🚀 go-pugleaf

nagle@netcom.com (John Nagle) writes:

>more_da@pts4.pts.mot.com (Dan Morera) writes:
>>Greetings and Happy Holidays Netters,
>>I am developing a system to remotely control a hot tub, and I have not
>>previously worked with the large AC voltages needed to do so.
>
>     Given your discussion, I suggest you get a licensed electrician to
>do the job.  You've missed a few key safety issues.
>
>     This is NOT to be taken as a complete list, but first, where you
>have water near power, you're usually required to use a GFCI breaker,
>and for a hot tub, you definitely should.  Second, you need low-water
>and overtemp detectors for the heater to prevent fire should the water
>stop flowing or be absent.  Most hot-tub heaters have these built in,
>but check.  Redundant overtemp switches are common, and may be required.
>
>     Switches where a wet person can reach them require special handling.
>The usual hot tub switch is an air button, a squeeze bulb connected by
>a tube to a pressure switch.  Just putting the controls on the +5 supply isn't
>good enough, because something might short to the low-voltage portion of
>the system.  UL-approved switches for very wet locations exist, but
>are expensive.

Another alternative is to build the controller as a battery operated
unit (use NiCads) with all the logic and switching there.  Then
couple the serial control signal optically to the line powered controller.
My favorite way to do this is using a 1200bps serial line over optic fiber
(Radio Shack sold a $5 kit with 1 detector, 1 LED and 6 feet of jacketed
fiber).  One other way to do it is to build your own (or buy an appropriate
chip set) IR remote interface.  In effect, you would have a remote for the
hot-tub, with a receiver on the wall several feet away.

-Dean Reece (deanr@sco.com)