Increasing frequency pulse generator

[jeremycondie]

Hi,

I have built a pulse wave circuit (pulses of equal duration) using a quad nand gate . I can set the duration and pulse length and at the moment I have five flashes before the LED output remains on.

I would prefer to have variable pulse widths whose frequency starts slowly and then steadily increases before the LED remains on. e.g. pulllllllse, pulllse, pulse, on ......

Any help is much appreciated.

[KMoffett]

Can you post your circuit schematic?

Ken

[jeremycondie]

I need a circuit to create this output similar to this. The pulse widths do not need to be exact ....

Thanks.

[KMoffett]

Your original circuit sounds like a circuit I designed and posted on a forum many years ago, for a flashing third brake light. (attached) Now, with the complexity you want, I would just program an 8-pin microcontroller like a PICAXE 08M2.

Ken

BrakeLight01.gif (21.36 KiB) Viewed 13018 times

[jeremycondie]

Thanks. I have already used this exact circuit but trouble is the pulse lengths are equal up to the moment the light turns on permanently.

I would like to change the circuit associated with R1, R2, R3, C1, U1 so the pulses increase in frequency as per my diagram above.

[KMoffett]

U1 (Pins 1/2/3) is configured as a monostable multivibrator that puts out "one" pulse with a width set by R1, R2, R3, and C1. Its output NAND'ed with U1(Pins11/12/13) switches the fixed frequency/width pulses from the astable oscillator U1( Pins 4/5/6 and 7/8/9) briefly ON to the Output (Q1 and Q2). I don't see an easy way at the moment to ramp the pulse width of the astable during the time the monostable is high.

Ken

[pebe]

I think it may be possible to make a circuit using 4017 outputs to feed power to several timing resistors of an oscillator. How accurate do the pulse widths need to be and what sort of output load does it have to drive?