[NTLUG:Discuss] OT: Hz

[Rusty Haddock]

Fred James wrote:
    >...
    >It would seem logical that since no circuit board is likely to run on 
    >household current directly, there must be a transformer of some sort in 
    >the mix.

Depends on what components/equipment is attached to the circuit board.
Having a transformer is NOT a MUST just because it's connecting to a
circuit board.

    >Might it be reasonable to assume that the resulting voltage 
    >applied to the circuit board(s) could vary, possibly considerably?

If a transformer is present, generally it will step down the incoming
voltage.  Incoming mains voltage of 120Vac might be stepped down to
24, 12, or 6Vac which means the voltage is scaled by factors of 1/5, 1/10,
or 1/20, respectively.  Any variation in the input voltage, say 10V,
would show up on the output voltage of the transformer scaled similarly,
say 2, 1, or 1/2Vac, respectively.

Electronic circuits, say involving microcontrollers or basic logic
circuits will generally have one or more voltage regulators on them that
will regulate their output voltages down, generally, to the range of
0.1 to 0.01 volts of accuracy, even if the input voltage varies greatly.

    >And
    >if it does, might that variation be enough to cause the circuit board to 
    >trip a solenoid, or switch, or some such thing?

No.  Solenoids would probably be released if the voltage went down too
low, say in case of a brown out (voltage on the mains going below, say,
)00Vac, for more than a few 1/60-second cycles).  Still, the electric
companies, weren't planning on dropping the voltages THAT low.

    >If it is of any help in 
    >consideration of the matter, the appliance causing the most concern at 
    >the moment is an electric dryer.  And while symptoms might suggest that 
    >timer switch, diagnostics do not concur.

Sounds like possibly a corroded connector that's making a very
intermittent connection.  If there's a circuit board involved then
there's also the possibility of a conductive trace that's cracked and it's
opening the circuit briefly from either vibration or thermal variations.
Both are buggers to debug.

Hope this clears some things up for you, Fred!

	-Rusty-
-- 
   _____                Rusty Haddock  <=>  AE5AE
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