I once saw a project for a level sensor using a piece of ribbon cable
with the ends sliced at an angle. When you think about it, this is
really a very neat solution - Easy to terminate to the board, many
stages of level sense available, discrete.

My advice to a hobbyist would be use an off the shelf low voltage power
supply, e.g. a wall wart at say 12V, and try to get some valves that run
from 12V too. That way, someone else has done the 'scary mains
isolation' bit for you.

Regards, Kevin

> -----Original Message-----
> From: pic microcontroller discussion list
> [mailto:PICLIST@mitvma.mit.edu] On Behalf Of Reginald Neale
> Sent: 28 March 2002 09:29
> To: PICLIST@mitvma.mit.edu
> Subject: Re: [PIC]: Automated whirlpool tub ...
>
>
> Neil:
>
> Have you had these suicidal impulses for long? :-)
>
> I'm sure you are aware of the huge safety issues. Isolating
> all your line voltage switching circuitry from the control
> circuitry is not trivial. Relays are good, but there's
> creepage, leakage, physical barriers...
>
> Even for the level sensing, it's probably not a good idea to
> get your voltages wet. Aside from the safety issues, output
> from electrodes in contact with the water/chemical solution
> may not be stable. For level sensing, GEMS makes some
> float-type modules that are very reliable and inherently isolated.
>
> What does the existing control system use for temperature
> sensing? You can probably adapt that same sensor to your new circuit.
>
> Reg Neale
>
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