An issue I've noticed just recently with my Arduino during some of my projects is that on my Arduino Uno R3, both the 5 and 3.3 volt voltage regulators, and the FTDI USB-to-Serial chip are getting excessively hot under no external load (too hot to touch after a few minutes) and that my Arduino draws a whopping 240mA of current in what is essentially idle mode i.e. no external loads and running very simple code such as switching ports (with nothing connected to them) about twice a second and basic addition and subtraction. I'm sending 9 volts into the Vin pin. I've sent voltages as low as 7 volts and the chips still get hot, just not as fast.
I did some research and the Arduino Uno is supposed to only draw around 35~43mA while on idle mode, but mine is drawing nearly five to six times that amount.
Also, the FTDI chip gets hot even when I don't have a USB cable connected and don't have any sort of serial communication in the code that the board is running. Basically, the FTDI chip gets hot when it's doing nothing but simply being connected to power.
Those are the only chips getting hot; no other chips are getting hot. The ATMega328P runs cool and at room temperature.
Aside from being slightly finicky when connecting to USB when simultaneously connected to an external power supply (which is an issue I've noticed on other people's boards, so it's not just mine, and it's easily fixed by unplugging and plugging back in the USB connector), the board works perfectly fine. However, I'm worried that the board will eventually overheat and it is causing heat issues for external voltage regulators (an external regulator that I'm using to drop 24 volts down to 7 volts, LM317T to be exact) since those regulators need to dissipate a greater amperage (in this case, a whopping 4.08 Watts of heat instead of a manageable 0.731 Watts).
The only thing that I can possibly think of that could have caused this problem is a little while ago, I accidentally surged 9 volts through the board's components for a very brief period (fraction of a second) when some jumper wires connected to a 9 volt battery touched the output terminal of the 5v regulator (and thus bypassing the regulator) with the GND pin connected to the negative terminal of the battery. I noticed this because the ON led turned on. (Yeah, yeah, irresponsible on my part.) So, my best guess is that I might have burned out a resistor or two.
Any ideas on why my board is drawing such a high amperage and why the chips are getting so hot?
I could always get a new board, but that's 25 bucks :(.
Thanks!
EDIT: I just realized, (I think it's the Op Amp; has eight pins: four on, top four on bottom; and is next to the 3.3 volt regulator. I think it's the LMV358IDGKR, but on my board it looks like "28TI R5R" is stamped on it.) Op Amp is also getting excessively hot.