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Question about using a computer as a function generator

M

Mike McWilliams

Jan 1, 1970
0
Hello,

I'm interested in researching scorpion venom, and have come across
descriptions using DC voltage to stimulate venom excretion. Ranging from
6v DC at 120ish hz to 1.2kV at 10hz.

What I would like to do is use my computers sound card as a function
generator to allow me to change the frequency for the voltage desired.

I would imagine that sound card output is well below the voltages I
require, and from what I understand is AC coupled.

I would therefore like to take the signal generated, and use it to
modulate a separate DC source at the frequency of the generated function.


My question is what would be a good place to start in terms of
components? I have little experience in electronics design, though I
have put a few kits together.
 
J

Jasen Betts

Jan 1, 1970
0
Hello,

I'm interested in researching scorpion venom, and have come across
descriptions using DC voltage to stimulate venom excretion. Ranging from
6v DC at 120ish hz to 1.2kV at 10hz.

What I would like to do is use my computers sound card as a function
generator to allow me to change the frequency for the voltage desired.

I would imagine that sound card output is well below the voltages I
require, and from what I understand is AC coupled.

I would therefore like to take the signal generated, and use it to
modulate a separate DC source at the frequency of the generated function.


My question is what would be a good place to start in terms of
components? I have little experience in electronics design, though I
have put a few kits together.

use an off the shelf audio amp and a step-up transformer

Bye.
Jasen
 
Mike said:
Hello,

I'm interested in researching scorpion venom, and have come across
descriptions using DC voltage to stimulate venom excretion. Ranging from
6v DC at 120ish hz to 1.2kV at 10hz.

What I would like to do is use my computers sound card as a function
generator to allow me to change the frequency for the voltage desired.

I would imagine that sound card output is well below the voltages I
require, and from what I understand is AC coupled.

I would therefore like to take the signal generated, and use it to
modulate a separate DC source at the frequency of the generated function.


My question is what would be a good place to start in terms of
components? I have little experience in electronics design, though I
have put a few kits together.

For the computer function generator, you may want to have a look at my
DaqGen freeware at www.daqarta.com.

You are correct about sound cards being AC coupled, so the big problem
here is coming up with an amp that can give you a big DC bias. This
pretty much rules out transformers... they typically don't like much DC
on them. So I think you are right on target about modulating a
separate DC source. Do you require an accurate waveform? If you can
tolerate rectangular waves you can think about using a simple
transistor switching circuit driven by the AC signal. The transistor
needs to handle the full DC supply of course, so if you really want 1.2
kV this gets a bit tricky. (And dangerous!) Otherwise, and assuming
you don't need much current, you might be able to get away with hanging
a high-value load resistor between the DC and the collector (assuming
bipolar transistor), and connect the emitter to ground. Take the
output from the collector. Drive the base through maybe a 10k resistor
from the sound card output.

The sound card should have enough oomph to drive the transistor into
saturation.
Use a rectangular drive waveform to minimize switching losses. If your
transistor doesn't have enough gain (beta) you may need to a Darlington
configuration, with a small high-beta transistor driving the base of
the power transistor, collectors connected together, and signal to the
base of the input transistor.

If you want to try other waveforms (especially at the lower end of your
DC range) you can try biasing the input up, using a voltage divider
between the DC supply and ground. This will mean that the power device
will be conducting most of the time, so watch out for excess heating.
Don't expect to get good fidelity and high gain both from this simple
circuit.
From here on out the circuit design can get more involved if you need
good waveform fidelity at high voltages. You would basically be
designing a power amp like the early transistor home stereo amps that
used a single DC supply and AC-coupled the output... you'd just leave
off the output capacitor. Let us know if you want to go this route.
I'm sure I have plenty of old amp designs around here somewhere!

Best regards,

Bob Masta
 
A

Abstract Dissonance

Jan 1, 1970
0
Mike McWilliams said:
Hello,

I'm interested in researching scorpion venom, and have come across
descriptions using DC voltage to stimulate venom excretion. Ranging from
6v DC at 120ish hz to 1.2kV at 10hz.
What do you mean 6V DC at 120hz? Are you saying that you want rectified AC?
DC usualy refers to a constant voltage but technically is a voltage that is
positive. 120hz usually refers to a periodic wave form that oscillates
between + and -.

And easy way to do what you want is to use a pic to generate the wave forms.
You could make a nice litle device that is very compact and easy to use that
probably would cost under 15$ in parts. (pic, on/off button, batter,
resistors, capacitors, and pot for signal frequency and voltage. You could
maybe even through in a switch to select different wave form types.)

The other main thing would be to step up the voltage of the signal from the
pic. I'm thinking that it wouldn't be a good idea to use simply a
transformer since it would be a little big and inefficient over a wide range
of frequencies. I think there are a wide variety of ways to do this though
and not sure what would be the best. I'd imagine though that you could make
a small handheld device similar to a stun gun that will get what you want
and there would be no reason to use a computer.

Just some ideas,
Jon
 
Y

YD

Jan 1, 1970
0
Hello,

I'm interested in researching scorpion venom, and have come across
descriptions using DC voltage to stimulate venom excretion. Ranging from
6v DC at 120ish hz to 1.2kV at 10hz.

What I would like to do is use my computers sound card as a function
generator to allow me to change the frequency for the voltage desired.

I would imagine that sound card output is well below the voltages I
require, and from what I understand is AC coupled.

I would therefore like to take the signal generated, and use it to
modulate a separate DC source at the frequency of the generated function.


My question is what would be a good place to start in terms of
components? I have little experience in electronics design, though I
have put a few kits together.

Nice freeware generators and analyzers at
http://www.infinitespectra.com/index.html

You're correct that the soundcard doesn't have even close to the
levels you want. You'll need some bits and bobs to add the DC off-set
and amplification. You didn't tell what kind of power you need, but
1.2 kV at 10 Hz + DC sounds a bit scary, a step-up transformer won't
do at all.

There are some HV amps around, but you'll really need to ask someone
who knows what he's on about to buy/build and set it up for you.


- YD.
 
A

Alan B

Jan 1, 1970
0
Hello,

I'm interested in researching scorpion venom, and have come across
descriptions using DC voltage to stimulate venom excretion. Ranging from
6v DC at 120ish hz to 1.2kV at 10hz.

What I would like to do is use my computers sound card as a function
generator to allow me to change the frequency for the voltage desired.

I would imagine that sound card output is well below the voltages I
require, and from what I understand is AC coupled.

I would therefore like to take the signal generated, and use it to
modulate a separate DC source at the frequency of the generated function.


My question is what would be a good place to start in terms of
components? I have little experience in electronics design, though I
have put a few kits together.

Ah well, I found this site:

http://www.scielo.br/scielo.php?pid=S1678-91992004000100007&script=sci_arttext

and notwithstanding its very general description about the electrical
design, it doesn't mention anything about DC offset. Given your garbling
of terminology, i.e. "6v DC at 120ish hz," my guess is you've not done
enough research about what you need just yet. A web search on "Arthropods
Electronic Stimulator" didn't yield anything outside the given article. I
recommend a visit to the local college library. Once you're a little more
clear about your design needs, you'll get better help here.

--
"The equipment for venom extraction was developed in 1996... This equipment
was named ''Arthropods Electronic Stimulator''... It is an electronic
equipment that produce a high frequency of electrical stimulus, modulated
by low adjustable frequency (values among 0,5-2 Hz), with low intensity and
high voltage... It has an adjust system of exposition between 0 V and 1700
Vpp... For first venom extraction, scorpions submitted to a 1,250 kV
electrical stimulus at a frequency of 0,5 Hz...."
 
Y

YD

Jan 1, 1970
0
Ah well, I found this site:

http://www.scielo.br/scielo.php?pid=S1678-91992004000100007&script=sci_arttext

and notwithstanding its very general description about the electrical
design, it doesn't mention anything about DC offset. Given your garbling
of terminology, i.e. "6v DC at 120ish hz," my guess is you've not done
enough research about what you need just yet. A web search on "Arthropods
Electronic Stimulator" didn't yield anything outside the given article. I
recommend a visit to the local college library. Once you're a little more
clear about your design needs, you'll get better help here.

Am I right in assuming scorpions aren't very conductive, since they
can take that kind of voltage without frying?

- YD.
 
B

Ban

Jan 1, 1970
0
Mike said:
Hello,

I'm interested in researching scorpion venom, and have come across
descriptions using DC voltage to stimulate venom excretion. Ranging
from 6v DC at 120ish hz to 1.2kV at 10hz.

What I would like to do is use my computers sound card as a function
generator to allow me to change the frequency for the voltage desired.

I would imagine that sound card output is well below the voltages I
require, and from what I understand is AC coupled.

I would therefore like to take the signal generated, and use it to
modulate a separate DC source at the frequency of the generated
function.

My question is what would be a good place to start in terms of
components? I have little experience in electronics design, though I
have put a few kits together.


You want to torture those poor animals for your military organization? This
is ethically the most disgusting thing to do, you are a Nazi. We do not
support this kind of research, **** off!
 
M

Mike McWilliams

Jan 1, 1970
0
Alan said:


So 1250 kV at 0.5 hz

not too far out of the range I gave now is it. Plus it follows the trend
I've indicated that at high voltage, frequency is low.
and notwithstanding its very general description about the electrical
design, it doesn't mention anything about DC offset. Given your garbling
of terminology, i.e. "6v DC at 120ish hz," my guess is you've not done
enough research about what you need just yet. A web search on "Arthropods
Electronic Stimulator" didn't yield anything outside the given article. I
recommend a visit to the local college library. Once you're a little more
clear about your design needs, you'll get better help here.

How about you leave the biology to me, and the electronics to my next
visit to the local college library. electrically stimulating scorpions
to harvest venom is something that is just not covered in books. You
can't order a power supply specifically made for this purpose.
 
M

Mike McWilliams

Jan 1, 1970
0
YD said:
Nice freeware generators and analyzers at
http://www.infinitespectra.com/index.html

You're correct that the soundcard doesn't have even close to the
levels you want. You'll need some bits and bobs to add the DC off-set
and amplification. You didn't tell what kind of power you need, but
1.2 kV at 10 Hz + DC sounds a bit scary, a step-up transformer won't
do at all.

There are some HV amps around, but you'll really need to ask someone
who knows what he's on about to buy/build and set it up for you.


- YD.
turns out I can probably use a muscle stimulator commonly used in
physiotherapy. Certainly not a cheap alternative. Plus not quite as
geeky as using my soundcard to generate the frequency. Ah well, you
can't win them all
 
M

Mike McWilliams

Jan 1, 1970
0
Ban said:
You want to torture those poor animals for your military organization? This
is ethically the most disgusting thing to do, you are a Nazi. We do not
support this kind of research, **** off!

Harvesting venom has plenty of legitimate uses. This has nothing to do
with torture. The scorps are fed, kept in clean cages, and released.

The stimulation occurs only in the far end of the tail (telson), and
doesn't cause distress even in proportion to that caused by handling.

If you are going to use the word ethics, maybe you ought to put forward
a reasonable argument, and not shoot straight from your gut reaction.
When that happens, I find no reason to take your emotions seriously.
Furthermore, comparing me to Nazi's is a little more than sensational.

Besides that, it turns out I don't need help from this newsgroup as a
few more hours of research paid off. I've found my solution.
 
B

Ban

Jan 1, 1970
0
Mike said:
Harvesting venom has plenty of legitimate uses. This has nothing to do
with torture. The scorps are fed, kept in clean cages, and released.

The stimulation occurs only in the far end of the tail (telson), and
doesn't cause distress even in proportion to that caused by handling.

If you are going to use the word ethics, maybe you ought to put
forward a reasonable argument, and not shoot straight from your gut
reaction. When that happens, I find no reason to take your emotions
seriously. Furthermore, comparing me to Nazi's is a little more than
sensational.
Besides that, it turns out I don't need help from this newsgroup as a
few more hours of research paid off. I've found my solution.

Yeah, also Dr. Joseph Mengele was doing research with the same
argumentation. And I wonder what this vernom is used for? Maybe it protects
us from Bin Laden?
You sold yourself to a deathbringing organization, far worse than any whore,
and you call yourself a scientist? No other job available because too dumb?
And you are so stupid to use this address to post to an international NG?
Defence R&D Canada - Suffield
Man, you are a risk for these cannucks, be careful. I'm gonna report you to
your superiours, if you write another line here.
 
B

Bob Masta

Jan 1, 1970
0
So 1250 kV at 0.5 hz

not too far out of the range I gave now is it. Plus it follows the trend
I've indicated that at high voltage, frequency is low.


How about you leave the biology to me, and the electronics to my next
visit to the local college library. electrically stimulating scorpions
to harvest venom is something that is just not covered in books. You
can't order a power supply specifically made for this purpose.

Mike:

I've done a lot of electronics for biological purposes.
I wonder if maybe the waveforms used in the article are
actually pulses or pulse trains. All the biological stimulators
I have ever seen were pulses. The typical approach is to
use a bipolar (biphasic) pulse, where the no-signal condition is at
0 V and each pulse goes positive for a duration and then negative
for a duration, followed by a return to zero for a dwell period..
These biphasic pulses are then repeated at some pulse repeat rate.
They are often used as trains of some number of pulses followed
by a silent interval.

The biphasic approach is used to avoid delivering net charge to
the subject, and also to avoid (or reduce) any plating reactions
at the electrodes. Stimulators may allow independent control
over the duration and amplitude of the positive and negative
phases for those situations where you want to have no net
charge, but give a big positive pulse with a narrow duration
followed by a smaller negative pulse with a longer duration that
balances the charge.

I mention all this because a pulse-type stimulator might be
much easier to build than amplifying a low-level signal,
if you really want the high voltages. Since the output
devices are either off or on, they are simple switches and
don't need to dissipate much power themselves.

Best regards,


Bob Masta
dqatechATdaqartaDOTcom

D A Q A R T A
Data AcQuisition And Real-Time Analysis
www.daqarta.com
Home of DaqGen, the FREEWARE signal generator
 
A

Alan B

Jan 1, 1970
0
Am I right in assuming scorpions aren't very conductive, since they
can take that kind of voltage without frying?

Mebbe they have a ceramic exoskeleton?
 
A

Alan B

Jan 1, 1970
0
Alan B wrote:


So 1250 kV at 0.5 hz

not too far out of the range I gave now is it. Plus it follows the trend
I've indicated that at high voltage, frequency is low.

Well, actually, it is really far off. Regardless of the frequency, DC is
DC and AC is AC. You described wanting DC at 120 Hz. Sorry, you can't
have it. You can't have DC at 0.5 Hz either. You can have AC with a DC
offset, you can have pulsed DC, which is another way of saying the same
thing, or you can modulate a lower frequency with a higher. There are
several ways of producing high voltage with any of these methods, but until
you know what it is you need, you won't be able to design a circuit and
produce it. Is that clear enough? And oh by the way, where oh where in
any of your inquiries is the mention of power? Is your intent to extract
venom, or to make fried scorpion hors d'ourves?
How about you leave the biology to me, and the electronics to my next
visit to the local college library. electrically stimulating scorpions
to harvest venom is something that is just not covered in books. You
can't order a power supply specifically made for this purpose.

Now I'm confused. You're getting snippy about my response, and yet you
admit that you need further study in electronics. Interesting.
 
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