Refrigerator door alarm - DIY help

[hommeg]

I was trying to build a refrigerator door alarm based off this maker post I saw using a dollar store window alarm. My problem is my circuit is a little more complex than the one posted by the user. I'm trying to figure out where I should add my 2k resistor and 22uF capacitor in the circuit (see attached images) to create a time delay for the refrigerator alarm. I'm a novice so any assistance would be greatly appreciated.

[eccerr0r]

Re: Refrigerator door alarm - DIY help

Nice, I would have thought they would go to COB design instead of going to SMT.

It looks like what the maker hack is to put an RC delay across the switch contacts. In picture 3.JPG the "P1-" connection is the upper right, and "P2" is lower right - the terminals across the reed switch.

No guarantees this will work, seems reasonable but if it doesn't work, you keep the broken pieces.

[budm]

Re: Refrigerator door alarm - DIY help

That 2.2K resistor in series with the cap connected across the reed switch contacts is not going to do much for delay time since the charge up of the cap will be done mostly by the 105 resistor that is connected to the VCC and the reed switch, 2.2K will affect how fast the cap will discharge when reed switch is close but it will be very short time, you can look up RC time constant calculate the time.
The schematic is basically what you have on your board. The cap will have to low leakage cap otherwise the Transistor will be bias on based on the leakage current.
YL3710 schematic.

[hommeg]

Re: Refrigerator door alarm - DIY help

Thank you both! I just wired it up as pictured below, I get about a 1 minute delay which is prefect for me!