I have a B+ connected to a H-bridge which is connected to 4 AA batteries and 4 motors, and they work fine, but now I want to add a distance sensor, which requires 5v, so do I need any extra batteries?
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You can use the 5v output on the gpios of the Raspberry Pi. However be careful, you mustn't connect the echo pin directly to the gpio. Instead you can make a voltage divider on the wire connecting the echo pin because the b+ can't handle anything over 3.3v. Not using a voltage divider will damage your Raspberry Pi.
You can use a 470 Ohm and a 1K Ohm resistor with the 1K connecting echo and ground. Refer to the diagram below if you are unsure.
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@Vedbot It is risky, I can't guarantee the voltage will be around 3.3v without a voltage divider. Maybe someone else can tell you. – Linus Oct 25 '15 at 14:46
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The official line has always been that any current at a voltage greater than 3.3V will eventually kill the GPIO/Pi. I can't see the official line changing. A voltage divider is safest. If you can only use 1 resistor I suggest a value of 10k or more. – joan Oct 25 '15 at 14:52
