Rising Edge Detection of digital signal

[maz_yp]

rising edge detector

Hi
I have three digital inputs (0-5V) and i want to detect the rising edge of each signal and determine which one was set logic high (5V) last

Unfortunately i cannot use a simple processor and I must use logic gates, flip flops, etc

I cant figure out quite how to do this and would appreciate any suggestions

Best Regards
Maz

 

[ctownsend]

rising edge detection

Unfortunately i cannot use a simple processor and I must use logic gates, flip flops, etc

Why not? It would be easier to do this with software. Is this an assignment requirement?

 

[maz_yp]

detect rising edge

Yes i agree software would be easier, but i have just started doing a 3 month internship at an electronics company and I was asked to develop this circuit.

They cannot use reporgrammable logic devices (somehting to do with insurance and approvals)

 

[the_edge]

rising edge detector circuit

This is simple edge detection circuit.

The invertor on output is connected to aynchronous clear input, so you will get a short impulse on output as input signal goes high... It will look something like this:

So you need 3 Dff and 3 iinverters.

 

[maz_yp]

edge detection circuit

Thanks for the advice but the difficulty in this matter is that I need to determine which of the three signals was set high last?
.......... ____________
in1___|
..............____________
in2_____|
.....................____________
in3_______|

Thus i need a means of knowing input 3 was set high last?

 

[the_edge]

electronic edge detector with simple logic gate

Does signals when they rise stay high?

 

[maz_yp]

rising edge detection in dsp

I actually considered this and thought of using an integrator but the signal does not necessarily stay high.

 

[aupa]

rise edge detector

I think this circuit will help you.

it is very easy to understand.

there are rc filters to detect a rising edge for each input, and the sr flip-flop remembers which input was last pressed. there are 3 outputs, each one indicates which was last pressed.

 

[the_edge]

raising edge digital signal

You can use something like this:


STOP can be generated with edge detectors from my previous post.

 

[maz_yp]

signal detect edge

Thanks alot guys. rc filters and the sr flip flops are relevent to what I need.