Picture of 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

Picture of 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.

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Candymanproductions (author) 4 years ago
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.
ShyG1 month ago

i read this in electronics for dummies but cool tho

mohammadqa3 months ago
John PaulS8 months ago

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?

Candymanproductions (author)  John PaulS8 months ago

Yes, but add a resistor in series with the LED. 470 ohms should do it.

Rocker5171 year ago

Is it possible to use a photodiode instead of a phototransistor on this project?

Candymanproductions (author)  Rocker5171 year ago

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_sha1 year ago

what type of IR transistor are you using,

can you tell it's serial no. ?

can we get it from any home appliance ?

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.

da_noah1 year ago

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

Candymanproductions (author)  da_noah1 year ago

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 P1 year ago
What does the resistor do? I'm kinda new to electronics.
Candymanproductions (author)  Jacky P1 year ago
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.
bertwert2 years ago
You could easily make this into a receiving end of a laser tag system by changing the led into an alarm and add a switch that can stay on.
To make the sending end, connect a IR led to a battery, resistor and micro switch.
m1s73r3 years ago
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?

I added some NPN transistors and whoa! i made a perfect IR proximity sensor !
Candymanproductions (author)  m1s73r3 years ago
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.
mraghib3 years ago
How do I differentiate between infrared phototransistor and infrarered led?

Thank You
Candymanproductions (author)  mraghib3 years ago
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!

mraghib3 years ago
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
axeman9113 years ago
is an Infrared Phototransistor the same thing as a infrared LED?
Candymanproductions (author)  axeman9113 years ago
No, an infrared LED emitts light, but an infrared phototransistor senses light.
so what would happen if i were to replace it with an infrared LED would that detect anything or would it like interrupt signals or anything?
Candymanproductions (author)  axeman9113 years ago
No, that would only make the project act like a infrared flashlight and won't have any detecting abilities at all.
kill-a-watt4 years ago
Don't you need a filter that passes (near)-IR only as a filter, or is the detector itself sufficient to avoid triggers from visible light?
You shouldn't need a filter because if you use an Infrared phototransistor, it will only trigger when pointed to IR light.
The detector though will register some IR light when used in sunlight, as it containes light from the infrared spectrum.
aesquivel4 years ago
Will the battery drain if no IR is detected?
Candymanproductions (author)  aesquivel4 years ago
No because if no light is detected, the IR Phototransisitor won't let any electricity flow.
I'd measure that to be sure. If it's only a few milliamperes then you won't notice any difference compared to the shelf life of the battery, so it would not matter. Otherwise, adding a switch or removing it from the battery should do the trick.
Yes, a switch would be a possibility.
On the other hand, you could just remove the detector from the battery to be sure that no eletricity is wasted.
arbita24 years ago
good good good
kel noseh4 years ago
simpleness is greatness
skrubol4 years ago
You have the LED labeled as Infrared LED. That should be visible LED shouldn't it?

If you need higher sensitivity, there are also photodarlingtons, which, if you aren't familiar with darlington transistor configurations, have 10-100x the gain.
Candymanproductions (author)  skrubol4 years ago
Oh thanks, I'll fix that right away.
Now, if this does what i'm assuming it does, the LED should pulse with the frequency of the IR code being sent to the transistor.
if so, one could replace the LED with another IR LED, (and potentially an extension lead) and create a low-cost IR repeater, for using remotes across corners, in other rooms, etc.
(I tend to find practical uses for things like this)
XOIIO4 years ago
Not a bad idea, I used to build these to test if remotes were working. As for detecting night vision cameras, they do horribly. Not enough LED's to pick them up well, and these IR LEDS are weak, they only work well within 10 feet, otherwise they barely do anything.
robot13984 years ago
the same instructable
I would argue that this is not the same. This build is quite a bit more elegant and therefore worthy of its own instructable.
u r correct
AT4 years ago
I just love simple! Great project.

I know why you used a 330 ohm resistor. Not everyone will. Could you add a simple calculation on why a 330 ohm resistor with the 9v battery? :-)
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