Author Topic: A Simple Sensor Question  (Read 647 times)

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Offline sherbyTopic starter

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A Simple Sensor Question
« on: December 30, 2012, 02:12:33 PM »
Here is a question that i have.
I was working on a project, the aim is for a Infrared Sensor to behave as a switch for closing connections between 2 wires to switch ON a motor. Cant this be done without using a micro, or by simple using a transistor?
I am yet to test this.

Offline jwatte

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Re: A Simple Sensor Question
« Reply #1 on: December 30, 2012, 07:06:02 PM »
In one word: Yes.
Specifics matter, though.

Offline sherbyTopic starter

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Re: A Simple Sensor Question
« Reply #2 on: December 31, 2012, 06:41:18 AM »
What specifics jwatte?
Can you link me to a circuit for this?
Thanks

Offline jwatte

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Re: A Simple Sensor Question
« Reply #3 on: December 31, 2012, 02:12:47 PM »
It depends on the specifics of your sensor, and the specifics of your transistor. The transistor, in turn, should be chosen to support the motor you want to use.

The circuit could be as simple as a MOSFET transistor, and the sensor to transistor gate with a pull-down (or pull-up) resistor, and a big enough MOSFET for your motor -- it all depends on the sensor, and the transistor, you need.

A more generic circuit would use an opamp or comparator in between, and a potentiometer to set a reference level, and use the output of the opamp to drive the transistor.

So, pick a suitable transistor for your motor, and for whether you want top-side or bottom-side switching (P-channel or N-channel MOSFET, or PNP or NPN BJT transistor.) Then look at the data sheets to find things like turn-on voltage for the transistor, and output voltages for the sensor. Then, you may be able to figure out how to do it. If not, please post those values in a request for more specific help.

Btw: Do you want the motor to run for any particular amount of time, or just for as long as the trigger is triggered? If you want it to keep running after the trigger goes un-triggered, or you want it to stop running after a while even if the trigger stays triggered, you may need additional circuitry -- something like a 555 timer, say.

Offline arigid

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Re: A Simple Sensor Question
« Reply #4 on: December 31, 2012, 02:32:48 PM »
I also was working on something similar sherby, I just made a small curcuit on paint and sent it to you jwatte, pls check it out.
I will let you know sherby once i get a reply.

Offline jwatte

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Re: A Simple Sensor Question
« Reply #5 on: January 01, 2013, 02:34:30 PM »
I also was working on something similar sherby, I just made a small curcuit on paint and sent it to you jwatte, pls check it out.
I will let you know sherby once i get a reply.

I don't think that private consultations though PM is a particularly good use of forum resources or my time.
I think you should post your diagram in this thread, and then many people can both post suggestions, and learn from the answers.

Btw: Whether your diagram will work or not depends entirely on the specifics of the IR detector and transistor in question.
You should build it, and then measure the voltage in different locations, and then try to draw conclusions about the circuit based on those measurements!

Offline studyembedded

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Re: A Simple Sensor Question
« Reply #6 on: January 07, 2013, 05:55:42 PM »
Transistor's can be used as a switch...i remember that was one of the first thing i learn in my academic years. As they are available of two types NPN and PNP...you have understand what exactly your circuit demands and select it. For sensors i found a link while goggled http://www.zembedded.com/sensors-in-embedded-systems/...thanks

 


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