Picture of A very simple proximity detector
Gadget freaks, model railroaders, roboticists or cat-hosts will love the versatility of the Sharp IS471 infrared proximity detector. It is the size of a transistor, operates over the 4-16 volt range, and can detect objects about 4-9 inches away by reflected IR pulses.
The basic implementation requires only the IS471, an IR LED and a 9 volt battery and can be built by most any tinkerer in less than 10 minutes.
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Step 1: Gather the parts

Picture of Gather the parts
The parts you'll need are:
1) the Sharp IS471 (available for $2 at: http://www.junun.org/MarkIII/Info.jsp?item=46 or $3 from www.digikey.com, and others)
2) a 940nm IR emitter (such as the Fairchild QED-234, available from www.mouser.com for about 50 cents, and other sources)
3) Something to mount the above two items on. You've got a lot of options here. There are several excellent Instructables on making your own PCBs. If you want to try it out before doing the etching thing you can use a pluggable breadboard (not shown) or go with a small piece of perf-board (pads on .100" centers, shown at bottom left).
4) 9 volt batter and battery clip
5) Soldering iron & solder, diagonal cutters (if not going the breadboard route).

If you'd rather not etch, but still want something snazzy you might drop me a line about the very small custom perf-boards I had made at www.pad2pad.com (shown at bottom right), priced at $2 each for the bare boards, postage included).

Step 2: Putting it together

Picture of Putting it together
Insert the leads of the IS471 into the perfboard close to an edge. The leads will need to be spread out just a bit, since they are spaced more narrowly than the average perfboard holes/pads. Note that the flat side of the IS471 needs to face outward, since this is the side that "sees".

Bend the IR LED to the right as shown below. With the LED positioned as shown the short lead (the cathode) is on top.

Step 3: Mount the IR LED

Picture of Mount the IR LED
The LED is best mounted to the bottom of the perfboard as shown below. The board will act as a light barrier, so the IS471 will only see light that is reflected off objects rather than direct illumination from the IR LED, though you may need to add a strip of black tape when assembly is completed to prevent the IR pulses from shining through the holdes in the perfboard.

Position the IR LED so the short lead (cathode) of the IR LED is two holes behind pin 3 of the IS471, and the anode (long leg) of the LED is two holes behind pin 2 of the IS471.


Step 4: Make some connections

Picture of Make some connections
Time to get the soldering iron hot!
1) Tack down all the pins of the IS471 and the IR LED just to keep them in place.
2) Connect the cathode (short leg) of the IR LED to pin 4 of the IS471 (just bend the leads together then solder to make this connection).
3) Connect the anode (long leg) of the IR LED to pin 1 of the IS471 (just bend the leads together then solder to make this connection).
4) Solder the red wire from the 9volt battery clip to the IS471 pin 1/IR LED anode connection.
5) Solder the black wire from the 9volt battery clip to pin 3 of the IS471.
6) Solder a wire to pin 2 of the IS471. This is the "Low on Detect" signal.

Step 5: Test it!

Now you get to test your new IR proximity detector!

Before snapping on a battery, check your work for solder bridges, there should be no connections other than those given in the previous step.

To test your proximity detector:
1) Connect the battery, then connect the leads from a volt-meter between the black (ground) wire of the battery clip and the "Low on Detect" wire.
2) Point the detector off into empty space and you should see about 8 volts on the meter. (Sometimes just laying it on a tabletop will allow enough reflection to trigger it, so you might have to raise it up just an inch or three).
3) Put your hand about a foot in front of the detector and slowly move it closer while watching the meter. Somewhere in the 4-9 inch range you will see the meter fallto 0 volts. You have been DETECTED!

NOTE: Location and placement is important. Sunshine will "blind" the receiver, greatly decreases detection range. I've found that just a little bit of a sun-shade takes care of this most of the time.

Step 6: Fun time!

Picture of Fun time!
Just making a meter twitch isn't very flashy, especially to your non-geek friends.

How about triggering a Radio Shack 20 Second Record/Play module? This is good for adding sounds to a model train layout, or mysteriously playing the theme from "Twilight Zone" when you wave your hand over it? Or using it to automatically play a startling noise when triggered by your cat jumping onto your work-bench?

Step 7: Mysterious sounds!

Picture of Mysterious sounds!
Connect your detector module to the circuit board of the Record/Play module according to the picture below.

Step 8: Controlling a relay

Picture of Controlling a relay
For larger tasks you might want to use the proximity detector to control a relay.
I've used the circuit below and find it very versatile. You can hang several detectors off it and it will pull the relay if any of them see an object.

Step 9: Whatever you want it to do...

The open collector output of the IS471 makes it perfect for so many things it's hard to decide just which way to go.

Robot builders love it for non-contact obstacle detection, pet-owners can use it as a doorbell for their pet doors, model railroaders can trigger sounds or animations without reed-switches or track cuts... heck, I jsut like making things happen with a wave of my hands (just like in the sci-fi movies).

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Odie Sr.O3 months ago

Adding a small piece of shrink tubing to the LED will keep a side view from triggering the sensor.. . . Can be used for directional sensing. . . . I have used this method since I found out that transistors make good light sensors, about 1955. . . Have fun. . .

johnyradio6 months ago

is the trip-distance adjustable on this project? thx!

Does anyone have a recommendation for a proximity sensor that can detect 1' - 25'? Basically I'd like to make a set of bat-ears for my completely blind grandmother. I'm thinking something that steadily puts out a tone over a 1-ear headphone. Closer things get higher tones, more distant things get lower tones..etc. Any suggestions? I'm a complete noob at this, but I'm smart & learn quickly.
offlogic (author)  wiglessbuzzard7 years ago
I might recommend looking at some of the ultrasonic modules available at www.sparkfun.com or a something IR based on the Vishay TSOP series. Send me an email and we can talk.

Any solution found for this one? thx

offlogic (author) 9 months ago

Anyone interested in an Instructable on a programmable PIC based prox detector good for several feet?

Laz4741 offlogic9 months ago

Yes Please, I need my sensor to work for at least 2-3 feet.

offlogic (author)  Laz47419 months ago
Lemme dig up my notes and codes and schematics for the PIC-based project. It was good to 4 feet or so, I generally was quoting 'one meter' using high output IR-LEDs.
It was a pretty easy intro to making SMD PCBs then assembling the same the easy way. "I know stuff", as the saying goes.
Let me get to work on the quick+cheap PIC-based dingus I cooked up using an agile PWM LIDAR (for individuation of competing units)
offlogic (author) 9 months ago

Just brouse the Sharp opto-electronics lines on mouser.com or digikey.com you'd be amazed at the sensors out there.

offlogic (author) 9 months ago

Laz, nah, it's only rated at 50ma max. Drive a transistor or gang a bunch of 40106 or 4016 to give it a kick easily. Go browse Mouser for driver ICs.

I'm unable to find IS471F can you tell me alternative of it..,,,n please reply as much as possible....it's urgent
offlogic (author)  rahulkhairnar1 year ago
I'm not aware of any alternate parts off the top of my head.
I know they have them in stock here: http://www.junun.org/MarkIII/Info.jsp?item=46.
You might be able to put something together with a tone-decoder (LM567), led and a phototransistor or something.
offlogic (author)  offlogic9 months ago

I was able to make a pretty nifty prox detector that worked at 3-4 feet using a low pin count PIC, IR LED and IR detector. might look at that?

Laz47419 months ago

Does the final product have a power out for when the sensor senses whatever is in range? I plan to add a piezo buzzer.

s444kee1 year ago
Brilliant!!! This is just one half of a circuit i am trying to build.

I am trying to activate upto 12 LEDS consecutively with each detection from the proximity sensor.

To make the circuit more bespoke i would ideally like to have the 12 LEDs in 4 banks containing 3 LEDs each. From a four-position selector switch I would like to choose whether the LEDs 1 - 3 light, 1 - 6 light, 1 - 9 light or 1 - 12 light.

Any help greatly appreciated.
offlogic (author)  s444kee1 year ago
Sounds like you've got it pretty well figured out.
I'm unable to find IS471F can you tell me alternative of it..,,,n please reply as much as possible....it's urgent
Flanders882 years ago
Which program do you use to draw your circuits schematics?
Tobor19772 years ago
I'd like a LED to light up when the detector detects something, is there a simple way to do that?

Thanks for the help.
Tobor19772 years ago
Great thank you for the quick reply, just ordered the dectors.
Tobor19772 years ago
Nice circuit. Two questions... how long did it takefor the company to make the custom perf boards and do you know if these components are available at Radio Shack? Thanks!
offlogic (author)  Tobor19772 years ago
I used Pad2Pad to handle the fab, and pushed it out to 3 week turn to keep it super cheap (under 20 cents per board). And, no, gotta order the detectors from the Internets.
esg.8273 years ago
Im making an array of LEDs , i want them to turn on and off with something like this, would it be possible??
offlogic (author)  esg.8273 years ago
The datasheet is at http://www.junun.org/MarkIII/datasheets/IS471F.pdf
Raw output is good for sinking 50mA.
offlogic (author)  esg.8273 years ago
Subject to the raw current output of the IS471, yes.
Otherwise add a transistor buffer or a driver chip to up the current capacity.
fbujold3 years ago
ir-detector for about 10$ you suppply 5 V you get an analog output .5 to 4 volt. No hassle garantee!
offlogic (author)  fbujold3 years ago
Yeah, that's a great device if you need proportional analog output.
It's expensive, but great if you don't just want a simple OC output!
Radio shack has changed this chip (276-1323) recently (somewhere around January 2008). If you get it from radio shack make sure it's the one you want!
thank u
rthapliyal3 years ago
does it give analog output???
coz it's not clear from the instructions that i does...
and also is IS741 available in india???
offlogic (author)  rthapliyal3 years ago
Nope, it's a discrete logic level, 1 or 0.
Not sure about availability in India, check local Sharp distributors or order via Junon over the interwebs.
shaunwhite4 years ago
Is the Vcc using 9v? because base on the datasheet of the QED234 Fairchild, it says tht the forward voltage is only 1.6 volt and a forward current of 100mA. Wouldnt it spoil the IR LED at tht voltage? Please educate me as i'm just a newbie in this sort of things
offlogic (author)  shaunwhite4 years ago
If you hooked up an LED straight to the 9V batt it wouldn't work for long! :)
The Sharp part is made to handle this matter. It works just fine, trust me (as Bernie Madoff used to say).
Also if i run the 5V my PIC works on? Nice sensor by the way
offlogic (author)  sde meeter3 years ago
Yep, seems to work fine from 5VDC.
I think 4.5VDC will be at the lower limit, though, so no 3.3VDC.
reajrdn3 years ago
Stumbled onto all this info. Really exciting even for an ol' guy like me.
Far too many years from making PCBs and little widget circuitry.
At 80 yrs. old, am again starting a new company and the IR LED and Sharp IS471 may solve a problem--- better, create an opportunity.
I'm in Folsom, CA Home 916 989-3005
Office in Fair Oaks, CA
Would like to find some people who are into making PCBs and Proximity sensors. I need some help because my electronic savvy is too far lost in deep core.
And, possible opportunity for anyone looking to join an emerging company.

Carl Rea Jordan reajrdn@yahoo.com www.optx-ltd.com (emerging)
I have several other start-up and need some entrepreneur-type minds.
offlogic (author)  reajrdn3 years ago
I'm sending you an email, Carl. Curiosity and all. :)
Mike Nelson3 years ago
Not sure how hard it would be, but could you setup the "Alert" to go off when the IR Detector sees the IR light? So reverse basically? would it be a NOT chip or is there an easier way?

I want to setup an IR LED on one side of the cat food container and the detector on the other side, and have it light up a separate light when the food is low enough for the IR LED's path to not be blocked by cat food... so the path would be normally blocked...

offlogic (author)  Mike Nelson3 years ago
It's doable. The detector output is good to 50mA at up to 16V.
Just reverse the logic, so that your device operates on a logical 1 instead of a 0. For the step 8 example, you'd use an NPN transistor instead of the PNP shown.
Or an inverter chip, if you like.
cwienands3 years ago
Nice instructable. For the lazy amongst us, check out optoswitches such as the "Photo Reflective Sensor (SEN130A3B)" from Seeedstudio. Disclaimer: I'm not related to Seeedstudio in any way, it just happens that I ordered a couple of them the other day and had the part number available.
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