Boat project 1 - Fridge controller

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cpedw

Senior Member
My other hobby is sailing boats. I sail a 33ft boat on the west coast of Scotland. I have devised several projects for use on the boat; though they may have applications in other areas.
So far, there are 4 projects:
Fridge controller
Barograph
Electric consumption meter
Lead-acid battery load tester.

This thread is devoted to the fridge controller. It is a thermostat using the DS18B20 and checks the battery to avoid flattening it. It's intended to connect to a Peltier cooler. The description was written with non-experts in mind; experienced users may find it low-browin parts. There is a list of part, circuit diagram, possible layout on stripboard and the program.

Derek
 

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davidwf

Senior Member
Hi again,

I am just about to install this excellent project into my coolbox.....I wondered how difficult would it be to make it also heat ?

I tried reversing the Peltier element and it worked a treat, this could be done with a changeover relay (I can manage that !)

The part I would struggle with would be the programming, presumably we need to raise the trigger point read from the temp sensor but also somehow need to provide output when the temp is below setpoint rather than above it.

Hang on...another wayward thought just occurred....leave it so that output from the PIC is provided when above set temp but have a secondary circuit to invert that and provide power....I can't quite decide if that would work or not.

Another thought....as the PIC and peripheral circuit is so cheap why not run a second almost identical circuit programmed to provide power when temp is below setpoint and a simple relay changeover or perhaps even a switch - sorry to use swear words like that but it may be the easiest solution.

Oh well, if anyone has any suggestions........

thanks
Dave Faulkner
 
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cpedw

Senior Member
To work as a heater you need to:
1. As you say, reverse the Peltier polarity.
2. Set a different target temperature (line 21).
3. Change ORFF to ORN in line 42 so the heater switches on if temperature is less than Target.
4. Change ORN to ORFF in line 43 so the heater switches off if temperature is high.

I think that's all you need.
Derek
 
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