9V IR Detector




This is a great, simple project to make a small and robust 9V IR detector. It can be used to seek out security cameras that use infrared light to "see" or to check if your remote control is still working.

Step 1: What You Need

For this project you will need:
-A 9V battery clip with a flat cover made of plastic
-A 9V battery
-LED (any color although it should be clear in order to see it better)
-330 ohm resistor (orange-orange-brown-gold or silver)
-Infrared Phototransistor
-perf board (see 2nd picture)
-double sided mounting tape
-needlenose pliers
-wire snipper
-dremel or hack saw to cut perf board
-clear epoxy-like glue
-Soldering equipement:
      -soldering iron
      -solder with flux core

A shematic is given in step 12, picture #4.

Step 2: Assembly Part 1

First up is putting the LED in. Bend the leads over and insert it in the perf board like in the picture (note that you should start in the corner to make our application as small as possible)

Step 3: Assembly Part 2

Next, put in the 330 ohm resistor like in the two pictures.

Step 4: Assembly Part 3

The last step is to insert the IR Phototransistor like in the pictures. Pay attention that with this part the long lead faces the negative pole.

Step 5: Soldering

After step 2-4 you'll need to solder the parts to the perf board to make your detector usable.
If you're a first-time solderer, you should watch this video: http://www.youtube.com/watch?v=I_NU2ruzyc4 .
(I didn't make the video, thanks go to CuriousInventor)
After soldering, your project should look like the example in the first picture.
Then, clip off the excess component leads, making sure not to break the solder joints.

Step 6: A Bit More Soldering

To finish off the soldering part, you'll need to connect two soldering pads like in picture 1.
For the bridge you can take a snipped off lead from one of the components. I first bent my lead to put it through
the holefor stabilisation like in picture 2, but you don't have to. The result is all that counts.

Step 7: Cutting

After soldering, you'll need to saw/cut off the excess perf board.
Make sure you leave space for the negative & positive wires that are connected to the battery.

Step 8: Attaching the 9V Battery Clip

Take your hardcover 9V battery clip and cut it's wires to about 1/2 inch (1,4mm) lenth like in the 2nd picture.
Then solder the battery clip to your detector and make sure you get the polarity right!
After soldering your gagdet should look like pictures 3 & 4.
To prepare it for the next step, twist the 9V battery clip so it can be bent under the circuit like in picture nr.1.

Now is a good time to check if your device works. Carefully clip it on a 9V battery.
If you try it out during the day, the LED will be partially on depending on how bright it is where you are.
To be sure that it works point the Phototransistor to the sun/roomlight and put your finger over it.
The LED should get dimmer when your finger is in the way. If nothing works, check out the last step for possible solutions.

Step 9: Using the Mounting Tape

Next up is fastening the circuit to the battery clip, the most efficient way I found is to use double sided mounting tape.
To keep everything in place for the tape to stick and for the next step I used wire to wrap it up.

Step 10: Glue Is the Solution

To ensure the detector's long life, glue is used. Just cover up the circuit (except for the LED and the IR Phototransistor), the border on both sides of the mounting tape and the wires from the battery clip with a thin coating of epoxy glue. Let the glue dry over night.

Step 11: Last Step!

After letting the glue dry take off the wire used to let the mounting tape & glue bond.
If you have problems taking off the wire then you've put too much glue on, but that won't affect the
functionality of your device.

Step 12: You're Done!/Problemfixes&circuit Diagram

If you jumped to this step because you have problems with your devices:
1. Check if your battery has enough juice (the "putting the contacts on the tongue" trick will work)
2. Make sure all the solderconnections are nice & smooth
3. Check if there any shorts in the circuit (solderbridges that shouldn't be there)
4. Check if any leads/wires from the parts or battery connector are broken, sometimes too much stress
    on the parts makes them break.
5. Did you put the LED & Phototransistor in the right way around / did you get the polarity right?
As a help I added a circuit diagram as pic #4.

For all the others:
Fetch a 9V battery and try your IR detector. Clip it on and... you're done! Have fun!

Comment, rate & follow!



    • Classroom Science Contest

      Classroom Science Contest
    • Fandom Contest

      Fandom Contest
    • 1 Hour Challenge

      1 Hour Challenge

    83 Discussions


    8 years ago on Introduction

    I now added a circuit diagram, as seen on step 12, picture #4.
    I hope it answeres most of your questions, if not, let me know.


    3 years ago on Introduction

    i read this in electronics for dummies but cool tho

    John PaulS

    4 years ago on Introduction

    if im going to make an ir transmitter for this receiver can i just connect a 9v battery to an ir led near the ir receiver?

    1 reply

    Reply 4 years ago on Introduction

    No, this won't be possible. A photodiode is not a "switch" that closes when light hits it. Think of a photodiode as more of a solar cell that creates a current when light hits it. You will need a phototransistor that will switch currents when light hits it.

    Source: https://en.wikipedia.org/wiki/Photodiode

    yo ksh_sha

    5 years ago on Introduction

    what type of IR transistor are you using,

    can you tell it's serial no. ?

    can we get it from any home appliance ?

    1 reply
    Monoclecatyo ksh_sha

    Reply 5 years ago on Introduction

    This project is a while back, I cannot find the source I got it from.

    Any IR transistor that isn't frequency-specific will work.

    You can get IR transistors from TVs.


    5 years ago on Introduction

    great instructable but one question. the arrow with a line at the end, where it is circled and 2 arrows are pointed outward. what is that represented in this specific instructable? i'm kinda new to this

    1 reply

    Reply 5 years ago on Introduction

    That's the schematic symbol for a LED (Light emitting diode). It's the circuit component that lights up when in use.

    This schematic symbol without the circle and the arrows pointing outward would be the symbol for a standard diode.

    If you need more information check out this wikipedia page:


    Jacky P

    5 years ago

    What does the resistor do? I'm kinda new to electronics.

    1 reply
    MonoclecatJacky P

    Reply 5 years ago on Introduction

    Because we are powering the LED with a 9V battery, which would blow the LED as a result of too much current flowing through it, we need a resistor (could be 330 to 1k ohm, depending on the color of the LED) to regulate the current so that it doesn't blow the LED.


    7 years ago on Step 12

    Is it possible to increase the range of the IR Phototransistor? I've tried it with my TV remote but it does only work in range of approximately 4 inches... Also, I have an idea, couldn't you add a red LED, which light up if no Infrared Signal is in near?


    2 replies

    Reply 6 years ago on Introduction

    I added some NPN transistors and whoa! i made a perfect IR proximity sensor !


    Reply 7 years ago on Step 12

    It's not that easy to increase the range of the phototransistor because if you would, you would also get more false readings because the natural light would be recognized more. The actual reason why the remote must be in a range of 4 inches is because th IR LED of the remote is too weak. The TV can sense the IR LED because the remote lets it flash at a certain frequency, which makes it possible for the TV to concentrate on the remote's light and cancel out other IR light sources, linke natural light.
    You could add a red LED, but that would use up too much circuit board space to make it fit on a 9V battery clip.


    7 years ago on Introduction

    How do I differentiate between infrared phototransistor and infrarered led?

    Thank You

    1 reply

    Reply 7 years ago on Introduction

    I think your problem could be that you accidentally used an infrared LED instead of an IR transistor.
    IR transistors and IR LEDs are very hard to differentiate by how they look like,
    but the way you described your problem lets me think you used an IR LED.
    To be sure, plug in your 9V battery and take a digital camera (or the camera in your cellphone) and point it at the IR LED. If you see a light coming from the LED on the display of your camera (note that you cannot see this light!) you know that you've used an infrared LED and not an infrared trasistor like you should.

    I hope I could help you fix your problem, if now I'll be glad to help some more!


    7 years ago on Introduction

    Dear Sir,

    I think my detector is not working. When i connect it with the 9 volt battery the LED turns on from first only and when I bring it near to my tv remote and press the tv buttons nothing special happens! I have checked and rechecked the steps.

    By the way in step number 13 you did not mention how or when will 'it' turn on, you have just written it should turn on. Please help!

    Thank You


    7 years ago on Introduction

    is an Infrared Phototransistor the same thing as a infrared LED?