Peltier devices

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.

Based on how special Peltier driver devices like this:

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:

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.

--
__          __ 
#_ < |\| |< _#

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

A thermostat available through

for about 4$ U.S. can regulate the temperature with hystersis.

The thermostat I'm thinking of was reviewed and given good marks by

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  
little classification in the DSM*." 
David Melville (in r.a.s.f1) 
(*Diagnostic and Statistical Manual of Mental Disorders)

The gentleman in question has youtube video where he describes the precise steps to program the module widely available at

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.

$4

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.

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  
little classification in the DSM*." 
David Melville (in r.a.s.f1) 
(*Diagnostic and Statistical Manual of Mental Disorders)

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.

Just wasted an hour looking.

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.

switch/32225252366.html

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

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  
little classification in the DSM*." 
David Melville (in r.a.s.f1) 
(*Diagnostic and Statistical Manual of Mental Disorders)

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

Big Clive reviews cheap Chinese thermostat.

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

Thanks,interesting, but no reference to peltier, will just have to experiment

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  
little classification in the DSM*." 
David Melville (in r.a.s.f1) 
(*Diagnostic and Statistical Manual of Mental Disorders)

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.

The Chinese make these things in volume, he got his ebay.uk

I got mine, more cheaply, at aliexpress.

I referred to Big Clive because his was the explanation as to how to program the device.

To date I've never had a problem with a vendor on that site though I do have to wait a bit for the item to cross the Pacific in a container.

I also downloaded the programming instructions using the Linux cclive youtube downloader for future reference should I forget the first button cycles through the various parameters to be set.

hystersis being of some importance with a peltier.

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.

--
__          __ 
#_ < |\| |< _#

In this particular case lower temps are not as much a worry unless very cold.(keeping chocolate)

On - off works just fine for this application.

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

On 25/12/2015 12:11, Wayne Chirnside wrote: [...]

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