Use an Infrared Phototransistor




About: Im into electronics and computers so thats the instructables you will find frome me

Do you have an old TV lying around? Want to do something fun with it? Are you hanging around radio shack all day and cant find anything to do there? (get a life *ahem*)
Then pull out those screwdrivers, or... wallets, because there is an interesting use for them!

Step 1: Parts: the Easy Part

N-P-N transistor
Infrared phototransistor
9V battery
2 yel,vio,brn resistors

Simple eh!

Step 2: Assemble

First get the phototransistor, disasemble the tv (after its disconnected, and youve hit the power button a few times to discharge the capacitors) the infrared reciver will usually be near the buttons and looks like an led.
i will give a schematic and for advanced viewers, instructions

Step one connect the infrared phototransistor to the NPN so it will amplify it
connect the led to the transistor so the amplified current will flow through the led
(remeber to use resistors)

Step 3: Grab Your Tv Remote!

Connect power and aim your remote at the infrared phototransistor and hit the power button! Now you can see the behavior of your remote!

Step 4: Extra: Other Uses

Know when there is too much infrared waves in the area (the led will glow like mad!)
there are various experiments to try with this eg point a different red LED at it and see if  makes infrared waves, how about a flashlight?
This was just a fun experiment to do when your bored and has no actual usage and if it does its by coincidence i apologize for your wasted time XD



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    8 Discussions

    Jaden Massey

    1 year ago

    I am new to this kind of stuff, and I don't understand any of the diagrams because I know nothing about this. I am trying to use a phototransistor to power and LED light and I can't figure it out. Can anyone help me with this.


    5 years ago

    hey Maxx-on, infrared light is the base signal


    6 years ago on Introduction

    I'm confused by the diagram. There are 2 diodes, one looks to be the IR input since there are arrows going towards the diode, but we are talking about a phototransistor, in which case where is the base (that is assuming that the others are the collector and emitter) connected to?

    Thanks for the help.


    2 replies

    Reply 5 years ago on Introduction

    It's a bit confusing, but the base is on the transistor itself. In diagram form, a phototransistor looks like a diode with two arrows pointing at it, since there are only two connections to connect to. It's third connection, is a light sensor, which picks up light, and pushes energy passed the junction. In fact, this is how a Solar Cell works, because it actually is one, It's just undersized! Hoped this helped you to understand.


    Reply 5 years ago on Introduction

    I see. The terms phototransistor and photodiode are used interchangeably. I have seen some that are 3 pin and 2 pin. I just figured that 3 pin would be called phototransistors and the 2 pin called photodiodes.



    8 years ago on Introduction

    Very nice. Simple. Love it! The original schematic has a note that a part is backwards, could you explain please? Or update the drawing please? Thanks AlDude999!

    1 reply

    Reply 8 years ago on Introduction

    I drew the LED's polarity wrong. Just reverse the polarity if it dosnt light up to Infared waves. Thank you for your feedback!