Iontophoresis Device to treat Hyperhidrosis

[Hackitt]

Hello all,

I've had a look around the forum and have seen the above subject mentioned, but have a question. I have made my own device to treat this condition and it works well and I am very pleased with it.

For those that don't know, Hyperhidrosis is excessive sweating, usually of hands or feet. My machine simply passes a DC voltage of 24 Volts across two trays of water into my hands, and obviously a current. Current is typically around 15mA.

Some of these commercially available units boast a feature that I would like to include in mine. At full current, if I withdraw my hand or hands with the machine on, I get a sudden shock known as The Electric Fence Effect. Some of these machine manufacturers boast that this does not happen as it is suppressed internally.

My question is: How do I add this feature? I don't know exactly what causes this effect so not sure how to suppress it. I'm guessing something like a reversed bias diode across the output. Any thoughts on this would be appreciated.

 

[cowboybob]

As you suggest. The diode "dumps" any inductive (or other) reverse "kick" voltage that developes as a result of you breaking the circuit by removing a hand from the water bath.

(As an aside, I must say your post represents the longest period of time I've ever seen between joining a forum and then posting a comment/query...).

 

[ramuna]

Hello Hackitt,
Incorporate a way to reduce the device's output voltage as far down as you can, ideally to zero, before you remove your limb from the water to break the circuit. How exactly to achieve this depends on the means you are using to produce the 24v dc. One obvious way is to have an old-fashioned rheostat in series with your limbs. Measure the current in the present circuit with your limbs in place & calculate the resistance between your limbs. Construct or obtain a rheostat with say, 20 times this resistance at its maximum. Put the rheostat in circuit, with its resistance set to max. Place your limbs in the water, and gradually reduce the rheostat resistance to zero. Similarly, for shutdown, gradually increase the rheostat resistance to max and only then withdraw your limbs from the water. Suitable rheostats are available on Fleabay.

 

[Hackitt]

As you suggest. The diode "dumps" any inductive (or other) reverse "kick" voltage that developes as a result of you breaking the circuit by removing a hand from the water bath.

(As an aside, I must say your post represents the longest period of time I've ever seen between joining a forum and then posting a comment/query...).

Thanks for the reply. I went to join and found I was already a member!

 

[Hackitt]

Hello Hackitt,
Incorporate a way to reduce the device's output voltage as far down as you can, ideally to zero, before you remove your limb from the water to break the circuit. How exactly to achieve this depends on the means you are using to produce the 24v dc. One obvious way is to have an old-fashioned rheostat in series with your limbs. Measure the current in the present circuit with your limbs in place & calculate the resistance between your limbs. Construct or obtain a rheostat with say, 20 times this resistance at its maximum. Put the rheostat in circuit, with its resistance set to max. Place your limbs in the water, and gradually reduce the rheostat resistance to zero. Similarly, for shutdown, increase the rheostat resistance to max and only then withdraw your limbs from the water. Suitable rheostats are available on Fleabay.

That's the set-up I have at the moment. Providing the current is reduced to near zero there is no shock. It would be nice to add something to stop the effect. Do you know why this Electric fence effect happens?

 

[ramuna]

No I do not know why the shock occurs when the circuit is suddenly broken. However, it appears to be a universal problem with these devices. For example, read:
http://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfmaude/Detail.CFM?MDRFOI__ID=318815
and
**broken link removed**
Read under Precautions in the second link above. Bullet point 1 has a typo. It should read "if you do not, you will receive an unpleasant shock..."
This effect doesn't appear to be an inductive kickback effect, since you will experience it even when you use series connected batteries to produce the 24v that you need, with no inductors involved.
It appears to be a physiological effect, perhaps a nervous reflex.

 

[ramuna]

Yet another method to produce the same gradual reduction in current before shutdown, in the case where your present device is powered by ac mains, is to interpose an off-the-shelf lamp dimmer switch between the mains and your device. Then turn the dimmer down before withdrawing your limb from the water.

 

[Hackitt]

Yet another method to produce the same gradual reduction in current before shutdown, in the case where your present device is powered by ac mains, is to interpose an off-the-shelf lamp dimmer switch between the mains and your device. Then turn the dimmer down before withdrawing your limb from the water.

It's Battery operated for safety. I may consider a mains operated option and probably will use a nice toroidal transformer and rectification. I'd hate to be found lying in a heap on the floor from accidental electrocution!

 

[ramuna]

In that case (ie battery operation), consider having the load (ie the electrodes with your body in between) as the emitter resistor of an emitter follower. For normal operation, the emitter follower's base will be at Vcc, giving you max output voltage between emitter and ground. Then have a shutdown switch which ramps down the base voltage to zero over a few seconds. That would solve the shock problem and would be less bulky than having the rheostat. You'd need to mount the transistor, a TIP122 or suchlike, on a heatsink though.

 

[cowboybob]

Hackitt,

Maybe have someone interrupt the ciruit (unplug a lead somewhere in the circuit while your hand(s) remain in the water) and see if the shock is still occurs.

If not, then perhaps install a foot mounted push On/Off toggle switch, for instance, to kill the circuit prior to removing your hand(s).

My thinking is that as you remove your hands(s), at the last moment they are in the circuit, the resistance your hand(s) represents suddenly goes quite high (they're no longer surrounded by water) and, assuming a consistant or even increasing current flow, that would simultaneously jack the voltage across your hand(s) to, conceivably, the max voltage available just prior to the circuit break.

 

[KMoffett]

Hello all,

... I have made my own device to treat this condition and it works well and I am very pleased with it....

Mind posting the schematic for the device you made? It would help!

Ken

 

[Hackitt]

Mind posting the schematic for the device you made? It would help!

Ken

It's basically 4 x 6 volt lantern batteries in series with a 10k lin pot together with 0 to 30 mA meter in series wired to two stainless trays filled with water. Turning down the current before removing limbs results in no shock. I'm wondering what an electrolytic in parallel with the trays may work. I'm a bit of a coward and hate shocks, although it's harmless it still makes you jump.

 

[KMoffett]

I used to make those for clinical diagnosis at a pulmonary function lab. Except the early ones used 67.5V batteries, an pot and a meter... at 1.5mA. I made newer ones later that used 4xAA batteries, DC-DC converters, constant current regulators and timers. You might add in a timer and indicator that times your treatment. It would shut off the current and indicate it's "safe" to exit.

Ken

 

[Hackitt]

I used to make those for clinical diagnosis at a pulmonary function lab. Except the early ones used 67.5V batteries, an pot and a meter... at 1.5mA I made newer ones later that used DC-DC converters, constant current regulators and timers. You might add in a timer and indicator that times your treatment. It would shut off the current and indicate it's "safe" to exit.

Ken

The mark II version will use a DC to DC converter, probably at 30 volts to get a little more current. I'm a bit wary of mains units. What did you use to limit the current? LM317? I like the idea of a timer etc...

 

[KMoffett]

Attached!

 

[alec_t]

probably at 30 volts to get a little more current

Beware. It takes only a few tens of mA through the heart to kill you. With your hands in two trays of water there is a current path through your heart.

 

[KMoffett]

I agree with Alec. You are pushing the limits.

Ken

 

[Hackitt]

Point taken about the heart. Most of the current is shunted elsewhere fortunately. The condition has ruined my life. If it's time to go.....

 

[ramuna]

Regarding safe current levels, I spent some time Googling and came up with this:
https://www.sweathelp.org/pdf/Treatment of palmar HH by ionto - Stolman.pdf

Look at the first paragraph in the Right hand column of the first page of the paper for current levels. It gives 12 - 20 mA for 20 minutes. I did some work on iontophoresis involving feet some years back. The same idea:two trays containing water, one connected to +ive DC, the other to -ive. The patient puts a foot into each tray and turns on the current. I seem to recall that the optimal current levels were around 20 mA for 20 minutes. But note that these were feet, not hands. It seems more likely to me that the current would take the shortest path, ie through the groin rather than through the upper torso.

That said, Alec is right. seek professional dermatological advice on safe & therapeutically effective current levels before planning your Mark 2.

 

[Hackitt]

Regarding safe current levels, I spent some time Googling and came up with this:
https://www.sweathelp.org/pdf/Treatment of palmar HH by ionto - Stolman.pdf