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How to add 2nd battery to circuit or increase voltage Answered

I have a Normally Closed NPN inductive proximity sensor which operates at 10V. I use it to control a load (light bulb), which is normally on, and goes off when the proximity sensor detects metal. The problem is that I need to work with portable batteries, or something like an acid battery, and ideally not exceed 12V for safety reasons. Since the sensor needs 10V to operate, this only leaves me with 2V for the light bulb. I need to increase the voltage to the light bulb so that I can use a decent light source. Is there a way of adding a 2nd battery to the circuit so that the bulb has its own power source, yet that too is controlled by the sensor (otherwise the bulb would just stay on continuously). Any other solution would also be appreciated. Current circuit diagram attached. Thank you.

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nathanimate

3 years ago

If the sensor operates at 10/12v, its current output is 3A, the bulb is a 12v/5w led, should I go for a TIP120 or a MOSFET? Would I need to add a resistor in either case?

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mpilchfamily

3 years ago

Your diagram is of no help. You need more than just the proximity sensor, battery and a light source. The sensor is going to give a small voltage based on it's proximity to the source. You'll need additional electronics to take that info and directly translate it into powering the light. A transistor switch circuit between the sensor and the light will be needed. You'll need to know the output of the sensor at the point you want the light to turn on and choose the correct transistor that will trigger on that output and can handle the power from the battery through it to the light. Often people will use a micro controller to read the sensor and then turn on the light when the reading is in the defined range. This also gives them the ability to light up different lights based on the distance the item is from the sensor.

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nathanimatempilchfamily

Reply 3 years ago

thank you for the comment. The sensor's current output is 300mA so as you said I will need a transistor that can handle 12V.

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Downunder35m

3 years ago

The Sensor needs 10V (12V version) but you can use the full battery voltage for the light.
Those sensors provide a signal, but usually not a "switch" as such.
So instead of connecting the light directly to the sensor you add a transistor.
The sensor switches the transistor and the load is between transistor and supply.

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nathanimateDownunder35m

Reply 3 years ago

thank you I will post a diagram in a bit just to check I got what you're saying. Any type/power of transistor in particular?

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LightBug

3 years ago

Can you leave a picture of the circuit diagram, it hard to find a solution with just this details.