Iontophoresis Device to treat Hyperhidrosis

[Hackitt]

Excellent article found Ramuna, I've read it through. The reason I want to have more current available is: If I have not treated my hands for a few weeks, I have difficulty in conducting more than about 10mA. For some reason, as the treatment progresses, the current rises and needs to be turned down to a comfortable level. Most of the commercial machines instructions say that 20mA for feet and 15mA for hands. I wonder why conductivity of my hands are poor if not treated regularly?

 

[crutschow]

If your hands are busy, why not add a foot-switch to control the current.

 

[ramuna]

Or incorporate a constant current feature, eg an op-amp whose output drives the base of an NPN power darlington via a current limiting resistor. The load is placed between Vcc and the transistor's collector. The emitter has a low value (current sensing) resistor to ground. The emitter/resistor junction is connected to the inverting input of the opamp & a voltage reference (proportional to the desired current level) connects to the non-inverting terminal. You can also interpose a non-inverting dc amplifier (say, using the second opamp of a LM358 with the first committed to the aforementioned current control) between the emitter/resistor junction and the inverting opamp input. The dc amp would allow you to use very low value resistors at the emitter and easily realisable potentiometers to vary the current control voltage at the non-inverting terminal.

Placing a high value resistor between the pot's wiper and the non-inverting input, and a capacitor between the high value resistor/noninverting input junction and ground would create a soft-start/ soft-shutdown feature which would (a) eliminate the shocking problem due to abrupt shutdown and (b) allow the body to acclimate to the target current level over a period of time.

 

[Hackitt]

Soft start and shutdown sounds good.

 

[flatfootskier]

Why not have a waterproof switch in the bottom of the tray? Switch it on and off whilst hands are under water

 

[Pommie]

I think the commercial ones must sense that your hands are leaving the water and reduce the voltage automatically. I would do this by monitoring the current and when it starts to drop switch off the supply. An opamp configured as an integrator would be the best way to detect the dropping current.

Another possibility is to have only 6V normally and only switch up to 24V when a particular current is reached. This would mean that as your hands leave and the current drops the voltage will automatically drop to 6V.

Just thinking out loud.

Mike.