Help to make circuit for Nerve Stimulation Device

[samoel12]

Hi, My name is Sam, I'm new to this site, i would like someone to help me to make circuit design which can be used as a Nerve Stimulation Device, my ideal circuit would be with current adjustable switch and voltage adjustable switch both fixed.

The output current will be variable and adjusted by the current switch: 10 position rotary switch
0.5ma- 1.0ma-1.5ma-2.0ma-2.5ma-3.0ma-3.5ma-4.0ma-4.5ma-5.0ma

The output voltage will be variable and adjusted by the voltage switch: 10 position rotary switch
3v-4v-5v-6v-7v-8v-9v-10v-11v-12v

The output will have one jack for electrode.

The device will have a switch to power ON/OFF. The device will have LED light indicator as well.

The device will be powered by 9 volts battery.

No voltage or current interference, i mean when increase or decrease the voltage that will have no affect on the output current and vice versa.

I was looking for diagram in the internet, but didn't find the diagram exactly as the diameters required for my project.

 

[samoel12]

Hi, My name is Sam, I'm new to this site, i would like someone to help me to make circuit design which can be used as a Nerve Stimulation Device, my ideal circuit would be with current adjustable switch and voltage adjustable switch both fixed.

The output current will be variable and adjusted by the current switch: 10 position rotary switch
0.5ma- 1.0ma-1.5ma-2.0ma-2.5ma-3.0ma-3.5ma-4.0ma-4.5ma-5.0ma

The output voltage will be variable and adjusted by the voltage switch: 10 position rotary switch
3v-4v-5v-6v-7v-8v-9v-10v-11v-12v

The output will have one jack for electrode.

The device will have a switch to power ON/OFF. The device will have LED light indicator as well.

The device will be powered by 9 volts battery.

No voltage or current interference, i mean when increase or decrease the voltage that will have no affect on the output current and vice versa.

I was looking for diagram in the internet, but didn't find the diagram exactly as the diameters required for my project.

 

[KlausST]

Re: Help needed to make a circuit with fixed current and fixed voltage output.

Hi,

fixed current and fixed voltage output

Impossible.

The very basic formula in electronics is Ohm´s law: R = V / I
You can´t fix Voltage and the same time Current ... this is only possible if the R has the exact value of V/I.
But with nerve stimulation you are (usually) not able to set the value of "R" to an exact value.

*****

The output will have one jack for electrode.

Again not possible.

Any electrical current flow needs a loop. A flow from electrodes from node A to node B.

Thus every battery, power supply, mains outlet has (at least) two contacts (for two electrodes in your case).

***
Re-think your requirements.

Klaus

 

[Audioguru]

How will you connect the current simulation circuit a nerve? With two painful needles?
Maybe you were thinking to squeeze the two probes in two hands. I measure 3M ohms between my hands so if the voltage is 3V then 3V/3M= 1uA of current will flow, no more unless I increase the voltage or decrease my resistance.
How will you get 5mA to flow? By increasing the voltage. 3M x 5mA= 15 thousand volts! And your circuit must keep the current from exceeding 5mA even when the voltage is 100 thousand volts or more.
Silly, isn't it?

 

[samoel12]

How will you get 5mA to flow? By increasing the voltage. 3M x 5mA= 15 thousand volts! And your circuit must keep the current from exceeding 5mA even when the voltage is 100 thousand volts or more.
Silly, isn't it?

Hi, Thanks for the update. Sorry I didn't clarify up my question enough.
This formula means it can be done. But with controlling the resistance.

To find the Voltage, ( V )
[ V = I x R ] V (volts) = I (amps) x R (Ω)

To find the Current, ( I )
[ I = V ÷ R ] I (amps) = V (volts) ÷ R (Ω)

To find the Resistance, ( R )
[ R = V ÷ I ] R (Ω) = V (volts) ÷ I (amps)


If i follow the formula. for example if i need to keep the output current at 5ma while changing output voltage from 12V to10V
12V/0.005A=2400R if i need to decrease the voltage to 10v/0.005a= 2000R

so by controlling the resistance will control the flow of the current, sure the resistance value will change if either the voltage or the amperage are changed.

 

[c_mitra]

Have some practical ideas:

Voltages produced in common nerve signals is (usually) less than 1V.

The currents involved (depends on the nerve size) is of the order of microamps.

Is you device is going to be used for research or for other medical application?

To measure the voltage, you need to make contact with the solution inside the nerve.

The other electrode can make contact with the solution outside (commonly a buffer solution).

What you will be measuring is the voltage across the walls of the nerve fibre. You can also measure the current flow across the membrane.

In biological nerves, the conduction takes place by ions and not electrons. Therefore you will need special electrodes that can connect to the inside/ outside of the nerve.

You can also measure the current flow at a fixed voltage. For that, you need to apply a fixed voltage just outside the nerve.

The voltage and current values you are talking about does not make sense.

 

[KlausST]

Hi,

This formula means it can be done. But with controlling the resistance.

In case your definition of output_voltage and output_current both are the values to stimulate nerves:
(Otherwise, please clarify the meaning of your values)

I'd like to know how you want to control the (skin) resistance of a body.
As this is the only way to fulfill your requirements of post#1.

*****

For sure you can build a variable resistor inside the device, but then still you are not able to control output_voltage and output_current at the same time to two desired setpoint values.


Klaus

 

[samoel12]

Have some practical ideas:

Voltages produced in common nerve signals is (usually) less than 1V.

The currents involved (depends on the nerve size) is of the order of microamps.

Is you device is going to be used for research or for other medical application?

To measure the voltage, you need to make contact with the solution inside the nerve.

The other electrode can make contact with the solution outside (commonly a buffer solution).

The voltage and current values you are talking about does not make sense.

Thanks for the reply Mitra,

- I've seen devices that uses more than 1v it could reach 50 volts like TENS machine.
-The current is measured in ma
- The device will be used for myself.
- This device will be non-invasive nerve stimulation, the electrode doesn't need to touch the nerve just on the skin where the nerve is located, with two electrodes not far from each-other.
-The electrodes will be used with conductive gel solution.
-So if my voltage and current values don't make sense how can be figured out?
- What's the best circuit that can be used for this project?
- LM317 can be used as voltage regulator to adjust the output voltage, is there any thing other than that with less heat to use in a circuit to get the selectable output voltage?

thanks

 

[c_mitra]

- I've seen devices that uses more than 1v it could reach 50 volts like TENS machine.

Yes, I have heard about them but do not know much about them. I thought they are quack devices. It has been claimed that they can relieve pain (and other conditions) by stimulating nerves.

A Warning: they can be dangerous (can be fatal) if appreciable current does flow through the body.

But what I said remains correct: signals produced by nerves are approx 1V (called action potential).

Current conducted by single nerves are of the order of microamps.

If you are passing 1mA, you are likely stimulating 100s of nerves at the same time.

If you are applying around 50V, using electrodes (similar to the ones used in ECG electrodes) with a salt gel, you may experience severe pain and it can also cause heart failure.

Yes, it can be so dangerous.

With a dry unpunctured skin, 50V may give a mild sensation (but you should not try on any living person).

With two electrodes physically close to each other, the dangers can be much less (because little current can reach the heart).

Remember that pain sensation is felt in the brain but the signal is produced at the sensors located at the end of the nerves (at various locations).

It can be complicated.

 

[samoel12]

Hi,


In case your definition of output_voltage and output_current both are the values to stimulate nerves:
(Otherwise, please clarify the meaning of your values)

I'd like to know how you want to control the (skin) resistance of a body.
As this is the only way to fulfill your requirements of post#1.

*****

For sure you can build a variable resistor inside the device, but then still you are not able to control output_voltage and output_current at the same time to two desired setpoint values.


Klaus

Thanks Klaus for the reply,

As i understand the voltage is a pressure of energy from point (a) to point (b), and amperage is a flow of the energy traveling from point (a) to point (b), so my values in post 1 are not that important, just an idea.

-Why do mean to control the resistance of the body?

-What if i build two circuits one to limit the voltage and the other to limit the current, in that case i'm not able to reach the desired set-point of both the current and the voltage at the same time?

Thanks Klaus

 

[samoel12]

If you are applying around 50V, using electrodes (similar to the ones used in ECG electrodes) with a salt gel, you may experience severe pain and it can also cause heart failure.

My ideal device will not reach that level of voltage at all 50v is kinda lot, i'm looking at max 10v may be 12v, but my set up will be at 2v with variable current between 1ma-5ma

 

[KlausST]

Hi,

-Why do mean to control the resistance of the body?

Ohm´s Law:

R = V / I

in your case:
V = the output voltage of your device (between both of your electrodes)
I = the putput current of your device (through your electrodes, through the body)
R = the load resistance ( resistance between the electrodes = skin resistance of the body)

If you want to set V and you want to set I, then you need to "adjust" R to apply to ohm´s law.

Example:
You want V = 10V and I = 1mA

Then according Ohm´s law: R = V / I = 10V / 0.001A = 10.000 Ohms.
No other resistance value can fullfil both your needs for V and I. It needs to be 10.000 Ohms.

But how do you manage the the body resistance = 10.000 Ohms?
--> You simply can´t.

-What if i build two circuits one to limit the voltage and the other to limit the current, in that case i'm not able to reach the desired set-point of both the current and the voltage at the same time?

Impossible. You can´t ignore Ohm´s law. You can´t ignore physics.

Klaus

 

[c_mitra]

-What if i build two circuits one to limit the voltage and the other to limit the current, in that case i'm not able to reach the desired set-point of both the current and the voltage at the same time?....

Very interesting indeed! Let me try to explain in my way.

Voltage is analogous to a force (it is actually a potential and derivative of the voltage is a force) and current is like a flow (of electric charge).

One is a cause and the other is an effect.

One is an independent variable and the other is a dependent variable.

In school, the voltage was taught as an analogue of water pressure. The current was the flow of water.

In any given experiment, you cannot control both current and voltage.

Just like you cannot have low water pressure but high flow of water at the same time.

In electrical circuit, resistance is nothing but a friction to the flow of charge. Just like viscosity for the flow of water.

 

[c_mitra]

-What if i build two circuits one to limit the voltage and the other to limit the current, in that case i'm not able to reach the desired set-point of both the current and the voltage at the same time?

You can limit both at the same time. Say you set the voltage not to exceed 50V (voltage compliance) under any condition and also limit the current not to exceed 50mA (say).

You can also set power points (say 100mW) with voltage priority (or current, for that matter).

The possibilities are endless.

But if you want to set the voltage (different from the voltage limit) at say 20V and also the current at 10mA (just a random example value), you fix the load.

You need to fix one electrode and move the other electrode so that the desired readings are seen on the display.

But does that serve the purpose of what you are trying to achieve?

 

[Audioguru]

Put two circles of conductive gel on yourself where you want nerve stimulation and place the two electrodes not far apart. Then measure the resistance of your skin with a digital voltmeter that you will not feel because its voltage is 0.2V and its current will be about 4uA to 10uA. The measured resistance will be about 25 thousand ohms (25k). If you want 2mA of current then the voltage must be about (2mA/8uA) x 0.2V= 50V. If the resistance of your gelled skin measures 100 thousand ohms (100k) then for 2mA the voltage must be 2mA x 100k= 200V.

Do not let the circles of conductive gel touch each other because then the current will flow in the gel instead of in your nerves.

I think you should limit the maximum current in you with a current limiting circuit to about 4mA. When you turn up the voltage then the current will also increase. When you turn down the voltage then the current will also decrease.

Is this for pain relief? Then which hurts more, the original pain or the pain of this electrocution? Don't the two pains add?

 

[Nik_2213]

"I thought they are quack devices."

Sadly, they are often touted as a 'panacea', which they are NOT.
But, used appropriately, they can ease muscle cramps, persistent pain, slow-healing breaks etc.
( Been there, done that, astonished my consultant by rapid progress. YMMV...)

FWIW, they also have 'recreational' uses...
;-)

You MUST ensure current does NOT cross the chest / thoracic stuff.
Err on the side of safety: Better too-wary than body-bagged.

TENS units usually have one or more channels, usually with a 'mono' 2.5 or 3.5 mm audio jack per channel. The cable splits, each end going to an electrode adapter, via blunt 1 mm plug or stud/clip similar to those on ECG pads. There are some proprietary connectors, of course, of course, the better to 'lock you in' to that branded TENS unit's disposables...

In my experience, the pulses really tingled at first but, as initial sensitivity diminished, I could turn up the power and frequency.

Weirdly, running such stimuli down my compound fractured shin, I became aware of those breaks' exact locations. This sensation diminished as mending progressed under medical supervision...

As ever, Due Care, Please.

 

[c_mitra]

I also mentioned my ignorance about the TENS devices. I just now looked up and found several mentioned in google search.

The good news that
https://www.webmd.com/back-pain/guide/tens-for-back-pain
says
it is usually considered safe.

I rest my case.

 

[samoel12]

What is best and efficient way to get multiple output voltage let's say 2v-3v-4v-5v-6v-7v-8v like in circuit design, what are the components used to control voltage output? I know resistors can be used. LM317 can be used as voltage regulator to adjust the output voltage, is there any thing other than that with less heat to use in a circuit to get fixed variable output voltage?

 

[KlausST]

Hi,

I know resistors can be used.

So, why do you ask? Are resistors too simple?

is there any thing other than that with less heat to use in a circuit to get fixed variable output voltage?

You did not do a simple search on your own...otherwise you already know "buck converter" and "boost converter".

Klaus

 

[samoel12]

Hi,


So, why do you ask? Are resistors too simple?


Klaus

Thanks for the reply, I ask to know more it could people with more knowledge than me who can help me, you are in a foreign country you don't have the information needed to reach specific place, don't you ask the locals to get you faster to your destination? sure you can find the place eventually with effort and search, but will take you time, till now i didn't receive one straight answer from anyone in this forum who can provide a circuit diagram, not specifically what i'm looking for, but with same working idea, explaining its function. I don't know if resistors use are easy or not but i'll try, but i found few diagrams online which use resistors to control the output either voltage or amperage. For example cranial electrotherapy simulator.

You did not do a simple search on your own...otherwise you already know "buck converter" and "boost converter".


Klaus

I was busy for quite sometime, therefore i couldn't search for more information online. I know about them, but i need something that can be small at the same time usable in the circuit i'll design.

What are they?

-Resistors from their name explains their function a given amount of resistance in a circuit.
- capacitors store the energy in the form of an electric field can be used in the input and output of the circuit to make smooth start and stop of the device.
-Transistors is an electronic device used to control the flow of an electric current.
etc .....

Anyone here able to provide a circuit diagram it could be TENS machine circuit diagram, just for education purposes, available online explaining the function and process of it?

Thanks