### resistors and watts

I know how to use ohms law to calculate what size resistor I need but what I really need to know is how to tell/calculate what watt rating I need to use whether it be 1/4, 1/2, 1/8, 1,10 and so on.

Topic by pattyshaw   |  last reply

### convert to watt?

I am thinking of buying a acid battery. Its specification says that it is a 12 volt one and it's AHC@20 is 200. Can anybody calculate the watt output. I am not sure but AHC stands for Ampere hour capacity. Thanks RajibAzam

Question by RajibA   |  last reply

### 5 watt LED

Hello, forgive me if this is not the right blog to post i was just not sure where to ask. i have a 5w led that came off a flash light i would like to either do my own flash light or install it in my house as a light, how can i do that and what do i need to power it, the only thing i know about the flash light is that is a 5 watt. also i dont know much about leds so if you guys can help that will be really cool. thanks

Topic by Nelson_Yepez   |  last reply

### 100 watt LEDs

Hi there I am wanting to drive 5 100 watt Cool white LEDs at half power total of 250 watts. Each LED spec is 32-34 volts DC @ 3.5 amps. Ideally I would like to drive from one power supply. or 2 at most, any advice would be welcome. please email me at tn21@live.co.uk

Topic by JohnT10   |  last reply

### conversion ratio of kva : watts?

Question by lokoboy   |  last reply

### 4000 watts @ 220 volt?

How can i (step by step) generate 4000 watts and 220volt from a car alternator ?

Question by nicobotha12345   |  last reply

### If i reduce the voltage coming into something with a resistor, will it reduce wattage as well? if so, how much?

Question by fishing4life13   |  last reply

### I have 2 questions (in details) First: a way to measure Watts? Second: Rotating Camera Mount?

so as I said I have 2 questions. First: Is there a device that can measure the watts of an appliance? I just got a hold of a cheap generator (900w normal 1000w peak) and need to find out the wattage of some appliances. (None have stickers/plates on them at all to help me calculate it.) Second: Can anyone direct me to an instructable on motorized rotating camera mounts or anywhere that can show me how to build one? I want to be able to watch the sky from inside we get some nice weather here but hard to watch it from inside hehe.

Question by BlueSuneLIght   |  last reply

### LED help!!

Hello, forgive me if this is not the right blog to post i was just not sure where to ask. i have a 5w led that came off a flash light i would like to either do my on flash light or install it in my house as a light, how can i do that and what do i need to power it, the only thing i know about the flash light is that is a 5 watt. also i dont know much about leds so if you guys can help that will be really cool. thanks

Topic by Nelson_Yepez   |  last reply

### what would happen if resistors of lower wattage are connected to a power supply of higher wattage?

The power supply i'm using for a circuit has a higher power rating than a bunch of resistors i bought. What would happen if they are all wired together in one circuit?

Question by hmddeen   |  last reply

### What is the maximum power (ohms/watts) available from a headphone port?

I happen to have a set of 8 ohm speakers (which say 20 watt max) and wondered about using them so I can listen to my mp3 player in the shower.

Question by Andale_The_Great   |  last reply

### How do watts, watt-hours, etc. relate to voltage, current, and resistance? Answered

I've worked with 12v and 5v a fair amount, and I've got a good understanding of Ohms law, series and parallel circuits, etc. But, I get a little sketchy when it comes to wattage ratings, KWHs, etc. and their relation to (now) my electric bill, (but hopefully soon to my off-grid, alternate power sources/power banks) and what I can handle as far as power consumption, etc. Any theory, links, book suggestions, practical examples, etc. will be GREATLY appreciated. Thanks so much in advance, everyone!

Question by sykotik   |  last reply

### How do I measure Wattage? Answered

Alright, in my cold fusion set up I need to measure the watts going in and the watts going out.  How can I do that?

Question by Kalrag   |  last reply

### 5000 watts power inverter

5000 watts power inverter with the circuit diagram using SG3524

Question by santos4eva   |  last reply

I know watts equal amps times volts. But why? What is the benefit? Hypothetically, I wanted charge a laptop with some batteries ( instead of with the charger cord). The charger cord says 65 watts or some such, but what does that tell me?  Is 65 watts the same as 13 volts at 5 amps? Or 13 amps with 5 volts? what voltage/amperage would I need to charge this laptop? Thanks!

Question by nepheron   |  last reply

### wattage

I was out buying the parts for the free electricity from telephone port in wall, but the resistors have no wattage posted. The man at the electronics store said he needs the wattage for the correct resistors.

Topic by 3l3ctr1cman   |  last reply

I have a transformer with 13v input can i give it 240v without it melting and can you please tell me the math of transformers  am new and any information helps

Question by mohamed amin   |  last reply

### How can I combine my 400watt and 750watt AC/DC inverters to get 1000+ wattage out of them?

I have both inverters and they both still work.  Instead of going to buy an expensive 1000 plus watt inverter I'm looking for a simple way to just combine the two I have to handle the wattage I need them for.  I go camping a lot and I like having hot coffee in the mornings, so I need an inverter to handle a coffee pot.  I could stoke the fire and put a perculator over it or crank up the generator and plug in the pot but I'm a simple guy who likes simply plugging in the coffee pot to my truck!

Question by WildBill76   |  last reply

### Testing a 3 watt LED? Answered

I recently purchased 13- 3 watt LED's. I'm trying to establish a high out-put LED light. I also purchased a LED Driver Transformer 48 Watt 120 Volt to 12v DC 4 Amp. First I would like to test each LED using the same divider. I'm thinking that if I create a voltage divider two 330 ohms to limit the current and reduce the voltage to about 6 volts that would allow me to test with the driver that I purchased. Secondly, will this driver be enough to drive all my LED's and would I have to reduce the voltage down too since it appears to push out enough wattage and amperage for the total number LED's I'm putting together? I'm building my circuit based on this video. http://www.youtube.com/watch?v=4qYZahe2s5o&NR;=1 Link to website data of 3 Watt LED. http://ledsupply.com/indusstar-1up.php Assistance would be greatly appreciated. Regards,

Question by lancruz   |  last reply

### Need a 30 watt "LASER"

Looking for an inexpensive laser cutting/engraving system. I will be taking it apart and  customizing it to fit onto another machine.  Currently, we have a rotating blade to cut sheets of material, but this set-up causes many issues.  A contact free solution would be best.  So I want to mount the laser carriage above the cutting area; the rest of the laser parts will be contained in a metal cabinet under the machine.  The laser would need to be able to travel 12-16 inches in 1-2 seconds and cut through 1-5 mil paper/poly material. I have a fair amount of experience with lasers, I have know how to sight them in and understand the technology.  We currently have 45, 100 and 400 watt galvo head lasers, as well as a 90 watt XY laser set-up. So, what website would you direct me to, to purchase an inexpensive laser system?

Topic by benjaminleebates   |  last reply

### 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   |  last reply

### KWH , Watt giving me a headache...

Morning Guys Need a bit of help with the maths. Hoping to run a fridge on a inverter / battery / solar panel. If it has a energy consumption of 0.43 KWH, I think it would be about 43 watts not sure here. What size battery and solar panel would I need? Big Love Chris

Question by Handyperson1   |  last reply

### Do Amps matter?!?

Ok, I need a charger for my motorolla two way radios. I have the dock, only need a DC power supply. on one of them it states "18Volts DC +/- 20%, 15.3 watts" .Lets say I get 18VDC 1amp power supply, that's 18W,it means it's an overkill? or 15V 2Amps? As I understand, usually amps don't matter, as the item draws as much as it needs, but since it is a charger.. Cheers for the teh help!

Question by zhgutas   |  last reply

### SSR and a hotplate

Dumb question. Have a heating plate that uses 1100 watts and runs on 120 volts ac. if 1100 watss / 120 volts = more or less 10amps, Could I safely use a 10 amp rated ssr aka solid state relay or use something higher.

Topic by Computothought   |  last reply

### What is a 4 pin power connector that can handle a lot of current? Answered

For a project powering red, blue, and green LEDs, with a common positive, I am hoping to power around 250 LEDs with around 5 amps. This means that each wire needs to be able to handle 5 amps of current at 12 volts (or 60 Watts), with the other three wires acting as grounds. I've looked at PC peripheral molex connectors, capable of handling around 5-8 amps however that is over all four wires. I need something stronger, most molex connectors use 20 gauge wire (which handles 1.5 amps), while the national electrical code suggests a 14 gauge wire to handle 5.9 Amps. It doesn't matter to me what the connector is supposed to be used for, if it's an audio plug, power plug, or whatever, this project will be very jerry-rigged. I would greatly appreciate any suggestions for a suitable plug.

Question by QuackMasterDan   |  last reply

### What is a 1/4 watt resistor? Answered

Alright, So I know the basics about resistors and what-not, but as I was buying beginner supplies, I noticed there were resistors in OHMs and Watts, What's the difference between the two? And like, can the unit Watt be transfered into OHMs? And which one would I use when my general area of working would be around basic LED work and noob stuff like that xD?

Question by E D E N   |  last reply

### 20 watt PA amp transformers.

Today I bought a 20 watt PA amp at a garage sale for 5\$, and there were 2 big transformers in there. Any ideas of what I could make?

Topic by mrbubl3s   |  last reply

### MXDL 3 watt joule thief? Answered

Can anybody make sense of the joule thief inside a MXDL 3 watt luxeon torch? I can post a rough picture of it if needed.

Question by .Unknown.   |  last reply

### 100 watt sub woofer amp

I'm looking for or to make a 100 watt amp, I can't seem to find any. If you know where i can find one online or a schematic to build one please let me know! Also is it possible to resist or lower the amps from an amplifier or will I have to specifically get a 30 watt amp for the mid range speaker. I am attempting an "led music box on steroids" project hahaha.... basically what I am going to do is make a clear plastic box and put leds and speakers and a 6" sub in it. Kinda bored and looking for a fun project and this came to mind. I'm open to any suggestions to make it better or ideas on how to power the speakers. Thank you in advance! The sub woofer I'm looking to power http://www.electronix.com/100-watt-woofer-speaker-ohm-p-13521.html and the mid range speaker http://www.electronix.com/30-watt-midrange-speaker-p-13507.html Might think about putting a tweeter in too

Topic by zcm87   |  last reply

### Is it true? 2 watt led has 1 diode, and 3 watt led 2 diodes? Answered

Is it true? 2 watt led has 1 diode, and 3 watt led 2 diodes? or can a 3 watt 700ma have both?

Question by MistaMasta   |  last reply

### 8 Watt Guitar Amp Help

I've been fartin around with electric and acoustic guitars for about the past 5 years. Only now am i getting decent (by no means good, but better, i guess...). I've been wanting to make a small amp with a small speaker for some time now.I saw this circuit the other day. Its VERY simple.http://www.aaroncake.net/circuits/amp.aspIt says to reverse the values of R1 and R3 for use as a guitar amp. there's some other stuff too. I was going to see if i could pick the stuff up at radioshack tomorrow, and maybe make it an after-work project for the week. Maybe cut up some wood and make a nice box for it. 1)Do you think these parts would be available at radioshack? and what do i need to look for if i cant find the exact IC? 2)Any special soldering tips? 3)What kind of pot do i need to add, and where, for a volume knob?4)Is there any extra things you think that needs to be added?5)Are those triangle things grounds? as in 12v negative? And what about the other wire from the guitar? 6)Also, what ohmage speaker do i need to use? What am i looking for in a speaker?7)Will 8 AA batteries do the job?8)Do i need to add like a fuse or something somewhere? Going straight into the IC...i dont know. If anyone knows of simpler or better designs, let me know. I seem to really [insert proper four-letter word here] up electronic things. I think thats all the questions i have here. To respond you can just go like..1)i think that....like that. Hopefully that will make it easier to answer all my ignorant questions.Thank you!Jason(sorry if i seem like a a\$\$ here. Its 1:35am, I've been looking this stuff up for two hours, and i dont feel like i got any further....)And since i dont have a suitable picture, have yourself a look at my LEGO steam engine: (after the third try of trying to post the video with unsuccessful results, i realized that i was posting the embed code int eh URL place...need....sleep....)

Topic by John Smith   |  last reply

### Designing a Solar powered sign. Need help determining how many watt solar panel? Answered

I am trying to run a sign off of solar power. The sign has 40 LED modules. Each module has 3 individual leds. The specs for each module are 12v, consumes .7 watts, and 50 mA. Multiplying watts and amps by the number of modules you get 28 watts and 2 amps. I'm looking at solar panels from walmart and they come in 10,15,20,30 ,60 watt panels. If the sign is ran 12 hours a night(6pm-6am), That means 28 watts x 12 hours = 336 watts used per night. If the solar panel gets 8 hours of sunlight to charge(8am-4pm), that means 336 watts/ 8 hours means I need a 42 watt solar panel? Also, how big of a battery do I need? 2 amps x 12 hours = 24 AmpHour battery? EDIT: I'm going to use a 12V timer relay so I can run the LEDs from 6-11 pm and 5-7 am. This decreases the on time to 7 hours and 196 watts. With 8 hours of sunlight, that means 25 watt charge. Also 2 amps x 7 hours = 14 AmpHour battery.

Question by tallemertes   |  last reply

### how many watts does my rock tumbler use?

I just bought a rock tumbler off ebay. the brand name is "chicago power tools". its a basic 3lb capasity rock tumbler/ lapidary rotary tool. now, because i live in australia, i have a problem, my power outlets produce 240v , and the rock tumbler can only take 120v, and so when i pluged it into a power adaptor (us-aus), the transformer gegan to work, then overheated and produced smoke, fortunately it still works . now, i am going to go and buy a stepdown transformer and have learnt that if the device is using more than 90% of what the transformer supplies, the transformer will overheat or break or something. now, on my tumbler, and everywhere a description for it is put, it mentions nothing on wattage consumption, and so i am asking , how many watts will it use so i may accordingly select a stepdown transformer for it.

Question by oldmanbeefjerky   |  last reply

Watts = amps times volts, correct? So if I had a laptop that charged with a 60 watt power supply, could I: -Charge it with 10 amps at 6 volts? (that is the same as 60 watts) -Charge it with 6 amps at 10 volts? (that is ALSO the same as 60 watts) -Charge it with 5 amps at 12 volts? (that is ALSO the same as 60 watts) -ect... Watts is just how much 'energy' passes a single point every second (or whatever), so it doesn't matter how you get the watts, watts is still watts? I'm still trying to grasp the whole concept of watts, so yours answers are infinitely appreciated!!!

Question by nepheron   |  last reply

### Is it reasonable to convert energy to power over time?

I have recently been talking with another person on instructables about converting 33 megajoules into a standard comparable electric unit, watts.  Now the formula for joules just so happens to be watts times seconds, but he still thinks this is wrong.  He says I can't just assume time.  Now I can assume any amount of power for any amount of time I wan't to as long as it adds up to 33,000,000 joules in the end right.  So if I wan't to consume one watt every second, then I have to set the amount of time as 33,000,000 seconds or roughly 9,166.7 hours.  This all seems fine to me right, because one watt for 33,000,000 seconds is equivalent to 33 megajoules. Now I originally didn't understand all of this so I just fumbled around and ended up converting to hp and got roughly 12, which is very close for being a rounded off number.  It comes out over one hour to equal just over 32 megajoules.   I can't seem to understand what the problem is, the DEFINITION OF ENERGY/WORK IS POWER *(OR OVER THE PERIOD OF) TIME Is there really such flawed logic here that "joules could be converted to cubic meters?"

Question by jj.inc   |  last reply

### can you answer a few questions i have on SLA batteries? Answered

1.As you can see in the diagram i have eight 4.5 AH SLA batteries joined together to make four 12 volt 9 AH batteries. how would i incorporate my bigger 7 AH 6 volt SLA into this? 2.Is my math correct that i did up in the corner? 3.Does an amp an hour storage in a battery mean it will supply one amp for one hour? 4.If so and my math is correct i would have 516 watts of power for one hour stored in these batteries?

Question by harry88   |  last reply

### How do you use a solar panel to light a 10w light bulb at night? And what kind of a solar panel would I need?

I want to make my own solar panel (a small one) for a school project, but I also want it to be useful for after the project as well. I need a small light to light something outside, but at night (because, obviously, I can see during the day). So apparently you need a battery to store the energy during the day, and a charge controller is really important. I've found a lot of useful sites and videos (and instructables) that show how to make solar panels, and a few that show how to connect the solar panel directly to a light bulb, but I can't seem to find anything that clearly explains the battery and charge controller part. Please note that I know nothing about the technology of solar panels, watts, volts, etc., and have never taken apart or made even a simple electronic device of any sort. The most experience I had with this stuff was when I made a small circuit with a light bulb, battery, and alligator clips sometime around the sixth grade, but I have no idea how all that works and all the numbers that you need to keep in mind (I did learn the basics a couple years back, but I've forgotten everything), so when I find brief explanations online that say you need a battery, charge controller, and you need to somehow calculate the correct capacity and voltage, I'm totally lost. Can someone please help me out and explain? Or at least provide a useful link or something? I've scoured the Internet, trust me. Unfortunately, I was unable to find anything clear or something in a "How-to" format. Also, I'm flexible on the 10w thing. A 10w light bulb was just the lowest I could find and I thought the lower the better. So what kind of a battery and solar panel (how many watts/volts, etc) would I need? Low cost is ideal.

### Resistor power rating increase in parallel?

Let's say I need to have a resistor in a circuit rated for 10 Watts. If I had two resistors rated for 5 W, could I wire them in parallel to make the equivalent power rating 10 W? I know my resistance will be different but I'm not sure how the power rating would differ.

Question by ishmal1103   |  last reply

### Car stereo puts out much less power than speakers need?

I'm fairly new to car audio. I just put in a Pioneer MVH-370BT headunit into my car, and while it is working great right now, it is evident that I'm going to need new speakers soon because the factory ones are not very good. I was looking at either the Kicker 40CS54 2-way speakers or the Kicker 41DSC54 2-way speakers because many people have recommended these speakers. The problem is on the website, the pioneer headunit only says it puts out 14 watts RMS power while the speakers say that they use up to 75 watt RMS. I'm trying to avoid getting an amp because I'm going to be putting the speakers in myself and i don't want to have to drill a hole through the firewall. So, my question is what will happen if I run the speakers with the 14 watt RMS receiver? Will it just not play very loud? Will the sound be very distorted if I try to play it loud? Is this bad for the speakers? Thanks!

Question by JoeG4   |  last reply

### 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   |  last reply

### rectify electricity before transformer?

Can you rectify the US mains (120vac, 60hz) as it, and used the pulsed dc to feed into a transformer and get a dc voltage out of the transformer? I'm asking this because it would be much much more efficient for high current situations. Here's my specific situation:I want to build a capacitive spot welder and a capacitive discharge cutter in an all in one device. To charge the enormous capacitor rapidly (1.5 farads in my case), I need a very high current power supply. I'm using a modified microwave transformer that was rated at 1kw, and it is now modified so that it outputs 12 volts AC at around 80 amps (probably less because of losses). This must be rectified to charge the capacitor.Assuming a perfect transformer (for arguement), it would have:120volt, 8.34 amp input12volt, 83.34 amp outputthe following is with full bridge rectifiers, assumed voltage drop: 1.4vIf the power was rectified before the primary, the loss on the bridge rectifier would be: 11.67 wattsIf the power was rectified after the secondary, the loss on the bridge rectifier would be: 116 wattshuge differenceso once again, the final question is: Does rectified input of a transformer = rectified output? Does the 120hz pulsed dc (as opposed 60hz ac) matter? Could this setup charge a capacitor?

Question by guyfrom7up   |  last reply

### How can you tell or measure how many watts a resistor can handle.? Answered

Let's say I salvage a few resistors from an old electronic, how can I tell if it's a 1/8 watt or 1/4 watt etc? I have a multimeter if need be.

Question by surlistyc   |  last reply

Well i was thinking, 5mm LED's take about 1/10 of a watt, correct?  and from this calculator found out Cree 5mm led's are .806 lumen's. i assume they are 1 tenth of a watt. well, my calculator states they are 8 lumen's per watt (if i could run them at a watt.)  i figure they are 1/10 of a watt because because this 500 led light makes takes about 50W as in the video and led's give less than a lumen of light. so far, it seems leds just last long and emit blueish light. is incandescent light better? with 20 lumens per watt from halogen?

Question by -max-   |  last reply

### Why are some 7-watt night light bulbs much brighter than other 7-watt bulbs?

Question by brab   |  last reply

### how does a kill a watt work exactly?

Hey everyone i was just wondering how watt meters work. most of you already know the Kill-A-Watt. this is basically what i am looking to understand. Kill-A-Watt may get a little complicated as a device, but i would like to know what the basic idea is behind the meter.is there an instructable on how to make your own simple meter? any help is greatly appreciated. thanks

Question by mohissa   |  last reply

### stereo plus amp is how many watts?

For instance if my stereo is 20w rms and I put an amp of 45w rms will I have 65w rms?

Question by RichardB263   |  last reply

### How to power 8ohm 1 watt speakers?

I'm working on a project for school that consists of a wireless speaker. They will be mono speakers.  I have an 8 ohm 1 watt round speaker. I would like to power these.  I've read on lm386 and tsa7052 ic to do this. For the wireless I was going to use dexdex's instructible bluetooth headset hack I'd like to power it all with a 9volt or a lithium hacked out of old product. Are there any things i should know for the amplifier in relation to the type of speaker i will be using?  Will i be able to power the bluetooth headset and the amplifier from the 9v? thanks for your time!

Question by williamhaze   |  last reply

### 50 watt electric and bass guitar amp?

Good day to all, i'm new to this site hope i can gain more knowledge in electronics here, since i have been doing alot of programming lately.. i am planning to build my first higher wattage amplifier for both guitar and bass, i already have built smokey amp and its other cousins like the ruby amp and some guitar effects. i will build the two amps simultaneously and put  it in one housing.. the speakers will be separated and also the circuits and all.. does any one have schematics for this kind of amplifiers?? it should bea solid state amplifier, because its hard to find tubes here and also it is expensive.. correct me if i'm wrong 1. "instrument >>>preamp>>>poweramp>>>>speaker" ? 2. is it possible for example to use a smokey amp as the preamp section and connect it to a 50 watt power amp? 3. what type of speaker should i use for the guitar and for the bass? should it be a woofer or sub-woofer? coz i dont have a clue on speakers.. tanx in advance..

Question by VAustin89   |  last reply

### I think i have flawed results and I need somebody's opinion. Answered

I have been working on a small generator and i need a dynamo to generate the electricity so I did a little experiment to find out what motor i had was most efficient at generating power so I know what I should use a in the upcoming project. On each motor which was spun at the same speed by my Dremel all the results were ordinary except for one motor which surprised me with its super high reading. Upon seeing this I thought it might be my multimeter going dead and giving me false readings i changed out my multimeter and got the same exact readings for the motor. Is this because it really can produce 120 watts or am i doing something wrong? My formula for finding watts was V*A=W the motor was producing around 8.5 amps at 14 volts. I'm pretty sure the formula is correct as well. Help would be appreciated greatly thanks.      Harry

Question by harry88   |  last reply