Peltier Controller Schematic - Page 2

Do you have a question? Post it now! No Registration Necessary

Translate This Thread From English to

Threaded View
Re: Peltier Controller Schematic


Quoted text here. Click to load it

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 /

We've slightly trimmed the long signature. Click to see the full one.
Re: Peltier Controller Schematic


Quoted text here. Click to load it

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.

Quoted text here. Click to load it

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).

--
Bill Sloman, Nijmegen


Re: Peltier Controller Schematic


Quoted text here. Click to load it

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.


Quoted text here. Click to load it

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 /

We've slightly trimmed the long signature. Click to see the full one.
Re: Peltier Controller Schematic


Quoted text here. Click to load it

That sort of thing always sounds more cool when boards are getting sent
off to the fab house at a nice high rate.  It sounds much less so when
the boards are back and built and only almost meeting spec because the
chips are never as good as they say they are unless you're using them
exactly as intended -- and then sometimes not then.

--

Tim Wescott
Wescott Design Services
We've slightly trimmed the long signature. Click to see the full one.
Re: Peltier Controller Schematic


Quoted text here. Click to load it

My only advice is; If you are going to air cool the TEC then make sure
the heat sink is big enough.  We use a ~10Watt TEC with perhaps a
square inch foot print and the heat sink is 6 inches by 4 inches.  My
boss was amazed that such a big heat sink was needed... but thermal
runaway is not good.

The electronics is pretty simple.  Thermistor->bridge->PI(D)->power
gain.

You can look at C.C. Bradley etal, Rev. Sci. Inst. 61, 2097 (1990)

George H.

Re: Peltier Controller Schematic


Quoted text here. Click to load it

The _only_ advantage those things have is that they are small and have
no moving parts.  It's interesting to educate someone who doesn't
realize how inefficient they are, or how much heat they generate, or how
you have to get that heat away.

--

Tim Wescott
Wescott Design Services
We've slightly trimmed the long signature. Click to see the full one.
Re: Peltier Controller Schematic


Quoted text here. Click to load it

Oh it's very nice that they can cool as well as heat.  Otherwise I'm
stuck running something above ambient...  And then dealing with the
fact that most likely I can get heat into the thing faster than it
comes out.... so the control loop has to follow the slow side.

Say with a micro controlling things could you have different time
constants for cooling and heating?  Do you do that sort of thing?

George H.

Re: Peltier Controller Schematic


Quoted text here. Click to load it

Yes and yes.

I'm not sure that is the best way.

If you could measure the temperature at both sides of the Peltier (or if
you had a way to estimate the temperature on the heatsink side) you
could take a heat flow command and turn it into a current command.  This
would keep the loop dynamics mostly independent of the temperatures --
except for the fact that you'd always have way more power to heat than
to cool.

--

Tim Wescott
Wescott Design Services
We've slightly trimmed the long signature. Click to see the full one.
Re: Peltier Controller Schematic


Quoted text here. Click to load it
My

That's what my paper describes, amongst other things. E-mail me if you
want a reprint.

--
Bill Sloman, Nijmegen


Site Timeline