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This thing always sits in the truck logging cab
compartment, so it is not exposed to anything too terribly awful. I have
decided to definitely add a choke and capacitor to the front end. I am
curious about your suggestion for transient protection. Are you thinking
of one of the little transient suppression diodes? If so, what value would
be appropriate? I think vehicle DC power is 13.8 volts nominal when the
alternator is fired up.
Thanks.
Syd
----- Original Message -----
Sent: Sunday, September 18, 2005 7:34
PM
Subject: Re: Bipolar Power Supply
I understand your environment very well. I have logged oil
wells. It's brutal. I stand by my assessment that you probably do not need
additional filtering but I would not want to bet my professional reputation on
it. A risk assessment would show you have temperature extremes; explosive,
toxic, gases (H2S, CH4 just to name a few); other explosives; severe,
mechanical shock; and difficulty to repair to deal with. The cost of
additional filtering is slight. I would also add transient protection too.
Plan for the worst and hope for the best.
Fred Townsend
Syd H.
Levine wrote:
This thing is a meter that shows when a casing collar locator (CCL)
passes a coupling in an oil well. It is a simple amplifier and a
microammeter that always runs off raw vehicle DC just fine. But the part
that needs the bipolar supply is an auxiliary board that is a simple
comparator circuit driving a Sonanlert annunciator when a collar is
detected.
This problem arises because the original manufacturer put one of those
potted "brick" bipolar supplies in the gizmo that runs off mains line AC
power (actually off of a generator or inverter in the truck). The way
the thing is rigged, it is profoundly unsafe since explosives are
dangling below the CCL. I have to get that line power out of the unit,
hence the DC / DC converter. In the abscence of the comparator circuit,
I would just run it on the vehicle 12 volt supply, but that dern
comparator needs the bipolar supply.
Sorry for not being more specific in the original post.
Syd
----- Original Message -----
To: "Multiple recipients of list CHIPDIR-L" <[email protected]>
Sent: Saturday, September 17, 2005 7:19 PM
I have no way of determining what will or will not problem because you
have not defined the sensitivity of your application. 'Little circuit'
doesn't tell me much. However the converter scheme you describe is about
as good as it gets. I would make sure that primary and secondary grounds
are NOT connected together. Otherwise I would not expect a problem.
Fred Townsend
Syd H. Levine wrote:
I have a little circuit that runs off the 12 volt power supply in a
vehicle. Part of the circuit needs a bipolar supply, and I was planning
to use one of the cute little DC / DC converters to output maybe 5 watts
off + and - 15 volt DC. The converter I have selected has a PI filter
on the input, accepts a wide input range (8-18 Volts), and is regulated.
My question is whether alternator hash will be a problem, Will I need a
choke and capacitor on the front end of this gizmo like we used to put
on car radios and the like? Or will the converter do its job OK with
raw vehicle DC?
Thanks in advance.
Syd H. Levine
AnaLog Services, Inc.
Phone: 270-276-5671
Telefax: 270-276-5588
E-mail: [EMAIL PROTECTED]
URL: www.logwell.com
--
Author: Fred Townsend
INET: [EMAIL PROTECTED]
Fat City Hosting, San Diego, California -- http://www.fatcity.com
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