A little less Simple DIY TDCS circuit using CRDs

There has been some important points brought up about the benefits (easy to build, robustness) and drawbacks (turn on transients and lack of accuracy) of the Simple DIY TDCS circuit using CRDs. Considering the lack of accuracy, this is a characteristic of the diode not the circuit.

For the E-102, the the datasheet only gives a range of 0.88mA - 1.32mA. But I have seen that there is a higher probability of finding them near 1mA (for example if you test 100 of them most will be between 0.9mA - 1.1mA), with some outliers at the full range. And physiologically, it is still not clear whether 0.9mA will be much different than 1.0mA will be much different than 1.1mA.

Regarding the transients at turn on, that is a circuit issue. So to remedy, it is easy to add an LC filter at the output (see picture below for new schematic). The LC filter acts to dampen any transients. Bench testing shows the ramp up to be 500ms, which is plenty to dampen any turn on pulses, but unfortunately not enough to prevent any flash that occurs with certain montages. At mouser.com, the L can be 22R105C and the C can be UKL1E100KDDANA.

The above explanation is for informational purposes only, and I take no responsibility for the use or intended use of this information. TDCS is currently not FDA regulated, and there is no intention here in providing a TDCS device. Also I suggest you read, read, and read more about TDCS, particularly any safety considerations before undertaking any project like DIY TDCS and contact your health provider if you have any particular questions about your particular condition.

UPDATE

I always attach the electrodes and attach all connections before I turn on at the Battery. Make a switch at the battery and the switch at the battery should be turned on last after the electrodes are attached. If you turn the battery on first, not only will you be putting on hot electrodes but there will be a transient probably higher than 1mA.

For a simple, more foolproof circuit see the Simple DIY TDCS Circuit using CRD's below.