I've never really had to consider exceeding a diodes PIV before so I played safe, since all the online resources about the subject I found suggested it would damage the diode. It was in the back of my mind that it doesn't damage the diode, especially when the current is so severely limited. The first one I made uses 1N4148 diodes.
I chose the resistive dropper because it's super simple, the components are likely to be found in any dabblers workshop, the current was deliberately very low for decorative effect and the shock risk after the resistors is low whichever way the lamp is inserted. I did toy with adding a capacitor, but theoretically it would have to be rated for open circuit voltage of at least 350V. The flicker is very low because the LEDs are lit for most of each half cycle.
The reason we have Bayonet caps in the UK is to do with a chap called Sir George Lane-Fox. He developed it and sold it to Brush Electric Lights, who then distributed it around the UK and thus is why we still have Bayonet caps now. They're also very good for trains, in both signalling and on the carriages as they don't work loose due to vibrations. Also, bulb theft is the reason why a lot of train signals have three-ear Bayonet cap sockets.
Wow, really simple design which we (engineers) learn in our second year but never put to use. thank you so much for sharing. PS: You got artistic soldering skills.
IIRC, 1N4148s have a reverse breakdown potential of about 70V and maximum rated currents of only a few tens of mA. As die power dissipation would be about 100 times greater in reverse breakdown than when forward biased for a given current, the diode in question may still fail if carrying a current more than 1% of its maximum rating, but it would be a somewhat uneventful death instead of a bang. I think.
Hi, i have watched the video. I really appreciate your efforts. Well i have couple of questions. 1. For 20 5mm white led's the required forward voltage is 72V. Now what is to be done if i specifically need to illuminate 5 Led's with 3.6v forward voltage and 20mA max forward current? Input AC voltage is to be considered as 240v 2. Is connecting 100K on both lines and rectifying it always produces 72V DC when powered by a 240V AC line? 3. Do we have any mathematical formula to design led lamps according to need?
Hi Clive, great video, I was wondering If I were to create multiple strings like this, without the bayonet fixing, would it be possible to run them all into one fixture, and if not, could you recommend a method of doing this, thanks.
If you exceed the peak reverse potential of a diode but limit the current so that the maximum die dissipation rating is not exceeded, the diode will just act like a zener/avalanche diode.
Hehe. It worked. I tried using SMD leds. I probably destroyed about 5 pieces by overheating them with the iron. But now, I have 20 in a row and they give a decent shine.
Hi, great video but I have a question. After making the bridge rectifier I thought I would check it with my DMM but when I put the positive probe on your negative side and the negative probe on your positive side I got a reading of 1.1v. Surely that would indicate that the positive and negative should be the other way round? Or am I missing something? Which wouldn't surprise me as I'm new to this. Can you clarify please?
I managed to get some of the purple LED strings in poundland. I think they might look nice stuffed in a lamp, but I'd probably need to run it off a capacitive dropper, as they're not in series. Do you think that would work out?
I believe the bayonet cap was invented as a safer alternative to ES. Safer because the cap itself isn’t used in the circuit and thus can never become live, making your finger a path to earth.
Hi clive :) a beginner question. doesn't the current limiting resistors dissipate more power? Ive read that a capacitive dropper is a better option as it dissipates a very little or no heat/power.
Can I use 1N4004 diodes instead of 4007s? (ordered the wrong ones) and can the resistors be lower value to get more out of the leds?, (I am in Australia so 240volt) Thanks
just out of curiousity whats the best way to calculate the resisters needed to drive the leds at a certian milla-amperage id love to build this on 120 ac but run 40 leds. which is 105 volts leaving 15 to 30 volts to drop depending on voltage of the evening. any help would be great.
Greetings. I'm just wondering what sort of Resistors you use. as there are a few of them. like metal film, carbon film. and 1/8W, 1/4W, 1/2W, 1W and 5W. If i where to make this what sort of resistors should be used? Thanks =)
Using lossy components such as resistors is never my trait. I would use a small capacitor; not a microamp would ever get wasted. Now you waste a lot of energy, negating the benefit of using LEDs in the first place.
Now your on it! That bridge teaching was the best I've seen. Simple, accurate, clear. Excellent. You are a teacher not a critic.
I've never really had to consider exceeding a diodes PIV before so I played safe, since all the online resources about the subject I found suggested it would damage the diode. It was in the back of my mind that it doesn't damage the diode, especially when the current is so severely limited. The first one I made uses 1N4148 diodes.
I chose the resistive dropper because it's super simple, the components are likely to be found in any dabblers workshop, the current was deliberately very low for decorative effect and the shock risk after the resistors is low whichever way the lamp is inserted. I did toy with adding a capacitor, but theoretically it would have to be rated for open circuit voltage of at least 350V. The flicker is very low because the LEDs are lit for most of each half cycle.
Very nice three-handed soldering technique there, Clive.
+mickey thompson He still struggles with the 4 handed technique, but thats why you can tin the wires first :P
what is the ohms of resistor
Mentioned right at the start Shafik... :)
The reason we have Bayonet caps in the UK is to do with a chap called Sir George Lane-Fox. He developed it and sold it to Brush Electric Lights, who then distributed it around the UK and thus is why we still have Bayonet caps now. They're also very good for trains, in both signalling and on the carriages as they don't work loose due to vibrations. Also, bulb theft is the reason why a lot of train signals have three-ear Bayonet cap sockets.
I never thought it would ever be that simple !!
Wow, really simple design which we (engineers) learn in our second year but never put to use. thank you so much for sharing. PS: You got artistic soldering skills.
IIRC, 1N4148s have a reverse breakdown potential of about 70V and maximum rated currents of only a few tens of mA. As die power dissipation would be about 100 times greater in reverse breakdown than when forward biased for a given current, the diode in question may still fail if carrying a current more than 1% of its maximum rating, but it would be a somewhat uneventful death instead of a bang. I think.
Hi, i have watched the video. I really appreciate your efforts. Well i have couple of questions.
1. For 20 5mm white led's the required forward voltage is 72V. Now what is to be done if i specifically need to illuminate 5 Led's with 3.6v forward voltage and 20mA max forward current? Input AC voltage is to be considered as 240v
2. Is connecting 100K on both lines and rectifying it always produces 72V DC when powered by a 240V AC line?
3. Do we have any mathematical formula to design led lamps according to need?
Hi Clive, great video, I was wondering If I were to create multiple strings like this, without the bayonet fixing, would it be possible to run them all into one fixture, and if not, could you recommend a method of doing this, thanks.
what ruffley is the voltage coming through to the LEDs I can't check my son has put multimeter in the toilet lol
After the current limiting resistors the voltage will drop down to whatever the combined forward voltage of the LEDs is.
If you exceed the peak reverse potential of a diode but limit the current so that the maximum die dissipation rating is not exceeded, the diode will just act like a zener/avalanche diode.
Hehe. It worked. I tried using SMD leds. I probably destroyed about 5 pieces by overheating them with the iron. But now, I have 20 in a row and they give a decent shine.
Hi, great video but I have a question. After making the bridge rectifier I thought I would check it with my DMM but when I put the positive probe on your negative side and the negative probe on your positive side I got a reading of 1.1v. Surely that would indicate that the positive and negative should be the other way round? Or am I missing something? Which wouldn't surprise me as I'm new to this. Can you clarify please?
Can i use it with color changing leds?
I managed to get some of the purple LED strings in poundland. I think they might look nice stuffed in a lamp, but I'd probably need to run it off a capacitive dropper, as they're not in series. Do you think that would work out?
Capacitive droppers are best suited to series strings. Better to use the USB and resistor approach.,
OK Ta. Maybe I should consider some of the other LEDs I have. I did get some individual purple LEDs.
I believe the bayonet cap was invented as a safer alternative to ES. Safer because the cap itself isn’t used in the circuit and thus can never become live, making your finger a path to earth.
It's like a cooking show, but with electronics.
Hi clive :) a beginner question. doesn't the current limiting resistors dissipate more power? Ive read that a capacitive dropper is a better option as it dissipates a very little or no heat/power.
Yes, the resistor is only suited to very low current applications as it does dissipate the voltage difference as heat.
Can I use 1N4004 diodes instead of 4007s? (ordered the wrong ones) and can the resistors be lower value to get more out of the leds?, (I am in Australia so 240volt)
Thanks
just out of curiousity whats the best way to calculate the resisters needed to drive the leds at a certian milla-amperage id love to build this on 120 ac but run 40 leds. which is 105 volts leaving 15 to 30 volts to drop depending on voltage of the evening. any help would be great.
+Aikouka Ookami 40 LEDs might be a bit too much, but the website version of this project may help. www.bigclive.com/diyled.htm
Greetings. I'm just wondering what sort of Resistors you use. as there are a few of them. like metal film, carbon film. and 1/8W, 1/4W, 1/2W, 1W and 5W. If i where to make this what sort of resistors should be used? Thanks =)
+flpsht I tend to keep a stock of quarter watt carbon film resistors.
Hi was wondering how would a switch be attached to this?
It's designed to be used in a standard lamp holder, so you could use a switched lamp holder.
bigclivedotcom Thanks
love it I'm gonna have to make one now.
Great video. Thank you so much for your information. Greetings and blessings.
Fantastic! Thank you for the video :)
I’m only watching this for homework and I’m bored af
I have 2000 resistors, 1000 leds but only 3 diodes. FUCK
good vid thanks
You really are extremely dexterous aren't you Clive! meh... who needs helping hands? lol
Using lossy components such as resistors is never my trait. I would use a small capacitor; not a microamp would ever get wasted. Now you waste a lot of energy, negating the benefit of using LEDs in the first place.