how to make a Fridge alarm?

Hi All,

I want to make a fridge alarm, but i dont know the right configuration or maybe I need to buy a different time delay module? 

Please help me

Kind regards,


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What is the alarm supposed to do?
I would just use a discarded fride thermostat and wire the buzzer to it.....

JonathanH243 (author)  Downunder35m1 month ago

Thank you for your reply. The idea is that I can set the timer (let's say 10 sec) and when the magnets break contact the buzzer will start to buzz after 10 seconds. The alarm can only be shut down when the alarms meet again.

Not sure if I bought the right components.

I have a cooled room in my packing house and I want to prevent people from closing the door properly.

Thanks in advance

Can you provide some meaningful info about the electronics you use?
Like a PDF datasheet or description on the functions and connections/buttons?
And why do you want to prevent people from closing the door properly, wouldn't that waste a lot of energy and maybe even spoil the cooled contents?

JonathanH243 (author)  Downunder35m1 month ago

Ah I meant to say that I want people to close the doors properly. I dont have any pdf datasheets, the only info available is on the picture.

the module is only programmable by time, not using different settings.

I realized that I might need to buy a different module. One that has different programmable settings and turns off automatically once the magnets meet again. I will update you once I found the right module. It requires some research on my end. Thanks again for trying to help me.

I the industry timer relays are still a quite common thing, both in normal and "latching" versions.
You provide power and on a latching relay the timer runs to finnish once activated.
The normal type only runs for as long as the input is active, so once the input is off the relay stays off even if the timer runs out.
Of course you also get variations for every possible scenario in between..
If you go for a 12 or 24V version of te relay thy you might be able t use the reed contacts you have otherwise you need a real switch, like a microswitch with a long lever mounted on the door frame.

JonathanH243 (author)  Downunder35m1 month ago

Actually I think what this project needs is a microswitch. Thank you for this suggestion.In this case I don't need to buy a new delay timer relay, with sophisticated programmable functions.

The magnetic switch doesn't turn the machine off, but the microswitch will.

Again thank you so much and I will let you know if my project turned out successful.

Well you are starting to it the right way now, the russian way that is ;)
Nasa wasted a few millions to develop a pen that would write properly in zero gravity.
Worked great in the end but the russians simply used an old style graphite pencil as every kid in school does...

Did some digging and I think your thingy is activated by a push button and once the timer is run out the relay is turned on.
The other button should reset all and the relay lets go.
But if, after programming, the device would also reset with the power switched off:
Check if the timer starts and continues to run if the start button is being kept pressed, if so then:
Bridge the start button to be continously on.
Use the micro switch to provide power to the circuit.
This way the electronics are only powered when actually used ;)

JonathanH243 (author)  Downunder35m28 days ago

I just finished and I wanted to show you the result.

I do need to tweak it a bit bc I need to make it more water proof. Im also going to make one with 2 batteries hooked up together. Ill send you an update.

JonathanH243 (author)  Downunder35m1 month ago
Well the relay is quite simple. You can set the time from 0.1 - 999sec.
Once it is powered on the timer starts and stays on unless you cut the power. Once the power is turned on again it will remember the previous setting. So thus the switch is just perfect for it