Hi everyone,

I'm working on a personal project to build a Transcranial Electrical Stimulation (TES) device, which can support tDCS (direct current stimulation) and potentially tACS (alternating current stimulation).

My goal is to understand and build a safe and functional prototype that can output 0.5–2 mA of current through scalp electrodes, with basic safety features, waveform control (especially for tACS), and session timers.

What I am looking for :

1.A complete understanding of the circuit blocks required for TES
2.List of essential components (op-amps, current source ICs, microcontrollers, etc.)
3.Schematic or references for building:
4.A constant current source
5.A microcontroller-controlled waveform generator (for tACS)
6.Safety features like current limiting, timer cutoff, etc.
7.Suggestions for electrode interface (types and connection method)
8.PCB design tips for compact and safe layout

Important constraints :
1.Max output current: 2 mA
2.Needs to be current-controlled (not voltage-controlled)
3.Compliance voltage: 15–20V max to overcome skin resistance
4.Safe for scalp usage (with all required protections in place)
I've read that TES uses common placements like F3-Fp2 (10-20 system), and I'm using saline-soaked sponge electrodes or rubber electrodes with gel for skin contact.

Any help with schematics, safety guidance, or component suggestions would be massively appreciated. If you've built or worked on anything similar (like tDCS, tACS, TENS, EMS), I’d love to learn from your experience.

 

You might benefit from my project:
https://forum.allaboutcircuits.com/threads/micro-current-electrical-stimulation-device.126578/

Since you need items 5 and 6 on your list, I'd recommend a microcontroller instead of the dual 555 timer I used to provide the waveform. But my current control scheme works well for this application.

 

Thank you wayneh sir for the valuable information will look forward and try to build the project and will send if any doubts regarding the project

 

Both tDCS & tACS are interesting, and research is ongoing. I was looking to design on using an MCU then I came across this project, which looks like a well thought out design with safety in mind, so I made it. It works as described, but I have left it on the side until I have enough time and a project where I can properly test it and record its effects.

 

What the TS is requesting is a serious engineering project. Several kilo-bucks worth of engineering effort at commercial rates.