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dmitrygr
> down to ~3.0V (discharged).

That is NOT how one uses lithium batteries one foe snot want to go boom. Consider 3.6V as empty. Discharging them down to 3.0 can cause them to go boom when recharged...

lambdaone
Monophasic waveforms are generally considered less safe than biphasic waveforms. That's why many TENS units have an output stage based around a pulse transformer, so they can deliver two pulses, one in each direction, shortly after each other. Leaving this out seems to me to be a false economy when you've gone to all the effort of building the rest of the system.
autonomydriver
Coming in a V2, semester just started again, so I have a little less time for it. Given that I also have some other projects on the way :)
clnhlzmn
I see

> Each electrode channel is tied to a finger pad

but the layout shows the finger pads are all tied together. What am I missing?

autonomydriver
Poor wording, should mean that each finger has a dedicated output, but you are right, they are all tied together
sowbug
My trusty TENS device has gotten me through a few bouts of whatever it is I have had for the last year (pudendal neuralgia, sciatica, pelvic floor issue, not sure). But it really is a pain in the ass (ha) to apply the sticky electrode pads.

Has anyone ever seen something like a TENS shirt or shorts that has the pads built-in?

autonomydriver
In my searches, yes, I found something like that from an italian university. Sadly can't find the paper now.
ricardobeat
That final paragraph smells of LLM. I might be becoming a bit too paranoid, but without any pictures or description of how well it works, can't tell if this is real or not.
zhouyisu
I tried to build some TENS device, but lost in "safety maze".

I reverse engineered some existing device, there are TONS of safety measures.

At least: current limiting resistor, transformer, voltage/current feedback, GND isolation, MCU protection.

After replicate all of these, I still not brave enough to try it myself, I just find it too dangerous.

PS: TENS device is fun. article seems like a bait.

autonomydriver
The two BJTs do limit current to 20mA on all finger outputs. Voltage feedback is also set up to ensure maximum 32V. MCU protection, well just a ferrite bead.
NoSalt
This is cool, and all, but you can buy a TENS unit for $20.00 to $40.00 on Amazon.
arresin
What do people use this for?
mrcartmeneses
I saw a CTO put an email send script in a while (true) loop like this and we only stopped dossing one of our investor’s email after our sendgrid bill hit £32k. Funny thing about emails is they get in a proverbial traffic jam all across the internet so no matter how many times the poor guy would clear his inbox more would magically arrive