12 volt differential controller [RE-wrenches]

[Tom Lane, Energy Conservation Services]

putting extra  "controls" on a dc pump is like admitting you do not know
what you are doing --stop the crap and match the IV CURVE  to the pump
requirements and the collectors square footage  and X Y slope '--it is
nonsense to add all  these extra compents it is like adding tits to a bull !
if you can not matched the pump to the pv module - sent me the  XY intercept
information and  collector area and I will let you know the exact  dc pump
and pv module options  gator tom---- Original Message ----- 
From: "Darryl Thayer" <daryl_solar at yahoo.com>
To: <RE-wrenches at topica.com>
Sent: Tuesday, October 14, 2003 11:28 PM
Subject: Re: 12 volt differential controller [RE-wrenches]


> hi Mark
> I put together a simple op amp comparator "schmitt
> trigger" circuit from radio shack parts and the
> circuit board.  It seems to work.  I used the LM324 op
> amp, and 10 k resistors, and a 100 K positive feed
> back resistor.  I hooked it up to a 12 VDC power
> supply.   give me the temperature range you would like
> and I will tell you how it works, by doing some
> calculations.  Send me your Fax number and I will fax
> a drawing.  This is not a refined circuit and cost
> about $8 or so. This is not a refined circuit, and the
> differencial will vary woth temperature.  The
> selection of the feed back resistor determines the
> switching hysterisis.   Please note I am not a circuit
> designer and only took a couple of design coursed at
> school, about 42 years ago.  So I was never good and
> now am forgetfull.  If some one else who has a young
> brain would like to help. please do so.
>
> Daryl
> PS the LM324 can only source 40 mills, to drive a
> relay you should use an emmetter follower and free
> wheeling diode.
>
> --- "Dean T. Newberry" <deant at dcn.org> wrote:
> > Quick note the LM 335 will work just fine on 12VDC,
> > you don't need the
> > AT power supply.
> >
> > Dean T. Newberry wrote:
> >
> > > Hi Mark,
> > > I think the basic comparator is the LM 335  from
> > National Semiconductor.
> > > A google search for "comparator LM335" found the
> > webpage, download the
> > > pdf for sample circuits. If you can read and build
> > from schematics
> > > you've got it. I'll bet you can buy singles at
> > Halstead or Fry's, some
> > > Radioshacks have them too. The rest of the stuff,
> > resistors,
> > > capacitors, case and relay's can be got from most
> > radio shack's or off
> > > their website. I think I would just use a power
> > supply form an old AT
> > > computer to get a nice regulated 12Vdc and +- 5
> > too if you want it.
> > > If you cut off all the computer pigtails and toss
> > the fan, there
> > > probably is enough room to pack your components in
> > the PS case, RS has
> > > some nice breadboards too for this kind of stuff.
> > >
> > > good luck.  deant at dcn.org
> > >
> > > Mark Downing, Hurshtown Alt. Power wrote:
> > >
> > >> I am in dire need of a 12V differential
> > controller that uses 10K
> > >> thermisters
> > >> for use on a Solar DHW system.
> > >> Does anyone have one or know where I can get one?
> > >> Can anyone supply a fairly simple circuit I can
> > build to accomplish this
> > >> function?
> > >>
> > >> Mark, Hurshtown Alternative Power
> > >>
> > >>
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