Turns out that just as LEDs make poor rectifier diodes, a rectifier diode makes a poor LED. I put 50,000 volts backwards on an IN4007 rectifier diode and it lit up but only briefly. Very briefly. And the smell! Oh my...
When I realised that this might be possible, in 1980 or so, I replaced the bulb in the taillight of my bike with 4 LEDs in bridge and a small resistor at the place where in a "normal" rectifier you would connect the load. The AC of the usual dynamo had a high enough frequency for a nice steady light, that lasted and lasted, where bulbs would blow wheevern you would pedal a bit too fast. A little later I used the same circuit, not with just red LEDs, but with 2 green and 2 red ones. Neatly arranged on a bridge diagram on a piece of white plastic I could demonstrate to my students the working of a bridge rectifier by feeding the bridge with the output of a powered tone generator at a low frequency, lower than 1 Hz. Very nice to see the diodes light up slowly (with a sine wave) and the small bulb (of a rear bycycle light!), alternating the red ones and then the green ones. As a rectifier the LEDs are not really efficient, bedause of quite a voltage drop...
I was disappointed that you didn't actually address whether it was possible to rectify AC using LEDs. You appeared to know beforehand that you were merely going to burn them up. Couldn't you have used a current limited input and reduced the voltage? Those poor LEDs never had a chance!
LEDs generally have a very low reverse breakdown voltage, typically 5volts. But they can handle a reasonable forward current. I took advantage of this when.i replaced the incandescent light bulbs which is connected in parallel with our doorbell push buttons. In this old traditional doorbell, the light bulb, provided a glow to illuminate the buttons at night. The bulb is powered by the leakage current through the doorbell solenoid coils. A circuit that is supplied from a 12 volt AC mains stepdown transformer. By connecting two matched diodes in an anti parallel configuration, the forwards voltage of the one diodes limit the reverse voltage to which the other is exposed on the AC cycle of the supply. So for each switch, the bulb was replaced by a series parallel combination of back to back super bright LEDs and a current limiting resistor. This not only increased the brightness of the doorbell glow, while reducing the consumed current, it also allowed the selection of the colour of the light emitted. The LEDs have now been working continuously for 30 plus years, without a failure or replacement. Two useful features of the LED current/voltage characteristic, is that the LED has a sharply defined forward voltage switch on point, which can be sharper than that of a Zener diode of equivalent voltage, they also have a low reverse leakage current. This makes two LEDs, connected back to back, in anti parallel, a low cost choice for an audio clipper. The diodes can be connected between the two stages of an op amp circuit, or between a microphone pre amp and an amplifier to limit the audio level. For examp!e the diodes can be connected between zero volts and the op amp output, using a series current limiting resistor, forming an effective voltage clipper divider circuit. If super bright LEDs are used, there is ample op-amp output current to make the LEDs glow when the input audio level is too high, thus providing an indication of this condition. Looking at the clipped audio waveform, it is remarkable symmetrical and we'll behaved. If the following op-amp is configured as an active filter, the clipping harmonics can be suppressed. This makes this circuit useful in radio transmitter audio input circuits. I once used this configuration in a professional radio system to limit the signal level generated by an FFSK modem into the telephone system, that connected to a transmitter network. The glow of the LEDs, proved useful to the technicians configuring the system, as they could use the LEDs as an indication of when the line level was set to the correct value. All that was necessary was to adjust the level to the point where the clipper LEDs started to glow and back off the signal until the LEDs just stopped glowing. This coincided to a line level of -14dBm 600. Just under the -13dBm maximum specified by BT regulations, for signal tones to line. I suggest it is worth taking a look at the operation of LED audio clippers on an oscilloscope, they do work really well, even at relatively high frequency.
They are good for real visualization of the rectification. Use at least 2 different color LEDs, make the rectifier, a resistor and an output indicating LED, Then use a 9v battery flipped back and forth for a slow alternating current source (i.e., at your hand frequency) to see how two LEDs in the rectifier conduct at a time making the output LED light. Of course, it uses about 9 volts to light one output LED,
This an amazing demonstration idea. I wouldn’t use the grid though. I think a lower frequency input around 2-5Hz would allow people to see the transition between the on & off states and build a lot of intuition
I wanna build something like this for demonstration purposes, but methods of getting to low frequency and low voltage AC before the LED rectifier feel off for the demonstration medium...
@@LightningHelix101 This is true, I suppose it doesn't all HAVE to fit or be visible I could stick a small sine wave generator circuit on the back side and just kinda ignore it the fact it's there lol. I just wanna build like 1 or 2 for my friend's kid and well ME lol.
Inspiring us all as usual, every time I watch one of your videos I’m just more and more eager to make another electronics repair video, thanks for the inspiration and keep up the good work :)
Thank you. You answered my dumb electronics question on this beautiful Sunday morning. Not sure why this is what I was thinking about when I woke up. 😂
OK, Stupid Question. What if you put a 1n4007 in SERIES with the LED, would not the 4007 provide the reverse protection for the LED. Another stupid question, If you put a resistor across the LED terminals and then to the 4007 in series would you not be able to adjust the resistor value to allow full mains voltage across the LED, Resistor + 1n4007 DIY bridge rectifer. Last stupid question, Why? If you want to know if you have power just put an LEDs on the DC side of the bridge rectifer with current limiting resistor.
That big cap also contributed to their demise... there should have been a current limiting res. ( to limit max led current within its limits ) in series with cap.
I had thought this, to create a AC LED lamp to a project, using a not polarized capacitor, availing the capacitive reactance, but as I can see here, if the reverse voltage is about 6V, the only way to make this work is use a transformer to drop the voltage down to 4,25 V AC (6V / ✓2), the LED reverse breaking down voltage of many is 5V, in this case the ac voltage has to be 3,5 V AC (5V / ✓2) this way the LEDs won't burn anymore, but this works for testing purposes.
All these years and I never considered this question or doing this - pretty unique if you ask me and great demonstration of the severely limited potential on the use of LEDs to rectify anything. Cool stuff!
@@learnelectronics obviously you misspoke, no problem there of course, however reacting negatively to one of you subscribers on a mistake you made, is not. Feel better?
@@darkphotons101 no, dude is right. If you're watching a video about the nuances of normal diodes vs. light emitting ones, you are smart enough to know voltage vs. current, and so would anybody else. So if you feel the compulsive need to correct everybody who makes a minor gaff, understand that's not actually helpful, nobody is impressed, and nobody likes those kinds of people. Go make your own videos, and see how graceful you are when they get picked apart by smart alec commenters.
Not only reverse voltage kills the LEDs, but also your ripple smoothing cap! That cap will make the startup current like a short circuit. Too big a cap, like millions of uf, will kill some real rectifiers.
Why would you even think a bridge rectifier made of LEDs would be possible? You need to point the camera down towards you a little you're out of frame quite a bit now. 😁 Thanks for blowing some LEDs and the video!
My student built one and the guy in the video did as well. So, why would you even think a bridge rectifier made of LEDs would be possible? Because a LED is a diode. The guy in the video accidentally blew his LEDs up because be put 16V into the capacitor. My student used a discharged capacitor and everything is fine. It's not efficient, sure. It's not high power, also sure. But you can see it blink, learn something and learn a lot about measuring that circuit with an oscilloscope.
Only half the fun - thought you'd use a function generator and a scope for display - and make it finally work ofc! Btw: You can also build a diode ring mixer with LEDs.
This reminds me of another video I saw on Styropyro's channel where he showed you could use LEDs as crude solar cells or used solar cells as crude LEDs lol, like you said Paul "You can but why, there is stuff made just for that". I think it's crazy that LOTS of electronics can be backwards.
@@Erudotic yeah... lol crazy I know but for real, photovoltaic cells... he applied a small voltage to a cell and looked at it in the dark with a cell phone camera because the light it emits is infrared (~800nm) but it works, I've tried. I love electronics I learn new crazy stuff everyday 😁
I maybe wrong remembering, but I think I saw $2 for 5 on this channel. And if you look at the website you see $5 for 10. Anyway. A good hint in any case!
Turns out that just as LEDs make poor rectifier diodes, a rectifier diode makes a poor LED. I put 50,000 volts backwards on an IN4007 rectifier diode and it lit up but only briefly. Very briefly. And the smell! Oh my...
the cap is way too big , leds didn't get any chance on the surge current charging it up :)
This can't happen when the circuit has 1k resistor on circuit's beginning.
FOOL BRIDGE RECTIFIAH
When I realised that this might be possible, in 1980 or so, I replaced the bulb in the taillight of my bike with 4 LEDs in bridge and a small resistor at the place where in a "normal" rectifier you would connect the load.
The AC of the usual dynamo had a high enough frequency for a nice steady light, that lasted and lasted, where bulbs would blow wheevern you would pedal a bit too fast.
A little later I used the same circuit, not with just red LEDs, but with 2 green and 2 red ones. Neatly arranged on a bridge diagram on a piece of white plastic I could demonstrate to my students the working of a bridge rectifier by feeding the bridge with the output of a powered tone generator at a low frequency, lower than 1 Hz.
Very nice to see the diodes light up slowly (with a sine wave) and the small bulb (of a rear bycycle light!), alternating the red ones and then the green ones.
As a rectifier the LEDs are not really efficient, bedause of quite a voltage drop...
I was disappointed that you didn't actually address whether it was possible to rectify AC using LEDs. You appeared to know beforehand that you were merely going to burn them up. Couldn't you have used a current limited input and reduced the voltage? Those poor LEDs never had a chance!
Today our teacher taught us about bridge rectifier in analog electronics class. And this experiment is awesome.
Nice video. You really should collaborated with Electroboom. Would have been hilarious
TL;DR leds basically suck as diodes
LEDs generally have a very low reverse breakdown voltage, typically 5volts. But they can handle a reasonable forward current.
I took advantage of this when.i replaced the incandescent light bulbs which is connected in parallel with our doorbell push buttons.
In this old traditional doorbell, the light bulb, provided a glow to illuminate the buttons at night. The bulb is powered by the leakage current through the doorbell solenoid coils. A circuit that is supplied from a 12 volt AC mains stepdown transformer.
By connecting two matched diodes in an anti parallel configuration, the forwards voltage of the one diodes limit the reverse voltage to which the other is exposed on the AC cycle of the supply. So for each switch, the bulb was replaced by a series parallel combination of back to back super bright LEDs and a current limiting resistor. This not only increased the brightness of the doorbell glow, while reducing the consumed current, it also allowed the selection of the colour of the light emitted. The LEDs have now been working continuously for 30 plus years, without a failure or replacement.
Two useful features of the LED current/voltage characteristic, is that the LED has a sharply defined forward voltage switch on point, which can be sharper than that of a Zener diode of equivalent voltage, they also have a low reverse leakage current. This makes two LEDs, connected back to back, in anti parallel, a low cost choice for an audio clipper.
The diodes can be connected between the two stages of an op amp circuit, or between a microphone pre amp and an amplifier to limit the audio level. For examp!e the diodes can be connected between zero volts and the op amp output, using a series current limiting resistor, forming an effective voltage clipper divider circuit. If super bright LEDs are used, there is ample op-amp output current to make the LEDs glow when the input audio level is too high, thus providing an indication of this condition.
Looking at the clipped audio waveform, it is remarkable symmetrical and we'll behaved. If the following op-amp is configured as an active filter, the clipping harmonics can be suppressed. This makes this circuit useful in radio transmitter audio input circuits.
I once used this configuration in a professional radio system to limit the signal level generated by an FFSK modem into the telephone system, that connected to a transmitter network. The glow of the LEDs, proved useful to the technicians configuring the system, as they could use the LEDs as an indication of when the line level was set to the correct value. All that was necessary was to adjust the level to the point where the clipper LEDs started to glow and back off the signal until the LEDs just stopped glowing. This coincided to a line level of -14dBm 600. Just under the -13dBm maximum specified by BT regulations, for signal tones to line.
I suggest it is worth taking a look at the operation of LED audio clippers on an oscilloscope, they do work really well, even at relatively high frequency.
They are good for real visualization of the rectification. Use at least 2 different color LEDs, make the rectifier, a resistor and an output indicating LED, Then use a 9v battery flipped back and forth for a slow alternating current source (i.e., at your hand frequency) to see how two LEDs in the rectifier conduct at a time making the output LED light. Of course, it uses about 9 volts to light one output LED,
"Can you make bridge rectifier from LEDs?"
Full Disco Recti-fryer!
*rectum fryer
This an amazing demonstration idea. I wouldn’t use the grid though. I think a lower frequency input around 2-5Hz would allow people to see the transition between the on & off states and build a lot of intuition
I wanna build something like this for demonstration purposes, but methods of getting to low frequency and low voltage AC before the LED rectifier feel off for the demonstration medium...
@@AmaraTheBarbarian could use a 555, and just explain it as a wave generator (oscillator) to focus on the rectification concept.
@@LightningHelix101 This is true, I suppose it doesn't all HAVE to fit or be visible I could stick a small sine wave generator circuit on the back side and just kinda ignore it the fact it's there lol. I just wanna build like 1 or 2 for my friend's kid and well ME lol.
I was wondering how much AC you were going to juice your unsuspecting breadboard with! ‘Certainly, he won’t put 120 VAC into it!’ 😮😃
i was thinking that too : ) but i couldn't see Paul making a mistake like that. Maybe Electro-Boom!! Now that i could see happen ; )
Only use I can think of for a bridge made of LEDs is an educational display fed a slow signal, just loaded with a resistor.
Exactly. And that's super educational.
Inspiring us all as usual, every time I watch one of your videos I’m just more and more eager to make another electronics repair video, thanks for the inspiration and keep up the good work :)
Perfect,now make A FULL BRIDGE RECTIFIER WITH LEDS,JUST LIKE ELECTROBOOM!
Thank you. You answered my dumb electronics question on this beautiful Sunday morning. Not sure why this is what I was thinking about when I woke up. 😂
i used a transformer to step down the voltage to 6v and put a resistor in series with the rectifier and it works (but the leds appear to just stay on)
It would have never occurred to me to ask the question. Fun!
No, we didn’t see them blink. You were out of frame as you often are. Please think about what your camera sees; that’s what we see. Thanks.
Another “what if” awesome concept/learning vid!! You the best mane!!!
Maybe some advantages for low voltage applications. 🇺🇸
🔫🔫🔫🔫🔫🔫🔫🔫🔫🔫🔫🔫🔫🔫🔫🔫🔫🔫🔫🔫🔫 salute.
😢 Poor LEDs have gone to silicon heaven.
still waitin' for ElectroBOOM's comment here ...
hehe
We didn’t do it because it was easy. We did it because it was cool 😅
Keep these videos coming our way. I've recently gotten very interested in electronics and all of this is speeding up my learning curve :)
Can you make a transistor from two diodes? 73 DE W8LV BILL
Just connect 240 VAC in series with a 1MΩ resistor and an led ez
OK, Stupid Question. What if you put a 1n4007 in SERIES with the LED, would not the 4007 provide the reverse protection for the LED.
Another stupid question, If you put a resistor across the LED terminals and then to the 4007 in series would you not be able to adjust the resistor value to allow full mains voltage across the LED, Resistor + 1n4007 DIY bridge rectifer.
Last stupid question, Why?
If you want to know if you have power just put an LEDs on the DC side of the bridge rectifer with current limiting resistor.
That big cap also contributed to their demise...
there should have been a current limiting res. ( to limit max led current within its limits ) in series with cap.
Led cannot be used as a diode but I have converted LED into diode.
Light AND Smoke emitting diodes.
Thank for explanation...
Thank you for your service.
I had thought this, to create a AC LED lamp to a project, using a not polarized capacitor, availing the capacitive reactance, but as I can see here, if the reverse voltage is about 6V, the only way to make this work is use a transformer to drop the voltage down to 4,25 V AC (6V / ✓2), the LED reverse breaking down voltage of many is 5V, in this case the ac voltage has to be 3,5 V AC (5V / ✓2) this way the LEDs won't burn anymore, but this works for testing purposes.
why? just to see it
good
Everything is possible if you can Haha... 😄👍
I think the O/p current is very low cause those LEDs are 1.5v 🙃
Interesting 🙂
Wow...
All these years and I never considered this question or doing this - pretty unique if you ask me and great demonstration of the severely limited potential on the use of LEDs to rectify anything. Cool stuff!
I "LOVE" that ripple measuring trick using the AC measurement on the meter.. : )
Yes you can. And they make fine voltage references too.
Can you provide an example of voltage reference using LEDs
@@alexstone691 ALL LED have a set forward voltage.
"they have a max. reverse CURRENT of six VOLTS" ?
voltage, i misspoke. thanks for pointing that out though, feel better?
@@learnelectronics obviously you misspoke, no problem there of course, however reacting negatively to one of you subscribers on a mistake you made, is not. Feel better?
@@darkphotons101 no, dude is right. If you're watching a video about the nuances of normal diodes vs. light emitting ones, you are smart enough to know voltage vs. current, and so would anybody else. So if you feel the compulsive need to correct everybody who makes a minor gaff, understand that's not actually helpful, nobody is impressed, and nobody likes those kinds of people.
Go make your own videos, and see how graceful you are when they get picked apart by smart alec commenters.
I have had that question for so long thank you for answering it
How would you go about reducing that ripple that you showed?
Try an arbitrary waveform generator set to sine wave 3 Vpp.
So a power led could do this job just fine?
Not only reverse voltage kills the LEDs, but also your ripple smoothing cap! That cap will make the startup current like a short circuit. Too big a cap, like millions of uf, will kill some real rectifiers.
But, the resistors on ac linking on circuit's beginning will limit the current, the inrush current won't be big.
Why would you even think a bridge rectifier made of LEDs would be possible? You need to point the camera down towards you a little you're out of frame quite a bit now. 😁 Thanks for blowing some LEDs and the video!
My student built one and the guy in the video did as well. So, why would you even think a bridge rectifier made of LEDs would be possible? Because a LED is a diode. The guy in the video accidentally blew his LEDs up because be put 16V into the capacitor. My student used a discharged capacitor and everything is fine. It's not efficient, sure. It's not high power, also sure. But you can see it blink, learn something and learn a lot about measuring that circuit with an oscilloscope.
Only half the fun - thought you'd use a function generator and a scope for display - and make it finally work ofc! Btw: You can also build a diode ring mixer with LEDs.
Diode ring mixer with led 's, please explain? Sounds interesting for my modular synthesizer.
Pretty cool demonstration! Good work.
This reminds me of another video I saw on Styropyro's channel where he showed you could use LEDs as crude solar cells or used solar cells as crude LEDs lol, like you said Paul "You can but why, there is stuff made just for that". I think it's crazy that LOTS of electronics can be backwards.
Solar cells? as crude led? How's that go down? Don't you mean photo diodes, or really actual solar cells?
@@Erudotic yeah... lol crazy I know but for real, photovoltaic cells... he applied a small voltage to a cell and looked at it in the dark with a cell phone camera because the light it emits is infrared (~800nm) but it works, I've tried. I love electronics I learn new crazy stuff everyday 😁
Shouldn't it be 2$ for 5? In your description I read "Get 5 boards in about a week for $22!"
Shipping is a large part of the price you pay depending on what shipping method you select and likely your location.
2$ for 5 would be a ridicilously low price, 22 is actually not bad at all.
I maybe wrong remembering, but I think I saw $2 for 5 on this channel. And if you look at the website you see $5 for 10. Anyway. A good hint in any case!
My question is can you use LED's as a flyback diode ? (For inductors)