For people who don't know, how do you connect a resistor to a LED light?
Topic by liketoblowthingsup48 | last reply
I bought 100 leds of ebay a while ago and it came with 100 free resistors. What im not too sure about is what ohm they are. On the ebay page it dosent say if they go with the leds the shop specialises in leds and gives similar resistors with almost every order. All it says on the page is that there perfect for working with 12v or something. I tried looking at those colour code calulators but I still couldnt figure it out. I knew someone here must know. The colours in the pic arent great so I wrote what they are aswell.
Topic by flyer3 | last reply
This might sound stupid, but being brand new to electronics i need to pose this question, i found a scematic with 3 resistors on, 1 is a variable rated as R1 100K, the second R2 1K, the third R3 270R, the problem is the third resistor, what does the "R" stand for?
Question by nicobotha12345 | last reply
I just got a back of about 130 resistors for a bag of 50 L.E.D's but some of the resistors ive never heard of, there are a few like 100ohm and 560 ohm but now im getting 1m ohm and 4.1Mohm and 100K ohm,1.5K ohm and 1K ohm. Ive never seen resistors like this before, i am very basic in electronics but i took a class at school have have made many many projects but never resistors like this and i only wanted to use them for a few L.E.D's, I dont really know what im asking for in here but i just sapose if anyone has any help or ideas or really anything with these resistors and matching them with L.E.D'S?
Topic by craig3 | last reply
I was just wondering if there is some kind of marking on a resistor that tells you which direction you should read it. I've seen brown bands on the ends of some resistors but not always, so I was just wondering if someone could help me out. Thanks Zealous
Topic by Zealous | last reply
Hey guys got a question. I want to add an ultra bright LED from my mini mag light to my atx benchtop power supply. The LED ran off 3v (2 AA’s.) The line I want to use is the 3.3v (14 amp) from the atx to power it. What size/power rating resistor should I use?
Topic by jmille38 | last reply
Hi Guys, I built a power supply (half wave rectifier) for a project. It simply rectifies normal 120VAC and gives me a pulsed 120VDC output. The resistors are rated for 20 Watts (I calculated that I only needed 4.32 Watts), but they still seem to get extremely hot and I think they are beginning to break down. Is there any way I could put a heat sink on them? Thanks
Question by transistorguy | last reply
Is there a way to find the wattage rating of resistors and such mathematically? or is it something that has to be tested in real life? I have quite a few resistors that I'd like to use, but don't know the wattage rating of them. I only know their resistance, and I could calculate other values if I put voltage across them with a multimeter. Also, what type of variable resistor would you recommend to control a 12 VDC device that draws 12 amps?
Question by tylervitale | last reply
I am relatively new to electronic projects building and I have noted that some projects do not state the power and tolerance of the resistors. How should I proceed, are there any guide lines to establish the tolerance and wattage? Thatnks.
Question by ajax70 | last reply
Question by porternick | last reply
I'm going to build an 8x8x8 LED cube and I am confused about what resistors I should get. Here is a link to the blue LEDs that I bought: http://www.ebay.com/itm/110942426746?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649. This step https://www.instructables.com/id/Led-Cube-8x8x8/step14/Choose-your-resistors/ says to use the burst load of the LEDs but the chart on the item page is somewhat confusing to me. I know that with the resistance equation it would be R=3.2v/0.02A but I don't know if that is the right mA. I am pretty new to electronics so any help is appreciated.
Question by Arya42 | last reply
I'm trying to teach myself resistors through a LED project. My LED's typical FW voltage is 3.5 under a 4.5 supply voltage and a FW current of 20mA. If I've done the math right I should need a 50ohm resistor. correct? I'm hoping to buy the resistors from Radioshack and looking at there supply they only have resistors ranging from 48ohm to 68ohm. I know I could just use the 68ohm resistor, but have also read that wiring resistors in parallel will reduce the resistance. So using two 100ohm combined should work. It just seems too simple and close to Ohm's law's outcome. Would this be safe for the LED?
Question by GodCent | last reply
I have am writing an arduino sketch for a mini traffic light projects that will require both 220Ω & 330Ω resistors, I ordered them, the problem is that the resistors I received don't add up when looking at the bands. this is the color band ORANGE+ORANGE+BLACK+ORANGE+BROWN 3 -------------3------------0----------x3------------1%-------- does not this mean 330 x 3 @ 1% so the 330 is actually 3,300 or would it be 330kΩ It's been years since I've looked up color bands , can I even use these ones for simple 5v led projects or should I just re-order the 330Ω resistors now? thanks in advance robert
Question by rdlockrey | last reply
This is one of the exercise from the book, "The Art of Electronics." They do not give answers and i wanted to know if i did it right. I got the answer of 1.44 watts, but i am not sure if this is correct.
Question by cooldude01 | last reply
I posted a very similar topic a couple minutes ago but I'm pretty sure noone can see it, so I'm copying and pasting the body. I just want to check this before I blow up my mosfet (I've never used mosfets before) Is it correct that you don't have a resistor from the voltage source to the gate (unlike bipolar transistors) Should or shouldn't you have a 1M ohm from gate to ground? Let's say I'm driving a mosfet from a 555, should I have a resistor from the output pin to gate? I think the schematic I'm reading just through a mosfet in where a bipolar use to be without changing that resistor.
Topic by guyfrom7up
Hello,I am building a multi-touch surface using the FTIR method and after the surface is powered for about 10 minutes there is a heated smell in the room, I have noticed that the resistors are very warm and that a couple have started to brown or burn. I really need this table to be able to be safely powered at least 18 hours a day.Here are my specs:LED's:I am using 88 Infrared LED's (T 1 3/4 INFRARED LED, http://www.allelectronics.com/make-a-store/category/340250/LEDs/Infrared/1.html )--8 LED's per series--forward voltage of 1.5v --forward current of 100mAResistors:I am using 2, 10 ohm 1/4 watt resistors parallel (so 5 ohms) with each of the 11 series'Power Supply:The power supply output's 12 volts DC and 1.2 ampsWhen I calculate using http://led.linear1.org/led.wiz it says I only need 1ohm 1/4 watt resistors, I haven't tried this yet but it doesn't seem to me that this would rectify the situation. My guess was that I need 1 watt resistors, but the calculator didn't seem to agree.Any thoughts as to what my problem is? is it safe to go with 1 ohm 1/4 watt resistors? or do I need 1 watt resistors? Any help would be very appreciated, thank you!
Topic by hapticdata | last reply
I am designing a led array consisting of 17 leds in parallel using 4.5 volt power supply.The led calculator is telling me to use 62 ohm resistor on each - leg of the LEDscould I just use one 62 ohm resistor right after the power supply? Or maybe like 1 or 2 100 ohm resistors? I'm using blue leds 3.3 max voltage 20 Ma
Question by the_burrito_master | last reply
The motor will be driving a small belt and a paper towel tube. This project is for Halloween. I'm trying to create a mechanical fade circuit for a fluorescent tube. The motor came from an old printer and runs at full speed when 12v is applied. I want to get the motor down to a speed where the tube rotation is as slow as possible.
Question by javajunkie1976 | last reply
I was wondering if someone could help solve my problem as follows. I shall make as much detail as possible: I am running 12 (5mm led) in parallel of 3 in series. (So four rows of three leds) The Manufactors spec is Forward max Voltage = 4v Forward max current = 100mA Power Dissipation = 100mW This is all been run off 12V DC supply. So by my calculations (which may be wrong) it would require 1ohm, 1/4W resistors? However with all the above been used the last LED in each series of three has blown. Could anyone explain why or give advice please.
Question by goafer | last reply
I WANT TO KNOW HOW TO CALCULATE THE TOTAL RESISTANCE OF THIS CIRCUIT ! I CAN'T FIGURE OUT WHAT THE RED MARKED RESISTOR PLAYS CAN ANY ONE PLEASE EXPLAIN?
Question by ubdussamad | last reply
So I see a lot of projects with like 60 LEDs of the same type or something like that, and they use a separate resistor for each LED. Why do they do this? Why not just get one resistor and hook it up to ground or VCC? Please explain, thanks!
Question by HavocRC | last reply
Hey. I'm changing all the LEDs in the switches in the car. All is going well except one switch, there is 1mm distance between a circuit board and the LED. The LEDs are 12v no resistors. I'm using ultrabright red LEDs that need resistors. However, I'm sure I've seen circuits that resistors go on the negative and positive leg before the LED. Would this work or would the LED still blow? Thanks.
Topic by Josho | last reply
I'm making diode bridges to have a nice supply of DC. I'm making a high voltage bridge for a 7.5kv nst and a low voltage bridge for regular 120v wall outlet . My high voltage bridge im going to make with several 1N4007 but i read that they should be "shunted" with 10Mohm resistors im not sure what is meant by this. Does it mean resistor, diode, resistor, diode or does it mean diode and resistor, diode and resistor. The pic says it better than i do. Also, do i need resistors for a bridge for 120v bridge?, im going to use the diodes from a fluorescent light power supply.
Question by jaydenr | last reply
I know i need resistors for leds, i know how to calculate what i need, etc. etc. but what im wondering about is why. why arent leds like glowing bulbs, what makes the difference in needing the resistor. also, why cant 1 resistor take care for multiple leds at the same time? please, if ur answering my questions, make it understandable english. im not comfortable enough in the world of science to understand that kinda stuff... (otherwise i wouldnt be asking these questions :D )
Question by godofal | last reply
I found this schematic from Make Magazine and it gave in my eyes a vague description of a certain Resistor. They label it as a variable resistor, but I've narrowed it down to it probably being some sort of knob that turns. I was just wondering if http://www.taydaelectronics.com/servlet/the-1874/47K-Trimmer-Trim-Pot/Detail is the right resistor? Any help would be great! Here is the page for the 'Lie Detector'. http://www.apogeekits.com/lie_detector.htm To be honest this is my first ever schematic into circuit I have ever done, and I have done a lot of research. Hope it goes well.
Question by soapdude | last reply
I know how to calculate resistive losses, but do different types of resistors have different amounts of losses (power in vs power-out, in watts) From my own observations, connecting a 10 ohm resistor across a barrey will cause significant heating in both the resistor and battery, and cause the wires to get warm. All of this is resistive loss, but when I exchange the resistor for a 10k resistor, there is virtually no heating at all. What if I use a 0 ohm resistor (direct short). The only thing getting hot would be the power supply, due to internal resistance. Does this mean higher resistance is less lossy and by definition, more efficient, or is this simply due to the fact that there is less current flow, and less power loss, and efficiency (% of power loss) With an ideal constant current source, will the losses though any resistive load be equal? ( X amount of watts lost/dissipated @ 1A) Is it possible to limit current like a resistor without losses? (I know PWM techniques are more efficient, but I want actual resistance rather than chopping current flow and filtering with an inductor/capacitor RC filter)
Question by -max- | last reply
I just finished soldering a board to flash an IR LED using a 555 timer, and attached it to 9V PP3 battery, and the LED burnt out.The LED was rated at 1.7V 100mA and I was using a 100ohm series resistor. By my reckoning I should have only needed a 73ohm resistor, (9V - 1.7V) / 0.1A = 73ohms, so 100ohm was more than enough.Any ideas?
Topic by evilad | last reply
In the circuit diagram(which I've uploaded),I intent to use a NPN transistor(BC 547) as a relay.The 9 VDC is stepped down to 5 VDC by a LM7805 and should be the trigger to the transistor,completing a circuit which needs the 9 VDC.The Collector is given the common negative of both the voltages and the trigger gets the positive 5VDC.I need a bit help to calculate R1 and R2.I had used two random resistors previously but the Load got powered by the 9 VDC even before the trigger was applied to the transistor.I figured out that the problem might be related to the resistors used. (I haven't included the caps used at the terminals of the regulator in the schematic)
Question by Adarsh_tronix | last reply
Can anyone help me I'm not very good with electrics but I would like to know how to find out what type of resistor I would need to run power from my ps3 power supply to the fan... If I wire it straight it's running way to fast and would like to set it to a lower speed. I have used a 220k potentiometer in the past but dont want to have to adjust it plus they are to bulky is heir a certain kind I should b looking at??
Question by s3xo turbo | last reply
Hello. I bought some Christmas LED replacement bulbs but they have no specs with them. I decided to wire one up. I figured I would go with 1 . 5 volts at 7 1/2 mA. Using a 9 volt battery, I have a 1K ohm resistor. 9 - 1.5 = 7/ .0075. My problem is, when I put my meter on it, the one side of the resistor is showing 9 volts, correct, but the other side is showing 3.5 volts. Shouldn't it only be reading 1.5 volts? What is wrong? *I've had the LED lit up for over 25 minutes so far and it hasnt burned out yet. Thank You. EDIT: I just added a 10K resistor, so now I have 11K (in series), yet I am still getting a reading of 3.5 volts. I'm missing something here. lol I'm also getting a reading of about 9mA with 1K and 11K ohms. I'm lost.
Topic by pennsteve | last reply
Http://img86.imageshack.us/my.php?image=picture433pb4.jpgI ripped this out of a car audio system, i don't know the input volts, or whats what. I use to have it connected to a 3V battery to change a LED from 0 to 3V. Well, i pulled it out, wires gone. resolder wires as you can see. problem: WHAT IS WHAT?! All i know by the labels is it says RED on the lowest rail. the rest, dont know. If someone can please help me id love that. It switches on/off as well as changes volts. so i need 4 wires connected.
Topic by Killa-X | last reply