Changing pulsed 12V to continuous

[TimFR]

Hi
How can I go about changing a pulsed 12V output to continuous?

A position sensor is outputting 12 volts on & 12 volts off at a rate of about 1 second of each. I would like to changing this to continuous 12V to operate a relay on and when the pulsing stops to switch the relay off.

 

[MikeMl]

Is there any information in the width of the pulse?

How long after the pulsing stops are you willing to wait for the relay to drop out?

 

[DerStrom8]

The first thing I would think of wold be a large capacitor, but there are definitely better solutions. Of course, this would depend on the answers to MikeMl's questions, but you may be able to use a 555 in monostable mode.
Der Strom

 

[Reloadron]

A position sensor is outputting 12 volts on & 12 volts off at a rate of about 1 second of each.

So if I read you correctly you have about a .5 Hz pulse rate with a 50% duty cycle (1 second on and 1 second off). Should that be true I would do as mentioned and configure a 555 timer chip as a retriggerable one shot (Missing Pulse Detector) along these lines. As long as pulses were coming in the output would remain high, if the pulses stop the output swings low until more pulses come along. Something like that what you have in mind?

Ron

 

[Mr RB]

Signal through cap and resistor, (AC pass) and then a diode into a 470uF capacitor (low pass filter) into the base of a NPN transistor. The transistor collector switches the 12v relay. Don't forget the diode across the relay coil.

 

[TimFR]

[LATEX]Is there any information in the width of the pulse?

How long after the pulsing stops are you willing to wait for the relay to drop out? [/LATEX]

Sorry MikeMl I dont have the pulse width, any thing between 5 to 10 seconds would be fine.