On 2014-10-17, tdacon wrote:
I know this isn't a metalworking topic, but you guys have a lot of
collective knowledge. I'm installing a refrigeration system in my boat. It's
a holding plate system, powered by 12V DC, turning a motor that draws about
25 amps when it's running. It will probably run about an hour or so a day,
at unpredictable times. I'd like to be able to measure how many hours in a
day it runs, without having to sit there and time it when it turns on and
off. How would you go about that?
Is the 12V cycled at the same time, or is the 12V stable, and
switched inside the holding plate?
If the former -- find an old automobile clock (which runs from
12V and hook it in parallel with the plate. The really old ones used to
have a spring which was wound once every few minutes (a "thunk" at that
time), so your resolution would be limited to how long to took to run
down without power.
Fancier would be a digital counter and an 555 generating a pulse
per minute or a pulse per second, depending on how much precision you
wanted. Just remember to read the data before you turn it off for the
day.
Or -- there are running time meters. Most that I have are 115 V
60 Hz, but I know that there are versions designed to run from 28 VDC,
and are likely also for 12 to 14 VDC.
O.K. Here is an aircraft one on eBay which works from 6V or 12V
DC:
#131238077504
And here is a cheaper one from 8V to 50V DC:
#161450172146
And some 10-80 VDC ones:
#161261318398
So -- I've found you several choices on eBay. The search string
is:
elapsed time meters
and just wade through looking for ones which will run on somewhere
around 12-14 VDC/ (All of the above which I have found will do so.)
Too late to go any deeper into the search results. And
specifying the voltage in the search string will miss a number, as the
voltage is not in the header. Sometimes you have to look at the box
images, or labels on the instruments.
Good Luck,
DoN.
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