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???
07/12/09 10:54
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 		 #167106 - Open-collector alarm output
Responding to: ???'s previous message
You haven't shown where you have connected the 8051 chip.

But the text in the link says that the alarm pin is open collector which means that the alarm pin will sink to ground on alarm.

In your case, the LED will glow weakly when there is no alarm (10k doesn't allow much current to the led - 3V over 10k means 0.3mA) and on alarm, the alarm output will sink to ground, turning the LED off.

With an open collector alarm pin, you should connect one end of the LED to the alarm pin, and not to GND. That will light the LED when the open collector alarm output gets activated and sinks the current to ground.

List of 39 messages in thread
TopicAuthorDate
PIR Sensor Does not work            01/01/70 00:00      
   Open-collector alarm output            01/01/70 00:00      
      Yes I know            01/01/70 00:00      
         How do you know it doesn't work?            01/01/70 00:00      
            IT DOES NOT TURN OFF THE LED            01/01/70 00:00      
               Forgot about the "modify" timestamp?            01/01/70 00:00      
                  You are really sick            01/01/70 00:00      
                     intuition problematic for technical discussion            01/01/70 00:00      
                  That's always the trouble with allowing editing!            01/01/70 00:00      
                     Editing is not the problem...            01/01/70 00:00      
                     Isn't this ?            01/01/70 00:00      
         Sensitive pir, expected behaviour or sw error?            01/01/70 00:00      
         Use a transition-activated external interrupt            01/01/70 00:00      
            Look            01/01/70 00:00      
               maybe            01/01/70 00:00      
                  Generation gap ?            01/01/70 00:00      
                     Threshold            01/01/70 00:00      
                        Menus ?            01/01/70 00:00      
                           Cheap portable            01/01/70 00:00      
                              Not just cheap            01/01/70 00:00      
                                 menus            01/01/70 00:00      
                                    Not easy if you don't understand the terminology            01/01/70 00:00      
                                       Lessons            01/01/70 00:00      
                                          Own curiosity is the most important factor            01/01/70 00:00      
                                             True words.            01/01/70 00:00      
                           Lots of fine print            01/01/70 00:00      
                              back to the topic            01/01/70 00:00      
                                 Similar to how you let an 8051 output sink to ground            01/01/70 00:00      
                                 What is the purpose of your scheme?            01/01/70 00:00      
                              age            01/01/70 00:00      
                                 It's all a matter of what you're accustomed to using            01/01/70 00:00      
                                    USB control box much wanted            01/01/70 00:00      
   from ready made            01/01/70 00:00      
   I have used it ones            01/01/70 00:00      
      Confusing...            01/01/70 00:00      
         I am sure            01/01/70 00:00      
            inside PIR            01/01/70 00:00      
   you need a frnsel lens            01/01/70 00:00      
      Sherif Gamal            01/01/70 00:00      

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