Sweeping Output Frequency Pulse Generator

Thread Starter


Joined Mar 23, 2010
Hi, New here and hoping to get some assistance.

I hope to build a sweeping output frequency pulse generator (from 1Hz to 50KHz) using the attached sweeping output frequency siren circuit.

Will someone advise whether this will work as intended. If yes, please let me know how I could adjust it to output 1Hz to 50KHz.

Any help will be appreciated.





Joined Feb 26, 2010


hmmm I've got the same circuit.. & its funny Ive not yet had time to test it, been working on another complex thing, which works one minute then not the next.. :rolleyes:

Anyway buy looking at the diagram, (but dont bank on it) I would first build it, and measure the the output with frequency counter.. do you have one? they are handy for accuarate results... right... then once you tried it.. and it dont sound like you thought it would, dabble with the R2 timeing resistors.. and the bit I noticed is the 330uf electrolitic cap... I personally would try increasing that say to 470uf... it holds more charge, and take more time to sweep up, is that what your after.. Ive done it but I can say its not easy if Im honest.. ie with all the other components combined..

I dont know if this would help but it gives you base frequencies.. here goes..

This is a test circuit.. rig up a timer in astable mode.. ok
now you can choose what ever cap you like.. with the above set up, and a 100uf cap in pins one & two a Led will flash once a second.. ok.....reduce that to 10uf it with flash at six time a second..

1uf electro =58hz
100nf=580hz cos you have times it by ten..
10nf normal caps^^^^ =5.8khz
1nf 58khz
ok Ive tested all of them & they come out right..
thats that bit ok now to try and sweep, the frequency up.. do or try this put a 100k preset pot on a blank space on a prototype breadboard.. put the wiper of the preset to pin 7 of the timer.. and the inner back leg of the pot to pin 6.. then rotate the preset with a screwdriver... and it sweeps up... from low to high well to where you cant hear it any more... BUT you got to get the Caps right and the resistance right here.. as I say Not easy but yes it can be done.. cos Ive made a generator just for fun.. and that sweeps from 300hz to 16khz which was ok for me could go lower but me personally did not need as low a 1hz...

OK phew..
hope this helps .. Yes theres alot of info here.. so give it a go..
Good luck
could go even deeper but my brain hurts.. lol....