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I am very new to electronics. I am using a reed switch with 2 pin. Which acts as a switch near to magnet.

I want to keep the switch ON when magnet is not near and OFF when its near to magnet.

I thought to use BC547 as it can act as a switch as well. And can help me to perform this task. But doing this, I realise it keep drawing the voltage and current even in OFF state.

Someone can please help with this, where it don't consume any additional voltage and break the circuit when magnet is close to switch.

Thank you!

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    \$\begingroup\$ Use a fixed magnet (opposite polarity) fixed close to the reed switch or explain what circuit you are trying to control. \$\endgroup\$ – Andy aka Jan 9 at 11:09
  • \$\begingroup\$ You're new to electronics, we've all been there! Just search around and see what others do then to the same. We're not going to "hold your hand". Using an NPN transistor (like the BC547) as a switch is easy and done and discussed before. I suggest you search this site for "use NPN as switch" to see how it is done. \$\endgroup\$ – Bimpelrekkie Jan 9 at 11:09
  • \$\begingroup\$ @Bimpelrekkie I got the circuit build. But there is some current and voltage leakage even when my ground is not connected. I guess adding a diode might help. I will check that if that is helpful. \$\endgroup\$ – user3201500 Jan 9 at 11:27
  • \$\begingroup\$ @Andyaka I am using ESP-01 which is connect with a coin cell (3v) using reed switch to send a MQTT message when my door will open. I want to send an MQTT message on door open basically. I hope you got the point. I want to power the ESP-01 as soon as the door open and reed switch get away from magnet. \$\endgroup\$ – user3201500 Jan 9 at 11:33
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    \$\begingroup\$ I got the circuit build Then show it. Even if it is a "trivial" circuit, just include it for completeness. You did not show a circuit so I assumed that you didn't know what circuit to use. That would not have been the case if you included the circuit you're using. \$\endgroup\$ – Bimpelrekkie Jan 9 at 11:46
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seeing as you want to run this from a coin cell, using electronics to invert the operation of the switch is probably not going to work well.

That leaves you with two options either use a reed switch that turns on in the absense of magnetic fields - a normally closed reed switch, or a dualr throw reed switch; or use a second magnet to convert your read switch to normally closed and then use a magnet on the door to cancel the second magnets effect (allowing the switch to turn off)

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