They are inexpensive and are ideal for use in your Robotics, Quadcopter, and Internet of Things projects. Today DC motors range from huge models used in industrial equipment to tiny devices that can fit in the palm of your hand. Since then DC motors have been part of countless pieces of equipment and machinery.

Make sure GND of the Arduino's power supply is connected to the L298's GND.The first practical DC (Direct Current) motor was invented by the British scientist William Sturgeon in 1832. Make sure V_SS is connected to the logic supply voltage (see AnT's comment).

ditch the L298 and use single bipolar transistors, depending on the output current.

ditch the L298 and its high voltage drop Darlingtons and use a MOSFET H-bridge motor driver, such as the TB6612FNG, see also.

temperature, so this might work now under certain conditions and fails horribly another day

saturation voltage is related to output current and other parameters, e.g.

this circuit is now operating at the fringes, one might call it shady at best, intolerable at worst.

The actual restriction is that the motor supply be somewhat greater than the logic '1' input, but that need not match the logic supply. So driving the L298's logic inputs with a lower voltage for logic 1, i.e. And here's the trick that might make it work: as noted V_S (the supply voltage) needs to be at a level of V_IH + 2.546V while V_IH could be as low as 2.3V and 2.3V + 2.546V < 5V. Which would explain that the circuit works at 7.2V under the assumption that the logic inputs (enable A and B as well as inputs 1 through 4) are at close to 5V high levels.

V_IH, Input High Voltage, ranging from 2.3V to V_SS.

V_SS, Logic Supply Voltage, pin 9, typical 5V (min.: 4.5V, max.: 7V).

V_S, Supply Voltage, pin 4, Operative Condition V_IH + 2.546V (max.: 46V).

There are only two supply pins on the L298 with the following electrical characteristics:

I will assume that the ' 12V-35V input pin' is the V_S pin, despite that label. Note: Since all vendors (checked Mouser, Octopart, and Sparkfun) link to the L298 datasheet when listing the L298N I will assume they are reasonably equivalent.

L298n motor driver connection