How to make a very slow relaxation oscillator ?

[Externet]

Hi.
From a 120VAC or 240VAC source, with no transformer, I want to rectify it and slowly charge a capacitor that at certain level will discharge by driving with a pulse of not more than one second once a minute to a LED or buzzer or both.

In other words, when AC is present, be warned it is on. No batteries involved.

Like the opposite of a smoke alarm that chirps when its battery is low : To chirp when is on.
Is there such thing in the market ? Perhaps some gadget works like that ? Would be extraordinary if fits in an AC plug if is not asking too much. As to plug it in an outlet and be reminded it is on.

 

[rjenkinsgb]

A basic diac circuit as used in a minimal triac light dimmer, with very high value feed resistor would probably work? Replace the triac gate with the light source -

eg. Connect the diac in series with a led+resistor, and possibly a shunt resistor across those to shorten the pulse?

 

[ZipZapOuch]

https://www.amazon.com/Woods-Tradesman-Adapter-Lighted-1-Outlet/dp/B000H5T5RM/ref=pd_bxgy_d_sccl_1/130-2141955-2346813?pd_rd_w=aQk07&content-id=amzn1.sym.101c7dca-f8ef-4330-838b-ed6e9ebb9e52&pf_rd_p=101c7dca-f8ef-4330-838b-ed6e9ebb9e52&pf_rd_r=M9KF6DHM307SBW6A6NDC&pd_rd_wg=xJITT&pd_rd_r=bfb0cf74-bab2-48c6-a53a-555392baaa5c&pd_rd_i=B000H5T5RM&psc=1

 

[alec_t]

Is the usual neon indicator unsuitable for some reason?

 

[Externet]

Thanks.
A neon bulb is acceptable but flashing ~once a minute.
A pluggable lamp (as a night light) does not flash once a minute.
A diac can perhaps do it; a zener that will conduct at a certain level could be part of it...

 

[augustinetez]

Look up Neon Relaxation Oscillator - 1 diode, 1 or 2 resistors, 1 capacitor & neon globe.

 

[Roff]

The obvious advantage of an audible indicator is you don't have to remember to look at it.

 

[danadak]

This might help, all things about Neon Lamps :

https://drive.google.com/file/d/1QoPwrcgv9CDhjgdRB_J557wwZHRJ-hwF/view?usp=sharing

Regards, Dana.

 

[Fluffyboii]

This might help, all things about Neon Lamps :

https://drive.google.com/file/d/1QoPwrcgv9CDhjgdRB_J557wwZHRJ-hwF/view?usp=sharing

Regards, Dana.

It says access required

 

[danadak]

Try it now.


Regards, Dana.

 

[Externet]

Thanks, gentlemen.
Solved, done, tested, working, finished. A chirp ~every minute with adjustable loudness.

 

[AnalogKid]

Solved,

Excellent. But . . . . . . how? Circuit / device / photo / ?

Did you need three 555's, or only two? And, which Arduino model?

ak

 

[schmitt trigger]

Yes, please post the schematic. Everyone will benefit