VIN from Lead Acid Battery

Hey all. I’m wanting to power my UNO from a 12v DC system. I purchased “BaiFM Buck Converter LM2596” to power the Arduino.

Everywhere I’ve read says a different story. Some say the vin can handle 12v. Some say no more than 9. Others say only 5.5.

I adjusted the buck converter down to 5.5 and it wouldn’t power on. Since a lot of people say either 12v or 9v… I decided to adjust my voltage to 8.5 to be safe. I hooked the + into the VIN and - to ground.

After turning one of my unos into a smoke machine, I’m assuming my “to be safe” voltage wasn’t safe after all.

Can someone tell me how to hook this darn thing up? or is there a diagram on how to power the Arduino with vin? I thought simply + into vin and - into ground was the way to do it.

Vin feeds into a 5v regulator that requires a minimum of 7.5v in to give 5v to the electronics. It can handle higher voltage at LOW current. It should work at 8v.

Did you have any other connections to the board? The regulator is only rated to about 0.5A.

Weedpharma

I had an 4x20 LCD connected to it. How else can I power the board with my 12v battery and step down? The Arduino has an LCD, voltage sensor, temp & humidity sensor and a 5v relay board hooked to it. I'm looking for a more permanent way to power it. USB wouldn't be feasible because once I put it in the enclosure, the usb port will be notched out for software updates. I don't want an extra wire going from battery to outside the enclosure. There are a positive and negative 12 bus bar on the inside of the enclosure already. Running another wire to it seems kind of messy.

If you have all your add ons powered through the onboard regulator, there will be too much current drawn and the regulator will overheat.

Buy a switch mode supply rated at the current drawn by your circuit. You can then power the extras from the switch mode and Arduino from the 12v. Separating the power supplies reduces interference into the Arduino.

Weedpharma

There should be no smoke at all with 8.5V on Vin. Something else went wrong.

The 4X20 LCDs that I am used to working with have a backlight which draws a relatively large amount of current. The Uno regulator cannot provide this amount of current when powered from 12V, even though it is within all other specifications. You can calculate this from the specs of the voltage regulator, if you are interested.

Do you have another 5V supply? If you have a trusted source of 5V then you can power the Arduino 5V pin directly. Your smoked Uno may still work this way. I would buy a non-adjustable 12 to 5 converter and just use that.

Power dissipated in on-board regulator = (Vin - 5.0) * total_load_current, so the more current you draw the lower the Vin you can get away with (down to about 6.7V when the 5V rail may start to droop due to regulator voltage drop).

will the Arduino power up if I only use a separate 5v adapter to run all powered objects connected to the Arduino (lcd etc). If an external source of 5v is connected to the 5v pin of the Arduino, this will power the Arduino as well?

j0ker31m: will the Arduino power up if I only use a separate 5v adapter to run all powered objects connected to the Arduino (lcd etc). If an external source of 5v is connected to the 5v pin of the Arduino, this will power the Arduino as well?

Depends on what "all powered objects" are and what amperage this 5v adapter can provide.

You basically just asked "can a battery power some things?" Yes. No. Maybe.

as stated before I'm using a BaiFM Buck Converter LM2596. It is rated at 3a max. My question is more directed at using 5v on an Arduino 5v pin. Will this power the Arduino or do I need it hooked to the vin?

The buck converter will also be powering the LCD, and sensors, etc. I have the amperage. I'm not concerned about that. Just wanting to know if hooking + to a 5v pin on the Arduino and - to the ground will power it.

5v put into the Arduino 5v pin will power it. Officially it is not recommended as you are bypassing the board's protection circuits, but if you trust your power source to be well regulated, it is fine.

You never put 5v into the Vin pin.