Here you can see the current state of the robot “The little one”.
In this state I use NiMh cells with 7,2 V together,
The drive train:
There are two gear motors, controled by the L293D circuit. Important is that you connect the 7.2 V directly to the L293D circuit (Vdrive). You need also 5 V to connect to the L293D circuit (Vcc). Five pins are connected to the Arduino.
There are three pins: Vcc, GND and the control pin (connected to the Arduino).
The ultra sonic sensor:
There are four pins: Vcc, GND, Trigger and Echo. Both, Trigger and Echo are connected to the Arduino.
This is a voltage regulator. The Input voltage is 7.2 V (battery). For the most components we need only 5V. Currently I use this circuit to transfer 7.2 V to 5V.
The Arduino is connected to the battery (7.2 V).
The Video on YouTube: