555 based flasher with dual timimgs

[sherazi]

hi friends,

i want to implement a 555 based flasher using a relay..
i have two digital signals a Enable signal (thats active low)and a Freq_selection signal that selects the frequency of flashing or we can call it a duty cycle selection...
i am not concerned with the exact freq. rather i want the flasher to look as flashing fast at logic 1 on this signal and slow on low logic... is there any way to do this or i have to use two 555?

would it be favorable to use a 8 pin AVR for this purpose?only if the 555 circuits are complex enough....

 

[KMoffett]

http://home.cogeco.ca/~rpaisley4/LM555.html#3
Run the 555 at 5VDC. Parallel R1, with a second resistor and PNP transistor (2N3906) in series. PNP's emitter to (+), PNP's collector to one lead of the second resistor, the other lead of the second resistor to Pin 7 of the 555. Another resistor (~10K) from the PNP's base to your +5V logic.

Logic high (+5V) keeps the transistor OFF and the frequency is low, set by the R1. Logic low (+0V) turns the transistor ON and the frequency is higher, set by R1 and the second resistor in parallel.

Ken

Just noticed another method: http://home.cogeco.ca/~rpaisley4/LM555.html#16