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negative edge trigger

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Hello, I am trying to design a negative edge detector using a d-type flip flop which recieves a signal from two cascaded binary counters which are used to reset when the desired value has been reached.The design should include a window frequency but i am not sure how to implement it. I have tried to implement it however i could but i am not sure if it is working. Any clue???

Message 1 of 6

Hello,   thanks for response


look, your design does work, meaning it does something.


frankly I do not understand what it should do according to your description.


what exactly window frequency means?


what is the purpose of second counter?


components U14 and U13 are  redundant - output of U13 is a copy of U10-12.


your schematic is a mess - please use more of VCC and Grnd connectors instead of dragging these lines all over your schematic.


be aware - you use together TTL and CMOS families. U10 has VDD connection (10v ) and logical levels might be different.


please rephrase the description and revise the schematic. . 

with hope it helps
good luck


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Message 2 of 6

I should design a counter that counts up to 52. When 52 is reached an LED would illuminate and the counter would reset. Fortunatelly this is achieved, now the thing is that i have to design a negative edge trigger.

The idea behind the concept is to design the behaviour of a proximity sensor. The counters are incrementing  "the distance" from the wall and the LED represents that the distance has been reached. Then the counters will then reset.

This process should represent the transmiting state of the proximity sensor.

The negative edge trigger would need to detect the receiving state of the proximity sensor.

Message 3 of 6
Accepted by topic author Zvaro

Hello, thanks for response


sorry, but I guess I am not  smart enough to digest your description.


I ve got this -

you have to build counter for 0..51 with reset  - you have it done.


you have to build  flipflop( FF) with triggers on falling edge.


possible solutions are -

- you could use rising edge FF  if you would invert triggering signal.

check out different types of FF, some of them work on falling edges

with hope it helps
good luck


Message 4 of 6

Thank you very much for your concern my friend and propably my description was bad, will do as you instructed.


Message 5 of 6

Hello, thanks for response

I am glad it helped.

if you see the situation as solved, please mark the thread as solved and kudo my posts

thanks a lot

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Message 6 of 6