Maker Pro
Maker Pro

Cheap, simple way to generate 200Hz sine wave

R

Rich Grise, but drunk

Jan 1, 1970
0
Some things just aren't cheap and simple.

Anybody want to bet a beer that he'll never be back again? Another one
for the googlegroupie bin, I fear.

Cheers!
Rich
--
-----BEGIN GEEK CODE BLOCK-----
Version: 3.1
GAT(E P) dpu s: a++ C++@ P+ L++>+ !E W+ N++ o? K? w-- !O !M !V PS+++
PE Y+ PGP- t 5+++)-; X- R- tv+ b+ DI++++>+ D-? G e+$ h+ r-- z+
------END GEEK CODE BLOCK------
 
D

David L. Jones

Jan 1, 1970
0
Ancient_Hacker said:
As others have noted, youy're unlikely to be able to get 1% stability
(I assume you mean frequency stability) without an adjustable pot, and
that's going to blow your budget, unless you're content with filing
away at a resistor to tune it.

About the lowest-cost really stable solution I can think of:

a tiny crystal (62 cents, Digi-Key)
an oscillator-divider chip (approx $1)
a few resistors to do a simple D/A ( 10 cents)
one transistor amplifier (12 cent transistor, two resistors)

Under $2. I don't think you can do much better than that, unless you
go to high quantities and have a custom microcpu masked.

The PIC 10F200 series have a 1% internal oscillator which should be
good enough, cost is around 50 cents in volume.
Add an RC filter to the PWM output and you have a three component
soution for under $1.

Dave :)
 
Is there a simple way to generate a 200Hz sine wave? I'd like something
with no tuning involved, 1hz accuracy, powerable from 2 to 3V. I
believe harmonics are okay, but I dont know how to quanitify them. They
should be quiet enough to not be audible when listening to just the
tone on headphones. The cost of the circuit needs to be less than 50
cents.

How about building an electrically sustained thumb piano? Little piece
of spring steel cut to length and sitting over some sort of magnetic
transducer that couples it to an oscillator circuit. Optionally run it
on an overtone and divide if a piece resonant at 200hz would be too
big. With luck you'd only have to tune it for each batch of steel, and
not each individual piece.
 
P

Peter Heitzer

Jan 1, 1970
0
Is there a simple way to generate a 200Hz sine wave? I'd like something
with no tuning involved, 1hz accuracy, powerable from 2 to 3V. I
believe harmonics are okay, but I dont know how to quanitify them. They
should be quiet enough to not be audible when listening to just the
tone on headphones. The cost of the circuit needs to be less than 50
cents.
The cheapest solution would be a small PIC or Atmel microcontroller
with on chip oscillator and building a "magic sinewave" as in Don
Lancaster`s cmos cookbook as some others already mentioned.
 
K

Ken Smith

Jan 1, 1970
0
Is there a simple way to generate a 200Hz sine wave? I'd like something
with no tuning involved, 1hz accuracy, powerable from 2 to 3V. I
believe harmonics are okay, but I dont know how to quanitify them. They
should be quiet enough to not be audible when listening to just the
tone on headphones. The cost of the circuit needs to be less than 50
cents.

Tell us more about the headphone. Can it have a resonant piezoelement in
it?
 
K

Ken Smith

Jan 1, 1970
0
The cheapest solution would be a small PIC or Atmel microcontroller
with on chip oscillator and building a "magic sinewave" as in Don
Lancaster`s cmos cookbook as some others already mentioned.

That depends on how many you are making. If you have to provide 1 to
every person on earth, a custom IC would be the way to go. It would take
far fewer transistors.
 
it seems to me that the magic sequence pwm method is the best. if I
sample a 200hz sinewave at 1MHz and turn it into a bitstream which
matches an rc filter response, the results are very good (at least,
eyeballing it in excel). This would only take 5000 BITS of storage, a
1MHz clock, and an rc filter, so its cheapy weepy. Okay, and now, I
will cheat: I dont really need the 1Hz accuracy anymore. I originally
thought I needed it because I have to have two tones seperated by a
certain frequency which was only a few hertz to begin with. But the way
I will implement this, with a parallel flash or eprom, will 'lock' the
two tones together, so even if the clock is inaccurate, the tones will
track each other because they will both experience the same error from
the clock. So now the solution is:

cheap 16kbit (or whatever size, only need 10kbit) parallel eprom/flash
(whichever is cheaper)
1MHz RC oscillator (few passives and digital gate)
RC output filter

the tones (200hz/210hz) will each be sampled at 1MHz and encoded into a
bitstream which takes into account the response of the output rc
filter, to reproduce the tones. the bitstream will be burnt into the
eprom, into the upper or lower two bits (or whatever two bits) of each
byte, so that clocking the eprom data out will simultaneously clock
both tones out.

tada!

i assume in 100k+ quantities this will be less than 1$

oh and sorry for totally changing the requirements.
 
F

Frank Bemelman

Jan 1, 1970
0
it seems to me that the magic sequence pwm method is the best. if I
sample a 200hz sinewave at 1MHz and turn it into a bitstream which
matches an rc filter response, the results are very good (at least,
eyeballing it in excel). This would only take 5000 BITS of storage, a
1MHz clock, and an rc filter, so its cheapy weepy. Okay, and now, I
will cheat: I dont really need the 1Hz accuracy anymore. I originally
thought I needed it because I have to have two tones seperated by a
certain frequency which was only a few hertz to begin with. But the way
I will implement this, with a parallel flash or eprom, will 'lock' the
two tones together, so even if the clock is inaccurate, the tones will
track each other because they will both experience the same error from
the clock. So now the solution is:

cheap 16kbit (or whatever size, only need 10kbit) parallel eprom/flash
(whichever is cheaper)
1MHz RC oscillator (few passives and digital gate)
RC output filter

the tones (200hz/210hz) will each be sampled at 1MHz and encoded into a
bitstream which takes into account the response of the output rc
filter, to reproduce the tones. the bitstream will be burnt into the
eprom, into the upper or lower two bits (or whatever two bits) of each
byte, so that clocking the eprom data out will simultaneously clock
both tones out.

tada!

i assume in 100k+ quantities this will be less than 1$

oh and sorry for totally changing the requirements.

Stuff a little dual DDS in one component, PIC10F202, sot23.
 
F

Fred Bloggs

Jan 1, 1970
0
Okay, and now, I
will cheat: I dont really need the 1Hz accuracy anymore. I originally
thought I needed it because I have to have two tones seperated by a
certain frequency which was only a few hertz to begin with...
the tones (200hz/210hz) will each ...

If that's what's needed then a dog simple 205Hz oscillation, AM
modulated by 5Hz, will produce the two tones cheaply.
 
J

John_H

Jan 1, 1970
0
Fred said:
If that's what's needed then a dog simple 205Hz oscillation, AM
modulated by 5Hz, will produce the two tones cheaply.

I'll bite:
So, what's a chaep, simple way to generate 205Hz sine waves?
 
J

Jim Thompson

Jan 1, 1970
0
I'll bite:
So, what's a chaep, simple way to generate 205Hz sine waves?

A 205Hz sine wave oscillator ?:)

...Jim Thompson
 
F

Fred Bloggs

Jan 1, 1970
0
John_H said:
I'll bite:
So, what's a chaep, simple way to generate 205Hz sine waves?

Things are simplified greatly by using a 205Hz square waveform to
modulate a 5Hz sine waveform by +/- polarity switching- then LP the
resultant. See National LB-16 for a way to produce stable low frequency
sines.
 

Similar threads

N
Replies
24
Views
8K
RobertMacy
R
R
Replies
9
Views
2K
Phil Allison
P
K
Replies
3
Views
1K
Fred Bartoli
F
Top