Hello. I think I've broken my 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.
The battery needs to be on VCC. The chip with 8 MHz clock will run fine at those levels. The 3.3V regulator will act weird at lower voltage levels.
Sounds like something is drawing a lot of current from the USB 5V port.
Can you make an adapter to between the USB adapter and the Promini so the 5V can be disconnected?
Here's an example. I had Rx & Tx swapped on my board, made an adapter to swap them. Follow the black & brown wires.
The battery needs to be on VCC. The chip with 8 MHz clock will run fine at those levels. The 3.3V regulator will act weird at lower voltage levels.
I first connected the battery to VCC, but as I realised that VCC isn't regulated, and my battery has a maximum of 4,1 V, I reconnected it to RAW. So are you saying that 4,1 V is safe in VCC, even if VCC doesn't have a regulator? If so, then I could think that this "little" (0,8 V) excess on VCC didn't "fry" the 328 chip or any other component (if fried, it would be internally: externally all of them are spotless).
Sounds like something is drawing a lot of current from the USB 5V port.
Can you make an adapter to between the USB adapter and the Promini so the 5V can be disconnected?
I have a CP2102 adapter. Obviously I used the 3,3 V pin of the adapter to feed the board, not the 5V pin. I have wires like the ones you use on the photo. I can plug them individually, so 5 wires: VCC 3,3V, GND, RX, TX and DTR, correctly plugged both on the adapter and the board. The 6th pin, VCC 5V, isn't used/connected. I connect the adapter to the PC through a USB 3.0. I don't think this will be the problem, as it is the USB where I connect the Arduino Uno. Of course I've checked I'm using the correct COM port for the adapter on the IDE, as the correct version of the board.
I've also made a little experiment: I've used a CR2032 button battery, as it has a little less voltage. Led color was red instead of white (steady, not changing if I rotate the encoder -it should be-), full intensity again… until the battery hadn't enough current/charge, then LEDs dimmed until they were off.
It may not be part of your issue, but USB3.x can cause some issues for some users.
Where possible always use a USB 2.0 port or a powered USB 2.0 hub between USB 3.x port and the Arduino.
Hi all. As my PC has (fortunately) a USB 2.0 port, I've done what Bob suggested: try to connect the adapter to it… and sadly no changes.
As the board can load programs (checked, so apparently no chip damage), 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. I've checked resistance (of course without any power supply connected to the board) and voltage, and values are consistent between the two boards (Uno and pro mini). Basically, these are my theories:
Damaged board on manufacturing.
Quartz oscillator not working properly.
Not hardware related, but IDE related: I use one the Arduino IDE the AVR ISP option. It works fine 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).
I'll have to buy another mini pro, and see what happens.
Hello David. Directly through the battery + and - terminals, and through the 8 pin of the board the data terminal. On the Uno board (the "test board", we could say) it works as it should when I power the WS2812 the same way.
I ask: as first I connected the battery to VCC, could I have damaged (accidentally, not on purpose) the voltage regulator by back-feeding it? I mean, as I put 4.1 V to VCC, could these 4.1 V have gone to the output of the regulator (not having any voltage on its Vin input), as it has a Vout of 3.3 V?. If so, then probably I also could have damaged something else. What I don't understand is, if that's the case and the regulator is damaged, how could have affected to the rest of the board, or the 328 chip itself, from the very first time.
I'm not familiar with the regulator, so don't know if it would have been damaged. If you are getting 3.3V on VCC with the 4.1V connected to the RAW pin, then it is probably OK. I doubt anything else on the board was damaged, unless the capacitors are rated below 5V, and that would likely either short the capacitor, or blow it apart with obvious damage. You are well within the operating voltage range of the atmega328.
If the regulator is dead, just remove it and supply power directly from the battery, the board will work fine with that voltage unregulated. The genuine SparkFun designed pro mini has an isolation jumper you can cut to isolate the voltage regulator and power LED from the circuit for low power operation, making it easy to reconnect by soldering over the jumper.
