I want to generate a trigger circuit to detect that a WHEEL is stationary. The wheel has slots on its periphery.
There is a LED transmitter in front and a photodiode behind the wheel.
As the wheel rotates and the slots come in front of the LED and then pass by, there are pulses recorded by the photodiode.
When the photodiode comes to rest with the slot in front of LED, there is continuous DC signal output.
The difference between motion and stationary wheel appears as a pulse train and continuous DC respectively.
Based on this, I would appreciate your assistance to design a trigger mechanism that discriminates between pulse train and Continuous Dc and triggers only due to the continuous signal?
The pulses are about 10-20ms wide and occur every 50ms, as shown in attachment.

 

You could lookup retriggerable monstables but your question is wide open to a wide range of solutions especially if you have a processor involved.

 

A simple 555 timer circuit would do it. Download the NE555 data sheet and read the applications section, or read this

 

What kinds of the WHEEL?

What's the detector and controller of power come from ?

If the power is provided from battery, then you can choosing the cmos type 555 as ICM7555, and make a oscillator for the LED transmitter, and make a 555 monostable as a receiver.

The output of 555 monostable → diode rectifier and cap filter → DC output.

It means that when the output side of the receiver is Low then there is no signal from the LED transmitter, if the output side of the receiver is High then it has received the signal from the LED transmitter.

 

What kinds of the WHEEL?

What's the detector and controller of power come from ?

If the power is provided from battery, then you can choosing the cmos type 555 as ICM7555, and make a oscillator for the LED transmitter, and make a 555 monostable as a receiver.

The output of 555 monostable → diode rectifier and cap filter → DC output.

It means that when the output side of the receiver is Low then there is no signal from the LED transmitter, if the output side of the receiver is High then it has received the signal from the LED transmitter.

Thanks everybody.
The wheel is similar to the optical encoder wheel.
It rotates on a shaft and has slots in it.

The LED is powered by constant current driver such as LM555.

 

The optical encoder usually use it to counting the length of wires, types, clothes or something needs to know the length.

Could you take a picture for the optical encoder and shaft and slots?

 

why not just simply use a capacitor to couple the pulses?