guys, help me out this...

[aq_mishu]

I'm gonna use NE555 for this... it will be a police lamp that will alternate. common astable multivibrator with alternating led is like with 50%duty cycle, one set of LED on while another is OFF. it is like...

_____________________ __________________
|.....................................|'''''''''''''''''''''''''''''''''''''''''''''''''''|.........................
|.....................................|'''''''''''''''''''''''''''''''''''''''''''''''''''|..........................
|.....................................|'''''''''''''''''''''''''''''''''''''''''''''''''''|...........................

Where the frequency is 1Hz. and duty cycle 50%

But it need something like... Each half cycle of 1Hz devided into 4 total full cycles. So at the time of each half cycle of 1Hz, the first LED set will blink for 4 times. then while the first LED set is turned off, the second LED set will blink for 4 times again. So 4 blinks for first set and the alternate to second set and 4 blinks and then first set again....

The timing may vary, means instead of 1Hz frequency, it may be 0.5Hz (1s per half cycle) but all the time, four blinks per half cycle...

________________________ ________________
|..........................................| |
|___|'''''''|___|.....|___| |___| |
|.....|'''''''|.....|.....|.....|......| | |
|.....|___|.....|___| |___| |________________________|
| | | | | | | |
| | | | | | | |
|----| |----| |----| |----|

Guys, help me out.... plz....:?:

 

[VVV]

If you really want to use 555 ony, then you may use 3 of them. One will produce the 1Hz signal and alternately enable the others, which will run at 8Hz, so that you get 4 blinks per half period of the 1Hz signal.

Enabling the 555s can be done through the reset pin.

 

[aq_mishu]

schematic?? for idea infact... i tried in some way... but not worked... so if you kindly provide a schematic... and plz if there are some other ways, let me know...

 

[Kral]

aq_mishu,
If you're willing to use some logic parts in addition to the 555, Here's one way:
.
Set up the 555 for 8HZ, as VVV suggested. Use the output of the 555 to clock a shift counter, that consists of a 4 stage shift register with the complement of the last stage connected to the data input of the first stage. Use the Q output of the last stage to gate the 8 Hz output of the 555. Use the Qbar output of the last stage to gate the output of the 555. The two gate outputs provide the desired output.
Regards,
Kral

 

[aq_mishu]

not clear....

I'm planning to drive an 555 for 1Hz. the output will drive a pnp and npn transistor (for positive and negative pulse) as a switch and that switch will drive two other 555s. 8hz each. and the out put will drive another two npn transistor to drive only the +ve pulses for the LED arrays... what it sounds??

advice...