I've been studying brain waves for a while and I want to do a project like this for educational purposes, manufactured TENS devices do not have an "audio input" they are programmed with an operating pattern, it would be necessary a circuit that "receives" the analog signal from the output sound from my phone to the board input control. I did a lot of tiring research and I didn't find any similar circuit that worked like this, about converting audio into light pulses it would be something like a step up dc-dc amplifier which in this case the trigger would be the amplitude of the audio signal

 

You can feed the beats of music into a modified TENS device. Then you get zapped with each beat.
There are many common circuits that light LEDs with the beats of music.

I think that a TENS device has an adjustable zapping frequency but music does not.

 

I think that a TENS device has an adjustable zapping frequency but music does not.

Exactly, I use an app that plays and changes the Frequencies in Hertz according to my own presets in each session, that's the key. I don't know which is more expensive in this case, buying a new TENS or assembling everything from scratch. If I have to modify the device, I need to know which pins on the board I should solder to the audio wires, would it be next to the physical control buttons?

 

Do you have a painful medical problem that needs a TENS device to overload your nerves then reduces the pain?
Or are you lazy and let a TENS device exercise some of your muscles?

To add a music input to a complex TENS device then you are modifying it. To modify a complex electronic circuit then you need to understand how it works and what each part does. Then you need its schematic, its parts list and its pcb layout with all parts labelled.

Audio is AC but the TENS device probably need DC pulses on an input. You need to find out if your DC pulses that you make from audio are positive or negative and if they must be capacitor-coupled.

 

I've had a worse problem, but time changes things, a long story of a student who was about to go to college and had an accident and long years of medical follow-up. Brainwave frequencies have contributed a lot to my health, so it doesn't hurt to go deeper studying about

 

(For some, TENS = Transcutaneous Electrical Nerve Stimulation)

Has TENS been used as you propose? Can you point us to any references of TENS being used with audio?

Do you just want to inject current that is proportional to the instantaneous value of the audio waveform, following @Audioguru again 's question, do you want to use the audio signal to modulate the amplitude of a DC current or do you want the AC audio signal converted to an AC current?

 

I assume that a TENS user that has continuous pain adjusts the frequency of the high voltage zaps so that the zaps overwhelm the pain nerves or the brain. If the frequency is too low then the original pain is felt between zaps, but if the frequency is too high then the zaps themselves might be too painful.

For people using a TENS device to do exercise, with music for modulation then perhaps a loud drum beat might injure the person.
"No doctor, I was not in a car accident. My modified TENS device did this to me".

Therefore, having music amplitude modulation of the high voltage zaps is torture, not TENS.

 

I just checked - I can get a TENS device for about US $5 including shipment including 4 sets of pads. They are advertised for more than pain relief, like for massage and relaxation besides pain relief. Must be a quality product at that price

 

Better know that limiting the frequency modulation and adjusting the duty cycle wouldn't be as painful as supposed, a fixed base frequency also should not be ruled out.

"No doctor, I was not in a car accident. My modified TENS device did this to me".

I've been free from my chronic pain for just over 14 months, you need to understand that the focus here is not treat a pain itself, but any brain response to the sessions.

 

@DickCappels
Look at the top of this website http://lunarsight.com/freq.htm

CYCLES PER SECOND (HERTZ), and Correspondences to MENTAL STATES, PHYSIOLOGY, COLORS, NOTES & PLANETS

These frequencies are of all types; light, sound, electrical, etc. The two- or three-character source codes after each frequency are defined in the bibliography.

LIGHT, SOUND, ELECTRICAL

 

I recently had a very painful bee sting. I ignored it then the pain went away without a anesthetic medicine or a TENS device.

A TENS device is not frequency modulated. I assume you can adjust the repetition rate (frequency) of the zaps. Maybe the duty cycle can be adjusted.

 

I read the part of the page that you recommended. It did not tell me what you want to do with the audio.

From what I have been able to read isochronic frequencies have been applied as audio. It appears that there is no established protocol of applying these frequencies electrically. I do not think you will find the expertise needed to apply isochronic frequencies on this website. What is apparently needed is some insight into the mental and biological effects.

 

So I come to the conclusion that it is better to buy in sequence:
1 - Bluetooth 5.0 audio module (5V, 2A input supply)
2 - DC to DC Step UP Booster within the 40-120V output range (which is the working output range of a TENS device, with milliamps not harmful to the body skin)
3 - Two 5W LED's

That would be a more affordable option, but probably the speakers audio channels would be muted when I plug in the headphones jack, something must be modified on the bluetooth receiver board for the amplified output and the headphones to work simultaneously, so I connect the wires to the amplified output of the board on some of the Step UP Converter IC pins (I don't know much about electronics, I could even be wrong, that was the reason to seek help in the forum), then comes the LEDs part, being only necessary to detect the largest amplitude of audio output and avoid a dimmer/linear light

 

So, @DickCappels in fact it is not only used in audio, look at this article https://en.m.wikipedia.org/wiki/Mind_machine
Theoretically, my project will be a modified version of this one with greater results adding electricity

 

...do you want the AC audio signal converted to an AC current?

AC Audio Signal -> DC High Power (120V max.)

 

The "mind machine" uses DC pulses of light and pulses of sound.
The TENS device produces electrical shocks but we do not know if it is AC or DC.

 

To @Audioguru again 's point, there may be a great difference in side effects between AC and DC stimulus.

andmailcontra wrote:
AC Audio Signal -> DC High Power (120V max.)

To be clear, you might need relatively high voltage to get the current you need but you don't want high power unless you want to cook something.

Personally, I would not use a 120V source if the current could exceed 500 microamps. Below 500 microamps electrocution would not be a worry, but at that voltage I would worry about how good the contact between the pads and the skin was because I would be concerned that dry pads of another cause of poor contact could lead to skin irritation. I have my concerns about DC causing ion migration that might eventually lead to skin problems, though it is noted that tDCS uses DC without apparent problems.

 

The correct one must be AC, I was wrong, because:
"In contrast, alternating current has an inverse relationship between voltage and amperage, which means as voltage increases, maximum amperage actually decreases"

The supply source for the whole project will be 5V and 2A, a common phone charger.

"Basic TENS devices have simple circuits that typically generate no more than 40-60 volts. Prescription devices may provide 100 volts..."

What can you tell me about these converter?:
https://www.ebay.com/itm/185370250829

 

I thank you so much for every answer from your guys

DickCappels wrote:
I have my concerns about DC causing ion migration that might eventually lead to skin problems

With more research I came across what @DickCappels said

In the description of the module mentioned above is: 75V AC fixed output

 

The voltage converter module uses an old-fashioned transformer then its (unknown) output frequency is probably only 60Hz.