Adding Power LED - Page 1
Forum section: electronics / beginners

author: WayneRandom
author_rank: Newbie
timestamp: September 08, 2022, 05:37:35 am
content: Hi everybody. I have just built this Buffer Interface. It works fine and I am quite happy with it. Now I would like to add a green power LED, so I can see if is powered on. But since I am a absolute beginner, can anybody tell if these parts are correct and where in the circuit they should be put into?LED:https://www.distrelec.ch/en/led-570nm-green-mm-everlight-electronics-383sygc-s530-e2-h2/p/17501653?origPos=30&trackQuery=cat-DNAV_PL_020103&pos=1&filterapplied=filter_Leuchtk%C3%B6rper%20%28Durchmesser%29~~mm%3D5%26filter_Durchlassstrom%20%28If%29~~mA%3D20%26filtersCleared%3Dtrue%26filter_Linsenform%3DRund%26f%3D1%26filter_LED-Farbe%3DGr%C3%BCn&no-cache=true&origPageSize=50&track=true&marketingPopup=falseResistor:https://www.distrelec.ch/en/axial-wirewound-resistor-5w-330ohm-rnd-components-rnd-1555w330rf/p/30165926?origPos=601&trackQuery=cat-DNAV_PL_030715&pos=3&filterapplied=filter_Widerstand~~Ohm%3D330%26filter_Nennleistung~~W%3D5&no-cache=true&origPageSize=50&track=true&marketingPopup=falseLED Socket:https://www.distrelec.ch/en/led-holder-5mm-fischer-elektronik-dh/p/17507514?origPos=1&trackQuery=cat-DNAV_PL_020202&pos=1&no-cache=true&origPageSize=50&track=true&marketingPopup=false

author: tooki
author_rank: Super Contributor
timestamp: September 08, 2022, 05:54:29 am
content: In principle those parts will work — for 9V. But since the input voltage is 9-36V, I would do two things:1. Choose a much higher resistor value (1.68k ohm = 1680 ohms) to limit the current to 20mA at the maximum input voltage.2. Choose a modern emerald green (~520nm), or blue or white, LED because even at the 0.3mA the resistor above would produce at 9V input voltage, it’ll still be visible.Other suggestions:I’d choose an LED with a diffused package, not the water clear. Water clear ones are super bright head-on, but not as visible from the side. Diffused ones are much better as indicators. Alternatively, use very fine sandpaper to completely sand the outside of the LED to a matte finish. (Helpful since nowadays, so many LEDs are the water clear type.)Also, you don’t need a 5W resistor — you’ll be dissipating 1/8W at most with the 330 ohm resistor, even less with the 1.68k. So a 0.25-0.6W resistor will be fine, and much smaller.

author: WayneRandom
author_rank: Newbie
timestamp: September 08, 2022, 06:32:01 am
content: Thank you for your quick response!These are some good suggestions. Thank you. Would these parts be correct?LED:https://www.distrelec.ch/en/led-575nm-green-mm-vishay-tlhg44k1l2/p/30119211?trackQuery=cat-DNAV_PL_020103&pos=2&origPos=184&origPageSize=50&filterapplied=q%3d*%26filter_Lens+Colour%3dDiffused&track=trueResistor:https://www.distrelec.ch/en/resistor-600mw-6kohm-vishay-mbb02070c1601fct00/p/16059220?trackQuery=cat-DNAV_PL_030712&pos=1&origPos=203&origPageSize=50&filterapplied=filter_Resistance~~kOhm%3d1.6&track=trueLED Socket:https://www.distrelec.ch/en/led-holder-3mm-fischer-elektronik-dh3v/p/17507512?trackQuery=cat-DNAV_PL_020202&pos=3&origPos=3&origPageSize=50&track=trueI have no idea what would be the correct way to solder the parts into the circuit. Do you have a recommendation?

author: james_s
author_rank: Super Contributor
timestamp: September 08, 2022, 06:56:47 am
content: That resistor is 600mW which is still quite a bit higher power than you need. It will work, but it is physically larger than needed. The LED is 562nm which sounds like the older yellowish green, it will work but there are others that will appear brighter. You can buy assortments of LEDs from online sellers very cheaply that work fine and give you a selection of colors to play with.You can solder the parts together like anything else, wrap a wire around the lead and solder it. If you don't know how to solder properly that's something to learn separately and practice on some scraps.

author: mariush
author_rank: Super Contributor
timestamp: September 08, 2022, 07:25:38 am
content: You can also have two resistors in series instead of just one.Decide on some current amount you want for your LED and then you can figure out the rest.For example, let's say you want 5mA going through the LED in the worst case scenario where you feed the circuit with 36v DC.Therefore you need to calculate the resistor value using Ohm's law : input voltage - forward voltage of led = Current x Resistance = > Resistance = (Vin - Vled) / Current = (36 - 2) / 0.005 = 34/0.005 = 6800 ohmThe power dissipated in the resistor will be P = I2xR = 0.17 watts, so you should be fine using a single 0.25w 6800 ohm resistor, or you could maybe use 2 3300 ohm resistors each rated for 0.125w in series - yes, you'll get 6600 ohm in total, but it's close enough to 6800 that it won't make much of a difference.You need to make sure the LED will still light up at lower input voltages with this resistor value ... so reuse the formula : 9v - 2v = Current / 6800 => Current = (9v-2v)/6800 = 0.001 A or 1mA ... and I think the led will still be visible at 1mA.But, if you think most of the time the board will be powered with more reasonable voltages, lower the overall resistance a bit to give the led more current at lower voltages. A 4.7k resistor would probably be a better choice to make the led a bit brighter with lower input voltages.

author: WayneRandom
author_rank: Newbie
timestamp: September 08, 2022, 08:11:07 am
content: The interface will probably always be powered by 9V. I have it plugged into a pedalboard power supply which supports 9V and I don’t think that I am ever going to change this.I have looked for another LED and resistor and found this. Sorry, the pages are in German only. But have the items have an English document.LED:https://www.conrad.ch/de/p/quadrios-2111o169-led-bedrahtet-gruen-rund-5-mm-2500-mcd-30-20-ma-3-v-2583910.htmlResistor:https://www.conrad.ch/de/p/tru-components-tc-mf0w4ff1601a20203-metallschicht-widerstand-1-6-k-axial-bedrahtet-0207-0-25-w-1-1-st-1585041.htmlAre these going to work with the 9V and deliver a decent result?My problem is that I know how to solder but I have no Idea about electronics. I added two different drawings (LED V.1 and LED V.2). Which one of these would work, if any?

author: mariush
author_rank: Super Contributor
timestamp: September 08, 2022, 10:32:47 am
content: The long lead / small metal bit inside the led is the anode or positive. That part receives the voltage.The short lead / bigger metal bit inside the led is the cathode or negative.Doesn't matter on which side the resistor is placed.. as long as it's in series with the led, it will limit the current going through the led.So as far as I can tell, the first picture is the correct one. Well, second picture also seems right, but I'd solder the negative wire to the DC in connector.As for soldering ... tin the leads and wires with solder then solder the wires to the leads or to the contacts of the connectors. It's not rocket science.Watch Dave's soldering tutorial if you feel like you need to, Pace has a soldering tutorial series on their Youtube channel as well.

author: WayneRandom
author_rank: Newbie
timestamp: September 08, 2022, 02:48:07 pm
content: Ok. Thanks for all the replies.I will try it with the parts listed in my last post and use the method in picture one.

author: WayneRandom
author_rank: Newbie
timestamp: September 14, 2022, 07:44:07 pm
content: I have now added the LED, and everything works fine. But the LED is way too bright.Is there a simple way to reduce the brightness?I am using this LED and resistor.https://www.conrad.ch/de/p/quadrios-2111o169-led-bedrahtet-gruen-rund-5-mm-2500-mcd-30-20-ma-3-v-2583910.htmlhttps://www.conrad.ch/de/p/tru-components-tc-mf0w4ff1601a20203-metallschicht-widerstand-1-6-k-axial-bedrahtet-0207-0-25-w-1-1-st-1585041.html

author: james_s
author_rank: Super Contributor
timestamp: September 14, 2022, 07:55:41 pm
content: Yes, use a higher value resistor. I often use a pot for testing purposes, something like 10k, adjust to the desired brightness then remove the pot, measure the value and select a fixed resistor that is close to that.

author: WayneRandom
author_rank: Newbie
timestamp: September 14, 2022, 08:46:47 pm
content: Ok. I ordered now higher value resistors and weaker LEDs. I hope this will do it.

author: tooki
author_rank: Super Contributor
timestamp: September 15, 2022, 09:04:52 am
content: “Weaker” LED?? No need for that. Just use a higher value resistor.You could just put two of the resistors you already have in series and see if you are happy.

author: WayneRandom
author_rank: Newbie
timestamp: September 15, 2022, 10:09:06 am
content: The LED I have installed has 2500 mcd. I already tested it with two 1.6 k resistors and it barely made a difference.That is why I ordered LEDs with 1300 and 700 mcd. I also ordered a variety of different resistors (2.4, 3.3, 4.3, 5.1, 6.2, 7.5, 10, 15, 22) to test wich resistor value and wich LED works best.Just to make clear what my setting with this LED is:The LED is mounted in a small box and is facing up. The box is on my pedalboard on the floor right in front of me. At the current brightness it almost makes me blind.

author: rdl
author_rank: Super Contributor
timestamp: September 15, 2022, 12:59:55 pm
content: What is the wavelength of the LED? If it's down around 520-525 nm it's probably InGaS and those are ridiculously bright. You may need to get the current down into the micro amps range, which will take a fairly large resistor value. I had to use a 50k for this one.https://www.eevblog.com/forum/beginners/how-can-i-determine-the-resistor-value-for-an-unknown-type-of-led/msg2893554/#msg2893554

author: WayneRandom
author_rank: Newbie
timestamp: September 15, 2022, 01:38:26 pm
content: The wavelength is 520 nm. It is this one:https://www.conrad.ch/de/p/quadrios-2111o169-led-bedrahtet-gruen-rund-5-mm-2500-mcd-30-20-ma-3-v-2583910.htmlThe other ones I have ordered are these:https://www.conrad.ch/de/p/quadrios-2111o168-led-bedrahtet-blau-rund-5-mm-1300-mcd-30-20-ma-3-v-2583909.htmlhttps://www.conrad.ch/de/p/quadrios-2111o170-led-bedrahtet-gelb-gruen-rund-5-mm-700-mcd-30-20-ma-2-v-2583911.htmlhttps://www.conrad.ch/de/p/tru-components-led-bedrahtet-blau-rund-5-mm-500-mcd-50-20-ma-1577334.htmlDo you think that one of these in combination with a higher value resistor should work?

author: tunk
author_rank: Super Contributor
timestamp: September 15, 2022, 03:36:54 pm
content: The only way to find out is to test it. I would start witha 22k resistor and see if that's too bright or not.

author: james_s
author_rank: Super Contributor
timestamp: September 15, 2022, 05:04:21 pm
content: There is no reason to change the LED, more efficient is almost always better. You can go as high as you need with the resistors, common cheap resistors are made up into the megohms, all you have to do is add a high enough resistance.