Arnan Sipitakiat Dept. Compute Engineering, Chiang Mai University

What’s wrong with this circuit? A microcontroller usually supplies limited current (i.e. 25 mA). This is ok for LEDs but not enough for high current loads like a motor

Transistors Using transistors as a switch

Using a transistor

Relays

Relay “Poles” and “Throws”

Driving load with a relay

Solid-State Relays

H-Bridge: A bi-directional driver

Relay H-Bridge

Transistor H-Bridge

H-Bridge IC / Module

Conclusions There are many ways to drive output devices Transistors are good for low power applications Relays are suitable for AC power applications or when low loss and high current is needed H-bridge is for bi-directional applications Choose the right tool for the job!