Arduino pro mini probably broken/crashed?

Development Boards Arduino
1

Hello. I think I’ve broken my sparkfun pro mini board (3,3V, 8MHz), as I think I put the input voltage on the incorrect pin. I explain:

I have a 3,7 V battery (like the ones for electronic cigarettes, a 18650); when fully charged is 4,1V. I’ve soldered it on the VCC pin instead of the RAW pin. The project I’ve loaded on the board works 100% fine on a “normal” Arduino Uno (it has a WS2812 led strip on the 8 pin, changes color, intensity and so on; rotary encoder on pins 10&11 “encoding”…) but on the pro mini LEDs are always at full intensity; even if I touch them, they are a bit hot. No color changes (always white), no intensity changes, rotary encoder not “encoding”…

I’ve “re-soldered” the battery to the RAW pin, but no changes. Could the board be “dead”? If not, could it be “fixable”? Of course I’ve checked if any connection was wrong, but everything is soldered where it has to be. When I put the battery, a red led on the board blinks a couple of times, and when is off, WS 2812 leds are on, and a green led on the board is also on. If I try to load the program, also the red led on the board blinks 2-3 times when load is complete.

I’ve also noticed that the usb adaptor for programming the pro mini also warms after 2-3 minutes (even if I don’t connect the pro mini to it). Is this normal? I didn’t noticed that when I loaded the program the first time.

Thanks in advance. Sergio.

2

You may have destroyed the on board voltage regulator, by back-feeding it with a higher voltage than it puts out. However, that normally would not damage the ATMega328 chip, which can tolerate up to 5.5V.

I would remove the regulator by “swiping” it off with the tip of a hot solder pencil, and try powering the Pro Mini via the Vcc pin. The RAW pin won’t work any more, of course.

I have done the above surgery on Pro Minis many times, and also remove the power LED, in order to turn them into the equivalent of a “bare bones” Arduino for low power battery operation.

3

Hello.

You may have destroyed the on board voltage regulator, by back-feeding it with a higher voltage than it puts out. However, that normally would not damage the ATMega328 chip, which can tolerate up to 5.5V.

I don’t get what you are saying. I mean: I first put the battery positive to VCC (if I’m correct, VCC on a mini pro board isn’t regulated), and since the first moment, led strip didn’t work as it should be (like I said, through a rotary encode it should change the color or intensity, something that it doesn’t happen: always white at full intensity). Then, thinking that as my battery has a maximum voltage of 4.1 V, I connected the positive to RAW (OBVIOUSLY disconnecting before that from VCC) and led strip still lighted white steady, full intensity. So if, as you said it, I “destroyed” the voltage regulator, probably I also “destroyed” the chip itself, as VCC is for 3.3 V or less (I think) and I put 4.1.

I have to say that I doubt that the regulator for RAW input is destroyed, as I have the voltage connected to RAW, and the mini pro, apart the fact that the program doesn’t work ON IT as it should be (it works perfectly on an Arduino Uno, so no programming errors), works fine: voltages are consistent with the ones I measure on the Uno (+/- 0.1 V), the green led lights on, I can load programs… So if regulator was destroyed, it would mean no voltage on the chip->unable to load programs->no red or green on board lighting->no output voltage… and I have all of this.

Plus: how can a voltage regulator be “back-feeded”? Voltage was connected only to VCC OR RAW, not both at the same time. If IIRC, voltage regulators have 3 pins: Vin, ground and Vout. If on the board is “back-feeded” by design (not by me as I haven’t ever connected the battery to both VCC and RAW simultaneously), I think it’s a GREAT design mistake/failure.

I only can think that the signal sent to the led strip (I mean l, the FORMAT of the signal) is, I don’t know how or why, wrong. Basically, these are my theories:

  1. Damaged board on manufacturing.

  2. Quartz oscillator not working properly.

  3. Not hardware related, but IDE related: I use one the Arduino IDE the AVR ISP option. It works fine be on the Uno board, and it has the same chip.

All wires are well soldered where they have to be (triple checked); no tin “little balls” making a “shortcut” (also checked).

Is there any way to see/analyze the signal that pin 8 (the problematic one) sends to the led strip? I don’t have an oscilloscope. And no, the serial monitor is not an option (at least for the pro mini itself).

Sergio.

4

I first put the battery positive to VCC

Yes, that was clear. That means you applied perhaps 4.1V to the output terminal of a 3.3V voltage regulator.

You obviously damaged something. You are welcome to continue guessing what else that might be.

5

Hello. Thanks for the help, specially to everyone that read this topic and didn’t answer. I don’t know where is the failure, so I’ve bought another board. I hope I don’t have the same issue with the new one.

BTW, jremington, when you said:

You obviously damaged something. You are welcome to continue guessing what else that might be.

Obviously it didn’t help me at all. You could have told me “measure voltages and post the results”, or “check this”, or something like that, and then with your answer (and answers from other people), I could figured where the problem is. I don’t have time for “guessing”: there are 5 capacitors, 4 resistances, 2 LEDs (working), 1 regulator (working, at least if I put RAW/Vin 4 V, I get VCC/Vout 3.3V), 1 oscillator (working) and the 328 (working? if so, at 100%? I don’t know). The issue is with one of them (at least), I don’t know where, but I don’t have a pencil solder (I mean, thin enough to not damage or shortcut another component; 1 mm is quite thick), and the price of it plus the price of component(s)… better I buy (as I did) another board. I don’t want to be in the situation where “the flowers are more expensive than the wedding dress”, as a bride would say.

The last I have to say is: I don’t know where can I get help, but definitely I know where I will NOT find it. Please don’t answer (anybody) to the topic, as I won’t read it anymore.

6

jremington was simply trying to help you and had a valid point about back feeding the regulator. Just because you don’t understand what he was saying doesn’t mean he was wrong.