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Iontophoresis units are in general very expensive, although the production price is negligible. Building such a device is very easy and costs about $15. Its main purpose is to reduce sweating, or to quickly deliver medication under skin.
The transistors I used are logic level MOSFETS - PA605, any decent boost convertor module will do and the whole unit is powered by one 18650 battery. Any cheap USB charging module can be used.
The opamps are LM6142 - low power, low supply voltage, rail-ro-rail inputs and outputs, low price.
The circuit is tuned to deliver around 6ma of current through the wet skin. I find such current to be the most personally comfortable. Of course that can be changed and a pot can be added. What I didn't include in the schematic is a "low battery" indicator module, but one is easy to make with a single opamp, one diode and a couple of resistors. Perhaps someone has a better solution, so I didn't include it. The 220uf capacitor and Q4 make sure that the current rises and falls gradually and smoothly.
Now, the transistors Q1, Q2 constitute electrode open circuit protection. As soon as current through LED5 stops flowing, Q4 opens and shunts the "big" capacitor. Don't use a red LED for that!! The idea is red leds have about 1.98V forward voltage, which is too low for reliable opening of Q1. I personally use a violet led, which drops about 3V. The 91ohm resistor serves as a current sensor, so the unit is overcurrent-protected. 91ohm shuts the unit off at about 7.5ma, the lower the value of the resistor, the higher current is allowed. D2 constitutes protection from the boost-convertor getting nuts and giving all of a sudden ridiculously high voltage. In terms of resistors - I use 1W ones. I strongly encourage to use no less than 4 resistors, just to cover a potential hazard of one of them falling short (practically impossible).
Well... that is it, works fine for me.
The transistors I used are logic level MOSFETS - PA605, any decent boost convertor module will do and the whole unit is powered by one 18650 battery. Any cheap USB charging module can be used.
The opamps are LM6142 - low power, low supply voltage, rail-ro-rail inputs and outputs, low price.
The circuit is tuned to deliver around 6ma of current through the wet skin. I find such current to be the most personally comfortable. Of course that can be changed and a pot can be added. What I didn't include in the schematic is a "low battery" indicator module, but one is easy to make with a single opamp, one diode and a couple of resistors. Perhaps someone has a better solution, so I didn't include it. The 220uf capacitor and Q4 make sure that the current rises and falls gradually and smoothly.
Now, the transistors Q1, Q2 constitute electrode open circuit protection. As soon as current through LED5 stops flowing, Q4 opens and shunts the "big" capacitor. Don't use a red LED for that!! The idea is red leds have about 1.98V forward voltage, which is too low for reliable opening of Q1. I personally use a violet led, which drops about 3V. The 91ohm resistor serves as a current sensor, so the unit is overcurrent-protected. 91ohm shuts the unit off at about 7.5ma, the lower the value of the resistor, the higher current is allowed. D2 constitutes protection from the boost-convertor getting nuts and giving all of a sudden ridiculously high voltage. In terms of resistors - I use 1W ones. I strongly encourage to use no less than 4 resistors, just to cover a potential hazard of one of them falling short (practically impossible).
Well... that is it, works fine for me.
