Arduino Mini Pro, serial2usb and power

Hello :)

I'll use an Arduino Mini Pro with a DC/DC converter in my car, to load the code I need a serial2usb converter. I got both. My question is: how to power the Arduino while flashing?

There is a 5V pin on the converter, is it to power the arduino board through the USB during flash ? Or do I need to power it externaly before connecting the converter and loading the code?

The USB is very limited with current, and I'm afraid to burn something during the first start after loading the code.

thank you

It depends on what is connected to the Mini Pro. If that does not need a lot of current, the USB power is good to power the Mini Pro and the USB-ttl-serial converter.

Normally a USB-ttl-serial converter has a 5V output from the USB cable. You can use it to power the Arduino. To be sure, you could give a link to it or upload a photo.

The USB of the laptop could perhaps be less than 5V, if it doesn't work, you might have to measure the voltage. The USB it is current protected, so things should not burn if something is connected wrong.

If it's possible to power the board externaly before loading the code with the adapter it's ok for me.

Here is some pictures of the prototype:

You can power the board externally, why would that be a problem ?

The RAW pin is the power input for 5-12V.

Because of the 5V coming from the external source and the USB port, both are connected together through the pins of the Arduino. I'm using an onboard DC/DC converter to power the Arduino (not seen on the picture, it's under the upper panel).

If you connect the DC/DC converter to the RAW pin, and the 5V of the USB is connected to the 5V pin (or other pin), the current of the DC/DC converter could flow into the computer.

You want to avoid it, but most of the time, it is not a big problem.

I have it often with a test circuit I'm using right now. I use a 7805 voltage regulator and if it is getting very hot, the current is going into the computer over the USB bus.

The Arduino is powered through the 5V pin, not the RAW pin. The DC/DC converter is supplying a regulated 5V.

Ok, that's fine. If you connect the USB-to-ttl-serial converter, don't connect the 5V. Otherwise the 5V of the DC/DC converter could flow into the laptop.

Without the DC/DC converter (only USB power), it should be able to upload the sketch, I think. Also if current flows into the computer, that would not harm it (but I'm not sure about that).

Ok, good.

Thank you :slight_smile: