How to Make Crystal Radio Amplifier for Speaker - Increasing volume on iPod with Mini Voice Amp

How to Make Crystal Radio Amplifier for Speaker


Hi Gang!
I've been asked a lot how to make an amplifier
for a crystal radio,
one that plays loudly on a speaker.
As you can see I got a little fancy and made
a permanent one in this jar.
I'll show you how I made it step-by-step,
and how you can make one too.
I originally saw the circuit from this good
book.
It uses an LM386 amplifier chip.
When I looked up LM386 online,
the first document I found was from the chip
maker's website,
Texas Instruments.
And in that document I found the very same
circuit
with additional details about the chip.
The book information and the website link
are in the description below this video.
Here's the circuit for my crystal radio.
And here's the earpiece that's used to listen
to the radio.
That's the part that this amplifier replaces.
And here's the amplifier circuit it gets replaced
with.
And this is how I arranged it all on my perfboard.
I'll be following that step-by-step.
Here are the parts you'll need.
First the capacitors.
Two 10 micrfarad electrolytic capacitors.
A 0.1 micrfarad ceramic capacitor.
Two 220 microfarad electrolytic capacitors.
And a 0.047 microfarad ceramic capacitor.
For controlling the volume,
you'll need a 10 kilo ohm potentiometer,
or variable resistor.
The volume will be controlled by turning the
knob.
Mine is audio tapered, or log tapered.
The alternative is linear tapered.
The type of taper tells you how the resistance,
or volume in this case,
changes as you turn the knob.
Here's a graph showing you a linear taper.
You can see that when the knob is turned halfway,
the volume will be at half.
But in this audio, or logarithmic graph,
when the knob is turned halfway,
the volume will be around 16%.
At least that's what I got when I measured
my audio potentiometer
at what looked like halfway.
Audio ones exist because of the way humans
tend to expect volume to change
as they turn the volume knob.
You'll also need a 10 ohm resistor.
A simple on/off switch.
A 9 volt battery,
and some way of attaching to the battery.
A small speaker, usually one that's 8 ohms.
This is a permanent magnet type of speaker,
which I took from a toy electric guitar.
And an LM386 amplifier chip.
My local electronics store didn't have an
LM386
but they had an equivalent one called NTE823.
If you can't find an LM386,
just look for an equivalent or replacement
part.
I didn't want to solder directly to the pins
on the chip
so I got a socket for plugging it into.
I'll solder onto the socket's pins instead.
I want this one to be permanent.
So instead of doing my usual breadboarding,
I got this perfboard for soldering everything
on to.
And now for how to make it.
The first thing I did was to plug it all into
a breadboard,
to test it.
The placement of the holes in the perfboard
match the holes
in the breadboard exactly,
so it's easy to move it all permanently to
the perfboard afterward.
The whole thing will be mounted inside this
plastic jar.
So taking into account the breadboard and
the size of the jar,
I mark the perfboard,
and cut it.
The battery will be mounted on the board.
So I drill out some larger holes,
and use some tie straps to hold the battery
in place.
I pull them only tight enough to hold it
while still allowing me to slide it out for
replacement.
I'll start with the chip.
Looking closely at it you'll notice it has
eight pins,
and in this corner is a round dot.
That dot means the pin at that corner is pin
1.
From there we know that this is pin 2, 3,
4, 5 and so on up to pin 8 right here.
I'll be soldering to the socket and not the
chip directly,
so I put the socket in the perfboard,
in a place that corresponds to where the chip
is in the breadboard.
On the back I bend a few of the pins to hold
it in place.
On the breadboard,
this row of holes are all electrically connected
together.
I use that row for connecting to Earth ground,
and battery negative.
So I make a mark on the perfboard along the
corresponding row.
Put one end of a red wire in this hole and
the other end in this hole.
Make sure there's plenty of bare wire on both
ends
for soldering to things.
That'll connect pin 6 to battery positive
later.
Put one end of a black wire in this hole and
the other end in this hole.
That connects pin 4 to ground.
While we're at it, connect a wire from this
hole to this hole.
That connects pin 2 to pin 4, but remember,
pin 4 is connected to ground.
So we're really just connecting pin 2 to ground.
Put one end of a red wire in this hole and
another in this hole.
Later we'll be putting a few other things
in these holes
to connect them together.
So pin 5 will be connected to them too.
And lets do a similar thing by putting a wire
in these holes.
That'll connect pin 8 to something else.
That something else is this 10 microfarad
electrolytic capacitor.
Since it's an electrolytic capacitor,
it has a positive leg and a negative leg.
The negative leg is indicated by this stripe
or minus side here.
Put the positive leg in this hole next to
the red wire we just put in.
Put the negative leg in this hole next to
pin 1.
So in the last two steps we just connected
pin 1 to pin 8
through this capacitor.
We did it in two steps because the chip will
be in the way.
It's getting a little crowded back here
so I'll solder a few things together to make
room.
To save headaches later, after each solder
I check it with a magnifying glass and my
meter.
The solder joint was successful so I trim
the excess wire and move on.
And here's the result after this batch is
done.
Put the 10 ohm resistor in these holes.
That connects one end to ground.
Put the 0.047 microfarad capacitor in these
holes,
oriented either way.
That connects it between the 10 ohm resistor
we'd just put in, and pin 5.
And to finish off that area,
get one of the 220 microfarad electrolytic
capacitors.
Put the positive leg here and the negative
leg here.
That connects it between pin 5 and the speaker,
which we'll put in later.
Next, put the 0.1 microfarad capacitor in
these holes.
Orient it either way.
That connects it between pin 7 and ground.
And lastly for that side of the chip,
take the remaining 220 microfarad capacitor
and put the positive leg here and the negative
leg here.
That connects it between pin 6 and ground.
Take the remaining 10 microfarad electrolytic
capacitor
and put the positive leg here and the negative
leg here.
That connects it between pin 3 and the middle
of the potentiometer,
which we'll connect next.
The potentiometer has 3 legs to connect to.
So I solder a black wire to this leg,
a yellow wire to the middle leg,
and a red wire to this leg.
The wires have to be fairly long since this
potentiometer will be
mounted in a hole in the side of the jar.
To connect it up, I put the black wire here,
the yellow wire here
and the red wire here.
That connects the black to ground,
the yellow to the 10 microfarad capacitor
we'd put in during the previous step,
and the red will go to the crystal radio's
output later.
I'll put a very long red wire in the hole
beside the red wire we'd just put in from
the potentiometer.
That will be going out a hole in the jar
for connecting to the crystal radio's diode.
Next for the speaker.
I'll put the black wire here and the red wire
in this hole here.
The polarity doesn't really matter.
That connects the speaker between ground
and the negative leg of this 220 micrfarad
capacitor we'd put in earlier.
I've soldered some long wire to two legs of
the switch
because the switch will be mounted in a hole
in the jar somewhere.
I'll put one wire here and the other wire
here.
That connects one end to the red wire that
goes to pin 6
and the other end to the battery positive,
which we'll do next.
This is the connector for plugging into a
9 volt battery.
I put the red wire, which is battery positive,
into this hole and the black wire here.
That connects the positive to the switch and
the negative to ground.
As you can see,
I've been soldering and testing connections
as I went along.
The last thing to do is solder all these ground
wires together.
For that I prepare a long wire
with a long piece of insulation stripped off
it.
I put it in this hole
and bend the bare part to reach all the parts
that should be grounded.
And here it is all soldered.
Now I can insert the chip.
Remember to pay attention to the dot on the
chip
that tells you where pin 1 is.
And that's it!
Now to mount my crystal radio amplifier in
a jar.
First I permanently put on the tie straps
for holding the battery.
Then I make holes for the potentiometer, or
volume control knob,
and the on/off switch.
Then I make a nice big hole in the cover for
mounting the speaker.
I also cut two slits in the side
for the wires for connecting to the crytal
radio.
I put everything in place.
I hot glue the speaker in place.
I also attach alligator clips to the wires
for connecting to the crystal radio.
I painted the jar black
and made some nice labels for the volume control
and switch.
I fasten the potentiometer and switch,
and screw on the cover.
Done!
Time to have some fun!
Here's my so called indoor crystal radio.
I first connect the red wire to the crystal
radio's diode.
Then I connect the black wire to the crystal
radio's ground.
As you can hear, it's fairly loud.
Now to try out the volume knob.
And here's my portable crystal radio in a
pizza box!
Well thanks for watching!
See my youtube channel, rimstarorg for more
videos like this.
That includes one showing step-by-step how
to make
your own indoor crystal radio.
And another showing how to make a portable
pizza box crystal radio.
And for variety,
see how radiation works
using an Americium pellet from a smoke detector
as an example.
And don't forget to subscribe if you like
these videos,
or give a thumbs up or leave a question or
comment below.
See you in a bit!


Increasing volume on iPod with Mini Voice Amp


>>Wade: Hi. I'm Wade Wingler with the Indata
Project at Easter Seals Crossroad in Indiana.You
know we are using iPads for
lots and lots of different things especially
communication devices. However, sometimes
the speaker built into the iPad
isn't quite loud enough to do everything you
need it to do. So, Carol is going to show
us an interesting new speaker that
can make your iPad a little louder.
>>Carol: Good morning. The tech tip is more
for the SLP or speech language therapist because
you might have all this equipment
around. I know that one not necessarily a
complaint, but a comment that is made, is
that some of the speech programs that you
find on the iPad aren't loud enough. I have
on here I have one of the touchchat keyboards
and I have the volume turned all
the way up.
>>computer voice: i want a snack
>>Carol: and for some people they want to
have it so they can be able to hear it across
the room. Well, we have a solution
for that. Toby has the mini voice amp which
is this piece of hardward where you can take
and for someone who whispers, you
can take the head piece plug it in here and
let them wear it and you can hear their voice
across the room. Now, what I'm
going to do is to take an audio cord and put
it on the iPad. Plug it into the amplifier,
turn it on.
>>Computer voice: i want a snack
>Carol: it's very clear. You can turn it up
as loud as you need it.
>>Computer voice: i want a drink
>>Carol: Which is pretty loud there. But,
this is a solution that is readily handy for
someone who is the SLP and can
have that speaker available. There are other
speakers that we can use for the iPad. But,
that's another tech tip. Have a
great day.
>>Wade: So, that's a handy way to make that
iPad just a little easier to hear. And that's
your tech tip for this week. I'm
Wade Wingler with the Indata Project at Easter
Seals Crossroads in Indiana.