ralphbacon / 194-external-watchdog-timer-555-with-pcb

Prevent microcontroller latch ups and hang ups with this resetter

#194 External Watchdog Timer 555 (with PCB)

Prevent microcontroller latch ups and hang ups with this circuit re-setter.

See YouTube video #194 in my channel https://youtube.com/ralphbacon

We discussed the breadboard circuit in video #190 (https://youtu.be/wcRuVxXlEKw), but here we have the finished product, including the panelised PCB from JLCPCB together with some testing using a signal generator and an oscilloscope.

The 555 is the most popular integrated circuit ever manufactured. As of 2003, it was estimated that 1 billion units were manufactured every year. And we are using it this week in this timer watchdog that power recycles your Arduino (or other µController of choice) if it hangs up.

JLCPCB Only $2 for PCB Prototype any colour https://jlcpcb.com/

Special offer for SMT assembly.

List of all my videos

(Special thanks to Michael Kurt Vogel for compiling this)
http://bit.ly/YouTubeVideoList-RalphBacon

INFORMATION

Elektor Magazine Article (Wolfgang Borst)
UK: https://www.electronics-lab.com/free-elektor-circuit-ne555-watchdog-timer/
DE: https://www.elektormagazine.de/news/kleine-schaltungen-neu-aufgelegt-watchdog-mit-555-folge-6
https://www.elektormagazine.com/news/small-circuits-can-do-the-job-an-ne555-watchdog-timer-part-6

555 timer IC
https://en.wikipedia.org/wiki/555_timer_IC

HARDWARE

Surface Mount 555 chips, less than $1 for 10 pieces (plus shipping)
https://s.click.aliexpress.com/e/_Bfjexh5a

10pcs NE555 NE555P NE555N 555 Timers DIP-8
https://www.banggood.com/10pcs-NE555-NE555P-NE555N-555-Timers-DIP-8-TEXAS-p-1069802.html?p=FQ040729393382015118&utm_campaign=25129675&utm_content=3897

CJMCU-4599 Si4599 N and P Channel 40V (D -S) MOSFET
banggood.com/CJMCU-4599-Si4599-N-and-P-Channel-40V-D-S-MOSFET-Expansion-Board-Module-p-1350610.html?p=FQ040729393382015118&utm_campaign=25129675&utm_content=3897

10pcs 2N7000 N-Channel Transistor Fast Switch MOSFET TO-92
https://www.banggood.com/10pcs-2N7000-NChannel-Transistor-Fast-Switch-MOSFET-TO92-p-924050.html?p=FQ040729393382015118&utm_campaign=25129675&utm_content=3897

If you like this video please give it a thumbs up, share it and if you're not already subscribed please consider doing so and joining me on my Arduinite journey

My channel, GitHub and blog are here:

https://www.youtube.com/RalphBacon
https://ralphbacon.blog
https://github.com/RalphBacon

194-external-watchdog-timer-555-with-pcb's Issues

Not Quite There

Hi Ralph, I do apologise for seeking help so long after publication, but I have only just completed the board that you kindly gave me in 2020.

On first start up the unit appeared to be working as the output was around 2.1V switching off to a measured 0.5V approx every 10 seconds (with VCC=3v). However LED1 was not working and as my soldering of this looked a little suspect I decided to replace it. The good news was that this cured the problem and LED1 is now working but unfortunately the output is not switching and now is constant at 1.7V (I have tried changing VCC to 5V but no change). This is with the TRIG (SIG) left floating but sending it high as in your demo has no affect.

If you could give me a pointer as to what to look at, I would be most grateful.

Many thanks.

Brian