Need help adding a on off IR LED/Phototransistor as switch

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In summary, the individual is seeking assistance for a small project involving a 5rpm -12vdc motor and a Class 2 plug in transformer. They want to add an IR LED/Phototransistor to act as an on/off switch, with the distance between them being two inches. The suggestion is to use an arduino for a simpler solution, or use discrete components such as a photo-transistor and operational amplifier.
  • #1
mac37m
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I'm building a small project and would like some assistance from you folks.
I have this motor 5rpm -12vdc and I'm using a Class 2 plug in transformer (input 12VDC 60Hz 23W - output 12VDC 1000mA) to power it up.

I would like to add a IR LED/Phototransistor between the two to act as a on off switch.
when a solid item goes between the LED and phototransistor it will stop or turn the motor off
and when it's clear it will turn on.
the distance of the IR LED/Phototransistor will be about two inches.



project_1.JPG


thanks in advance.
 
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  • #2
for a small application like this motor, you should invest in an arduinio. By doing this all you really have to worry about is a handful of line of code, and the usage of a NPN transistor, a flyback diode (to prevent current surge damaging electronic components when the motor stops)

if you go this way, this youtube video should help out:
http://www.youtube.com/watch?v=js4TK0U848I&feature=relmfu
 
  • #3
With discrete components, you can do it this way (motor in place of lamp),

transwitcho.gif


with the switch & resistor replaced by a photo-transistor and operational amplifier.

photdet.gif


For details on how this works see:

Transistor Switches
Photodiode Light Detector
Phototransistors
 

1. How do I choose the correct IR LED and phototransistor for my project?

Choosing the correct components for your project depends on the specific requirements and specifications of your project. Factors to consider include the wavelength of the IR LED, the sensitivity of the phototransistor, and the power requirements. It is important to consult the datasheets of the components and do thorough research before making a selection.

2. What is the purpose of using an IR LED and phototransistor as a switch?

An IR LED and phototransistor can be used as a switch in electronic circuits to detect the presence or absence of an object or to trigger specific actions. When the IR light emitted by the LED is blocked by an object, the phototransistor is activated, causing a change in the circuit. This can be useful in various applications, such as motion detection, obstacle avoidance, and remote control.

3. How do I connect the IR LED and phototransistor in my circuit?

The IR LED and phototransistor can be connected in various configurations depending on the specific circuit design. However, a common way to connect them is by placing them in series with a resistor to limit the current flow through them. The cathode of the LED should be connected to the positive power supply, and the anode of the phototransistor should be connected to the negative power supply.

4. Can I use a different type of LED or phototransistor for this circuit?

While it is recommended to use an IR LED and phototransistor that are specifically designed for use as a switch, other types of LEDs and phototransistors can also be used. However, it is important to ensure that they have similar specifications, such as the wavelength range and sensitivity, to ensure proper functioning of the circuit.

5. Are there any precautions I should take when using an IR LED and phototransistor as a switch?

Yes, there are a few precautions to keep in mind when using an IR LED and phototransistor in your circuit. First, make sure to properly calculate the current and voltage requirements to avoid damaging the components. Additionally, avoid exposing the components to high temperatures or moisture, as this can affect their performance. It is also important to shield the circuit from external light sources to prevent false triggering of the switch.

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