At first i thought it said "laser tacometer" I was excited to finally measure the amount of tacos I had.

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

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.

Great, useful and crisp tutorial. Thanks!

I am so glad you are back! Your channel went dark for a while. As a fourth year EE student, I enjoy your videos!

You are a wealth of knowledge. Love your videos !! Please keep doing this for another 200 years.

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 video as always, thank you!

Awesome! Thanks for the explanation, very useful.

straight to the point video thanks for sharing.

Very good. Looking forward to your next video. Thank you.

Very cool! Thanks for the tip!

Lovely work Afro. Can you do a video about comparators and how to use them to make a short circuit protection circuit??

Afro, gawd I love you man.

Again another great videos thanks a lot!

Brilliant! Thank you!

Excellent video, thanks for sharing....

Thanks a lot my friend for this video .

That's so neat ! Thanks for the tip :)

wow this is fantastic! thanks for sharing :)

That was amazing!!!! Thank you!

As always an other great video. Tnx for sharing

cool stuff. another use of leds

I missed your videos!

Great videos! Looking forward to seeing more.

I really like this video. for a diy cnc encoder sensor perhaps.

Good stuff! thanks!

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.

Very Cool!

You are the best!!!! Thank you!!!

Very cool. 👍

I can't wait to try this! Awesome vid!

Nice one!

be cool to have more videos like these.

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.

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! :)

Awesome!

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.

You can also use multi-meter set to measure frequency.

Good tutorial. what about laser to measure distant ?

Didn't know that, thanks :)

Good one I like it

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.

I wub Afrotechmods

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.

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

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 ?

great

Interesting inddeed. Bu what type of lazer is used in this experiment, if I may ask?

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?

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?

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 .........

good

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.

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.

+Austin Hively its called the photo electric effect

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.

does it have to be a laser pointer? (ie: would it also work with an IR transmitter?)

could you have two led linked shine lazer at one and the other lights up?

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

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?

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.

do we need to connect the led with battery? any LED work? can I us the battery lezar?

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.

I wonder whether there is any disturbance when working in bright light environment.

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?

How difficult would it be to build a small circuit to be able to use it without an oscilloscope?

could you used any laser with any led or does it have to be red led and red laser beam ? thanks

Whats the effect called? I want to know how the laser produces an electric current through the LED

you're the beest hhh wow

I think it could be used for alarm system

so could we use this like speedometers?

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

Can you make a tachometer with arduino for 6 cylinder engine using this setup?

(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

Just so you know: This effect is described in one of Forrest Mims' books.

+Afrotechmods svaka ti cast teslin si naslednik vidi se da si srbin i hvala ti sto ima prevod

Thanks a lot i am engineer but i had no hell idea before that led can be used in that way..

can i use a simple multimeter instead of using a oscilloscope?

what about the distance between each blade?

am gonna trai it

Hi you share a arduino laser code and shematic for a rpm dc motor ?

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.

Interesting.... 🤔🤔🤔

Will a multimeter measure the frequemcy of half rectified sine waves?

i want to build a speed tester what would i need as i need to know the MPH

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?

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

So this is a photodiode, right?

So would this work on a bicycle wheel with the spokes?

Would love to find an Arduino version of this...cuz I just can't find a free o-scope laying around n I'm not buying one for the level of tinkering I do

KEWL!

But i guess having an oscilloscope to read rpm beats the purpose of cost and portability.are there any alternatives for an oscilloscope

Ok, but I need a circuit or IC that will actually convert this information in real time via an array of LEDs to indicate changing RPM without having to calculate all the time. Is this possible without using an arduino or other complicated/expensive purchased product? Thanks for the great videos

Hi, you share schematic and arduino code ?

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??

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 .

فكرة حلوة شكرااا

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...