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.
Remove these adsRemove these ads by Signing Up

Step 1: Gather the parts

Picture of Gather the parts
The parts you'll need are:
1) the Sharp IS471 (available for $2 at: or $3 from, and others)
2) a 940nm IR emitter (such as the Fairchild QED-234, available from 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 (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.
1-40 of 122Next »
johnyradio2 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 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

(removed by author or community request)
offlogic (author)  DELETED_EccentricNeko2 years ago
It's possible to add a flip-flop to do this, but the basic circuit alone won't do this.
The venerable 4013 or a pair of NAND gates can do this nicely.

do what? :)

offlogic (author) 5 months ago

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

Laz4741 offlogic5 months ago

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

offlogic (author)  Laz47415 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) 5 months ago

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

offlogic (author) 5 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'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:
You might be able to put something together with a tone-decoder (LM567), led and a phototransistor or something.
offlogic (author)  offlogic5 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?

Laz47415 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's urgent
Flanders881 year 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.
(removed by author or community request)
offlogic (author)  DELETED_EccentricNeko2 years ago
I can do better than that, I'll just send you a link!
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.8272 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.8272 years ago
The datasheet is at
Raw output is good for sinking 50mA.
offlogic (author)  esg.8272 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)  shaunwhite3 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 (emerging)
I have several other start-up and need some entrepreneur-type minds.
1-40 of 122Next »