Ohm's law?

So, i have a broken soldering iron, and i want to fix itcan someone =smart= calculate the required resistance of wire at 120v aci don't care about the amperage, as long as its under 2 ampsplease give me a range of resistance, i don't like to trip fuses, (my parents hate that!)

Topic by Sandisk1duo 10 years ago  |  last reply 10 years ago

Ohms on a Speaker VS Ohms on an Amp? Answered

I am looking fixing up my cars stereo and I am not sure about how to pair a sub with an amp.  I am using crutchfield.com.  I found some speaker I subs I would like to get, they are 12" kickers and there is an 8 ohm version and a 4 ohm version.  They are rated for 50 - 150 watts.  Now my guess was to buy a 2 channel amp (I wan't two subs) and use it.  The one I am looking at is 125 watts @ 4 ohms X 2 speakers.  I read that you may want to buy an over-rated amp so you don't blow it by trying to drive excessive speakers.  Is this an acceptable combination. 

Question by jj.inc 6 years ago  |  last reply 3 years ago

Ohm's Law watch...

Has anyone seen this?  "Ohm's Law Watch" For those of us that have difficulties with formulae, this looks like it might be handy :-)

Topic by Goodhart 8 years ago  |  last reply 4 years ago

is ohm's law applicable in transformer or not?

In a step up transformer we step up the votage and reduce the current but ohm"S law say V=IR or voltage is directly proportional to current then howz it possible ?

Question by 9 years ago  |  last reply 4 years ago

How can I power something that is ment to be plugged into a wall (12v dc) to something i can power through usb?

Livid Instruments produces the OHM which is a great device,but for increased mobiliity I would like to have it be usb power if that is at all possible. Their new model is usb powered but it's not up for pre-sales yet and i have a feeling it will be a bit more then their current model on sale for $699.here is the link to the OHMhttp://www.lividinstruments.com/hardware_ohm.php

Question by erick2687 10 years ago  |  last reply 10 years ago


Hi all,  I got two 3-way-speakers (8ohm) from my uncle, but I don't have an amplifier. I wanted to use these speakers as audio-monitors for my pc. Is it possible to make an (easy) amplifier-circuit for this use? And do I need one or two circuits (1 circuit-1 speaker / 1 circuit-2 speakers)? Thanks for helping me out! Arnout PS: Sorry if my english isn't that good - I'm from Belgium ;)

Topic by arnoutdejans 7 years ago  |  last reply 7 years ago

I need help correcting impediance on speakers.

Here's some background on what I'm dealing with: I run a haunted house in Nashville TN called Devil's Dungeon. We have a sound system that is controlled from a rack with 6 2 channel power amps. 4 of them are 260W by 2 channel and 2 are 500W by 2 channel. I have 10 cd players running to a 24 channel mixing console and the way I control each room on a separate channel is by using the post-fader sends (yeah, it's a really old peavey, but the new ones don't have post -fader sends per channel) as a line out per channel. IE: i run a line directly from the post-fader send per channel to the power amp's input. Here's my problem: There are more speakers than there are outputs, and the speakers are placed where they are needed in a particular scene. It is a large building and it would be highly laborious to try and correct the impedance by putting extra speakers and with series/parallel combinations and as we are already open this season and I don't want to re-engineer the entire system. Is there any way to correct the impedance with some kind of variable resistor? Everything I've seen so far that could handle the power is pretty large, and if possible, I'd like to put it in a relatively small project box. Can this be done with a potentiometer? I only need to correct it by a few ohms and the only POT's I've seen have been in K increments .

Topic by Scurge 10 years ago  |  last reply 10 years ago

can I run a 1 ohm stable amp with 4ohm subs wired to 2 ohms ?

I have a Hifonics Zeus 3216 and 2 sundown sa12 d4s. the amp is a 1ohm stable so can I use it to push them safely?

Question by NathanH163 1 year ago  |  last reply 1 year ago

What Ohm resistor do i need to turn 9volts into 5volts?

Question by dilydan 10 years ago  |  last reply 10 years ago

How many ohms is 1Kohm? Answered

Question by coolpizzadude 9 years ago  |  last reply 8 years ago

4 ohm subwoofer problem... Answered

I have received a 4 ohm subwoofer, that seems to be "stuck" , I don't know how I could fix this. I also need a way to test the subwoofer because I do not have an amp. Thanks

Question by squirt8500 10 years ago  |  last reply 10 years ago

help with leds and ohm resistors?

Im trying to make custom headphones from scratch, inspired by the daftpunk helmet of guy, and i want an led lightshow on my headphones. ive been researching how to do this, but ive heard that having an m3 or any kind of audio player wouldnt be enough power to support the leds? ive also heard that if you solder the leds straight to the wiring of the headphones if can create a short, and that placing the led on a circuit chip would help. however i know nothing about ohm resistors or circuit boards. i was thinking i could use an ohm to amplify the power from the audio player to support the leds if its even possible, and running wire through the headstrap to  solder the circuitboards with the leds on them. i need help. alot. any input is wanted, thanks! (ps: - does anybody know how much power i need to run a single blue led?)

Question by gabrielguy 7 years ago  |  last reply 7 years ago

How to convert ohms to volts?

I want to make a taser and the circuit i have needs an audio transfomer 1k to 200k but i cant find it coz im in india can anyone please tell me which power transformer am i supposed to use thanks in advance jumper1111(not my real name of course)

Question by jumper1111 6 years ago  |  last reply 6 years ago

Some help with Ohms and resistance? Answered

Hey guys, i know there are a lot of you guys out there that deal with electrical dealings and such, and im doing a science project, dealing with electrolysis, so i decided to compare two electrolytes to see which has a lower resistance, and to see which would be more efficient therefore. SO, the only problem is, i have no multimeter, voltmeter, or anything close to it, and i don't know anybody 'round her that does..So im asking you, could you help me with seeing the resistance of- * water (tap water) * water with Epsom Salts  * and water with Baking soda powder (either will work, but i would prefer powder, as baking soda is said to cause chlorine gas, and what not..whichever you have works) If you could take a picture of yourself using the multimeter, that would be stellar, thats all for now,  come on guys, i know you know this stuff, and i just cant figure it out, counting on you :)  

Question by fwjs28 9 years ago  |  last reply 9 years ago

Will and 8 ohm Speaker work where a 32 ohm Speaker is needed? Answered

I am asking because I bought this sound generator kit that has a 32 ohm speaker with it. But what I ultimately want to do with it is actually have a line out in order to hook up to external amps. The speaker is connected to a 15 ohm resister that is connected to pin 3 of a 555 IC on one side and the other side of the speaker is connected to a 10uf capacitor. The kit is the C4722 10 Note Sound Synthesizer from Chaney Electronics the circuit is similar to one i built and made an instructable for. On that one it has similar parts but the speaker is connected to one 10uf capacitor and negative. Do you think if I omitted the 15 ohm resistor I would be able to connect an 8ohm speaker or a line out? I haven't tried anything yet. And I haven't started to build my box yet since I don't know if am going to have to use the speaker that came with it or if I can modify it they way I desire.

Question by powerman666 6 years ago  |  last reply 6 years ago

how can you determine if an audio amplifier circuit is for 4 ohm or 8 ohm speaker?

Most audio amplifiers are labelled "use with 8 ohm speaker" and a like. what if there is no label? how can you determine what speaker to be used? speaker impedance well suited for an amplifier circuit depends on what electrical component?

Question by codestroy7 7 years ago  |  last reply 7 years ago

how many ohm resistor do i need to get 5v from a 9v battery? Answered

Hello i am writing up an instructable on setting up a wireless receiver , however i requires both 5v and 9v output, and the whole point of it is that it is simple and cheap, so i need to know, how many ohm resistor do i need to step down 9v down to 5v? i do not wish to use a 5v regulator unless one can be bought for less than $2, or else the instructable will cost too much.

Question by oldmanbeefjerky 7 years ago  |  last reply 7 years ago

Mismatching speaker wattage?

Hey guys, So I've recently gotten into making DIY speaker systems, but I'm having trouble understanding the whole ordeal about wattage and ohms. I have four speakers I managed to salvage from some old speaker systems that I got from an old thrift shop. I have two 15W 4ohm speakers, a 20W 8ohm speaker and a 2W 8ohm speaker (but I don't think I'll find a use for that one, I'm not sure) I plan on buying the Lepai LP-2020A+ amplifier, it's a two channel amp and delivers 20W/ch with impedance of 4-8ohms. What I want to know is what set up would be best with what I have? Can I run the two 4 ohm speakers on 1 channel even though they would draw 30W of power? I'm a bit new at this, and my understanding is still a bit unclear so if anyone could please explain, I would very much appreciate it :) Thank you

Question by VoicesOnAir 5 years ago  |  last reply 5 years ago

I want do ipad controller, but there have have somtehing wrong?

I want do ipad controller, but there have have somtehing wrong after i saw   https://www.instructables.com/id/Simple-Ipod-Controller/ and i use ipod touch to test , there have have somtehing wrong . when i connect podbreakout my ipod touch, after took off it have sound normally. and i want to  ask   how to use podbreakout charging iPad? not charging all the time. I want use button to turn on/off charging iPad. who can help me? Here is my new  red circle is 500 ohm , blue A contro Play/Pause, blue B contro Next music , blue C contro volUp , blue d contro volDown

Question by 0928885086 7 years ago

Can any one tell me 0.218k ohms or 0.220k ohms = how many ohms and the color code of the resistor? Answered

Can any one tell me what is the color code for 0.220k or 0.218k resistor

Question by Soumojit 3 years ago  |  last reply 3 years ago

Would I be able to put one 100 ohm 1/4 watt resistor in place of two 50 ohm 1/4 watt resistors? Answered

The attached picture explains my question a little better. Thank you guys!

Question by Jakester98 4 years ago  |  last reply 4 years ago

does a 10k ohm potenimeter have the same connections as in weezoh's trimmer?

I got this: http://www.radioshack.com/product/index.jsp?productId=2062308 and i need to know if the 2 closer pins need to be touching or the middle and the far one.

Question by ipwnuall2 9 years ago  |  last reply 9 years ago

I have two speakers of 4 Ohms. Can it works fine with ONE amplifier KEMO m032 ? Answered

I have two speakers of 4 Ohms. Can it works fine with ONE amplifier KEMO m032 ?

Question by lemecool49 9 years ago  |  last reply 9 years ago

can i use a 220 ohms resistor in place of a 240 ohms resistor?

Question by hillbillyboy_316 9 years ago  |  last reply 9 years ago

what is the best ohm rateing for running speakers out of a mp3 player with no amp or any other equipment.

i just bought a new zune HD player today and i dont want to risk  damageing it  unfortunatly i dont have any other speakers besides some that i had laying around which are rageing from 3.2 ohm (somehow) to 6 ohm to 8 ohm which would be the best the 3.2 are what im useing now they suck but they are outloud if somebody could design a simple amp with -volume control -3 inputs -cabible to run differant ohms of speakers safely  -left and right channels -cabible of running a large numbers of speakers thank you

Question by fastcar123 8 years ago  |  last reply 8 years ago

How do I go about connecting speakers with different wattage & ohms to the same source?

I have a bunch of old speakers that I wish to use for a project but I'm unsure if they will all work together. I have: 4 x 60W 10Ω 2 x 20W 6Ω 2 x 25W 6Ω 2 x 5W 16Ω with DC in & component input (out of old computer monitor base) Will I be able to connect all the speakers to the circuit board with the power & input? What will I need to do or obtain to make them work together?

Question by apple_juicy 8 years ago  |  last reply 1 year ago

How to calculate resistance?

Ok, I need to figure out how to know what resistor to use. I know how to read a reistor, I just dont know how to use one. Say I hook an LED, a 9 volt battery, and a resistor in a circuit. I want to get the voltage down to 3 volts. How would I go about calculating a resistor reading? What ohm resistor would I use? How do I know?

Question by Adum24 8 years ago  |  last reply 8 years ago

What do 1/4, 1/2, 1 or 5 watts values mean on a resistor? Answered

I know that this is such a basic question but what do those values mean when selecting a resistor? 

Question by blkhawk 7 years ago  |  last reply 2 years ago

Choosing a relay?

I was about to make a project, I was all set then I realized that I hadn't chosen a relay yet. (Circuit http://2.bp.blogspot.com/-IdzxyPF4WYE/UfBCWb0deoI/AAAAAAAADZs/1-eYB2ufQCA/s1600/Clap+Switch.jpg) As I didn't know anything about relays or AC voltage I started studying. At the end I came to this. As I will be controlling lamps with either incandescent bulbs or led bulbs and phone chargers a 5v, 220v 1a relay will be enough, since Bulb 0.27 A, LED 100 MiliAmps and Phone Charger a few watts. So the question is that are my calculations right and what else should I know about relays e.g operating voltage resistance and other stuff. Oh and is there a 0.5a relay and if there is will that be enough? Thanks in advance. -Prickly Potato 

Question by SA-DIY 3 years ago  |  last reply 3 years ago

Laser ohm resistor project question

So I am doing a big modifiction of Kipkay's burning laser project. I am making it into a gun, and the only resistor I can find is a 4.7. Will that do? I have a 5mw module like his, and a 250mw 650nm laser diode. Also I am going to use two C-batteries, so its 12volts total. 

Topic by thedonquixotic 8 years ago  |  last reply 8 years ago

I need a 18 Ohm resistor

Does any one have a 18 Ohm resistor that they could stick in an envelope and send to me because eighteen bucks is a little steep for A resistor. oh ,and radioshack doesn't carry them either :( ~Matt

Topic by iman 10 years ago  |  last reply 3 years ago

What is the best ohm resistor for LEDs?

What is the best ohm resistor to use with a standard led to ensure that it won't burn out? Is it 330? Thanks!

Topic by sciguy77 9 years ago  |  last reply 6 years ago

Is a 1 ohm resistor really needed? Answered

I will be making an LED display. After calculating using the online calculator, I am told that I will need 1 ohm resistors for my series of LEDs. I am thinking that 1 ohm is really not a lot and if I can skip it. Thanks!!

Question by stella_7277 9 years ago  |  last reply 9 years ago

dual 3 ohm amplifier circuit.

I have two 3 ohm stereo speakers, which i wish to connect to a computer. What is the ic chip that i should use for best quality? Please help me with a circuit!

Question by rohinraj 7 years ago  |  last reply 7 years ago

Finding the wattage rating of resistors and variable resistors? Answered

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 7 years ago  |  last reply 7 years ago

Is there a simple audio amplifier circuit I can use with an 8 Ohm speaker?? Answered

Is there a simple audio amplifier circuit I can use with an 8 Ohm speaker? If you know of any, or have any, could you please post a link in your answer? Thanks! Also, I'm not very good at reading circuit diagrams, so if its easy to read, bonus points!

Question by Zem 9 years ago  |  last reply 9 years ago

Infinity divided by 0?

Does infinity divided by zero theoretically equal any number other than 0 or infinity? I heard something about ohm's law applied to a circuit with an ideal voltage source (which is only theoretically possible) and having the terminals shorted out and at 0 ohms, resulting in the current going up to infinity? 

Question by .Unknown. 8 years ago  |  last reply 7 years ago

Component Amperage Rating

Hi! I was browsing through an electronics retailer website looking for components to buy (particularly a LED) and i was wondering what the amperage rating of each component meant Does it mean: 1. the current flow across this component shouldn't be more than the amperage rating as it will cause damage? 2. or the current flow across this component should be equal to this amperage rating? please help me I'm really confused :(

Topic by La Tour Rouge 9 years ago  |  last reply 9 years ago

Need help understanding LED drivers

Ok, I'm a newb to electronics and i'm having trouble figuring something out. Inspired by Dan's instructable, I decided to try and build my own headlamp. However, I've run into a problem. I have no idea what LED driver to use. I'm planning on using three of these bulbs, at 3.7v each and a max wattage of 4. I know if I rig them in series, the LED driver needs to be at least 11.1V, but my question is does the wattage of the driver need to be 12? Or should I rig the bulbs in parallel from my power source, and have one of each of these rigged to them individiually? Also, advice on whether it would be preferable to rig them in series or parallel would be great. Any help would be greatly appreciated. Thanks in advance

Topic by The Insomniac 6 years ago  |  last reply 6 years ago

Unabel to find any Audio Transformers (the little cheap ones) 500 ohm to 8 ohm

The only one's listed on eBay are high end (fairly to extravagantly high priced) transformers. I just need a little 4 legged 500 ohm to 8 ohm audio transformer. All my catalogs seem to offer little help. No need for the C/T like the one pictured....

Topic by Goodhart 10 years ago  |  last reply 6 years ago

Audio amplifier 4ohm and speakers are 6ohm, does it matter that the ohm number is different on the speaker??

Hi, I want to make a portable speaker as a project, whilst gathering all my components together i realised that my speakers specs had 6ohm and  3watts. Where as my audio amplifier specs are 3 watts and 4ohm and 8ohm (listed on website). does the ohm levels on the audio amplifier have to match the speaker?? Please keep reply simple as i am new to this, thanks :)

Question by RookieSean 4 years ago  |  last reply 4 years ago

Is it possible to calculate what is the voltage need for and LED that is in a christmas light set?

It says that its 120 volt and 0,5 A but there are 2 resitors on each end of the set of light and there are a couple more solder to some LED(like 2-3..), but these resistors are not all the same...So is it possible to calculate to power require to light an LED in my set without burning it ? Thank you!?

Question by Patented 10 years ago  |  last reply 10 years ago

How can I identify the power rating (wattage) of my scavenged resistors? Answered

I am currently making a mini guitar amplifier, from this instructable, https://www.instructables.com/id/Make-a-Sweet-Portable-Guitar-Amp/, and i need a 1kΩ resistor. I have accumulated a few components by de-soldering and scavenging parts from old, and broken electronic devices. When I found out i needed a 1kΩ resistor, I looked up the ring code for that value and scanned over my broken electronic circuit boards to see if i could find a match. Which i did, but i do not know how many watts the resistor is rated at. The resistor in question is no more than 3mm in length. I know that quite a lot of resistors are more like 5mm in length. Can you tell from the physical size what the resistor I have is?(I will include a couple of pictures)

Question by mdog93 8 years ago  |  last reply 8 years ago

is this led array right?

+18V + -|>|- -|>|- -|>|- -|>|- -|>|- -/\/\/\- + R = 22 ohms + -|>|- -|>|- -|>|- -|>|- -|>|- -/\/\/\- + R = 22 ohms + -|>|- -|>|- -|>|- -|>|- -|>|- -/\/\/\- + R = 22 ohms + -|>|- -|>|- -|>|- -|>|- -|>|- -/\/\/\- + R = 22 ohms + -|>|- -|>|- -|>|- -|>|- -|>|- -/\/\/\- + R = 22 ohms this lay out has the resistor on the negative side is this right many thanks for helping karl

Question by kturner6 5 years ago  |  last reply 5 years ago

how many ohms does this resistor have in the led


Topic by dereklevine158 5 years ago  |  last reply 5 years ago

building a complex amp simple cheap

I need to build a complex amp for cheap and as simple as possible i need it to -run speakers at differant ohms safely -have left and right channels -have little distortion -have 3 inputs -have outputs that can run at least 6 speakers off of each channel -have volume control -off/'on switch -portable and have to run of of 9V batteries (as many as it takes) so how can this task be compleated

Topic by fastcar123 8 years ago  |  last reply 8 years ago

Amp for a homemade speaker box with car speakers?

The speakers are almost definitely going to be a pair Sony Xplod XS-R5743's Specs: 4-Ohm 190W Peak 35W RMS So with these power specs, what should the power ratings for the amp be? I considered building an amp, and unless there is something I've missed, it looks cheaper just to buy a car amp and just make it run from a wall outlet after a transformer. Especially when every amp that I see being built is a low power 1W LM386. Please, let me know the best method for amplifying the audio to these speakers and the required power. Thanks

Question by manouttatime 8 years ago  |  last reply 8 years ago

Using a Benchtop PSU to heat wires?

I modified a 300W ATX power supply that I got for $1 the other day to use as a benchtop power source, much the same way the people who have posted Instructables for this have done.  I want to do some experimenting heating up wires, but I don't want to harm the PSU.  I believe it has built-in short circuit protection, but I want to be safe anyways.  I think that if I put in a high-wattage resistor in parallel with the heating wire, that might save the PSU.  If I did this, what value resistor (ballpark range) would I need so that power would flow through the wire until it heated up too much (thus increasing resistance across it), causing the power to go through the resistor instead?

Question by Radioactive_Legos 8 years ago  |  last reply 8 years ago

how many ohms does it take to resist one volt?

How many?

Question by oweng4000 10 years ago  |  last reply 10 years ago