Any suggestion for device?

[jameschia]

I am now doing a project which using PIC16F877A to create an ultrasonic range finder.
When I receive signal from receiver, i need a device to trigger "active low" to send the signal to PIC immediately.
Is there any suggestion of device for example transistor, relay or any thing that is fast enough with minimum delay?

 

[Grossel]

Hi. You have given absolutely no relevant information that makes it possible to answer your question.

So until you provide any info, it will probably remain unanswered.

 

[WTP Pepper]

You need to send a burst of ultrasound and use a simple transistor circuit to detect the returning pulse.
About all I can offer at the moment.

 

[alec_t]

What is the voltage/current/frequency of the 'signal from receiver'?

 

[jameschia]

the receiver operate at 9V, it having 40kHz frequency and i do not sure about the current value.

 

[alec_t]

Post a schematic of the 'receiver' if you can. It's unclear whether 'receiver' means the ultrasonic transducer itself or the signal processing circuit which responds to the transducer output.

 

[jameschia]

I found a way to do it already. I will use opto isolator to trigger my circuit.
thanks anyway!!!