I plan using a AC to DC converted with constant current output (LED driver AUBIG A8HH20317) in order to light high-power LEDs (about 12*3W LEDs). The more LEDs, the higher voltage at the output, but the current is supposed to be stable (680mA). This will light a fish tank so the setup will be close to fresh water. I can protect the 220V side easily but on the other side of the converter, there will be much more wiring so that may be difficult.

Given the high humidity, am I risking electric shock if I put my hand on the constant current side ? Is my cat risking electric shock if he puts his tongue (...) in the same place ? I understand the final choice is up to me and of course you won't be responsible if I (or the cat) experience electric shocks.

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    \$\begingroup\$ The 36-75V / 680mA max output of that driver is above what would be considered 100% safe. But I must ask (jokingly) if your cat can get his tongue in the tank isn't there an additional risk to the fish as well? \$\endgroup\$ – PeterJ Sep 23 '13 at 13:31
  • \$\begingroup\$ What is the max DC output ({voltage,current}, or max. power?) that would be considered safe? Indeed there is a risk for the fish. I rely on the fact that the cat is lazy and will probably get bored very fast. However he is also curious and does weird things (like licking the border of my windows...?) so he might lick the wires as well. \$\endgroup\$ – Emilien Sep 23 '13 at 14:30
  • \$\begingroup\$ What happens to the voltage from your driver if one of the LEDs fails to an open circuit? Does the voltage just keep rising, trying to push 680mA? \$\endgroup\$ – Joe Hass Sep 23 '13 at 14:53
  • \$\begingroup\$ I upvoted your question because I look forward to informed answers, but I suspect it won't be as clear-cut as you expect and I'm not qualified to answer myself. But I do look forward to reaading good answers. \$\endgroup\$ – PeterJ Sep 23 '13 at 14:54
  • \$\begingroup\$ I'm not sure if the voltage keeps rising (I cannot check this at the moment), but I guess that's how a constant current source should behave, so it probably raises to 75V. \$\endgroup\$ – Emilien Sep 23 '13 at 15:27

In Europe there is the Seperated Extra Low Voltage specification that places limits on DC and AC voltages. It also specifies isolation from earth thus preventing a return path through ground if you touch a bare conductor carrying the voltage. The voltage limit is 60V in dry conditions but this voltage is lower in higher humidity conditions.

Your set-up is neither so it could not be regarded as falling into this category. What about direct AC powered fishtank U.V. lights - what techniques do these use to prevent shock at 230VAC - maybe you should research this and apply some of their techniques when wiring the fish tank.

I have a U.V. inline water purifier on my Koi pond and it runs from AC mains - it uses rubber power cable and rubber seals at each end of the U.V. strip. Underwater pumps are directly connected to AC mains power and I sure have worries (now and then) about the integrity of the cable feeding underwater but I use a residual current trip.

If you can ascertain that your AUBIG A8HH20317 output is isolated from earth or anything else then I believe the only reasonable chance of an electric shock is if you come into contact with both positive and negative feeds simultaneously. Try and put silicone bath sealant over exposed connections.


High humidity can turn into moisture, liquid H2O, in a very short time under the right conditions, even if only occasionally in the situation of your aquarium. So for the sake of a prudent design, I would assume this could happen at some point in time and avoid using a series topology in which voltage greater than, say, 35 volts can possibly be present. Even then you may get some conduction directly thru the moisture if there are certain mineral impurities present where the moisture condenses into liquid H2O. This may create electrical problems on its own independent of any human contact.

Even if the voltages present are not enough to cause actual harm, the "surprize factor" can be dangerous in itself. If someone gets even a harmless "tickle" when contacting your lighting system under certain conditions, they may jerk back involuntarily and knock into something or knock a nearby object over, perhaps with disastrous consequences.

If a cat's tongue is anything like a human tongue, it can be extremely conductive at very low voltages. (Take my word for it!) In my earlier days I had read in a science book that you could test the viabilty of a "dry cell" battery by touching its terminals to your tongue. I tried this with a 9-volt transistor radio battery and it knocked me off my feet. If your cat has a good sense of humor and is as curious as you indicate, you might set up a simple tempting experiment with a single AAA cell to see his reaction to even that level of voltage.


protected by Kortuk Sep 23 '13 at 19:38

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