building a photophone

[grungemusic3001]

Has anybody here ever built a photophone? I know there are many
variations from the one Alexander Graham Bell Invented, but I'm
interested in the AM lightwave transmitter and reciever.

In the schematic it shows an operational-amplifier with the number 741
on top of it. I know what an op-amp is but whta does the number mean?

There are some parts for the project I can't find anywhere, even at
Radio Shack and Fry's Electronics. Could anybody recommend a good
on-line electronics supplier I can order componets from?

Any help would be greatly appreciated,
Thanks

 

[Winston]

grungemusic3001 wrote:

Has anybody here ever built a photophone? I know there are many
variations from the one Alexander Graham Bell Invented, but I'm
interested in the AM lightwave transmitter and reciever.

In the schematic it shows an operational-amplifier with the number 741
on top of it. I know what an op-amp is but whta does the number mean?

There are some parts for the project I can't find anywhere, even at
Radio Shack and Fry's Electronics. Could anybody recommend a good
on-line electronics supplier I can order componets from?

Any help would be greatly appreciated,
Thanks

741:
<http://www.digikey.com/scripts/DkSearch/dksus.dll?Detail?Ref=275395&Row=52031&Site=US>
USFourty-two cents, each.
This is the 8 pin DIP package.

Still available in a TO-5!
http://www.digikey.com/scripts/DkSearch/dksus.dll?Detail?Ref=275395&Row=276399&Site=US
Those are US$ 2.90, each.

I like http://www.digikey.com/ a lot.

--Winston

 

[Tim Wescott]

grungemusic3001 wrote:

Has anybody here ever built a photophone? I know there are many
variations from the one Alexander Graham Bell Invented, but I'm
interested in the AM lightwave transmitter and reciever.

In the schematic it shows an operational-amplifier with the number 741
on top of it. I know what an op-amp is but whta does the number mean?

There are some parts for the project I can't find anywhere, even at
Radio Shack and Fry's Electronics. Could anybody recommend a good
on-line electronics supplier I can order componets from?

Any help would be greatly appreciated,
Thanks

That's "the venerable 741" to you, buddy. It's just the '70s most
popular op-amp. It will probably do just fine; there are newer ones
that would do better but (a) you might not notice a difference, and (b)
it's up to you to make sure they'll work in that particular circuit.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

 

[Winston]

Winston wrote:

grungemusic3001 wrote:

Has anybody here ever built a photophone? I know there are many
variations from the one Alexander Graham Bell Invented, but I'm
interested in the AM lightwave transmitter and reciever.

In the schematic it shows an operational-amplifier with the number 741
on top of it. I know what an op-amp is but whta does the number mean?

There are some parts for the project I can't find anywhere, even at
Radio Shack and Fry's Electronics. Could anybody recommend a good
on-line electronics supplier I can order componets from?

Any help would be greatly appreciated,
Thanks


741:
http://www.digikey.com/scripts/DkSearch/dksus.dll?Detail?Ref=275395&Row=52031&Site=US

USFourty-two cents, each.
This is the 8 pin DIP package.

Still available in a TO-5!
http://www.digikey.com/scripts/DkSearch/dksus.dll?Detail?Ref=275395&Row=276399&Site=US

Those are US$ 2.90, each.

I like http://www.digikey.com/ a lot.

--Winston

'My data set has expired', huh.

Well, just type in 741 at the search prompt.
Scroll to 'Amplifiers - Instrumentation, OP Amps, Digital(35 items)'
Click on your package style and then click on 'Apply Filters'
underneath the selection boxes.

For a 741 in a 8-DIP package style, you will see:

296-11107-5-ND UA741CP IC GP OPERATIONAL AMP 8-DIP Texas Instruments Tube
General Purpose Single 8-DIP Off-Set Voltage Null Capability 2557 0.42000

LM741CNNS-ND LM741CN IC OP AMP HI PERFORMANCE 8-DIP National Semiconductor Tube
General Purpose Single 8-DIP Overload Protection 10952 0.47000

LM741CNFS-ND LM741CN IC OPAMP SINGLE 0-70DEG C 8-DIP Fairchild Semiconductor Bulk
General Purpose Single 8-DIP Overload Protection 3267 0.50000


--Winston

 

[Walter Harley]

"grungemusic3001" <grungemusic3001@yahoo.com> wrote in message
news:e8dbefb4.0404262320.6e65c507@posting.google.com...

Has anybody here ever built a photophone? I know there are many
variations from the one Alexander Graham Bell Invented, but I'm
interested in the AM lightwave transmitter and reciever.

In the schematic it shows an operational-amplifier with the number 741
on top of it. I know what an op-amp is but whta does the number mean?

There are some parts for the project I can't find anywhere, even at
Radio Shack and Fry's Electronics. Could anybody recommend a good
on-line electronics supplier I can order componets from?

Digikey was already suggested; but you might be happier with Mouser
(http://www.mouser.com), which has no minimum order fee. Digikey charges $5
extra for orders below $25.

What sort of parts are you looking for, that you can't find at Fry's? It's
possible there are more modern substitutes we can suggest.

Is the schematic online? Can you post a link? If not, can you scan it and
post it to alt.binaries.schematics.electronic for folks to see?

 

[Ben Bradley]

In sci.electronics.design, Winston <Winston@BigBrother.net> wrote:

grungemusic3001 wrote:
Has anybody here ever built a photophone? I know there are many
variations from the one Alexander Graham Bell Invented, but I'm
interested in the AM lightwave transmitter and reciever.

In the schematic it shows an operational-amplifier with the number 741
on top of it. I know what an op-amp is but whta does the number mean?

It's a part number for an op-amp. The 741 has been one of the most
popular analog IC's over the last three decades or so. Here's one
manufacturer's data sheet:

http://www.national.com/ds/LM/LM741.pdf

There are some parts for the project I can't find anywhere, even at
Radio Shack and Fry's Electronics. Could anybody recommend a good
on-line electronics supplier I can order componets from?

Any help would be greatly appreciated,
Thanks

741:
http://www.digikey.com/scripts/DkSearch/dksus.dll?Detail?Ref=275395&Row=52031&Site=US

"Your dataset has expired. Please search again."

USFourty-two cents, each.
This is the 8 pin DIP package.

Still available in a TO-5!
http://www.digikey.com/scripts/DkSearch/dksus.dll?Detail?Ref=275395&Row=276399&Site=US
Those are US$ 2.90, each.

I have a few of those from the '70's that I got at Radio Shack (or
maybe Lafayette). I was hoping they would be collector's items by now.
I'm quite disppointed to know that they're still available in TO-5.
I'm surprised anything is still made in quantity in TO-5.

I like http://www.digikey.com/ a lot.

--Winston

 

[Max Hauser]

"grungemusic3001" in news:e8dbefb4.0404262320.6e65c507@posting.google.com...

Has anybody here ever built a photophone? I know there are
many variations from the one Alexander Graham Bell Invented,
but I'm interested in the AM lightwave transmitter and reciever.

Simple or short-distance ones were projects in electronics hobby books that
I saw in the 1960s.

German military communications equipment in the 2nd World War included
high-performance telescope-based optical telephones with a few km range. I
know someone who has one, functional. (He is a hobbyist of
zweiten-Weltkrieg military technology.) His most impressive project was
restoring a four-rotor "Enigma" encoding machine but he not longer has that,
since the re-sale market was, so to speak, brisk.

In the schematic it shows an operational-amplifier with the
number 741 on top of it. I know what an op-amp is but
whta does the number mean?

Don't worry, many later op-amps were designed to fit the same pin
configuration even if you can't get a 741. The original part number for
that product was Fairchild Semiconductor ?A741 (mu for monolithic or
microcircuit, A for amplifier -- L was used for logic, in contrast; all
often with a C after the number for commercial temp grade), designed by Dave
Fullagar if I recall and introduced commercially in 1967. Sold for $1.30
each, C temperature range ($4.50 military) in 1971 when I bought my first.
In a pinch, most of the National LF150/250/350 or Texas Instruments
TL060/070/080 families will substitute readily, many later products also.
The 741 became so popular that it eclipsed the George A. Philbrick
Researches K2W, introduced 1952, as the "prototype" of the op amp, at least
in the popular imagination. Beyond that, a little research would yield rich
rewards.

 

[Max Hauser]

In case it is of interest, I forgot to mention that the 741 has a composite
npn-pnp differential input stage with balanced "helpered" npn current-mirror
load, the "helpered" mirror then establishing DC balance to a
Darlington-connected npn second stage with a single-pole minor-loop
frequency-stabilizing capacitor around it, and a complementary class-AB
push-pull output stage with series-sensing current limiting kicking in at
about a Vbe resistor drop, if I recall right. The built-in stabilizing
capacitor renders this amplifier AC-stable even at 100% negative feedback,
but at the cost of bandwidth in many higher closed-loop gain connections,
important at audio frequencies for example, but possibly OK for just comm
fidelity. Jim Roberge in his classic book _Operational Amplifiers_ devotes
some eloquence to the squandered bandwidth of the 741 in many non-DC
applications.

 

[Walter Harley]

"Max Hauser" <maxREMOVE@THIStdl.com> wrote in message
news:108uolaeia59m78@corp.supernews.com...

The built-in stabilizing
capacitor renders this amplifier AC-stable even at 100% negative feedback,
but at the cost of bandwidth in many higher closed-loop gain connections,
important at audio frequencies for example, but possibly OK for just comm
fidelity. Jim Roberge in his classic book _Operational Amplifiers_
devotes
some eloquence to the squandered bandwidth of the 741 in many non-DC
applications.

Wasn't there a decompensated version of the 741? The LM149 is a
decompensated quad 741, but I thought there was a single too. Can't
remember a part number, though.

 

[Spehro Pefhany]

On 28 Apr 2004 17:23:08 GMT, the renowned "Walter Harley"
<walterh@cafewalterNOSPAM.com> wrote:

"Max Hauser" <maxREMOVE@THIStdl.com> wrote in message
news:108uolaeia59m78@corp.supernews.com...
[...] The built-in stabilizing
capacitor renders this amplifier AC-stable even at 100% negative feedback,
but at the cost of bandwidth in many higher closed-loop gain connections,
important at audio frequencies for example, but possibly OK for just comm
fidelity. Jim Roberge in his classic book _Operational Amplifiers_
devotes
some eloquence to the squandered bandwidth of the 741 in many non-DC
applications.

Wasn't there a decompensated version of the 741? The LM149 is a
decompensated quad 741, but I thought there was a single too. Can't
remember a part number, though.

LM748

Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
speff@interlog.com Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com

 

[Max Hauser]

"Spehro Pefhany" in news:b2rv8015a1f7nj4lucmr018lj7ac3q6h68@4ax.com...

On 28 Apr 2004 17:23:08 GMT, the renowned "Walter Harley":

Wasn't there a decompensated version of the 741? The LM149
is a decompensated quad 741, but I thought there was a single
too. Can't remember a part number, though.

LM748

Since this is a nit-picking situation, permit me further to pick. (Intact
infinitive form, even in English! Not bad, eh?)

L M for Linear Monolithic (or Microcircuit) I believe, as D M for Digital
Monolithic and L H for Linear Hybrid (e.g., LH0024, LH0063).

Those prefixes of commerce imply N+tional S+miconductor, of course.

The products at issue were designed and introduced at Fairchild
Semiconductor and only later second-sourced by N+tional (among other firms).
Fairchild prefixes corresponding to NSC's LM and DM are respectively uA (my
earlier "mu" did not survive posting) and uL. ("Micrologic," or in
low-power forms, mWuL, "Milliwatt Micrologic.")

To cite National op amps, suggest LM101 for the uncompensated and LM107 for
the compensated, corresponding respectively to the uA748 and uA741.
Slightly different input stages from the Fairchild products, of course
(extra credit for drawing from memory, right now). Fairchild offered
contemporaneously fast (uA715), precise (uA725), dual 3-stage (uA739), dual
2-stage (uA749), and dual 2-stage internally-compensated (uA747)
alternatives. (A portfolio of related products always enhances a vendor's
ability to service the market.)

(BTW, I last had and referred to the information on Fairchild's product line
about 1972.)

(Spehro Pefhany, gainful employment awaits those who can solve useful
problems in this area. It is not necessary to squander much time on the
Usenet. If you are able and disposed, I encourage pursuing the usual
channels.)

 

[Scott Stephens]

grungemusic3001 wrote:

Has anybody here ever built a photophone? I know there are many
variations from the one Alexander Graham Bell Invented, but I'm
interested in the AM lightwave transmitter and reciever.

Forrest Mims wrote a bunch of books about "Light Beam Communications",
"Optoelectronics" and "LED's" et., including schematics and design
equations.

But today, with laser diodes so cheap and prolific, I'm sure a very
effective device could be made. I am interested in seeing what the top
modulation rate can be obtained with common diodes. I hear DVD laser
diodes are deliberately modulated at around 600 MHz to dither spectral
lines, prevent mode-locking.

In the schematic it shows an operational-amplifier with the number 741
on top of it. I know what an op-amp is but whta does the number mean?

Just use a more modern one, with lower current and a higher GBW product.
Just be careful for pin outs.



--
Scott

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DIY Piezo-Gyro, PCB Drill Bot & More Soon!

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