How to Reset a Circuit With a Schematic

IC datasheets provide schematics showing how to wire the circuits.

Reset circuits have many uses in computers and microprocessor projects. For example, they prevent the passage of power to integrated circuits until the supply voltage has met the minimum requirement for the IC to function properly. Additionally, some microcontrollers have manual resets that prepare the chips for loading new programs. You can find the manual reset button or add a reset to an existing circuit by looking at either the main circuit's schematic or the IC's datasheet.

Things You'll Need

• Switch (optional)
• Solder (optional)
• Soldering iron (optional)
• Wire (optional)
• Electronic components (optional)
• Stripboard (optional)

Instructions

1. Look for the reset pin on the IC. The pin or a portion of the schematic may be labeled "reset." If the pins aren't labeled in the schematic, obtain the IC's datasheet from the manufacturer.

2. Press the button attached to the reset pin on the circuit to manually reset the circuit. Capacitors, resistors, diodes or other components may be between the reset pin and the button. If a button doesn't exist, skip this step.

3. Add a reset switch to the main circuit. Look at the reset circuit's components on the IC's datasheet and compare them to the main circuit. If the reset circuit exists without a switch and the IC's datasheet recommends a switch, add one according to the recommendations. You may need wire in addition to using solder and a soldering iron. If no reset circuit is on the main circuit, skip this step.

4. Add a reset circuit to the main circuit. The IC's datasheet should provide you with a schematic for the recommended reset circuit. If the main circuit is on PCB, you may need to solder electronic components to a piece of stripboard and connect the stripboard to the main circuit with wire.

Tips & Warnings

• If you're building a reset circuit, test it on breadboard before soldering it to the main circuit.

• If the circuit resets internally, you don't need to add an external reset circuit.

• Circuits that automatically reset when they're turned on or during regular operation may not require a switch.

• Soldering components to a powered circuit may result in electrocution and cause damage to the circuit.

References

• Atmel: External Reset Circuit for a Microcontroller
• EDN; Why Microprocessors Use a Reset Circuit; Guillermo Bosque; May 2003
• ITP Physical Computing; Why Some Microcontrollers Use a Manual Reset; Carlyn Maw; October 2008