Mk125 power source 12v car battery?


Im going to using the mk125 for our automatic door opener on the chicken coop.

Its all off grid so I was hoping to use a 12v car battery to power it. I see it requires a 12vdc power supply for the board and looking at the connections it looks like a laptop or phone charger type socket.

Can I hook it straight up to the car battery with an in line fuse or would this fry it or just not work?

Thanks for any help


Shoud work fine with a 12V car battery.
Make sure to put a fuse in the line, as you say.

Thanks for that.

I’m using it for an auto chicken door opener.

There are a couple of issues I’ve run into.

The adjustment doesn’t seem to work with the battery as I need to keep adjusting it. I’m guessing its because the battery is changing voltage and amperage as the battery discharges and charges. Which should I try to maintain the amps or voltage as constant, and could you suggest a way?

Is there away to adjust the delay so its longer? Sometimes on a cloudy day it causes the door to open and close.

Thanks for any help


Increasing C3 can help on cloudy days.
To avoid influence from battery voltage fluctuations, you could replace the relay with a 6V type and run the complete circuit from a 6V regulator (e.g. 7806).

Thanks so much for the reply, I’m sorry I missed it for so long.

I’m an electronics beginner, I’m guessing when you say increase C3, which is a 100µF, you mean get a higher µF number, could you suggest one? Even a 5 min delay would be fine by me.

I see the UA7806 velleman sell might fit the bill to stabilise the sensor, but I can find any info about what it looks like or how to use it. I’m going to buy it and have a play.

Thanks again for your help


Please experiment with the values for the cap (220µ, 330µ, 470µ,…)
As for the regulator, the 78xx datasheets shows some basics on how to use them.