How to build a simple laser tachometer
Vložit
- čas přidán 14. 08. 2015
- Did you know you can use an LED as a light sensor? In this video I show you how to use this phenomenon to build a laser tachometer capable of measuring the RPM of mechanical devices.
Professional laser tachometer on Amazon: www.amazon.com/exec/obidos/ASI...
Check out my webpage for more electronic projects! www.afrotechmods.com - Věda a technologie
At first i thought it said "laser tacometer" I was excited to finally measure the amount of tacos I had.
I changed my name to I started making a video on laser tacometers but I found it impossible to get an accurate reading because I couldn't stop eating the tacos.
Afrotechmods Hehehe. But seriously though, great tutorial.
A phototransistor/photodiode would indeed be the logical choice. But I didn't have one lying around and I thought it would be more fun to show people the LED trick. In the video I was referring to CdS photoresistors being slow.
+Afrotechmods that was good video. I have photoresistors and infrared sensors and Emmitors, but didn't have idea about this trick.:)
Thanks
+Afrotechmods The solution here, is to Mount the led on the nose and the laser pointer module on the chin. I would call it: "Lazy" Tacometer.
God damn it... I wish this was released like 2 weeks earlier. I was curious how fast the tail blade on my 6h RC helicopter was rotating, and I didn't have a tachometer. My next best thing? Get a microphone, record the audio right next to the blade, put it in audacity, get the time between 2 peaks and convert it into RPM (then divide by the number of blades on the rotor) xD
Nice, that's a great solution
Jordan O'C I think your solution for this instance is easier. So I wouldn't cuss about it.
***** I am everywhere.
Jordan O'C If it's a Trex-style helicopter (with a shaft or belt to spin the tail rotor) then you can calculate the RPM from the main rotor RPM, I think mine was 7-to-1 tail/main last I checked.
DFX2KX My heli has a 6:1 ratio between the tail and the main rotor I think, but I didn't know the rpm of the main rotor either.
I love these tutorials. Ever since I was a kid, electronics have interested me. Much has changed over the past 55 years. While I don't build or do most of the stuff in these videos, I learn at least one thing from each. Great job.
I am so glad you are back! Your channel went dark for a while. As a fourth year EE student, I enjoy your videos!
With the right LEDs, you can use the one LED to power another LED. I had a setup while I was interning at NASA where one super bright red LED was shining on another one of the same LEDs, and that LED was connected directly to a 3rd red LED, powering it! I measured around 2V or so on my meter without load! It was very dim, you could just barely see the die glowing, but enough to be an impressive proof-of-concept. (I was measuring the slew rate of the LED as a sensor compared to other 'real' sensors.)
Great, useful and crisp tutorial. Thanks!
You are a wealth of knowledge. Love your videos !! Please keep doing this for another 200 years.
Great video as always, thank you!
Lovely work Afro. Can you do a video about comparators and how to use them to make a short circuit protection circuit??
straight to the point video thanks for sharing.
Awesome! Thanks for the explanation, very useful.
Brilliant! Thank you!
Very good. Looking forward to your next video. Thank you.
Afro, gawd I love you man.
cool stuff.
another use of leds
Very cool! Thanks for the tip!
Awesome! Thanks for sharing
As always an other great video. Tnx for sharing
I really like this video. for a diy cnc encoder sensor perhaps.
Another great video as always. I just wish I had a scope now.
Thanks!
ps - Any chance you could make a video on how to read schematics? I understand basic circuits but I get confused when multiple components are connected together. A 555 timer circuit for example, I don't know what goes where.
That's so neat !
Thanks for the tip :)
Thanks a lot my friend for this video .
That was amazing!!!! Thank you!
Again another great videos thanks a lot!
I've got another one for this! This morning, I wanted to know how fast a motor, which was not connected to anything, so had no fan blade or anything for a tachometer to work on, was spinning. I put a small neodymium magnet on the side of the output shaft and simply held my oscilloscope probe next to it. as it spun, it induced a very measurable voltage in the probe.
wow this is fantastic! thanks for sharing :)
Great videos! Looking forward to seeing more.
Simple and interesting
Good stuff! thanks!
Actually, you can hook up the LED to a headphone jack, and measure the frequency using an spectrum analyzer app or your phone.
And since it's only 1.5V, it can't fry your phone!
So whenever the LED is illuminated by the laser, it makes a "high" signal or it makes a "low" signal on the "microphone" input
And then you just divide the frequency by the number of blades, and multiply it by 60.
You can make an app that can measure the RPM for you, just enter the interruptions/1 rotation, and voila, you now know the RPM! :)
You are the best!!!!
Thank you!!!
Good tutorial. what about laser to measure distant ?
Very Cool!
I missed your videos!
Nice one!
You can also use multi-meter set to measure frequency.
Very cool. 👍
awesome idea, had to try it out. first important discovery is, that when working with red laser, it works only with red diode. I'll try it with green laser and diode, once I find the green laser pointer.
Interesting inddeed. Bu what type of lazer is used in this experiment, if I may ask?
Good video, I performed a lot of these tests back in the late 1970's but LED technology back then is nothing compared to LED's today. Most of the LED's I used back then were low intensity for indicators. Thanks .........
be cool to have more videos like these.
Awesome!
A nice experiment ! I wonder if you can use two same LEDs instead of using a laser for simplicity.
Could you even make a solid state relay using this with some sensitive MOSFET ?
does the voltage depend on the laser color? I wonder we'd get the same reading if a green laser was used on a red LED. I feel that we'd get a maximum reading for laser-LED systems that have approximately the same wavelength.
I can't wait to try this! Awesome vid!
Could you please make a video showing how to make an FM or AM radio? I know videos like this already exist but I would like to see your take on it.
An application im building needs me to measure the rpm and this is a great input to it. However, I do have a query. If the surfaces of the emitter or receiver is subjected to a dusty or mucky environmental conditions, I highly doubt the readings will be accurate or will emit any reading considering they are sort of blind folded. Any advice or other methods to overcome this?
do we need to connect the led with battery? any LED work? can I us the battery lezar?
I just though by hooking up the same thing to an arduino and using it to measure the minute changes in current and using an 8 bit display and output the RPM and just to complicate the project use an input mode for arduino and get the number of blades and use that to process too.
I wub Afrotechmods
This is great! I was contemplating something like this which is now in front of me. Unfortunately as we dont have oscilloscope, so is there a way to measure frequency of pulses?
Look for Saleae clones, that are cheap "Oscilloscopes" for around $10
I'd like to use this trick to make an oscillator where the rpm of the motor determains the pitch of the (square wave) note. Would this be possible (ofcourse it is). Would it be worth it?
could you have two led linked shine lazer at one and the other lights up?
Good one I like it
Is data logging possible on PC using this design? I need to count the number of rotations as well as changes in the RPM with respect to time.
Also, Is it possible to measure the RPM when keeping the laser source and sensor in the same direction (by reflection) as done by the available non-contact tachometer?. Please suggest
does it have to be a laser pointer? (ie: would it also work with an IR transmitter?)
Using this method i found out how to build on of those laser alarm things ypu see in movies using a signal amplifier and an arduino
I wonder what the physical mechanism is by which the LED is coupled to illuminated object. I would expect such coupling and its electric effects to diminish with distance.
In case of propeller rmp measurement on an airmodel, where can I place the laser? The sensor LED could be placed at the fuselage. Sorry for my bad english, I'm brazilian. Thanks.
so could we use this like speedometers?
Didn't know that, thanks :)
+Austin Hively
its called the photo electric effect
The video shows the laser shining on the fan's label. Does this work at all for a straight reading? A strobe tachometer works by reflection - not by the binary breaking of a beam - so it would work on continuous surfaces.
I would love to be able to point my tachometer at any rotating object and get a reading.
MattsInTheBelfry Sorry this was poor camerawork on my part. What is happening there is the laser is shining through the fan blades, then hitting the LED. The LED gets lit up very brightly, and since the fan's label is reflective it acts as a mirror and shows the camera the shiny LED. I am not measuring the reflection of the label, but I can see how it looked like that in the video.
How difficult would it be to build a small circuit to be able to use it without an oscilloscope?
Awesome Vid....might have to break this out in class to impress my electronics instructor. it will more that likely stump him at first! lol.
Can you make a tachometer with arduino for 6 cylinder engine using this setup?
I wonder whether there is any disturbance when working in bright light environment.
Hi you share a arduino laser code and shematic for a rpm dc motor ?
can i use a simple multimeter instead of using a oscilloscope?
what about the distance between each blade?
(anyone) at 0:23 the laser wires appear to have some shrink tubing around them, is that right? I'm have a similar laser which works fine but the wire is so thin I'm not sure how to hook it up for long term use. Just using some quick wire spring connectors for now. Any advice from the channel moderator or anyone one the boards is appreciated
could you used any laser with any led or does it have to be red led and red laser beam ? thanks
Maybe matching colors would generate the maximum voltage.
Trying this with an RGB LED would be interesting
Whats the effect called? I want to know how the laser produces an electric current through the LED
+Austin Hively Photovoltaic
Austin Hively pots the same way a solar panel works....you can actually builds an adhoc solar cell from LEDs
Thanks a lot i am engineer but i had no hell idea before that led can be used in that way..
Will a multimeter measure the frequemcy of half rectified sine waves?
That would depend on the frequency and the sampling rate of the DMM, my Fluke 87V is able to register them, for this i use the Hi Res function...
I think it could be used for alarm system
great
This is just a counter...then we have to do the calculation. It is the calculation which is the tachometer part. Is there a way to do this without an arduino? all tutorials her that I can find use the arduino.
So would this work on a bicycle wheel with the spokes?
With thick enough spokes I think it might yes
good
Hi!
Please , would you tell me where i cand find informations to build a tachometer using reflective laser as it is shown at 2:11 ?
I will use it with my arduino uno.
I try to use infrared emitters and receivers but i can't develop ranges up to 5 cm with this .I'm very intrested to build a sensor equal to the 2:11 .
Thanks for your attention .
Ferreira A . Use an LDR and a Laser.
Anvilshock sorry I didn't here what alfro said. forgive your land your landlorship. but can you tell me the time alfro saidnit.
Afrotechmods What is the reason for using a red LED for this? Is just what you had laying around or was it most compatible with the laser diode that you had?
SkaterK3 Well, I cant speak on the actual emitter, but I can say that since the plastic shell around the LED was red, red light passes through it better than any other color light, so a red LED combo's with the red laser would immediately be better for that reason.
Kakunapod Okay that's what I thought. I am wondering if a Blue LED (with a higher forward voltage) will produce a stronger response than a red LED. I think this is worth a try but I imagine that there is a small cost offset considering how expensive blue laser diodes are compared to red ones.
Just so you know: This effect is described in one of Forrest Mims' books.
Is there a way to figure out the max response rate of an LED? e.g., have a function generator control a laser and then see at which point the LED is no longer able to differentiate between the pulses?
Razor2048 Yup that would work. But you'd want to have a transistor amplifier circuit between the Fgen and the laser.
But i guess having an oscilloscope to read rpm beats the purpose of cost and portability.are there any alternatives for an oscilloscope
Laser tachometer...
It can be a good alternative, cheap and portable
i want to build a speed tester what would i need as i need to know the MPH
***** nope still confused dot com
Hi, you share schematic and arduino code ?
+Afrotechmods
svaka ti cast
teslin si naslednik vidi se da si srbin i hvala ti sto ima prevod
If you measure further away from the centre of the fan, won't you get a faster reading?
Kieran Hammond Nope.
Kieran Hammond Glebs has the answer. What you WOULD get, though, is different periods of open circuit time vs. closed circuit time, as the shape of the fan blades differs at different locations... but the number of cycles (open - closed) remains the same.
How is the "real" tachometer you use in the end built? What kind of sensor picks up the speed, and does the laser itself have anything with the measurement to do, or is just a "pointer"?
I´d like to build something like that to take control measurements of flywheel RPM on my boats engine so I can input the right dividing factor in the engine tach...
If you are serious about those questions I suggest you go back and play with wooden toys.
MrOperettalover I just wonder as I don't know, very sorry for being so uninformed! If you are still serious with your reply, I suggest you go back to the shithole you came from and be nice when you come back! Geeez...
Kenny Constanzo
I never understood nice. My goal in life is to collect enemies - preferably stupid ones like you. I suggest you limit your questions to the level you're on.
I pity you, goodbye.
Kenny Constanzo
Funny how they who need it the most are the first to feeling sorry for others.
Hey, I don't have an oscilloscope or DSO... Is there any cheaper way to study waveforms..??
+Rajat Tarade You could take the signal from the LED, amplify it to produce a 3-5V signal, and then hook it up to a digital input port on an Arduino or similar. Just count the pulses. You could also use an ADC port, but the digital port would allow higher frequency measurement. Use a transistor or op-amp for the amplifier.
The soundcard on your computer. Only AC-coupled. Don't exceed the maximum input voltage, at least not without current limiting.
So this is a photodiode, right?
What is the power rating of the LED Laser you are using? I can find 5 mWatt Laser Head diode modules on Amazon or e-bay; but I'm not sure they would be strong enough ? I have a Laser pointer I've used for doing presentations - but even when I put them directly on the head of a Red or Green LED - I only got sub-100 mV readings out of them on my scope - no where near the 1.5 V you got from your experiment ?? And once I pull the Laser out far enough to inter-position a small PC fan - the voltage drops to an unusable level. Any comments??
5mW should be plenty. Try different red LEDs? Green is unlikely to work well. Also try the 10x attenuation scope probe setting.
Thanks !! I'll try that !!! {:>)
this didnt work for me. what did i wrong? I conected my Oscilloscope to the LED -to- +to+ and nothing showed up. Also a Question: Can this setup be used to transmit serial data?
you could use that to replace broken car tahcometer
for the equation, i get how you get the 19Hz, but how do you get rpms from number of Hz
+Ryan Thornburg Hz is the number of times something happens per second. RPM is rotations per minute. Since there are 60 seconds in each minute you multiply by 60.
Afrotechmods alright, i guess i can see that. thanks for the clarification
am gonna trai it
Fucking great job 👍👍👍👍
I love your videos.... thats the way how an practical engeneer like you explain things in a useful way.... 🙏🙏🙏
Perfect ... it seems like Great Scot looks up to your channel or the other way 😁😁
Greets from Austria in Europe
you're the beest hhh wow
Could this be a simple way of making a motor encoder?
+Josh Savage Its only because I don't really want to spend a lot on encoded motors..
ooh i need siliscope, how about multimetter with out hertz reading
i think that is the same, it only need the oscilloscope for the frecuency measure