5v pin putting out 4.1v

[brownjeremy56]

Hi. I’m new here. Here’s the gist of what is going on.

I made an Arduino connected to a seeed can bus shield to control a servo motor. It worked great until…

-I decided to solder all of my connections
-I put my Arduino in a case
-I powered my Arduino off a 5v buck regulator because I read on this forum that using 12v dc was a bad idea.

My can shield stopped communicating, and I had a few other issues. Then I realized the 5v output pin is only providing 4.1v. I do not know why, or which 1 of my previous 3 changes have caused this.

The buck regulator is soldered to the Vin pin. I have 5.1v there. 4.1v out the 5v pin and no can comm. if I jump power directly from the Vin pin to the 5v output everything works great. Can I just install a jumper wire to fix this issue?

I figured the issue must be a bad Arduino because my voltage at the solder connection under the header of Vin was 5.1 and the solder connection of 5v out was reading 4.1. I swapped a known good Arduino r3 board in, and have the same problem.

Could the 5v buck regulator be the issue? Can I simply put 12v to the Vin pin?

[camsysca]

You're putting 5V into Vin, aren't you? Vin should get at least 6.5V(apologies, but please RTFM). Feed your 5V directly to the 5V pin.

[TomGeorge]

Hi, @brownjeremy56
Welcome to the forum.

@brownjeremy56

The buck regulator is soldered to the Vin pin. I have 5.1v there. 4.1v out the 5v pin and no can comm.

The Vin pin needs more than 7V to get 5V regulated on the 5V pin.
Vin feeds an onboard 5V linear regulator.

You should be able to connect the 5V output of the buck converter to the 5V pin of the UNO and it will power your controller with 5V.

Tom..

[brownjeremy56]

Excellent news. Thank you. I see how I messed up. I should not have connected the buck regulator to Vin.

[awneil]

@brownjeremy56

I read on this forum that using 12v dc was a bad idea.

Where did you read that?

It's not necessarily a bad idea:

You haven't said what Arduino you're using, but the specifications for the Arduino UNO R3 are 7-12V on Vin.

But the UNO R3 has a linear regulator; so the higher the Vin voltage, the more power it has to dissipate - which can become a problem if you're maxing the current output from the Arduino...