Archived Forum

That's really cool Fabrizio!

And that's a very bad joke!

..joke ?

Why ?

Hi Fabrizio,

Nice work! Thanks for sharing it with us.

Regards,

Bill
 

British humour Fabrizio, don't worry.

I'm planning to do the same thing effectively to add temperature control to a low cost cool box which runs either on 12v or mains. We had one in our camper van and it is either fully on on 12V, or has a control knob on mains supply. So an esp8266 taking power from the coolbox and acting as an access point will do the job I reckon. 

Not emoncms, but a great, cheap solution.

Simon

"..joke ?

Why ?"

Because JD described your project, that works at -20°C, as "cool!"

Very good idea, I could do with knocking a couple of these up. I'm impressed the wiifi signal is able to escape the freezer.

I read your blog and noted the use of the emoncms.org IP to save a dns lookup and therefore battery life, and that means re-editing the devices code directly if the ip address changes. I don't know if you use emonHub, but for those that do, sending to an emonhub socket at eg http://IP.OF.HUB.PI:50011 would allow the target url(s) to use DNS and the url(s) and apikey keys changed at will, plus not needing the apikey or variable name in the payload could help increase battery life further still by shortening the tx time.

(just added this to the "list of monitored stuff" list too)

Paul

I dont have emonhub but is true that it can reduce the payload of communication,  and transmission  time and this can increase battery life.

Probably also use fix ip instead of  dhcp can reduce draw of current by module.. i've to test this .

@Robert.. Thank for your reply.. i have some problem with British umor and also Google translator cant help me for this :)

Ciao,

Fa.

i recently bought some wireless tags http://www.wirelesstag.net/ and made an app on their cloud services that send the sensor data to emoncms. It uses a 3v CR2032 or CR2450 battery and i have set it up so that it only sends out the temprature data every 30 minutes. they communicate over radio frequncies and you need to have a tag manager to communicate with them. These tags can also be used to place inside a fridge / freezer. but they said somewhere on the site of the tags that the voltage / chemistry of the batteries drop when they are placed in cold environments see support page here : http://store.wirelesstag.net/pages/support quote from their page:

At the same amount of remaining capacity, battery voltage may be 2.5V at -20°C when it is 2.8V at 23°C.

so i don't know what batteries you are using but it could be they are showing lower voltages as well when being placed inside a cold environment

Great, thanks

Will try this out. Have all the hardware laying around. :-)

Interesting project, i want to do something similar but with a small solar panel and lithium-ion battery, only 1 question: why you place the esp8266 into the freezer???, with ds18b20 you can use a very long (and thin) cable, even you can use a weatherproof version, so you can place electronic inside a box... outside of the freezer.

I do this only for test.

If this system will work at least 1 year i think this solution is better than wire solution..

Eventually, the wire can damage the door seal but if the battery will run out energy in 2-3 weeks the card inside freezer is not the solution...

Now the card ( proto-board) is in a plastic bag..

Ciao,

Fabrizio

I think the battery last... between 1 and 2 months

Fabrizio,

Have you tried using Lithium batteries? They are good down to about -35F. I used them in my weather station outdoor electronics package when I lived in Montana, where wintertime lows routinely get between -20 and -40F.

Yes Bill, i already use Lion battery.

Referring to this link posted by Willems  ( joyrider3774 ) http://store.wirelesstag.net/pages/support , i do the same test with my battery ( CR123) .

( see the paragraph "The battery voltage drops very quickly when tag is placed in fridge/freezer.")

In the wirelesstag.net diagramm is tested a CR2032 battery, that have same chemistry as my CR123, but i do the test with 1 kohm resistance instead of 3 kohm (  more current should increase dropping in voltage ).

I get this result :

2,935 Volt @ +20 °C load = 1 Kohm

2,735 Volt @ -19 °C load = 1 Kohm.

I think this is very good result..

I plan to do the same test with 100 ohm load...

Yes Bill, i already use Lion battery.

Not Lithium Ion, just Lithium i.e. the non-rechargeable type. Different battery chemistry.

I use battery non-rechargeable at 3.0 volt...  You suggest rechargeable type or non-rechargeable ?

There is  another interesting non-rechargeable battery.. but is at 3.6 volt :

http://www.amazon.com/Saft-LS-14500-3-6V-Lithium-Battery/dp/B002GK406C

Ciao,

Fa.

I use battery non-rechargeable at 3.0 volt...

Correct. The non-rechargeable type gives superior cold environment performance, especially at sub-zero (F) temperatures.

Here's some additional info: http://toolguyd.com/flashlight-tool-batteries-cold-weather/