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Watchdog Timer (555 based)

1 year ago 3498
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Description

A 555 based watchdog timer. The timer must be reset periodically (patting the dog). If this reset is not set, then the micro-controller patting it will be reset.

Info - http://upperbound.com/projects/555-watchdog-timer/

Documents

Watchdog Schematic

Watchdog PCB

BOM

ID Name Designator Footprint Quantity
1 NE555DR U1 SOIC-8_150MIL 1
2 100nF C1 0805 1
3 Red LED1,LED2 LED-0805 2
4 510R R1,R4,R5 0805 3
5 1M R2 0805 1
6 4.7k R3 0805 1
7 22uF C2 0805 1
8 2N3906S Q1 SOT-23(SOT-23-3) 1
9 SOD4007 D1 SOD-123F 1

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Comments (3)

Lautaro Tourn Reply

Hi! I'm trying to simulate the circuit in Proteus but it does not work, neither in real life, are you shure this schematic is right?

lynxlabeling Reply

@lautatourn
The circuit is taken from another source as referenced in the Notes. I have not tested it yet myself, so no I am not sure the schematic is correct. You may want to compare to the original reference. If you find an error in my schematic, let me know and I will correct it.

aragocom Reply

I think that pin 2 and pin 6 should be connected to the junction of  R3 and C2 ?

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