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Arduino Hardware Reset Circuit Breadboard

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By: kurt

This circuit uses one pin to let you reset your Arduino in code. It pulls reset low for a couple milliseconds to ensure the Arduino has enough time to complete its reset cycle.

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Bill of Materials

Qty Part # Description Schematic ID Source
1 C14ff4b26e5b0d93cd1a4d9208acb56b9634d2bf NE555P TIMER SINGLE PRECISION,DIP8 ,0.5MHZ IC1 Source
1 8d17dc6357d99d17730430c3718a0a959d650925 CF14JT100R 1/4w 100 ohms 5% Carbon Film Resistors R4 Source
1 6ff6f1f238f6d58bf3404a4f2e252ec33d9a96cc CF14JT1K00 1/4w 1K ohms 5% Carbon Film Resistors R3 Source
1 D9a682fef3ecbdda1662c8ac0511fc8fe76d9200 CF14JT10K0 1/4w 10K ohms 5% Carbon Film Resistors R2 Source
1 4868eeaa367d124a5137abfd3185be624e37bef6 CF14JT100K AXIAL CARBON FILM RES 1/4W 100K OHMS 5% LF R1 Source
1 D1ab4aa047eff1b9c25b19a978b5f76604582418 EEA-GA1HR10 CAP ALUM 0.1UF 50V 20% RADIAL C1 Source
1 679f7dae6acf00a1d38d970c8e80263aa7d6d8d4 SR215C103KAR CAPACITOR, 0.01UF, 50V C2 Source
1 5456f27d24da35477b2d27b2da40d3216ffa1904 2N3904BU TRANSISTOR, NPN 200MA TO-92 Q1 Source
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11. Insert current-limiting resistor R4

Put a 100 ohm resistor between the emitter of the transistor and ground. This resistor limits the current that is sourced from the Arduino's reset pin. If the current got too high it could damage either the Arduino or the transistor Q1.


12. Insert base resistor R3

Insert a 1k ohm resistor between the base of the transistor and pin 3 of the IC. This resistor limits the current flowing into the base of transistor Q1. Transistors only need a small amount of current to turn on, so we limit the base current to less than 5mA with this resistor.


13. Connect input signal

Pin 3 of the IC is the input of the circuit. The input should normally be held high. When you want to do a hardware reset of the Arduino, pull this pin low in your code. You can use any of the Arduino's analog or digital outputs for this.


14. Connect output reset signal

Connect the collector of the transistor to the pin marked RESET on the Arduino.

Img_0352 Arduinouno_r2_front

15. Completed hardware

Now the hardware is finished, and you need to program your Arduino to use this reset circuit. The code needed for this circuit is very simple.

Img_0354 Img_0356

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7 - fixed steps 3 and 4
6 - fixed an error in the description
5 - fixed the text for the third step
4 - none
3 - changed name to indicate this project is built on a breadboard
2 - updated description
1 - Initial project release
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