12 volt differential controller [RE-wrenches]

[Darryl Thayer]

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
> >>
> >>
> >> __________________________________
> >> Do you Yahoo!?
> >> The New Yahoo! Shopping - with improved product
> search
> >> http://shopping.yahoo.com
> >>
> >> - - - -
> >> To send a message: RE-wrenches at topica.com
> >>
> >> Archive of previous messages:
> http://www.topica.com/lists/RE-wrenches/
> >>
> >> List rules & etiquette:
> http://www.mrsharkey.com/wrenches/etiquete.htm
> >>
> >> Check out participant bios:
> www.mrsharkey.com/wrenches/index.html
> >>
> >> Hosted by Home Power magazine
> >>
> >> Moderator: michael.welch at homepower.com
> >>
> >>  
> >>
> >
> > - - - -
> > To send a message: RE-wrenches at topica.com
> >
> > Archive of previous messages:
> http://www.topica.com/lists/RE-wrenches/
> >
> > List rules & etiquette:
> http://www.mrsharkey.com/wrenches/etiquete.htm
> >
> > Check out participant bios:
> www.mrsharkey.com/wrenches/index.html
> >
> > Hosted by Home Power magazine
> >
> > Moderator: michael.welch at homepower.com
> >
> >
> >
> 
> - - - -
> To send a message: RE-wrenches at topica.com
> 
> Archive of previous messages:
> http://www.topica.com/lists/RE-wrenches/
> 
> List rules & etiquette:
> http://www.mrsharkey.com/wrenches/etiquete.htm
> 
> Check out participant bios:
> www.mrsharkey.com/wrenches/index.html
> 
> Hosted by Home Power magazine
> 
> Moderator: michael.welch at homepower.com
>
> 
> 
> 


__________________________________
Do you Yahoo!?
The New Yahoo! Shopping - with improved product search
http://shopping.yahoo.com

- - - -
To send a message: RE-wrenches at topica.com

Archive of previous messages: http://www.topica.com/lists/RE-wrenches/

List rules & etiquette: http://www.mrsharkey.com/wrenches/etiquete.htm

Check out participant bios: www.mrsharkey.com/wrenches/index.html

Hosted by Home Power magazine

Moderator: michael.welch at homepower.com
--^----------------------------------------------------------------
This email was sent to: michael.welch at homepower.com

EASY UNSUBSCRIBE click here: http://topica.com/u/?bz8Qcs.bz9JC9.bWljaGFl
Or send an email to: RE-wrenches-unsubscribe at topica.com

TOPICA - Start your own email discussion group. FREE!
http://www.topica.com/partner/tag02/create/index2.html
--^----------------------------------------------------------------