Altering little schem

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bowser22

Member

• Oct 5, 2009

• #1

Hi guys id like to alter this circuit to allow flashing in the range of 8 to 16hz.
**broken link removed**
the circuit currently only allows flashing of 1 to 5hz. what parts can i swap out to give me the rate i desire?
Thanks!

 

microtexan

New Member

• Oct 5, 2009

• #2

Check this out from a Google search for "555 Timing Circuit":

555 and 556 Timer Circuits

 

B

bowser22

Member

• Oct 5, 2009

• #3

i alread purchased a kit for the circuit above though and was wondering before i put it togewther what i could alter

 

audioguru

Well-Known Member

Most Helpful Member

• Oct 5, 2009

• #4

C3 is 47uF. If you change it to 10uf then the frequency will be from 4.7Hz to 23.5Hz.
These capacitors are electrolytic so their tolerance is wide.

 

B

BrownOut

Banned

• Oct 5, 2009

• #5

You don't need PR2, D2, or D3 if you only want to change frequency. Those are for duty cycle adjustment, and this scheme doesn't work well anyway.

 

B

bowser22

Member

• Oct 5, 2009

• #6

how doesnt it work well? im looking to flash a halogen lamp or the like at 14hz

 

Last edited: Oct 5, 2009

B

BrownOut

Banned

• Oct 5, 2009

• #7

It's not a good design. The % of duty cycle that is adjustable changes with the frequency adjustment. Believe me, I tried this same scheme on my bench. It sucks.

 

Last edited: Oct 5, 2009

B

bowser22

Member

• Oct 5, 2009

• #8

ahhh i found that confusing as to the duration of the flashes coupled with the frequency, one variable has to be dependant on the other. what is a good circuit that i can get a kit for?
Thanks

 

B

BrownOut

Banned

• Oct 5, 2009

• #9

There have been a couple ideas posted on how to do this. Attached is my idea. It works in simulation, but I haven't tried building it yet. Have other projects on my bench right now. R10/R13 are intended to model the variable resistor used for duty-cycle adjustment. R9 is for frequency adjustment.

 

Attachments

• VarFreq&Duty.JPG

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Last edited: Oct 5, 2009

B

bowser22

Member

• Oct 6, 2009

• #10

i now realise a xenon tube would be the way to go. i need a ready to build kit that will take 12v say from a car battery and flash a xenon at 14hz.

 

MrDEB

Well-Known Member

• Oct 6, 2009

• #11

**broken link removed**

 

Mr RB

Well-Known Member

• Oct 7, 2009

• #12

Just change C3 from 47uF to 10uF. The the 0-5Hz goes to 0-25Hz or so.
That should give you plenty of adjustment to illegally operate traffic lights by pretending to be an emergency vehicle.