Ambiguous signal determination
Printed From: the12volt.com
Forum Name: Relays
Forum Discription: Relay Diagrams, SPDT Relays, SPST Relays, DPDT Relays, Latching Relays, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=139695
Printed Date: May 05, 2024 at 2:13 AM
Topic: Ambiguous signal determination
Posted By: curtis92
Subject: Ambiguous signal determination
Date Posted: November 09, 2015 at 1:48 AM
Background: Cheap light sensor unit, hooked up to headlights for automatic illumination in darkness. Works well, sensitivity is adjustable to determine how dark it must be before switching.
Issue: At the transition point the sensor can't determine whether it should be on or off and will rapidly flash until it gets light/dark enough to switch permanently.
Is there a way I can intercept the output signal to prevent it from switching until it has output a consistent signal for say, 30 seconds?
Replies:
Posted By: curtis92
Date Posted: November 09, 2015 at 2:40 AM
with a bit of reading it seems that my best bet is employing the use of an RC Snubber circuit. Does anyone know the calculations required to determine the size of the resistor and capacitor required?
Posted By: curtis92
Date Posted: November 15, 2015 at 4:11 AM
Thinking about it, a snubber wont work in the way I want it to. Can anyone provide any other suggestions? How do OEM automatic headlights determine it or will that be ecu controlled programming?
Posted By: curtis92
Date Posted: November 16, 2015 at 3:53 PM
Seeing as no-one is posting suggestions, I'll pop up some more of what I've found. I was close with an RC circuit, but its actually and RL that I need. The Resistance is already provided by the relay. A reasonably large inductor (0.5H) should give a minimum time period of ~10s given the specs of the relay offering a resistance of <50mΩ. Connecting the Inductor accross the terminals of the relay coil should prevent power going through the relay initially, and provide power when it is lost again. with a Time period of 10 seconds, it will take 50s for the relay to reach full voltage, potentially switching at around 30s. The only problem I face at this point is relay bounce as the current slowly rises and falls.
Posted By: curtis92
Date Posted: November 16, 2015 at 3:58 PM
Apologies, ignore the quoted figures, the coil resistance of the relay is 160Ω. If anything this makes it easier as I can use a much smaller inductor for the same time period; 0.05H would give a time period of 8 seconds for example. Please let me know if there is anything I have massively overlooked
Posted By: curtis92
Date Posted: November 16, 2015 at 4:00 PM
I am not doing well at all. Those calcs were based of RC equations. It makes it harder for myself. There must be an easier way!
|