Peltier Controller Schematic

Discussion in 'Electronic Design' started by iCod, Sep 14, 2010.

  1. iCod

    iCod Guest

    Can anyone point me to a schematic for a Peltier constant temperature
    controller?

    Thanks for any leads
     
    iCod, Sep 14, 2010
    #1
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  2. iCod

    Joerg Guest

    iCod wrote:
    > Can anyone point me to a schematic for a Peltier constant temperature
    > controller?
    >
    > Thanks for any leads



    http://www.analog.com/static/imported-files/tech_articles/37488110918229TEC_Application_Brief2.pdf

    Looks like they are finally ditching this chip but if you need a one-off
    prototype it'll work:

    http://www.analog.com/static/imported-files/data_sheets/ADN8830.pdf

    Maybe I am, to a small extent, guilty regarding its demise because I
    bought the demo kit and then decided I didn't like it that much, and
    rolled my own.

    --
    Regards, Joerg

    http://www.analogconsultants.com/

    "gmail" domain blocked because of excessive spam.
    Use another domain or send PM.
     
    Joerg, Sep 14, 2010
    #2
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  3. iCod

    Joerg Guest

    Tim Wescott wrote:
    > On 09/14/2010 06:07 AM, iCod wrote:
    >> Can anyone point me to a schematic for a Peltier constant temperature
    >> controller?
    >>
    >> Thanks for any leads

    >
    > AFAIK the important point to bear in mind is that the Peltier device
    > acts like constant-heat pump, driven by junction current, in parallel
    > with a resistor that shows I^2-R losses. So the overall heat pump
    > action will be nonlinear (because of the I^2 factor), and it's really a
    > good idea to not try to PWM the thing (because of the I^2 factor).
    >


    However, with a sizeable Peltier, one should PWM the driver and then
    lowpass accordingly so that the Peltier sees DC. Or almost DC.

    --
    Regards, Joerg

    http://www.analogconsultants.com/

    "gmail" domain blocked because of excessive spam.
    Use another domain or send PM.
     
    Joerg, Sep 14, 2010
    #3
  4. iCod

    Joerg Guest

    Bill Sloman wrote:
    > On Sep 15, 12:32 am, Joerg <> wrote:
    >> Tim Wescott wrote:
    >>> On 09/14/2010 06:07 AM, iCod wrote:
    >>>> Can anyone point me to a schematic for a Peltier constant temperature
    >>>> controller?
    >>>> Thanks for any leads
    >>> AFAIK the important point to bear in mind is that the Peltier device
    >>> acts like constant-heat pump, driven by junction current, in parallel
    >>> with a resistor that shows I^2-R losses. So the overall heat pump
    >>> action will be nonlinear (because of the I^2 factor), and it's really a
    >>> good idea to not try to PWM the thing (because of the I^2 factor).

    >> However, with a sizeable Peltier, one should PWM the driver and then
    >> lowpass accordingly so that the Peltier sees DC. Or almost DC.

    >
    > That exactly what I did. Unfiltered pulse width modulation has been
    > known to melt the solder inside the Peltier cooler, but if you can
    > keep the ripple down to less than - say - 10% of the peak current, the
    > extra resistive losses aren't dramatic. Radio-frequency interference
    > from the leads to the Peltier cooler can be a problem a ripple current
    > levels that won't generate significant extra heating and it can pay to
    > filter this current to reduce the ripple content to much lower levels.
    >


    Yup, RF-wise I filtered the dickens out of it. Ferrite bead, cap,
    another ferrite bead ...

    --
    Regards, Joerg

    http://www.analogconsultants.com/

    "gmail" domain blocked because of excessive spam.
    Use another domain or send PM.
     
    Joerg, Sep 14, 2010
    #4
  5. iCod

    Joerg Guest

    Bill Sloman wrote:
    > On Sep 15, 12:28 am, Joerg <> wrote:
    >> iCod wrote:
    >>> Can anyone point me to a schematic for a Peltier constant temperature
    >>> controller?
    >>> Thanks for any leads

    >> http://www.analog.com/static/imported-files/tech_articles/37488110918...
    >>
    >> Looks like they are finally ditching this chip but if you need a one-off
    >> prototype it'll work:
    >>
    >> http://www.analog.com/static/imported-files/data_sheets/ADN8830.pdf
    >>
    >> Maybe I am, to a small extent, guilty regarding its demise because I
    >> bought the demo kit and then decided I didn't like it that much, and
    >> rolled my own.

    >
    > They are now pushing the ADN8831. I've not been interested enough to
    > work out how it differs from the ADN8830.
    >


    I think that's the datasheet where I found some inconsistency in a
    formula or two and I let them know. Basically those chips are ok but I
    found it can also be done for much less money. I mean, over $7 is a
    hefty price. Even if you need a few dozen jelly-bean parts you can beat
    that. Or use a low-cost uC. I can't imagine the ADN8831 selling like
    hotcakes.

    --
    Regards, Joerg

    http://www.analogconsultants.com/

    "gmail" domain blocked because of excessive spam.
    Use another domain or send PM.
     
    Joerg, Sep 14, 2010
    #5
  6. iCod

    Joerg Guest

    Tim Wescott wrote:
    > On 09/14/2010 08:52 AM, Joerg wrote:
    >> Bill Sloman wrote:
    >>> On Sep 15, 12:28 am, Joerg<> wrote:
    >>>> iCod wrote:
    >>>>> Can anyone point me to a schematic for a Peltier constant temperature
    >>>>> controller?
    >>>>> Thanks for any leads
    >>>> http://www.analog.com/static/imported-files/tech_articles/37488110918...
    >>>>
    >>>>
    >>>> Looks like they are finally ditching this chip but if you need a
    >>>> one-off
    >>>> prototype it'll work:
    >>>>
    >>>> http://www.analog.com/static/imported-files/data_sheets/ADN8830.pdf
    >>>>
    >>>> Maybe I am, to a small extent, guilty regarding its demise because I
    >>>> bought the demo kit and then decided I didn't like it that much, and
    >>>> rolled my own.
    >>>
    >>> They are now pushing the ADN8831. I've not been interested enough to
    >>> work out how it differs from the ADN8830.
    >>>

    >>
    >> I think that's the datasheet where I found some inconsistency in a
    >> formula or two and I let them know. Basically those chips are ok but I
    >> found it can also be done for much less money. I mean, over $7 is a
    >> hefty price. Even if you need a few dozen jelly-bean parts you can beat
    >> that. Or use a low-cost uC. I can't imagine the ADN8831 selling like
    >> hotcakes.

    >
    > I never understood the need for a specialized Peltier cooler IC, unless
    > it's because they do something fancy to compensate for the nonlinearity.
    >
    > Unless your problem demands hugely tight regulation you can just design
    > a loop with enough margin to handle the nonlinearity, and if it _does_
    > need the tight regulation then you either handle it with a few discretes
    > or with a micro.
    >
    > So why a special chip?
    >


    Saves pick&place costs. But at $7 a pop, nah, that was too much for the
    privilege.

    My case did require hugely tight regulation. Any kind of regulator
    rumble or other noise on there would have messed up the signal we were
    after.

    --
    Regards, Joerg

    http://www.analogconsultants.com/

    "gmail" domain blocked because of excessive spam.
    Use another domain or send PM.
     
    Joerg, Sep 15, 2010
    #6
  7. On Wed, 15 Sep 2010 12:06:13 -0400, Phil Hobbs
    <> wrote:

    >On 09/15/2010 03:47 AM, Bill Sloman wrote:
    >> On Sep 15, 1:04 pm, Phil Hobbs
    >> <> wrote:
    >>> On 09/14/2010 09:35 PM, Phil Hobbs wrote:
    >>> <snip>
    >>>
    >>>> There's also some stuff on how to model TECs based on datasheet
    >>>> parameters in my (free) thermal control chapter,
    >>>
    >>>> ftp://ftp.wiley.com/public/sci_tech_med/electro-optical/thermal.pdf.
    >>>
    >>> Whoops, that's the first edition version. The second edition one (not
    >>> as polished as the rest, have to give it a going-over sometime) is at
    >>>
    >>> http://electrooptical.net/www/beos2e/thermal2.pdf.

    >>
    >> It's got a drop-off in section 20.6.2. Thermistors aren't carbon
    >> resistors, though NTC thermistors do have points in common with carbon
    >> resistors, like forming super-heated channels when over-loaded.
    >>
    >> http://www.epcos.com/web/generator/...en.pdf;/PDF_General_technical_information.pdf
    >>
    >> mentions that the good NTC thermistors in which we are interested are
    >> made by sintering a mixture of metal oxides at 1000 to 1400?C. The
    >> Yellow Springs Instruments application notes were a bit more specific,
    >> but the thermistor business was sold to Measurement Specialties and
    >> the link below no lnger works.
    >>
    >> http://www.meas-spec.com/downloads/Long_Term_Thermistor_Stability.pdf
    >>
    >> --
    >> Bill Sloman, Nijmegen
    >>

    >
    >NTCs vary a lot, especially in their (unspecified) 1/f behaviour. The
    >glass bead ones are often carbon, iirc, but I'll certainly chase down
    >the links and fix as necessary. Thanks for the input!
    >
    >That 1/f stuff is one reason why I really like thin-film platinum RTDs,
    >even though their sensitivity is 10x lower at room temperature.
    >
    >===========
    >RTD Advantages:
    >
    >Low 1/f noise
    >
    >Good thermal coupling (it's a lot easier to get good thermal coupling to
    >a flat piece of alumina than to a glass bead)
    >
    >Pretty linear, easily linearized in SW or with a small negative
    >conductance in parallel
    >
    >dR/dT reasonably comparable to linearized thermistors


    Much more stable at relatively high temperatures, IME.

    >===========
    >
    >Figure 20.
    >
    >
    >(I especially like learning from other people who have actually done the
    >thing under discussion--it saves my having to crawl out of the potholes
    >myself.)
    >
    >Cheers
    >
    >Phil Hobbs
     
    Spehro Pefhany, Sep 15, 2010
    #7
  8. iCod

    amdx Guest

    "Spehro Pefhany" <> wrote in message

    Hi Spehro,
    Please send me a private email, I tried to send one
    to you. I wonder if I'm not smart enough to decode
    your munged email address, anyway it didn't go through.
    Thanks, MikeK
     
    amdx, Sep 15, 2010
    #8
  9. On Wed, 15 Sep 2010 17:05:35 -0500, "amdx" <> wrote:

    >
    >"Spehro Pefhany" <> wrote in message
    >
    > Hi Spehro,
    >Please send me a private email, I tried to send one
    >to you. I wonder if I'm not smart enough to decode
    >your munged email address, anyway it didn't go through.
    > Thanks, MikeK
    >


    Done.
     
    Spehro Pefhany, Sep 15, 2010
    #9
  10. iCod

    Joerg Guest

    Bill Sloman wrote:
    > On Sep 15, 9:00 am, Joerg <> wrote:
    >> Tim Wescott wrote:
    >>> On 09/14/2010 08:52 AM, Joerg wrote:
    >>>> Bill Sloman wrote:
    >>>>> On Sep 15, 12:28 am, Joerg<> wrote:
    >>>>>> iCod wrote:
    >>>>>>> Can anyone point me to a schematic for a Peltier constant temperature
    >>>>>>> controller?
    >>>>>>> Thanks for any leads
    >>>>>> http://www.analog.com/static/imported-files/tech_articles/37488110918...
    >>>>>> Looks like they are finally ditching this chip but if you need a
    >>>>>> one-off
    >>>>>> prototype it'll work:
    >>>>>> http://www.analog.com/static/imported-files/data_sheets/ADN8830.pdf
    >>>>>> Maybe I am, to a small extent, guilty regarding its demise because I
    >>>>>> bought the demo kit and then decided I didn't like it that much, and
    >>>>>> rolled my own.
    >>>>> They are now pushing the ADN8831. I've not been interested enough to
    >>>>> work out how it differs from the ADN8830.
    >>>> I think that's the datasheet where I found some inconsistency in a
    >>>> formula or two and I let them know. Basically those chips are ok but I
    >>>> found it can also be done for much less money. I mean, over $7 is a
    >>>> hefty price. Even if you need a few dozen jelly-bean parts you can beat
    >>>> that. Or use a low-cost uC. I can't imagine the ADN8831 selling like
    >>>> hotcakes.
    >>> I never understood the need for a specialized Peltier cooler IC, unless
    >>> it's because they do something fancy to compensate for the nonlinearity.
    >>> Unless your problem demands hugely tight regulation you can just design
    >>> a loop with enough margin to handle the nonlinearity, and if it _does_
    >>> need the tight regulation then you either handle it with a few discretes
    >>> or with a micro.
    >>> So why a special chip?

    >> Saves pick&place costs. But at $7 a pop, nah, that was too much for the
    >> privilege.

    >
    > It also saves design and debugging time. Anything that is inside the
    > chip doesn't have to be put onto a schematic or laid out on a printed
    > circuit board, and the draftpersons involved don't get the chance to
    > do it wrong.
    >


    You'd be surprised how often I have unearthed bugs inside chips. At
    first it's "Oh, no, that can't be, that must be your layout". A few
    iterations and some bench tests at the manufacturer later ... "Oh s..t!"

    Board level design isn't that tough. Ok, costs time but the layout is
    not expensive. But then you know what it does and where its limits
    really are.


    >> My case did require hugely tight regulation. Any kind of regulator
    >> rumble or other noise on there would have messed up the signal we were
    >> after.

    >
    > The performance offered by the chips isn't impressive. Sticking a
    > pulse-width modulator inside the same chip as a sensitive high gain
    > analog amplifier isn't making life easy for the chip designer (or the
    > amplifier).
    >


    Even worse are chips with the power devices on there. That's like a
    seismic sensor on a Harley engine.

    --
    Regards, Joerg

    http://www.analogconsultants.com/

    "gmail" domain blocked because of excessive spam.
    Use another domain or send PM.
     
    Joerg, Sep 16, 2010
    #10
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