From: Bjorn Brandstedt (super_deuce@hotmail.com)
Date: Fri Apr 16 2004 - 05:02:13 PDT
Actually, the new switch, with its surface mounted components is probably a
lot less costly to manufacture than the original precision machined, silver
plated contact one.
Perhaps the worst condition one can impose on vehicle electronics is the
"load dump". This occurs when the generator/alternator is charging an almost
discharged battery and the connections come loose (never disconnect the
battery cables when the engine is running!).
A load dump can produce voltage spikes in excess of 125 volts for a few
milliseconds, enough to kill any unprotected/low voltage transistor.
Special electronic components called varistors, are used to protect
sensitive electronics. Does the new switch have one of these (cost less than
50 cents/ea in quantities)?
Plenty of solid state 25 amp regulators fried and must have provided lots of
repeat business for the makers because they didn't have this varistor. I
once purchased several 25 amp regulators from a seller on ebay and 2 out of
3 were damaged from from this condition.
The new switch must have power to operate. Is it always applied or is there
a switch to turn on the switch?
Bjorn
MVPA 19212
Meadows of Dan, Virginia
>From: "aee002" <foo@wavebuilder.com>
>Reply-To: MVlist@yahoogroups.com
>To: MVlist@yahoogroups.com
>Subject: [MVlist] Re: new light switch available - it can't just turn on
>the lights - right?
>Date: Tue, 13 Apr 2004 18:08:41 -0000
>
>--- In MVlist@yahoogroups.com, David Cole <davidcole@t...> wrote:
> > Somebody please tell me that the new $260 light switch does something
> > really special for that kind of money!
> >
> > I'm at a loss.
> >
> > Dave
>
>I think what it does is provide a nice juicy contract to some company
>which has been a reliable and generous donor to a key senator or
>representative.
>
>I'm an electronics engineer myself, and I prefer mechanical switches
>and relays over transistorized microprocessor-controlled electronics
>whenever possible if reliability is an issue. Yes, switch contacts
>theoretically wear out and transistors theoretically do not, but the
>heavy silver-plated contacts in the standard 3-lever switch have not
>worn out in 50 years, although the switches do get broken by
>incompetent drivers now and then. Transistors and microprocessors, on
>the other hand, get zapped by voltage spikes, fried by
>reverse-connected batteries, and even damaged by cosmic rays and
>nuclear radiation. Once something gets zapped, there's no telling what
>could happen -- all the lights could stay on or they could all stay
>off, some could go on or off intermittently, or any number of other
>annoying and dangerous combinations could happen. Furthermore, all
>those rubber pushbuttons still have mechanical switches behind them,
>which will still wear out or get dirty eventually.
>
>A standard 1950s MV with a generator (not alternator) contains no
>silicon electronics and is thus pretty well immune to neutrons, gamma
>rays, or nuclear electromagnetic pulse. With an alternator it becomes
>a little more succeptible, but when you start adding fragile
>transistorised micro-processor contolled stuff to it, power supply
>noise can easily destroy the whole system.
>
>I would love to have been able to do the qualification testing on this
>electronic light switch. I would have loosened up the alternator
>ground strap and revved up the engine. I would have put a worn-out
>brush in the alternator. I would have turned the voltage regulator up
>to maximum output. I would have disconnected the batteries and reved
>up the engine. I would have hooked the batteries up backwards. These
>are all things that could easily happen in real life, and none of them
>would damage the normal 3-lever switch, although some of them might
>burn out a light bulb. I strongly suspect that any one of those
>very-realistic mistakes would destroy the new electronic light switch.
>
>---David Sherman
>
>
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