I'm new to Arduino and a beginner in electronics.
I'm using a Leonardo and an Arduino motor shield r3 that controls a single 6v pololu DC motor. My setup includes 6 buttons, 6 photo interrupters CNZ1120, an 7 segment led display and about 12 leds (all leds including the 7 segment are connected to 3 74HC595 shift registers in series). The power is supplied by an old external HD adapter that supplies 12v to the board (via Vin) and 5v to the motor shield (in order to isolate the two lines I cutted the Vin connect jumper on the motor shield as explained here: http://arduino.cc/en/Main/ArduinoMotorShieldR3
The system (an Arduino-based dollyhouse with a fully functional model elevator) works perfeclty. However, I have a concern about the heat developed on what I suppose to be the voltage regulator of the Leonardo (the componend circled in yellow in the image below).
When the power is on (I tried with other 12v adapters as well) the temperature on the chip goes up to about 70°C in about 1 minute and then stays there, no matter if the system is doing something or not.
My multimeter says the current at the Vin in various system states (lights and motor on or off) is about 200mA +/- 90 mA (actually the motor current does not pass through Vin), which is well within the limits of the adapter. The voltage supplied to Vin is about 12.20 V, and is steady (I suppose the adapter is regulated, even if I'm not sure what it means).
I tried to isolate various parts of the system to see if the problem comes from some subparts of it, with no success at the moment.
The Leonardo board, with the same adapter, if used alone for very basic setups like turning a led on and off, is not overheating.
Well, before trying to enquire more in deep and set apart my dollyhouse, I'd like to know if 70°C can be considered "normal", or if I should look for short circuits somewhere (what could be the signs of these?). The converter is the only part that is heating like this. The processor and the other components remain cool. Also, I use quite a lot of cables (all in all several meters, and each one about 1 meter long). Could this be a factor?
Thanks in advance for any hints