Unable to make Pro mini run from external power

Projects General Guidance
1

Hi all.

I'm using a Pro Mini (5V, 16 Mhz) and I'm having an issue running my project from an external power source.
I'm using a 9V battery (dropped to 7.5V using a low dropout regulator) which is connected to the RAW. When I use the FTDI adapter, everything seems to work fine (including reading from serial monitor) but when I put it in my custom design board, the power led is on nothing else seems to happen. I'm also unable to upload to it when it is inserted.
I started by using "Blink" (which works flawless when I connect to the FTDI adapter), but since I use pin 13 in my board, I thought that might be the issue.

Any ideas on how to fix this?

Thanks

2

When you are powering the PCB from RAW (no FTDI), what is the voltage measured on the 5V pin to GND ?

3

5V.

RAW reads 7.52V.

4

Why the regulator on the raw input...???
At some stage, those little 9v smoke alarm batteries will cause you grief....better to go with a pack made up from AA cells.

5

Show us a good schematic of your proposed circuit.
Show us a good image of your ‘actual’ wiring.
Give links to components.

6

I wasn't sure if it would be too unstable voltage and vary since it depends on the level of the battery, so I thought to add it as a precaution.

7

If you are using a battery and regulator, the best approach is to use a 5V switching regulator and power the Pro Mini via the 5V pin.

This one from Pololu is extremely efficient, and my favorite (choose the appropriate output voltage for your project): https://www.pololu.com/product/2842

8

Thanks. I'll remember to use it in my future projects :slight_smile:

9

So the classic problem in questions here. Failure to adequately define your project. :roll_eyes:

A 5 V Pro Mini can be powered from a pack of three "AA" alkaline cells at 4.5 V (nominal). Connected to the "Vcc" pin of course. They may drop to 4 V with use which is OK.

So the question is - is there something else you failed to mention that you wish to power which is actually critical of voltage, such as a LCD display?

Batteries in particular, but please get into the habit of never using the "Vin" or "Raw" pin. The on-board regulator is basically useless. :cold_sweat:

10

Will do about the VCC in the future.

At a later stage of the project, I will use high powered LEDs, but they are disconnected right now.
At the moment, I only use a 8 to 3 encoder (5V) and a micro sd adapter (3.3V).

As for the project definition I didn't think I should explain what the end goal is if I can't seem to run the most simple program :sweat_smile:

11

Input power:

image
image1341×591 58.3 KB

(input and output have several capacitors not shown in this schem.)

12

Your converter GND is connected to the Arduino GND ?

13

Converter is connected to GND though Rset(R75), it doesn't have its own direct GND pin.

But all GNDs are connected.

14

Assume you have V(control) connected to Vin ?

image

Can you show us a good image of your actual wiring; all included ?

15

Wacko do-all do-nothing regulator totally unnecessary.

16

The package I use Vcontrol is tied to Vin.

Did you mean an image of the WHOLE schematic or the PCB itself?

17

An image that we can review of your wiring interconnections.

18

Even though I think most of it is not relevant, I'll attach the entire schematic:

image
image1920×1007 359 KB

19

image
image1795×446 82.1 KB

And 1G14 pin 4 (Y) goes to GND?

:open_mouth:

Your 5v Arduino connected to 3v SD card ?

1 Like
20

Rookie mistake lol

That's what happens when you do stuff like this an 2am :sweat_smile:

The connections to U6 were wrong, causeing the Arduino to be in permanent Reset.
Removing it solved the issue :slight_smile:

Thank you so much LarryD

P.S: The Arduino is not connected in any way to the 3.3V net.