Homebrew PCBs

On Mon, 11 Sep 2006 22:42:12 +0200, Dwayne Reid <dwayner@...>  
wrote:

>
> If I may make a suggestion: put a tiny air hole in the hose.  Place
> the hole at the highest point in the siphon - where the hose goes
> over the edge of the bucket.
> This hole need not be large - something on the order of a #60 drill
> bit is fine.  If the hose is plastic, even consider using a hot
> needle or a really small soldering iron tip.
> The purpose of the hole is to stop a vacuum from forming in the
> hose.  That stops accidental siphoning action.
> My tank is quite large (10 gallon tank filled with 7 gallons) and the
> air supply is a vacuum motor blower fed through 1" plastic pipe.  I
> used a 1/8" hole where the pipe goes over the top of the tank - I
> have way more air volume that I need and don't notice the air that is
> lost through the hole.
> Even though the blower motor is located about 40" below the top of
> the liquid, I've NEVER had etchant get down into the blower.
> I had initially considered using a 1-way valve but finding a valve
> that was low cost, low pressure drop, and impervious to the etchant
> seemed impossible at the time.  The air hole simply eliminated the
> need for the valve.
> dwayne


That's a good idea!

One could even plug the hole if the escaping air would be a problem,  
during etching, with a well-visible plug so it is not forgotten.

The no-return valves for fish tanks are very small (for a 3 or 4mm hose  
usually), but made of plastic and rubber parts so basically resistant.


ST