Trafo for building these projects

Hello all,

I have been diagnosed with poly neuro pathy, witch means the nerves in my extremities are dying, witch comes sadly enough with a constant pain in my toes. Using a TENS does help allot against the pain. The problem is that all machines turn themselves off after a while. I have experimented and came to the conclusion that if I would have a machine that would work 5 minutes every 30 minutes I would be mostly painfree, therefore my interest in this topic.

In almost every schematic that I find concerning this subject I see that a trafo is used. I have been looking online intensely but have not found any of those small trafo not the parts to wind one myself.

Is there anybody that either has a schematic that doesn't require a trafo, or otherwise a source online where I could find this part.

Also, does anybody know if the output voltage of these circuits would lower then 300Vpp, so that I can safely connect the outputs to my oscilloscoop, witch is brandnew and I would like to keep in a good working order. I have ordered a convertor so I can measure the current with my oscilloscoop, it has a BNC output.
Thanks to everybody for any help offered in this matter, I am on disability partly because I am in constant pain.

Sorry to hear about your affliction. By trafo do you mean transformer? If so, there are readily available parts to wind your own, at least here in the US (until Trump bans them). If you're trying to build your own unit I'd be very careful. Although the current in commercial TENS is fairly low, it is in the range of 100s of volts.

Hi,

A quick search leads me to think these cost from $25 to $1,000. Some are portable and some I guess are very large and will not run on batteries.

Do you have one of your own? If you have one already and it is a plug in the wall device, unless it's designing the device that you want to do, maybe a simpler solution is some kind of timer plug.

If battery powered, I'd personally be reluctant to tamper with it to try and insert a timer of my own making onto/into the power on/off button, unless I understood the circuit enough, but it's a thought.

d123 said:

Hi,

A quick search leads me to think these cost from $25 to $1,000. Some are portable and some I guess are very large and will not run on batteries.

Do you have one of your own? If you have one already and it is a plug in the wall device, unless it's designing the device that you want to do, maybe a simpler solution is some kind of timer plug.

If battery powered, I'd personally be reluctant to tamper with it to try and insert a timer of my own making onto/into the power on/off button, unless I understood the circuit enough, but it's a thought.

Click to expand...

I have 3 of these portable TENS machines, and they work well. I paid 67 Euros for each of them. They have to be battery powered, for mobility, and I would need 2 that work on a timer, because I need one for each foot. Since they use 4AAA batteries they use 6volts. This made me think I would be able to power an Arduino nano and program the outputs to like you mentioned manipulate the on/off button of the device. Then we have another problem, when turning the device on the intensity of the output is still set to 0. So I would need to manipulate the turning wheel switch with another Arduino output. I am currently in the process of taking one machine apart, without breaking it, so I can study the internals, but its very difficult to open without causing damage.

Thank you for your reply :thumbsup:

Mikeb1970 said:

very difficult to open without causing damage

Click to expand...

The risk is that you'll throw away 67 euros. In my experience the risk is not worth it. Tiny springs love to pop out as you open a unit. Small wires like to get detached from solder points. And do you know about precautions against ESD?

Suppose you make the easy modification first? Start with a single AAA cell, and boost it to 6V with a converter? A rechargeable type might last a few minutes. As it declines the unit shuts off automatically. When you start to feel pain, put in another rechargeable cell.

I did this for my wireless mouse, so I can run it on half-used D cells. It has a compartment for 2 AAA. So I shaped a piece of wood like 2AAA. I attached wires so they mimic battery terminals. I leave the mouse on for hours. I switch it off with the original switch. I never needed to take the chance of ruining it by taking it apart.