Too much power through programmer?

Other Hardware General Electronics
1

I have a project which currently involves one Nano, one ProMini, one GPS unit, one Compass unit, and a 2x40 LCD display. With the LCD display involved, it pulls over 50 ma. The whole thing is powered from a twelve v. battery, stepped down to 5 v. and 3.3 v. using two LM317's. All of that works fine.

However, sometimes the Nano or the Mini seem to lose track of the USB serial ports that are feeding them (on a MAC). When that happens, disconnecting the USB connector and reconnecting doesn't seem to help unless I power down the Nano or Mini, which I do by shutting off the battery input.

So here's the problem: the entire circuit is powered down, and I attach the ProMini through a little USB-to-serial adapter. The entire circuit is then backfed through my little programming adapter, which got quite warm and quit working.

That is of course a result I would like to avoid, and there appear to be two possible approaches.

  1. Is there some way to re-establish USB connection to the ProMini without powering it down?

  2. is there some way to avoid the 5v. pin on the Promini acting as a power supply when I attach power to it through a USB adapter?

At the moment, I'm supplying the ProMini USB through an Arduino, which seems to prevent the problem, but I'd like to simplify this to where I don't have this risk involved when programming the ProMini.

Thanks in advance for any tips.

2

Yes. Don't connect the power + to the pro mini, just connect the ground and other signals.

That said the real problem is the electrics attached to the power rails of the pro mini which must be drawing a lot of power and more than 50mA to cause a problem to the USB to serial converter which should be able to push out something like 500mA.