You might have supplied a copy of the sketch used to flash the array of leds you created. I know it is probably quite simple, but for a beginner, it is a basis to work forward from.
You use OHM's law : Voltage = Current x Resistance ... From this, you get: Input Voltage - Forward voltage of LED (or sum of all forward voltages if multiple leds in a chain) = Current x Resistance ... So for example, for 10mA (0.01A) and a 3.2v LED powered by 5v, then you have 5v - 3.2v = 0.01 x R => R = (5v - 3.2v) / 0.01 = 180 ohm. IF you get a weird value, you can go up and down a tiny bit and pick a common resistance value... ex if you get 155 ohms, you may use 150 ohm or 100+56 (two resistors in series) Anyway.. really bad start by suggesting to just connect the LED to a battery. It only works because the battery has a high internal resistance. Bigger batteries will have much lower resistance so you MUST add a resistor. Also, as LEDs are diodes, they have a maximum reverse voltage (listed in datasheet), and for these small cheap LEDs this reverse voltage is often 5v or less - if you connect a LED to a 9v battery the wrong way, you'll probably damage it permanently. If you want to determine the forward voltage of a led, you can limit the current of a psu (as shown at around 12 min) to something reasonable like 5-10mA, and then slowly raise the voltage. All leds will have a "full off" region, a very narrow region where the led will start to produce light but consume very little, and as soon as you get out of that narrow region, it will snap on and consume the full 5-10mA of current. You don't want to calculate a resistor for a forward voltage that would keep the led in that very narrow region, as these regions change (go wider or narrower) depending on the temperature of a led. You want the full on forward voltage.
@@mariushmedias well you see i have these UV leds and when i put them in the "full on" region, as you so technically described, they last about two weeks. so now i set up a little test jig with a voltage regulator, a led, and a LDR, and i'm going to try to set them as bright as i can without the light dimming over time...
@@tylerufen You would want to use a voltage regulator in current limit mode, or to actually use a led driver. LEDs are current driven devices, not voltage driven. As soon as the voltage is higher than the leds forward voltage the LED goes in its "full on" region and pulls as much current as you give it. A LED driver or a voltage regulator in current limit mode would limit the maximum current. The forward voltage of a LED will vary from LED to LED in the same batch, and will also vary with temperature: the LED may need 3v to go wild when it's cold, but as it warms up to 60-80 degrees Celsius that 3v may actually go down to 2.8v or something like that - so if you use the plain resistor formula Vin-Vforward = Current x Resistor you have to account for this variation in Vforward of the led due to temperature, and not set the default current to the highest value listed in datasheet. One more note: some infrared LEDs are "optimized" for remote controls, where the LEDs light up for a few milliseconds sending a series of pulses to the device infrared sensor and then aren't used for a few seconds or minutes. In such application, you actually WANT to give led up to 1-2A of current even if the led is rated for 20mA continuously, making it work like the flash of a digital camera and the led will survive this high current as long as the period is short (milliseconds at most) and then has seconds to cool down.
@@tylerufen Well 1. that's incredibly rude and ungrateful and 2. I didn't write it just for you, other people browse the comments. If you can't write anything helpful or express gratitude for people wasting valuable time to offer help maybe you shouldn't reply in the first place.
While your schematics are correct, it's incorrect to show flow of electrons from the + to the -. It's actually the opposite. Please stop confusing people who are learning. Perpetuating conventional current vs electron flow is bad form.
While you are technically correct, conventional current works just fine for pretty much everybody, and it's what is taught in schools from a young age. Trying to rectify hundreds of years of electrical teachings is just going to confuse more people.
@@BloodHound0827 I am not "technically correct". I am correct. Just because you learned the wrong thing in school doesn't mean people should continue to propagate erroneous information.
@@BloodHound0827 Well, first of all, we, as humans, do not have "hundreds of years" of understanding of electricity. Further, nobody is "keeping it the way it is today". There is no "dilemma". Electron flow was misunderstood in the past but this is no longer. But please, do keep thinking incorrectly. It just proves your insolent ignorance.
If LED s take2 volts or better to light, how come the lawn solar lights operate with 1.24 volt nicad volt battery?
Great video, thanks! By the way, I loved the background music, could you please let me know who's the author?
You might have supplied a copy of the sketch used to flash the array of leds you created. I know it is probably quite simple, but for a beginner, it is a basis to work forward from.
What kind of bench voltage supply is that?
Extech, the one shown is now longer made. Seen a few on amazon tho
nice video
i wish you'd explained how to determine voltage and current without the sheet because who has the datasheet for their leds? seriously..
You use OHM's law : Voltage = Current x Resistance ... From this, you get: Input Voltage - Forward voltage of LED (or sum of all forward voltages if multiple leds in a chain) = Current x Resistance ... So for example, for 10mA (0.01A) and a 3.2v LED powered by 5v, then you have 5v - 3.2v = 0.01 x R => R = (5v - 3.2v) / 0.01 = 180 ohm.
IF you get a weird value, you can go up and down a tiny bit and pick a common resistance value... ex if you get 155 ohms, you may use 150 ohm or 100+56 (two resistors in series)
Anyway.. really bad start by suggesting to just connect the LED to a battery. It only works because the battery has a high internal resistance. Bigger batteries will have much lower resistance so you MUST add a resistor.
Also, as LEDs are diodes, they have a maximum reverse voltage (listed in datasheet), and for these small cheap LEDs this reverse voltage is often 5v or less - if you connect a LED to a 9v battery the wrong way, you'll probably damage it permanently.
If you want to determine the forward voltage of a led, you can limit the current of a psu (as shown at around 12 min) to something reasonable like 5-10mA, and then slowly raise the voltage. All leds will have a "full off" region, a very narrow region where the led will start to produce light but consume very little, and as soon as you get out of that narrow region, it will snap on and consume the full 5-10mA of current.
You don't want to calculate a resistor for a forward voltage that would keep the led in that very narrow region, as these regions change (go wider or narrower) depending on the temperature of a led. You want the full on forward voltage.
@@mariushmedias well you see i have these UV leds and when i put them in the "full on" region, as you so technically described, they last about two weeks. so now i set up a little test jig with a voltage regulator, a led, and a LDR, and i'm going to try to set them as bright as i can without the light dimming over time...
@@tylerufen You would want to use a voltage regulator in current limit mode, or to actually use a led driver.
LEDs are current driven devices, not voltage driven. As soon as the voltage is higher than the leds forward voltage the LED goes in its "full on" region and pulls as much current as you give it. A LED driver or a voltage regulator in current limit mode would limit the maximum current. The forward voltage of a LED will vary from LED to LED in the same batch, and will also vary with temperature: the LED may need 3v to go wild when it's cold, but as it warms up to 60-80 degrees Celsius that 3v may actually go down to 2.8v or something like that - so if you use the plain resistor formula Vin-Vforward = Current x Resistor you have to account for this variation in Vforward of the led due to temperature, and not set the default current to the highest value listed in datasheet.
One more note: some infrared LEDs are "optimized" for remote controls, where the LEDs light up for a few milliseconds sending a series of pulses to the device infrared sensor and then aren't used for a few seconds or minutes. In such application, you actually WANT to give led up to 1-2A of current even if the led is rated for 20mA continuously, making it work like the flash of a digital camera and the led will survive this high current as long as the period is short (milliseconds at most) and then has seconds to cool down.
@@mariushmedias tl;dr
@@tylerufen Well 1. that's incredibly rude and ungrateful and 2. I didn't write it just for you, other people browse the comments. If you can't write anything helpful or express gratitude for people wasting valuable time to offer help maybe you shouldn't reply in the first place.
While your schematics are correct, it's incorrect to show flow of electrons from the + to the -. It's actually the opposite. Please stop confusing people who are learning. Perpetuating conventional current vs electron flow is bad form.
While you are technically correct, conventional current works just fine for pretty much everybody, and it's what is taught in schools from a young age. Trying to rectify hundreds of years of electrical teachings is just going to confuse more people.
@@BloodHound0827 I am not "technically correct". I am correct. Just because you learned the wrong thing in school doesn't mean people should continue to propagate erroneous information.
@@richard1113 then take it up with the people who hundreds of years ago faced this same dilemma and decided to keep it the way it is today.
@@BloodHound0827 Well, first of all, we, as humans, do not have "hundreds of years" of understanding of electricity. Further, nobody is "keeping it the way it is today". There is no "dilemma". Electron flow was misunderstood in the past but this is no longer. But please, do keep thinking incorrectly. It just proves your insolent ignorance.