Peltier devices

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Anyone know about peltier devices? Can you drive them at half voltage?
I wish to make a container  that is limited to  between 18 and 20  
centigrade and apparently they do not like to be cycled much for temp  
control,I would rather have it on constantly but at less than full  
capabilities.

Re: Peltier devices
F Murtz wrote:
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On further musing I would probably still have problems as the system is  
dependent on ambient temp so I would probably have to have a temp sw to  
switch on only when ambient is higher.

Re: Peltier devices
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Based on how special Peltier driver devices like this:
https://www.maximintegrated.com/en/products/power/switching-regulators/MAX1968.html
appear to work, it seems that they should function with varying voltage
levels.

More information about Peltier devices here, probably more than required
for your application:
https://www.maximintegrated.com/en/app-notes/index.mvp/id/3318

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Wouldn't you want it to heat the container then, in order to keep it close
to a "perfect" temperature? H-bridge circuits such as used in motor control
circuits appear to be commonly used for this purpose, in order to reverse
the current flow.

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Re: Peltier devices
On Thu, 17 Dec 2015 12:01:37 +1100, F Murtz wrote:

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You want a clean supply, no ripple.
Yes you can get different levels of cooling with less current.

A thermostat available through www.aliexpress.com for about 4$ U.S. can  
regulate the temperature with hystersis.

The thermostat I'm thinking of was reviewed and given good marks by  
www.bigclive.com

Re: Peltier devices
Once upon a time on usenet Wayne Chirnside wrote:
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Can you be any more cryptic? I clicked both links and after several minutes  
couldn't find what you were talking about.

(I bought a peltier a while ago to make a 'butter conditioner' - a device  
for keeping butter at that perfect spreading temperature but don't yet have  
control electronics for it.)
--  
Shaun.

"Humans will have advanced a long, long way when religious belief has a cozy  
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Re: Peltier devices
On Sat, 19 Dec 2015 12:48:29 +1300, ~misfit~ wrote:

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The gentleman in question has youtube video where he describes the precise
steps to program the module widely available at www.aliexpress.com for  
around 4$ and slightly under.
So search his videos for that then on to aliexpress too order one.
I used cclive in linux to download the youtube so as to have the  
programming instructions locally.
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$4

Re: Peltier devices
Once upon a time on usenet Wayne Chirnside wrote:
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Can you please tell me the title of the video? That would make it easier to  
find. I've just scrolled through nearly a dozen pages of bigclive videos on  
youtube and can't find it. Searches using his name, 'thermostat',  
'aliexpress' '$4' and various permuatations of those don't give me the  
desired result.

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Yep, I'm ready and willing to order it when I can find it.
--  
Shaun.

"Humans will have advanced a long, long way when religious belief has a cozy  
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Re: Peltier devices
~misfit~ wrote:
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I gave up looking, there was a thermostat for around  $4.00 among the  
more expensive ones, but nothing said about peltier the expensive ones  
mentioned controlling peltier.

Re: Peltier devices
On Mon, 21 Dec 2015 21:13:25 +1300, ~misfit~ wrote:

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Just wasted an hour looking.

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http://www.aliexpress.com/item/Freeshipping-W1209-Mini-thermostat-
Temperature-controller-Incubation-thermostat-temperature-control-
switch/32225252366.html

Not certain if I've used this vendor or not but the unit is ubiquitous on  
aliexpress and my experiences so far of some 70 orders 100 percent.  


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http://www.aliexpress.com/item/Freeshipping-W1209-Mini-thermostat-
Temperature-controller-Incubation-thermostat-temperature-control-
switch/32225252366.html

One vendor among many.
I'm buying five from a different vendor.
Do you think $1.90 to much to pay...



Re: Peltier devices
Once upon a time on usenet Wayne Chirnside wrote:
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I also gave up searching clive's stuff yesterday and settled for ordering a  
few of those from Aliexpress.
--  
Shaun.

"Humans will have advanced a long, long way when religious belief has a cozy  
We've slightly trimmed the long signature. Click to see the full one.
Re: Peltier devices
~misfit~ wrote:
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I ordered a couple also but the probably will get used for something  
else don't know whether they would be suitable for peltier control
Did not find the video where the steps to program the device was  
especially referring to peltier



Re: Peltier devices
On Wed, 23 Dec 2015 12:44:55 +1100, F Murtz wrote:

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Big Clive reviews cheap Chinese  thermostat.


https://www.youtube.com/watch?v=yVD0zkZTe00


Took me all of two minutes to find after not finding it on my local drive.

Re: Peltier devices
Wayne Chirnside wrote:
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Thanks,interesting, but no reference to peltier, will just have to  
experiment

Re: Peltier devices
On Thu, 24 Dec 2015 12:34:16 +1100, F Murtz wrote:

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I have eight peltiers here.

What they care about is smooth power, no ripple.
Then the thermostat is just a switch not caring what it is attached to as  
long as the relay amperage does not get exceeded.

just set an appropriate hystersis.

Re: Peltier devices
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I thought the aim was for a comstantly variable voltage to control the
temperature, and to avoid a switched action. That's how proper peltier
controllers seem to work.

Additionally, heating will be required if the aim is to keep the container
within the required temperature range over a wide range of ambient
temperature variation.

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Re: Peltier devices
Computer Nerd Kev wrote:
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In this particular case lower temps are not as much a worry unless very  
cold.(keeping chocolate)

Re: Peltier devices
On Thu, 24 Dec 2015 21:53:00 +0000, Computer Nerd Kev wrote:

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On - off works just fine for this application.

Now if heating *and* cooling are required you just flip the polarity of  
the peltier.

Re: Peltier devices
On 25/12/2015 12:11, Wayne Chirnside wrote:
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I wouldn't dispute that it works well, but you might find that with  
on-off control, the peltier devices don't last as long as with  
continuous current that varies only slowly (especially for large peltier  
devices and high currents). When the current is switched on and off,  
there is slight expansion and contraction of the ceramic plates, which  
could fatigue the semiconductor pillars within the peltier device  
eventually. At least some peltier device manufacturers recommend against  
on-off control. If you never experience failures than don't worry about it.

If you care about the input power requirement at less than full output  
then there can also be a very slight efficiency advantage with variable  
current rather than on-off, provided a very efficient switched-mode  
controller is used (with filter inductors and capacitors so that pure DC  
comes out). The efficiency advantage is because there are resistive  
losses inside the peltier device, which are proportional to I squared  
times R, and that works out to be more losses on average for e.g. 20  
Amps at 50% duty cycle than it is for 10 Amps at 100% duty cycle. It  
won't make any difference to the maximum cooling capability since even  
with on-off control that will produce 100% duty cycle, which is the same  
as you would get with variable current control.

Chris




Re: Peltier devices
On Fri, 25 Dec 2015 21:18:30 +1100, Chris Jones wrote:

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Got 3 yrs on the one to my left where I keep chilled gatorade on - off  
$2.30 peltier.
  
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I use an analog supply and a switching supply on two differing  
applications.

The switcher is more efficient however any ripply no matter how small
will lead to dramatic inefficiency to the point as to make the whole deal  
less than worthwhile.

I use a capacitance multiplier after the switcher and give away about 70  
millivolts in order to achieve the greatest possible efficiency.  


Re: Peltier devices
Once upon a time on usenet Wayne Chirnside wrote:
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I saw that in the search results but ignored it as you specifically said the  
thermostat came from Aliexpress.
--  
Shaun.

"Humans will have advanced a long, long way when religious belief has a cozy  
We've slightly trimmed the long signature. Click to see the full one.

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