Magnetic door sensor to turn on led light problem

[Mike Blair]

ok so what i am trying to do is.

12v led turns on when the door is open and turns off when the door is closed.

But my sensor does it backwards " when the door is open the light turns off and when the door is closed the light turns on... on my tester it shows closed circuit when the magnets are together and open when they are apart does anyone know where i can get a sensor thats the other way around?

 

[tazz]

Ok this is because the contact is a normally closed security reed switch....first problem is the cannot take much load 10mA max, so will burnt out in no time...The contacts need to be used with electronic logic circuits, if you handy with electronics, i can draw you out a circuit

 

[Mike Blair]

ahh dam the led im using pull 20mA at 12v what my plan was. in the room where my cctv unit is red leds labled with diffrent doors and wire them into the alarm of the cctv so the unit can text me etc. so for example "cam one point and door one. and door one opens the alarm goes of on cam one and it texts me

is there any door sensors you would recommend? kinda new to electronics i covered some in college but not a huge deal of it if you could draw me out a circuit that would be awesome XD

 

[tazz]

Ok little project may help others here....first how many doors..? and how are you switch cctv by relay or neg switching..?

 

[Mike Blair]

3 doors and relay thanks for helping btw

 

[tazz]

ok so you want 3 doors to operate the own relay (each door operates a relay)

 

[Mike Blair]

yeahh so led one lights when door one opens which sends a signal to the dvr "cam one point at door one

so on so on haha

 

[tazz]

ok so a circuit board with 3 leds and 3 relays for each door, with 3 sets of terminals to run to each door contact supplied on 12v supply....yes?

 

[Mike Blair]

yes

 

[tazz]

ok will post up circuit for you tomorrow

 

[Mike Blair]

thanks mate!

 

[Mike Blair]

btw what door sensor do i need?

 

[Darkwood]

What's your budget too ... we can make this simple and cheap or the bee's knee's...

 

[tazz]

any normal security alarm reed switch normally closed, as the circuit will only draw 25 micro Amps....0.025 mA

 

[tazz]

What's your budget too ... we can make this simple and cheap or the bee's knee's...

going to use a 4011 cmos logic chip 4 inputs / 4 outputs 40p job ....total £1 plus relays

 

[Darkwood]

going to use a 4011 cmos logic chip 4 inputs / 4 outputs 40p job ....total £1 plus relays

I see you gone for the bee's knees then as oppose to cost effective

 

[tazz]

Drawn the circuit up for you, note that a/b/c are all one 14 pin 4001 (yes changed my mind) The circuit draws only 1 micro Amp in standby, and thus through the contacts. It is the basis of most security alarms. When the mag reed is closed all is ok, open the switch and the led and relay are activated, close the switch and the are de activated. simples, hope this helps

View attachment CCTV Alarm input.pdf

 

[Mike Blair]

Thanks tazz! Il be doing this soon as i get the parts thanks!!