right..

i *did* previously realise that in the v=ir equation, smaller values of
r would mathematically increase v, and larger would increase :) i'm waay
shagged out, and haven't got any results any way. a week of failures.

okay, v=ir, right.

i've tried using resistors rated at a fraction than an ohm, but i'm not
getting any increase in voltage, and all the amplifier info i can find
uses a 'signal' voltage and a 'supply' voltage, ie. just using an amount
of the 'supply' voltage in proportion to the 'supply,' ie. like a
transistor.

did i miss this? is there any way to increase voltage, or are you stuck
with the max. output of your ps?

i'm trying to build some cute super mini synths and stuff for gifts, so
a bit frustrated since i'm on a deadline. i'm trying to power circuits
with single aaa batteries.. on it's own, not even enough to trigger most
leds and transistors. i have some resistors rated at .5 ohm.. it doesn't
make sense to me, but what they hey. if this can be done, i'd be cool
for some ideas on doing it cheaply, and in a small amount of space! :)

I recall a book called 'Electronics 101'. Is it still availalbe?
Where can it be found (online store?)?

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Funnily enough, your comment re the true earth provided the answer,
thank you. I rearranged it, and it works like a dream. Arcane it may be,
but it works very well:-) I thought the design looked strange -the
battery symbol's back to front for a start I think- so I've built it a
bit at a time (so as not to waste time). So far (I've done the rf and af
amps) it's worked very well.

Cool. Glad to have been of help, even if I barely had a clue :)

Anyone know how to quieten a switching power supply for use in audio
circuitry? I have a cheapy power supply laying around, and am curious...

-Darren

Funnily enough, your comment re the true earth provided the answer,
thank you. I rearranged it, and it works like a dream. Arcane it may be,
but it works very well:-) I thought the design looked strange -the
battery symbol's back to front for a start I think- so I've built it a
bit at a time (so as not to waste time). So far (I've done the rf and af
amps) it's worked very well. There are photos of a constructed Desert
Ratt at the end of

(I think that's the right link).

Dominic
Darren Reid wrote:

--

"Dominic Rivron" <karen.rivron@...> sez:

Thanks for this (and thanks to Joshua too. The amp in question is part
of:

Wow. Truly bizarre. I am too new to all this to comment usefully on such an
arcane construction...what the hell is that transistor on the inputs for? It
would seem to account for your prediliction to oscillation, if I can follow
what's going on. Anyway, you'd have a constant hum alright; there'd always
be something flowing across one of the inputs, right?

If you want a simple LM386 amp, check out National's app notes for the chip.
Use it like you'd use a standard op-amp, and you would be worlds ahead of
that strange device :)

-Darren

Darren Reid wrote:

Hmm. Did you build it straight from the app notes, or some other schematic?
Can you point us to the schematic you used, somewhere on the web? The hiss
might be from lack of a true ground...

Thanks for this (and thanks to Joshua too. The amp in question is part
of:


Dominic
--

Hmm. Did you build it straight from the app notes, or some other schematic?
Can you point us to the schematic you used, somewhere on the web? The hiss
might be from lack of a true ground...

I'm new to the world of electronics myself. I have successfully built an
LM386 amp, though....I think I used a mish mash of app notes and general
opamp theory to come up with my schematic, and I didn't get any hum or
oscillation. I *did* get nasty clipping artifacts when I turned up the
volume on my guitar :)

I built it in an empty 10-pack diskette box, BTW. They make rather
convenient small project boxes.

-Darren

Hi all

Great site, and just about at my level being fairly new at this
game. I am a pretty keen radio monitor on both VHF and UHF as well
as HF. I am very keen to get my hands on a circuit for a RF preamp
for VHF, I know they can be purchased ready made but this would be
my first project if I built it myself. I got a circuit for a mast
head preamp from
but I would Idealy prefer one that I can use next to the radio. Also
I have searched the catalogues for a transister BFY91 without
success, can another be used in its place?

If anyone has a circuit for a preamp or knows a site were I can get
one, or even a modification of the one I mentioned I would realy
appreciate the info.

Roger Harrison

If I'm not mistaken, there's a +15V gain on the LM386.... I think I read
this from National Semiconducter's PDF file on constructing sine wave
shapers...look on google, in the PDF file there's a couple of good
alternatives that don't suffer from the noise pickup.

Joshua

----
"I'm not a slave to a world that doesn't give a shit."
Pulse 8 - aim:jkerseyVCSO

I've just built an audio amplifier using an LM386, and found that though
it amplifies, there is an annoying level of backgound hiss, irrespective
of the volume setting or input. Also, it tends to oscillate at full
volume. Can anyone offer any suggestions?

regards
Dominic Rivron
--

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Lana@...

There are a lot of different ways to do this. You can
spend a lot of money and not so much time, or a lot of
time and save some money.

PLCs (Programmable Logic Controllers) are well suited
for this sort of thing. They will take in data from
your transducers and come equipped with all kinds of
switching relays and analog outputs. Look at

automationdirect.com

If you are planning on making money off this venture
and can't afford to be screwing around with things
that don't work for whatever reason, that is the best
way to go.

Altenatively you could buy a microcontroller kit,
learn to program it and get some D/A converters for
your signals, but you will probably spend a bunch of
cash on that too.

I do data acquisition and control with a program
called LabVIEW, that runs on a PC. It costs $3000 and
it lets you do all the PLC stuff, but with user
interfaces and a graphical programming language.

Omega.com is a good place for industrial transducers.

Another thought is to post to a hydroponics group.
They do exactly what you are doing but for hundreds of
acres of hothouse vegetables.
=]
Matt Hill

--- paksao@... wrote:

Hi I am a new guy here and to electronics. But I'm
hoping to learn
enough to complete some projects I have in mind.

I'm interested in setting up a system that will
control a vivarium
temperature humidity, lights pumps , etc and do it
based not only on a
schedule (ex mist 3 times a day) but also on the
current conditions(
ex too hot -> mist run fans,cut some lights). I know
I have a long way
to go before I could build it from scatch. So the
plan is to learn
the individual pieces then put them together.

some of the parts I need

build a circuit to control a relay to turn on and
off a light or pump.
build a circuit to monitor and display temp
build a circuit to monitor and display humidity
build a circuit to monitor and store temp ( probably
need a pic or pc)
build a circuit to monitor and store humidity (
probably need a pic or
pc )
...
...

Any suggestions on where to get started?

I already have some basic soldering skills and
programming skills but
i need to do a lot more.

Hope fully I can start to pick up some of what I
need here

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--- In Electronics_101@y..., justsuem@p... wrote:

a friend of mine is looking for a weller 12 volt soldering iron and
the serch hasnt turned up anything. if any one knows where to order
on it would be a big help. 73 kb9yet

Check out . I did a search using 'weller' and
'soldering iron' and there was a really big list of items. I don't
know if they have a 12 volt version. It would be worth checking out.
They also have a paper catalogue and a searchable cd-rom.

Hi I am a new guy here and to electronics. But I'm hoping to learn
enough to complete some projects I have in mind.

I'm interested in setting up a system that will control a vivarium
temperature humidity, lights pumps , etc and do it based not only on a
schedule (ex mist 3 times a day) but also on the current conditions(
ex too hot -> mist run fans,cut some lights). I know I have a long way
to go before I could build it from scatch. So the plan is to learn
the individual pieces then put them together.

some of the parts I need

build a circuit to control a relay to turn on and off a light or pump.
build a circuit to monitor and display temp
build a circuit to monitor and display humidity
build a circuit to monitor and store temp ( probably need a pic or pc)
build a circuit to monitor and store humidity ( probably need a pic or
pc )
...
...

Any suggestions on where to get started?

I already have some basic soldering skills and programming skills but
i need to do a lot more.

Hope fully I can start to pick up some of what I need here

I didn't see an answer to this. But, mail has been slow through my
server today. so forgive me if this is a repeat. "Rails" is a term
that refers to the power supply voltage, often times on a bipolar
power supply. So, if you have a typical power supply designed for op
amps and such, it might supply +15 VDC and -15 VDC. Some might
include +5 VDC is there are logic circuits. These power supply
points are often called the "rails."
Larry Hendry

--- jpotter2@... wrote:

What does "rails" mean?

For example:

"5V at the rails"

"rail to rail amplifiers"

"As for current delivery, most will do a few milli-amps, but
typically not near the rails"

"an opamp with a symmetric output swing at each rail"

"as long as your supply rails were properly adjusted."

"This pretty much slams the square right up to the rails"

Thanks,

JP

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a friend of mine is looking for a weller 12 volt soldering iron and
the serch hasnt turned up anything. if any one knows where to order
on it would be a big help. 73 kb9yet

What does "rails" mean?

For example:

"5V at the rails"

"rail to rail amplifiers"

Unless I'm mistaken (I'm still learning here), the rails are the maximum and minimum voltages the amplifier can go to. Whether it's single ended or double ended (one transistor, or two doing push pull), and what the supply DC voltage is will determine this. Of course, by the time you get to the 'rails' you've really distorted your signal...but that's good, to me. Many amplifiers are more efficient and distort the least with lower outputs. I like to turn things up to eleven though. But not for guitars. Look at what your DC supply voltage is, and that's probably the peak to peak output voltage of the amplifier, though it can be less than that depending on the circuit. In fact, it probably will be.

But I may have no idea what I'm talking about.

-Tavys

What does "rails" mean?

For example:

"5V at the rails"

"rail to rail amplifiers"

"As for current delivery, most will do a few milli-amps, but
typically not near the rails"

"an opamp with a symmetric output swing at each rail"

"as long as your supply rails were properly adjusted."

"This pretty much slams the square right up to the rails"

Thanks,

JP