Thread: Light out indicator
View Single Post
Old May 30, 2015 | 11:09 AM
  #16 (permalink)  
onehundred80's Avatar
onehundred80
Senior Member
Joined: Apr 2006
Posts: 25,432
Likes: 647
From: Ontario
Default Re: Light out indicator
Originally Posted by KDW4Him
Wow, they used to do that with relays? To monitor bulb current it's simple ohms law, voltage drop across a known resistance when the bulb is good and when the voltage goes away light a light on the dash is the theory but how MB accomplished it in the Crossfire, Hmmm....

Now to monitor excess current you gotta add some stuff...

From the picture below, the in and out would be to and from the bulb circuit on the car. The Rsens is the known value for the known bulb. The analog out would be to the cars computer programmed to monitor a range of X, outside range X would light the bulb out indicator. Yes, you can deduce from this if you wanted a ton of work to do you could change the value of Rsens for the LED's installed on your car and successfully monitor non CANbus compliant LED's. In doing so you would be locked in to the one LED brand and style of course. CANbus compliant LED's have a parallel resister in them to fool the car into thinking the correct bulb is out there by drawing the same amount of current as an incandescent bulb.


http://openenergymonitor.org/emon/si...rrentSense.jpg


The quote says 'it is not a relay', there are relays in that area is what I understand from that statement.
The system can detect at least a 3W drop.
 
Reply
0