Xbee Running Stuff that Requires More than 3 Volts

Question

Electronics newbie here.

I have an xbee remote that I want to control a model train smoker (6 volt) and a motor (6 volt) (separate channels). The remote runs off of 3 volts and puts 3 volts out in the output channels.

A guy at Radio Shack drew up a diagram for me, but it went out of business shortly afterward. When he drew it up we were going off of the published 5 volt requirement of the smoker, but subsequent reading suggests the smoker runs better at 6 volts. Since I don't need to step the voltage down to 5 volts for the smoker with a diode, can I skip the transistor too?

^{simulate this circuit – Schematic created using CircuitLab}

I guess my real question is why can't I just connect a 3 volt battery in series with a motor and the 3 volt output from the xbee? What's that transistor/resistor doing over there? Will I fry my xbee?

Answer 1

I don't know the specifications of your xbee controller, but most microcontrollers can only deliver fairly low currents - often less than 20 mA. The transistor can control the much higher currents that may be required by your smoker, or by relays or motors.