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Passive Infrared Detector - motion detector

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Re: Passive Infrared Detector - motion detector
« Reply #10 on: 07 / June / 2010, 19:49:08 »
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What is the voltage on the zener cathode /resistor junction when not connected to the camera ?

What value is the resistor ?

What voltage is the zener ?

What is the voltage across the detector '+' and '-'  ?

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Offline colinbm

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Re: Passive Infrared Detector - motion detector
« Reply #11 on: 07 / June / 2010, 20:48:03 »
Hi Microfunguy
The voltage at the zener cathode /resistor junction is 5volts.
The resistor is 3 kilo ohms.
The voltage of the zener diode is 4.7 volts.
The voltage at the detector is 9 volts.
Cheers
Col

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Offline colinbm

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Re: Passive Infrared Detector - motion detector
« Reply #12 on: 07 / June / 2010, 21:50:16 »
Microfunguy
Just to update, a description of how I have the wires attached to the terminal blocks (from the diagram in the first posting here).

The first four left hand terminals are used only, they are marked +, - & Alarm.

Terminal one has 9 volt battery positive & 3 kilo ohm resistor.
Terminal two has 9 volt battery negative, 4.7 volt zener diode anode & USB ground.
Terminal three has the joined 4.7 volt zener diode cathode & the 3 kilo ohm resistor (on a short lead).
Terminal four has the USB positive.
Cheers
Col

Re: Passive Infrared Detector - motion detector
« Reply #13 on: 08 / June / 2010, 04:52:19 »
So, the voltage at the zener cathode drops when you connect to the camera ?

Is USB V- connected to terminal 2 (ground) ?

« Last Edit: 08 / June / 2010, 06:11:57 by Microfunguy »


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Offline colinbm

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Re: Passive Infrared Detector - motion detector
« Reply #14 on: 08 / June / 2010, 05:25:45 »
Hi Microfunguy
I have been using a led to test first for polarity & circuit. Cheaper the a camera ;-)
Yes the USB V- is connected to the terminal 2 (ground).
Cheers
Col

Re: Passive Infrared Detector - motion detector
« Reply #15 on: 08 / June / 2010, 05:30:05 »
Have you connected the led (without another resistor) directly across the zener ?

If so, that would pull the voltage down.

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Offline colinbm

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Re: Passive Infrared Detector - motion detector
« Reply #16 on: 08 / June / 2010, 06:07:05 »
Hi Microfunguy
No I don't measure with the LED in the USB.
I just have the LED on a small board with a male mini USB plug just to show me if it is working & correct polarity.
I have another small board with a male mini USB plug so I can attach the multimeter to that.

I have been thinking, there should not be voltage at the junction of the resistor & zener diode as it is oneway, the other way ? I have rewired again after some cleanups & I don't get voltage there now, just at the battery terminals 1 & 2 & the end of the USB.
Cheers
Col

Re: Passive Infrared Detector - motion detector
« Reply #17 on: 08 / June / 2010, 06:11:08 »
Not sure what you are doing.
This is a very simple circuit.

If the end of the zener marked with a band (the cathode) is connected to the resistor there WILL be 4.7V.

Please confirm this without anything else connected.


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Offline colinbm

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Re: Passive Infrared Detector - motion detector
« Reply #18 on: 08 / June / 2010, 06:31:05 »
Sorry Microfunguy, I am not trying to wear you out.
OK I have got 3.25 volts at the cathode of the zener, with the 3 kilo ohm resistor.
When I connect the USB I get 3.15 volts at the end.
Cheers
Col

Re: Passive Infrared Detector - motion detector
« Reply #19 on: 08 / June / 2010, 06:51:41 »
I guess there is not enough current (about one mA) through  the zener to reach the breakdown voltage.

What is the exact device number ?

Do you have any resistors of a few hundred ohms ?
« Last Edit: 08 / June / 2010, 06:56:02 by Microfunguy »

 

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