Fridge Controller

[commanda]

So it's built and calibrated/tested. Just got to photoshop a meter scale and print a few labels for the switches and leds.

Meter scale is -25 to +25 degC. Push buttons are set-point and alarm-point. Toggle switch is alarm mute. Red leds are alarm and mute(flashing). Green leds are Power Request, Request Acknowledge, and Power Available. The 2 RJ connectors are one for the LM335 temp sensor and one to connect to the control box which turns on and off the UPS.

The control box will have a number of inputs, 2 of these boxes (fridge & freezer), as well as manual buttons for the microwave and washing machine and anything else. The control box has interlocks so you can't run everything at once.

The UPS is an APC 1600 watt pure sine wave. These have manual buttons for start and stop. The control box will switch a relay across the start & stop switches, so we have power-on-demand. Each power circuit also has a solid-state relay so the 240 volts is only fed to where it's supposed to go.

Main components are the LM335 temp sensor, an LM324 quad op-amp, a TL431 voltage reference, and a pair of BC547 to drive the alarm led/buzzer, and an open-collector feed to the control box. I had t run flying leads to the RJ connectors because it's only a single-sided board.

[BT Humble]

Morning Amanda.

I must have missed a post or two of yours recently - is this another take on the use-a-freezer-as-a-fridge thermostat?  Coincidentally I went to K-mart on Saturday to buy a $10 tub of grease and came out with a $200 chest freezer, I'm still not sure how that happened.  (The label on it says 270kWh/year, and it was marked down from $499).

By the way, do you want to come to the Unuaugural again this year?  May 3rd, same time and place.  I think Ashley is keen to talk to you again. ;-)

BTH

[commanda]

is this another take on the use-a-freezer-as-a-fridge thermostat?

Could be, although it doesn't have to be. I do have a chest freezer which I was going to run as a fridge for a while with this controller, but the family have put it back into service as a freezer.

I'll come to the unaugural, but only if Ashley promises to bring that blown-up controller that he promised to mail me after the last unaugural.

Amanda

[Opera House]

I got the bug a week ago and bought a chest freezer for the camp. One last attempt to see if I can run it on 150W of panels.  For temp sensor I am using 6 diodes in series which comes to about 12mV per degree C, 7805 as reference and Lm324 as active device.  Using a modified liquid level controller I designed that came back from UL testing with thermocouples epoxied to the board.  We all should recycle!  Control range will be 0 to 60 F.  Be another week for things to warm up before I can do some realistic testing.

[BT Humble]

Certainly, I'll twist his arm for you.

Can I interest you in a blown-up 1800W MSW inverter (supposedly 8kW peak)?

BTH

[richhagen]

Beautiful board, looks absolutely professional, but no surprise there.  Rich

[lemmiwinks]

Hi Amanda!  I'll be there and I'll make sure to bring the controller.  Sorry I didn't post it, I got as far as putting it in a box and bringing it to work but I stalled there and thought you were probably too busy anyway.

Cheers,

Ash