The special effects in a haunted house need to be well timed. The best way to do this is to use sensors to detect where your guests are in the haunted house. So I am doing a series of projects that demonstrate a variety of sensors that you can use to automate your haunted house. Last week I showed how to make a simple DIY pressure plate switch.

This week, I am going to show you how to make a proximity sensor and how you can implement it to activate special effects. 

Step 1: Materials

Here are the materials and tools that you will need to make a simple proximity sensor:

Infrared LED
Infrared Phototransistor
33 ohm Resistor
10 kohm Resistor
Black Heat Shrink Tubing (the same diameter as the phototransistor)
Perf Board

Soldering Iron 

<p>Yes, then it is surely a photo diode not a photo-transistor, plus the 33R should be of 2 Watt since the IR LED consumes 100mA not 20 mA with a forward voltage drop of 1.06v. The 10K should also be replaced with a 50M to do anything practically (car parking sensor) i guess. I free to an open minded discussion. LM358 can also be used. But the overall sensitivity I need 2-3 feet. This type of circuits are not as sensitive even compared to a TV remote control like things. I just tested it on my breadboard. What is your opinion?</p>
<p>The sensitivity also depends on the amount of ambient light in the area. If there is a lot of light hitting the photodiode, you might want to add a IR light filter.</p>
<p>From your finished circuit it appears to be that you used a photo diode, but all your diagram is showing a photo-transistor. Photo-diodes and Photo-transistors are quite different in nature. What should I use, a photo-diode or else? What is the actual component you used? Please resopnd early as I am going to build you circuit and I am confused with that component. Please help.</p>
<p><a href="http://comingsoon.radioshack.com/radioshack-infrared-led-emitter-and-detector/2760142.html">http://comingsoon.radioshack.com/radioshack-infrar...</a></p><p>These are the exact components that I used. </p>
<p>hai... can the sensor work with 330 ohm resistors............</p>
<p>Yes, but it won't be as sensitive.</p>
<p>Would there be any modification on the circuit if my phototransistor has a base? Beause the phototransistor I bought have 3 pins. Thanks :)</p>
In most cases you can just ignore the base pin and leave it unconnected. It is just there in case you wanted to be able to activate the transistor with other components when the LED is not on.
Can you give more information about the potentiometer
<p>The potentiometer in step 5 is just a regular 10 kohm potentiometer. It measures 10 kohms across the two side terminals and the resistance to the middle terminal changes based on how you have the knob turned. On end is connected to the ground. The other end is connected to 5V. The center terminal is connected to the OP AMP.</p>
<p>Hi,</p><p>muss the wavelength of the IR Phototransistor and IR LED match by 100% or is it enough to consider only the range of both?</p><p>I have been using following:</p><p><a href="https://www.reichelt.de/Fotodioden-etc-/SFH-300-FA-3-4/3/index.html?&ACTION=3&LA=5000&GROUP=A54&GROUPID=3045&ARTICLE=60552&START=0&SORT=artnr&OFFSET=16" rel="nofollow">https://www.reichelt.de/Fotodioden-etc-/SFH-300-FA...</a></p><p>and </p><p><a href="https://www.reichelt.de/Fotodioden-etc-/LD-274-3/3/index.html?&ACTION=3&LA=5000&GROUP=A54&GROUPID=3045&ARTICLE=65174&START=0&SORT=artnr&OFFSET=16" rel="nofollow">https://www.reichelt.de/Fotodioden-etc-/LD-274-3/3...</a></p><p>but it is not working properly I have changed the 33 Ohm resistor too, but the LED is either on or off and sometimes it looks like having interference Im not sure whats going wrong.</p><p>Thanks</p>
<p>Most IR LEDs and phototransistors should work. Check the polarity and look for shorts.</p>
<p>Typo! Is there any set petentiometer we should use? Thanks!</p>
No. You will probably need use some trial and error
<p>Hi. Cool circuit; I am trying to make with the op amp, but having trouble getting it to work. For the potentiometer, is there are set ratings?</p>
<p>I built this circuit, but my 33 ohm resistor is getting extremely hot. (5-1.3V)/33 = 112 mA, and P = I^2 R = 0.414 W, which is much more than the 0.25 W an off-the-shelf resistor is rated for. Did you experience the same?</p>
<p>That is a good point and I need to make that more clear in the instructions. Here are some solutions.</p><p>1. Use a larger resistor value and bring down the current to below 0.25 W.</p><p>2. Use multiple IR LEDs. Using three LEDs in series will have a combined voltage of 3.9V. So the voltage across the resistor would only be 1.1V. At 150mA that is only 0.165W on the resistor.</p><p>3. Use two 68 ohm resistors in parallel. This effectively gives double the wattage capacity.</p>
<p>what is the maximum distance that can be detected by the sensor..</p><p>thank you</p>
That depends mostly on how much interference there is from the surroundings. It will work best in the dark. But a few feet is the best that you could ever expect.
<p> Is it possible to make a more advanced version of this? Instead of a light, it sends a message to another device wirelessly?</p>
It is absolutely possible but that setup would be a lot more complicated.
<p>can i use regular phototransistor?</p>
It can work but it will get some interference from other light in the room
<p>thank you for your answer!</p><p>one more question, could connect your ir proximity (op-amp) in this schematic </p>
<p>Maybe. I am not familiar with the chips used in that circuit. So I can't say for sure.</p>
<p>Thanks for sharing! I am using it for my robot!</p>
<p>Hey there...</p><p>Thanks for the share but I have a problem with my circuit...</p><p>When I turn on my circuit, my LED remains on no matter what (OP-Amp), and when I adjust the 10K resistance, it just turns off at a point, has no effect whether the IR led is On or OFF or even Absent. Means the LED is operating independently.....</p><p>I really need your help on this one....</p><p>Thanks in advance....</p>
<p>It is possible that the light in the room is saturating the receiver transistor. Try it in a darker room.</p>
<p>I did sir, I completely covered the transistor with tape and even then couldn't get it to calibrate... I even tried inverting the output from high to low as you suggested (by swapping pins of op-amp) but still no result.....</p><p>If you don't mind, I can send you my E-mail ID and then on that media post you pictures of my bread board attempt so you can figure out what's wrong with it. Because for the life of me I can't.....</p>
I like that you write for an alternative to Arduino. BRAVO!
very nice, a question can we use the sensor reverce so to activate a relay when the beam is blocked? I wan to use it in automatic battery mini spot welder. So when i place the battery the singnal is stoped and this leads a relay to start arduino processing the welding menu on mini nokia screen with a menu of time msec times and number of spots <br>Also if your respond is yes can please help me with the code? <br> <br>thanks in advance
You would probably be better off basing your project on a beam interrupt sensor. Here is one kind of example: http://www.instructables.com/id/Laser-Tripwire-Alarm/
Hi, Can this sensor be used for detecting water level/tank full indicator?
This might be better for you: http://www.instructables.com/id/Water-Level-Indicator-with-Alarm/
It will not last long as sensors used are small iron nut+bolts which will soon become rusted and won't work effectively.
Get Stainless Steel nuts and bolts.They serve the purpose and are pretty cheap too.
I actually wanted to send you a link where they had used copper wire as a sensor but I couldn't find it.
In theory it could. But a conductive sensor is typically much easier and more reliable.<br><br>http://www.instructables.com/tag/type-id/?sort=none&amp;q=water+level+sensor
The question is how reflective is the surface of the water? That's not as simple as saying that water has a specific albedo, or reflectivity. If you are attempting to monitor the level of the water as the tank is being filled or emptied, you're going to have to deal with the fact that the surface of the water in the tank is not flat. As a result light from the source is going to be reflected in other directions, or absorbed.<br> <br> Another option would be to use a float with a retro-reflective surface to reflect most light back to the source, even if the float is being bounced all over the place. You will want to do some sample averaging to determine whether the tank is filling or emptying. and you'll need some way to have the float stay essentially where the sensor can detect it, perhaps with a pulley at the top and bottom of the tank, and fishing line looped through those pulleys and tied off to the float so that the float essentially rides up and down in a reasonably straight line. With that you wouldn't necessarily need to use IR leds and sensors, but you would want to do some testing to see which ones work best.<br> <br> An alternative to a fishing line and pulley system would be to have your float ride inside a piece of pipe that the light does not reflect back to the sensor easily off of. Perforate the pipe at the top and bottom to allow your tank contents to raise and lower the float freely.&nbsp;
This is probably a little far fetched but I'm in the process of making a astromech droid (from star wars) but instead of controlling it, I plan on automating it for the sole purpose of carrying things for me such as tools. Do you think your sensor would be able to and be strong enough be the droid's &quot; eyes&quot; and allow it to follow me around?
You would probably be better off with either ultrasonic transmitter/receivers or using radio.<br>Here is an example by Ben Heck:<br>http://www.youtube.com/watch?feature=player_detailpage&amp;v=tAyWrJoVUbs#t=1182
Ok, thank you very much.
Neat. Simple and useful, voted, good luck. <br>A description of this, with the link, went to my Blog: <br>http://faz-voce-mesmo.blogspot.pt/2013/10/inventor-brasileiro-vence-e-um-livro.html
Hi, Can this sensor be used for detecting water level/tank full indicator?
so, favorite button, we meet again.
Hey there, <br> <br>I like your sensor, its just what I need. <br>However, your image shows a sort of PWM on the IR led to the phototransistor. <br>The setback of having the IR constantly on is that the phototransistor can pick up ambient light. Do you know of a way to apply PWM: <br>The IR sends out pulses at 44KHz, for example, and the phototransistor only accepts 44KHz light pulses? <br>I've been trying to figure out an easy way to do this...
Well, this just got posted:<br>http://www.instructables.com/id/Reliable-and-low-cost-IR-Proximity-sensor/
That's perfect!<br>Thanks

About This Instructable


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Bio: My name is Jason Poel Smith I am a Community Manager here at Instructables. In my free time, I am an Inventor, Maker, Hacker, Tinker ... More »
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