James,
The IC regulators that are out there are spec'ed to work over the "industrial"
temperature range, that's usually -40 to 85 degrees C. Within that range the
accuracy of the voltage output depends on the goodness of the resistors you use
to set the output voltage, so a few pennies (or quarters, at low volumes) spent
here means you don't need adjustments.
As far as over/undervoltage spikes go, a good reference here is SAE J1211. I was
planning to provide a clamp diode to trigger at 50 volts or so (which is the
maximum that the regulator I had in mind can stand). The diligent experimenter
will be able to find ways to exceed that voltage, but that kind of stuff will
also damage other components in the car's electrical system, and the instrument
regulator will then be the least of your worries.
A dual output with adjustments on both is something that I was specifically
trying to avoid, since most folks are still using stock sensors and gauges
(correct me if I'm wrong here), and having adjustments would just mean that
everyone would then be dependent on the goodness of their voltmeter. My plan was
to offer a bolt-in (or solder-in, for those of you that like to tinker)
solution, no adjustments, no frills. Frills cost engineering time, and that
means everyone gets to pay more.
Theo
> -----Original Message-----
> From: James Barrett [SMTP:jamesbrt@mindspring.com]
> Sent: Thursday, July 15, 1999 4:35 PM
> To: Theo Smit
> Cc: tigers@autox.team.net
> Subject: Re: Instrument Voltage Stabilizer Spam
>
> Theo,
> Make it with an adjustment knob so when the Tiger over heats you can
> simply turn down the voltage and have a "cooler Tiger"&-)
> Alternate is with a cool tiger, turn up the voltage when you are about to
> run out of gas&-} .
> Seriously, as the original crap is a bimetalic strip I would assume
> that
> as the ambient temperature under the dash changes the, average voltage out
> of this
> original regulator would also change. This would also change the readings
> on the
> temp and fuel gauges.
> Are you considering doing temperature compensation on your circuit?
> Are
> you going to test it for EMC problems? (specifically for the case of excess
> voltage spikes due to jumper cables, bad voltage regulators, etc?). I have
> noticed
> that specifications for automative electronic components are often times much
> more strengent than MIL specifications for vibration, EMC, and temperature
> extreams. Will you pot it for dirt, humidity and mildew problems?
> I might be interested in replacing my Prince of Darkness regulator
> with
> your product if it was less than $15 and it had compatable connections.(
> Even without
> fancy specifications and tests)
> Final thought, a dual output with adjustments on both would be handy
> for
> those who are using a different temperature sensor/ or gauge and the other
> adjustable
> output for those who have changed their fuel tanks or sensor.
> James Barrett Tiger II 351C and others
>
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