002 expects a supply voltage of 18V (or two 9V batteries in series), it
will probably operate acceptably with much lower voltage (since you don't
need 8W output capability). Nevertheless if you use two 9V batteries, the
operating cost could be quite significant. The TDA2002 is massive overkill
for driving headphones. When operating from 18V it would probably be very
easy to configure the TDA2002 to produce way too much power which will end
up burning out your headphones and/or eardrums.

The LM386 is a much more suitable part for your application. It operates
from lower voltage, so a single 9V battery would supply it just fine. The
quiescent current draw is typically around 4mA, so expect dramatically
better battery life (and you only need one to begin with). As it is the
LM386 is still a fair amount more powerful than you actually need to drive a
set of headphones, however it should do just fine. As an added bonus the
LM386 is available in a DIP8 package, whereas those TDA2002 devices come in
what appears to be a relatively cumbersome TO-220-5 package. Five legged
TO-220 parts don't fit properly in a solderless breadboard, while the DIP8
fits nicely. I highly recommend playing with your circuits on a solderless
breadboard.

Standard headphone rail to rail input and output amplifiers can operate from
as low as 3V or less and still yield adequate volume for use with
headphones. A more advanced design running from two AA or AAA batteries
could be built from a part such as the TPA6100A2.

http://focus.ti.com/lit/ds/symlink/tpa6100a2.pdf

 

[Roger Johansson]

"phaeton" <blahbleh666@hotmail.com> wrote:

I was going to use this small practice
amp as a "disposable amp" project for testing homemade effects pedals
and such. I would hate to mis-wire something in a stompbox and damage
my Reverend :-(

To protect the input of a power amp you can put two diodes in
antiparallel over its input. That ensures that the input voltage can
never get higher than plus minus 0.6Volt. Add a series resistor 1k too to
protect against very low impedance sources which could blow up the
diodes.

It would also be useful to have a small portable amp

For headphones you can probably use common op-amps, like the TL071
series. A TL072 for stereo.

Or no amp at all. You probably use some guitar effects boxes before the
amp, and most of them have output power enough to drive earphones
directly. There are schematics for thousands of guitar effects on the
web, and they are suitable as beginner projects in electronics. Check out
geofex.com, for example.

Futurlec is awesome but they take forever to ship.

That is interesting.
Have you tried them or do you base that on some information?



--
Roger J.

 

[Rich Grise]

On Fri, 25 Mar 2005 13:28:48 -0800, rollajarhead wrote:

Hi

I am having trouble working out a solution to a control problem. What I
have is four (4) inputs needing to control six (6) outputs.

The inputs are, "Zoom", "Focus", "Menu" and "Common".

The outputs are, "In", "Out", "Near", "Far", "Menu"
and "Ground".

The two inputs, "Zoom" and "Focus", have momentary switches
(normally open) "In", "Out", "Near" and "Far" in that
order, corresponding to them. Input "Menu" has a switch aptly named
"Menu" and there is no switch with "Common".

At this point, I become hopelessly confused.

First, you say you have four inputs, Z, F, M, and C.
Then you say, Z and F have momentary switches I, O, N, and F.

That's ten inputs, so far.

I need a picture. (or at least an ASCII diagram.)

Thanks,
Rich

 

[Rich Grise]

On Fri, 25 Mar 2005 13:56:16 -0800, phaeton wrote:

Thanks to everyone who's responded. Yes I should have posted a URL to
the schematic:

http://www.generalguitargadgets.com/richardo/practiceamp/craig.gif

Or maybe some more info like what OpAmp it uses, wattage and such. I'm
sorry i didn't include that before. I'm sure that it will work on 9V,
and probably would be ok with 18V. I just thought that 12V is somewhat
of an odd requirement for something portable. Of course, the circuit
is a pretty old design (iirc 1970s) and i was too young to remember
what battery choices we had then :-D It's probably even closely based
on the datasheet for the LM383

It's probably lifted verbatim. The ranges on R3 and R4 tell me that.
And yes, they just used 12V because it was common. (as in ordinary, not
circuit ground. ;-) )

Rich- I haven't built it yet, no. But I intend to. ;-) Thanks for
the tip on similarities between mic pre's and guitar pre's. I had a
feeling that an amp is an amp is an amp (more or less). I figured i
could stack batteries like that, but i've never seen 9V batteries
stacked, or dissimilar types or sizes stacked like that before in
manufactured equipment. I assumed there's gotta be a reason for it

There is - there's no point to it. Nine volts will be fine. I'e noted
the schematic indicates ranges for R3 and R4 - so you'll have to play with
them to get the gain you need for your ax and phones anyway, so just do it.


It might not hurt to look at quiescent current - I don't know the figures
on the LM383, but it _is_ a power amp, so you might want to look at low-
power opamps or preamp chips (or discretes) if you're concerned about
battery life.

For street performance, of course, you'd want a car amp and golf cart
battery. ;-)

Cheers!
Rich

 

[Robert Monsen]

Roger Johansson wrote:

Futurlec is awesome but they take forever to ship.


That is interesting.
Have you tried them or do you base that on some information?

He is right. It takes a long time for them to ship. Also, the packages
have something that looks like arabic or farsi on them, which makes it
easy to spot them amongst various deliveries and rip them open immediately.

I think you can speed up their shipping by paying more.

--
Regards,
Robert Monsen

"Your Highness, I have no need of this hypothesis."
- Pierre Laplace (1749-1827), to Napoleon,
on why his works on celestial mechanics make no mention of God.

 

[Michael Black]

(sbben@comcast.net) writes:

Hi, I'm working on a biology project at my high school. I'm raising
worms in a small tank of dirt (about 1.5 feet long 1 foot tall 1 foot
wide). I heard worms could be drawn up through the soil by passing an
electric current through it. Here's my problem, I tried using my
teachers power supply connected to two iron nails in the damp soil. The
power supply plugs into the wall and provides from 0-20 volts either AC
or DC to the probes. I don't know an exceptional amount about
electricity but I used a voltage meter to measure the voltage passing
through the soil. I measured 10 volts through the soil when the supply
was set to its highest (20 volts). Is this sufficient information to
calculate current?

I don't know, but surplus stores used to advertise surplus phone

ringers (ie from military field phones) as useful for bringing worms
to the surface. These were hand-cranked generators, which I don't know
the output of, but if someone else does it might answer the question.

Michael

I was only able to draw up one worm with this weak amount of energy. I
understand it is current and not voltage that will be the determining
factor here. I would like to design a power supply of my own. I have a
transformer that is labeled with input 120 volt and output 24 volt. If
I use this what will the current be? Is it safe relatively safe? I
would like to give the worms a good shock without using something
capable of killing a human. What is the power range I'm looking for
and what do I need to get it there (just a transformer or more)?
Should I rectify the output?

All responses greatly appreciated, thank you.

 

[Andrew Holme]

mzypt1@kolumbus.fi wrote:

Hi,

Could someone explane me some basic issues of power tranfer in RF
amplifier stages.
1. How power is transferred from power transistor to antenna from
physical point of view, is antenna acting as a load.. Can it be
referred to AF amp and speaker.

Yes, the antenna is a load. There is an impedance transforming / matching
network between the transistor and the antenna. Ideally, the transistor
should "see" a resistive load. The amount of power depends on the load
"seen" by the transistor and the magnitude of current the transistor draws
through it.

2. how can I be sure the power is transferred to antenna and not just
to warm up the transistor when decreasing the value of series resistor
(increasing power) in amlifier transistor circuit.

This can be tricky. Possibilities include:

1. Use a forward / reverse power meter
2. Tune for a dip in PA current
3. Connect a bulb in series with the antenna
4. Check with a field strength meter
5. Adjust the transmitter with a dummy load

By "series resistor" do you mean a resistor in the emtter lead of the PA
transistor? In the case of a Class C amplifier, you may be able to increase
the power level by reducing this resistor, assuming the peak-to-peak AC
voltage at the collector is not already at twice rail.

3. Can successful impedance matching be measeured as emitter current
increase. Is measured current higher ja vice versa when antenna length
is corret and all transmitter power it transferred to air via antenna.

Sometimes correct tuning is indicated by a dip in PA current, sometimes you
must tune for maximum output. I don't think you want maximum emitter
current. That should be governed by drive level.