Electronics question

[pappaecho]

My Peltier (electronic) fridge does not come with a thermostat. We have tried switching the fridge on and off in 2 hour intervals and it seems to make little difference to the temperature of the food inside, and uses half the current.
I would like to get a simple thermostat which would switch on and off at about 6-7 degrees centigrade. Any body got any ideas as to where I could get such a unit. Google does not seem to find HVAC component suppliers, and RS components dont seem to have units which go that low in terms of temperature

 

[rickp]

Something like this?

Rick

 

[Anchorite]

Re: Electric reply

RS do a range of SPDT capillary thermostats (I have one) which should be easy to fit into your circuit.
+ + +
Thermostat,-30to+35degC Back to: Electrical, Automation & Cables» Process Control» Sensors & Transducers» Temperature Switches» Thermal Switches


RS Stock no. 250-6061
Availability S Y In stock
RoHS Status
RoHS certificate of compliance
Manufact. part no. IM-TR2/540043
Catalogue page 1-1416
Add item to my comparison table

Quantity Price: Each
1+ £13.57
6+ £12.49
12+ £12.09

Quantity:
See all in:
Thermal Switches
See all in:
Adjustable Capillary & Limit Thermostats

Description
Thermostat,std,adj,capillary,-35 to +35degC



Attributes
Category Thermal Switches
Maximum Switching Voltage 250Vac

Overview
Adjustable Capillary & Safety Limit Thermostats
Capillary thermostats which operate from a remote bulb linked with a 1m capillary, changeover contacts enable use with both heating and cooling loads (SPDT), supplied with chrome mounting bezel and knob
Safety Limit stats with manual reset temperature limiter and positive cut-off activated when capillary breaks (SPST or SPDT contacts)
Suitable for domestic/commercial applications
Technical Specification
Max. head temperature 80° / 150°C
Capillary length 1000mm
Min. capillary bend radius 5mm
Temp. rate of change 1°K/min

 

[savageseadog]

You could consider regulating it by monitoring the ambient temperature. ie when it's warm during the day it will run full pelt and at night when cooler it would run at a lower duty cycle. Think about it, not as daft as it sounds.
You could also wire it so when the engine/charger/generator is running the cooler is on full time.

 

[pampas]

I think the max temperature (colder) is about 15 degrees below ambient for this type of frig, thats why there is no thermostat fitted, to obtain the temps that you would like to see,may I suggest that you take up winter sailing. Had one of these units now changed to a compressor type cool box and finds that it does what is says +4 degrees C to -18 Degrees C brillaint bit of kit. Transformed sailing.

 

[cpedw]

I made a devic to do this using a microcontroller and an elecrtronic thermometer. It also monitors the supply voltage so, if it's very high (engine running) it operates flat out and if the battery is getting very flat it switches off to save the battery and sacrifice the milk. The cost of parts is around £20. If you want details (I wrote an article but PBO declined it) you're welcome to a copy of the details - send a PM.
Regards,
Derek

 

[pappaecho]

Looking at absorption fridges they have 240 volt thermostatic control, but when running on 12 volts they dont. When run on gas they have high and low settings.
I have found one fridge costing £550 which runs on 12 volts witha thermostat.
Regardless of whether I switch from the Peltier unit the 12 volts thermostat comes with me! Looks like either the RS Components unit or possibly the Maplin kit