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
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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.
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!
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.
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.
On Fri, 16 Jun 2006 13:14:43 -0600, in message , Mike McWilliams scribed:
Ah well, I found this site:
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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...."
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, f*ck off!
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.
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
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 w**re, 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.
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
On Wed, 21 Jun 2006 08:35:20 -0600, in message , Mike McWilliams scribed:
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?
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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