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Topic: Help with Solenoid/Keypad project. (Read 1 time) previous topic - next topic


I have a keypad that, if you enter the correct code, it opens a solenoid for 5 seconds.  This unlocks my shotgun or it will once I get the project done completely.  Here is the shotgun lock, if you are interested. http://www.policeproducts.com/santa-cruz-gun-lock-for-pump-shotguns-p-1038.html

I have a 9v wall wart powering the Arduino, but two 9 volt batteries powering the Solenoid.  Like so: http://www.instructables.com/id/Controlling-solenoids-with-arduino/

Can I lose the two 9 volt batteries and have one wall wart (110v to whatever DC) that powers both the Arduino and the solenoid?

I have just enough electrical knowledge to make my head hurt, so go easy on me.  This is my first project.  I am much better with the coding than the electrical.

In case anyone asks, it is for easy access in case of zombie attacks.  Of course.


Wow, that lock is really unclear about how it works. Is the solenoid already in it? If so, what is the voltage it requires? If you are sourcing your own solenoid, there are lots to choose from at different voltages. There is no reason you really HAVE to need 18v (the two 9V batteries) as there are solenoids that operate at a much lower voltage. So in that case, you could just power everything from the same voltage. Though, one suggestion is that solenoids usually need a lot of current quickly. Either a battery, or a very large cap to store some juice should be used for this, or you may find your arduino resetting when the solenoid activates.

You say "I have a keypad that unlocks a solenoid..." does that mean you already have a keypad that does this, or is that your project? I ask because they do sell keypads with all that built in (I have a couple.)



Yes, the solenoid is already in it.  It is really made to hook up to the DC current from a police car, but I use it in my closet.

It requires 12V, if I am not mistaken.

I already have finished the project with three 9 volt batteries.  It works as intended, but I do not like relying on batteries.  It would be better if it had a more reliable power source. 

I used one of those stick on keypads.  Works great!


Just power the whole thing (arduino and everything) off 12V then. If you have problems with resets, install a 470uF 16V to 25V cap or larger across the power supply to hold it up during the sudden current spikes of the solenoid.


Thanks for the help.  I will try that.


I got my 12v wall wart hooked up today.  It works!  Thanks again!


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