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nerve locator

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Hi, im trying to make a biomedical machine , the idea is to locate the nerve by supplying a current like 2mA or 0.2mA , so does i need to feed the nerve a 100V with a low current using a transformer ? or a transistor , i dont know really the idea ..
 
They do make equipment that does what you describe. I had testing done to help verify that my back was the cause of leg/foot problems. Leads were pasted on various locations - and a pulse was fired resulting in a brief muscle contraction. I've had people tell me how much pain they experienced with a test like this - while not pleasant I found it quite tolerable for a short period of time.

I'd expect that the information you need is in a biomedical reference book. I would expect that anything used on people would be designed so that it can't hurt someone - normally or if failures occur.
 
You probably should look up the term: electromyelography and its variants, such as electromyelogram. Just search on EMG and you will get plenty of hits regarding testing nerve conduction.

As for mapping nerves, you need to define the question considerably more. Are you talking about deep nerves, peripheral nerves, which nervous system, and why?

John
 
Dentists use a "nerve locator" during a tooth's root canal. It is probably a very low current. 2mA would blow the patient's head off.
 
It depends on the prerson and where the current is introduced.

I've never heard of anyone being killed by 2mA, it'd probaly only kill if it was directly introduced intot he heart.

I can't feel 1mA with my fingers, 2mA would probably ony cause a slight tingling sensation.

Dentist probably use a much lower current as the nerves in the mouth are more sensitive. The open circuit votage is also pretty low, <60V as the mouth is pretty conductive.
 
Hi, im trying to make a biomedical machine , the idea is to locate the nerve by supplying a current like 2mA or 0.2mA , so does i need to feed the nerve a 100V with a low current using a transformer ? or a transistor , i dont know really the idea ..

You need to build an adjustable current source with an open circuit voltage of >200 v.

DC?
AC?
What freq.?
I haven't a clue.
 
Go with DC - it's much safer.

A disposable cemera flash unit would probably do it.

Use a resistor to limit the short circuit current to above 1mA (below 1mA you probably won't be able to feel it) and under 5mA (the maximum current deemed to be harmless, according to Wikipedia and other sources), about 2mA is probably a safe bet, make sure the resistor is rated for the voltage (for safety's sake use two in series) and power.
 
thanks for the posts ,,
Is 200V will be harmfull ??
So what i only need is a transistor as a current source ?? and its VCC will be 200V ? and with calculations i will make a 1mA current ?
also another question , what is the ground of the human body ?? to test it , the 1mA should flow in the body , then there should be a ground and a positive terminal , where i will connect them ??
 
200V won't be harmful if the current is limited to a safe level.

There's a 1kV insulation tester at work and it doesn't even hurt me because the curent is limited to 1mA.

You just have to make sure that no single failure can allow more than 5mA to flow. Supose you use 200V and two 51k resistors in series, the normal short circuit current will be 1.96mA and if one of the resistors goes short circuit the current will be 3.92mA which would hurt but not kill. Using a transistor current source is more dangerous because if the transistor emitter collector goes short circuit then a potentially lethal current could flow.
 
I've already told you - a disposable camera flash unit.
 
I think the 200V was a joke. Nevertheless, you still haven't said clearly what you are trying to do or why. John
 
Sorry but i got a question why there should be a high voltage like 200V , while i can get 2mA using 10V/5k..

Almost certainly the current from a 9v battery across dry skin will be imperceptible, therefore the current is <1 mA. Even with skin wetted with salt water you probably won't feel anything.

A doorbell transformer with diode and capacitor will give you 40vdc, the phone line with no ringing signal will give you ~50vdc (and that I can usually feel) and line voltage will peak at 170v.

If you know how high the skin resistance will be for dry, calloused skin then you can adjust the current source compliance accordingly.
I don't think 100v would guarantee 2mA into dry skin but I've never tried it. As long as it's a current source you could go even higher with the open circuit voltage.

BTW, there are probably patents on the waveforms and the machines used to stimulate muscles. I'd be a little careful with this project.
 
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I think the 200V was a joke. Nevertheless, you still haven't said clearly what you are trying to do or why. John

A friend who is a doctor of anesthsia , asked me if i can make this device or not which he uses to locate the nerve , he said i've to supply the body current about 2mA , and he will use an injection then he will hit the muscle and it will contract hence he can put anesthsia to that nurve .. that's the story .
 
Are there no regulations in Cairo about medical grade devices? I'd worry a little if my doctor wanted to hook me up with a wet sponge and car battery.
 
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