Pro mini and 12v input

I plan to use the onboard regulator to accept 12vdc from a lead acid battery. The battery actually has 12.5 volts. Is this going to be a problem? I want to attempt to use this onboard regulator instead of a separate linear regulator. The pro mini will be controlling a relay. That is all. Possibly an LED. I am not sure of the current draw on the relay board I have but should be minimal.

Will the onboard regulator handle the current requirements of the pro mini and relay?

I would advise against your approach.
You will be making the regulator work quite hard.
Much better to drop the voltage to between 8-10 volts (max)

Relays will depend on the operating voltage which we don't know from this side of the screen as you didn't add any real details.

Current output on the Arduino pins is quite limited and relays can often draw more than the output pins can supply unless you are using some form of module that accepts the input to switch the relay. (missing details)

I've got Pro Minis working just fine at 14V with only their onboard regulator.

But I'm not powering relays. Tell us which relays you have.

My mini did poof when i had it on "12v car battery". That voltage actually goes up to 14 when the car is running so yeah that was pastvthe max specs for sure :slight_smile:

Well I guess it's gonna be 7805 for sure then. Thanks.

Or a simple buck converter

I found this just now. I'll use it in the project. All I have to do is remove the board from the housing and connect it to my 12v source.

Google Photos

This is the board wired for connection to the 12v system.

Google Photos

Why don't you get a 12V to 5V converter instead, like a mobile phone charger? That can connect directly to the 5V pin, and power the relay as well.

Still no details on the relays…

Not sure why your last post was pulled ?

And there is the reason for a better supply...those relays pull 100 mA which is way above the 40 mA the pins can supply at max. and the reason they need a seperate supply from the Arduino.

Phone chargers give off around 500 mA so the total load should be fine with your project as it now stands.
Don't forget the common ground from the relays to the Arduino or you may come up against other issues.

Still no details on the relays....


I just bought these but they are the same as the ones I already have. Just in single form.

I deleted my last post cause I was having trouble posting a link. I figured it out just now.

I'm going to start work on a fritzing project related to this. I want to have a schematic to post with the sketch in my online editor then I will share it here.

Fritzing - seriously?

If you want to do anything serious in this hobby get a real schematic drawing program, such as KiCAD or EagleCAD.

F**ing does have a lot of good features. You can even get a PCB made through the system.

Unfortunately most people only see the colorful breadboard viewer and never go past that.

Like all online services, you are up the creek without a paddle if the website ever shuts down. With a program on your PC like Eagle or KiCad, you always have your own data where you control it. If those services ever go away, your data is recoverable.

Actually my .fzz files are stored on my pc. You can share online but I have many projects on my computer's HDD.

I am downloading KiCad and will try it out. I have eagle but am wondering if kicad is any easier.

I simply stated earlier that I would use fritzing as it's quicker to use than eagle IMO. For me anyway. I would create the circuit and export the schematic image.

Kicad is probably easier. One of the greatest weaknesses of Eagle is every part on the schematic must have a footprint on the PCB. When I use it for plumbing schematics, every part has a dummy 14-pin DIP footprint.

It is also Eagle's greatest strength: you can't forget to place a part on the PCB.

I need to find a good kicad tutorial somewhere. Suggestions?