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


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


3000 watts inverter

Anyone knows how to build or make an inverter? a 3000watts inverter? can u give me the list of parts and picture diagram or schematic diagram? thanks guys

Question by dangzching   |  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


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


Math help needed for converting volts/watts in solar

Here's what I know: Watts (P) = Amps (I) x Volts (E). What I don't know is if I have a solar panel that is rated at 12v, 0.125 mW I can do the above equation to get that my amps are 0.01. Does that sound right? My real Q, is what is the best power battery to store this energy? Should I only use 8 "D" cells? Could I use a 12 v motorcycle battery? If I use Ni-Cd batteries, is the fact that the batteries are rated at 2500 ma make any difference? Is there a website where I can get a good feel for what batteries are good for what type of activity, solar cells, etc? thanx, sam

Topic by wanzie   |  last reply


Home made led light with 5w phone charger watt usage?

I have a led bulb which is 5w and I also have a homemade light bulb powered by a phone charger say also 5w. Question is Am I really saving any energy by using a phone charger unit it states it uses 5w? am I using 5w while is plugged 5w or am I using mAX OF 5W OF IT? DOES IT ALSO use 5w when it is only plugged but not powering my led bulbs . bulbs 5v 1 amp, 50 leds. thanks in advance. Also do you know a way to make a water proof glue at home?

Question by celalboz   |  last reply


Can the wattage of a resistor be greater than used in an Instructable? Answered

I am working on a project that calls for 1/4 watt resistors. I only have 1/2 watt at the moment... Is it OK to use these for this project? Thanks!

Question by ElectroFlex   |  last reply


Can a 500Kohm 2W audio taper pot replace a 500Kohm 1W audio taper pot?

I'm sourcing parts for a Theremin (http://www.therealcharleshobbs.com/keppingertubetheremin/) and the parts list calls for a 500K Ohm 1Watt Audio taper potentiometer. I cant find one rated at 1Watt, but I can find one rated at 2 Watts. Will the 2 Watt option be an acceptable replacement?

Question by smkoberg   |  last reply


Can someone help me with a simple audio amplifier?

I need to build a simple audio amplifier for an mp3 device for my A levels, but i dont know which amplifier to use, i would like the amplifier to have a variable gain of zero to the maximum and i also have 2 0.5 watt 8 ohm speakers. I was going to use the simple amp from here, but i am not sure if i can get the full 1 watt from the speakers using that amplifier. Any help will be appreciated.

Question by COOL_Q   |  last reply


LED Power consumption ?

I'm building a solar powered lighting for a farm, what will be the power consumption for a 10 white led.

Topic by yousaf65   |  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


5000 watts power inverter

5000 watts power inverter with the circuit diagram using SG3524

Question by santos4eva   |  last reply


Please explain WATTS to me! Answered

 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


Tweet a Watt now works with Google Powermeter

The Tweet-a-Watt is a cool hack that was made by Adafruit (Limor Fried and Phillip Torrone). It would tweet your energy usage from one outlet so you could be more aware of how much juice you're pulling through the lines. Now you can connect it with Google's Powermeter and get some nice graphs of your energy usage. Hit the link for more info and get the code to do it yourself. Tweet-a-Watt now works with Google Powermeter!

Topic by fungus amungus 


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


Testing 3 Watt LED's

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, 

Topic by lancruz   |  last reply


LED 3 Watt Testing

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   Assistance would be greatly appreciated.  Regards,

Topic 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


10 Watt LED Circuit

I am a software developer by trade and have little or no experience regarding LED and/or electronic designs. I am hoping someone here can help with a project I am working on using high brightness LEDs. I have studied several 'instructables' and specifically dan's "Circuits for using High Power LED's." My project consists of a few high brightness LEDs that will be placed in a high ceiling room with the brightness controlled by a microcontroller based on the light in the room (time of day, sun in window, etc). The microcontroller will use photocells to determine the brightness in the room and then adjust the LED using PWM pins. The LED is 10 watt and approximately 450 lumens. Attached is a circuit I drew as a starting point and would like help in determining if it will work, I am close or does it need to be trashed. I am not sure what the value for the resistor should be. Below are some calculations but not sure if I am on the right track or not. No need to be kind, I am more interested in getting it right and not losing any 'magic puffs of smoke' from any of the components. Here are the specs: LED IF: 1.6 A Peak Forward Current: 1.7 A Forward Voltage: 8 V LM350 (heavy duty version of LM317 IO_MAX: 4.5 A 1.2 - 25 V adjustable regulator BC337-40 Collection Current - Continuous: 800 mA dc Total Device Dissipation: 625 mW Resistor: 5W or 10W Voltage Amp Ohms Watt 8 1.60 5.0 12.8 8 0.80 10.0 10.0 8 1.10 7.5 8.5 Note: LED and components will have adequate heat sinks.

Topic by desnotes   |  last reply


High Power LEDs

I have 3 10 watt LED emitters to sell (2.9 cm x 2.0 cm x 0.3 cm) Colour temperature is about 6000K I'll ship anywhere in Australia I don't have a good quality camera right now Send me a private message and I'll see what I can do

Topic by .Unknown. 


resistor Q

I'm building an LED circuit and I have the right ohm but the W is 1/2 when 1/4 was calculated out?

Topic by mrshow555   |  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



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   |  last reply


electrical safety question Answered

1) how many 100 watt equivalent bulbs can i safely run into a normal heavier guage orange household extension cord? 2) can it be unsafe to leave the extension cord plugged in and powering the safest number of light bulbs on for days and weeks at a time?

Question by hobbssamuelj   |  last reply


Can I use (two) regular household fans for building an airhockey table?

I´m planning to build an airhockey table. Since the AIR source is from great importance, I would like to know whether I can use (two) regular household fans. If so, how powerful should they be (how many watts)? Thanks in advance

Question by casvandegoor   |  last reply


led driver for a 30w led i dont want to pay the 30 bucks for one, i need to know how to use it without the driver?

Do i need the led driver for a 30w led i dont want to pay the 30 bucks for one, i need to know how to use it without the driver? heres the led http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item;=160418184744

Question by antonbergjr   |  last reply


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   |  last reply


Help upgrading CFL circuit? Want to drive cfl's up to 25w.

Hello I have built this circuit, it can drive cfl's up to 15w, how do i modify it so that it can drive cfl's up to 25w?  I am using D313 for his project as the D882 didn't gave me the results i needed. Using 12v battery. Here is the original instructable link https://www.instructables.com/id/A-simple-low-voltage-inverter-for-fluorescent-lam/?ALLSTEPS (This question is optional) Do u think the transformer i made for this circuit can be used for the famous Jeanna's light (Joule's Thief). If yes then how it would connect on the circuit? I will be making two or three more transformers like this. Do u think it needs modifications for its working like number of turns for the primary, secondary and feedback, different wire gauge?

Topic by Clarkdale44   |  last reply


WickedLasers Unleashes 1w Blue Laser Upon the Masses, or All Your Lightsaber Dreams Have Been Fulfilled

The good folks at Wicked Lasers unveiled their latest handheld high power laser: the Spider III Pro Arctic packs a blistering 445nm, blue, 1W beam that can SET YOU ON FIYAH for a mere $197.97. Wait wasn't the last one like 2 grand? Yup. Go check it out yourself, the website is loading slowly, presumably trampled under cyber foot as loads of people go to drool and purchase theirs. I'll wait. ... Yeah, it is real. Yeah, I want one too. Lasting 2 hours on a single charge, and sporting a scifilicous anodized aircraft aluminum body, this beauty packs quite a punch, apparently it is capable of setting bare flesh on fire almost instantly. Ouch. Now I REALLY want one. Who needs a gun when the tactical laser will make any offender scream and run away?

Topic by KentsOkay   |  last reply


1 watt Frequency Doubled Violet Laser

I want to make a 1 watt violet laser, by using a 1 watt 808 nm laser and channeling the laser through a KTP crystal. Judging from my humble knowledge of second harmonic generation, That should create a 1 watt violet laser beam. Correct?

Topic by Nexoid   |  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


Is it possible to modify this watt dial to work with less current? Answered

I've got a few of these watt dials that I would love to use in a project, however, they will not be reading wattages and will rather be controlled with Arduino. Right now they are set up to read up to 3750 w at 125v, which is much more power than I can source with an Arduino or would be achievable with this project.  The way it is set up is that current goes through the magnetic coil and creates a magnetic field perpendicular, attracting a small magnetic block (slightly visible in the photo). Would simply rewrapping the coil with thinner magnet wire in more coils work?

Question by astroboy907   |  last reply


I am trying to find out why I need a 2 Watt resistor with a 3 Volt 700 milliamp Current LED? Answered

Hello: My name is Charles and I am 51 years old,all of this Computer Technology is all NEW to me as I am OLD SCHOOL if you know what I mean.I have had a Nervous Breakdown due to Stress,and have lost a lot of my Technical Memory.I am trying to pick back up on the Electronics for a pass-time,but things don't seem to make sense like they did before.I wanted to know how I can ask questions I have about the Electronics I am wanting to work on.As of right now,I need to see if someone can explain when using OHM's Law (Power is equal to Voltage of your Input times the Current needed in your Circuit).I have a 3 Watt Red L.E.D. which should run at 2.5-3.0 Volts with a 700 Milliamp Current.If using a 3 Volt supply times .700 would equal a 2.18 Watt Power for the Resistor.That does not sound right to use a 4 Ohm - 2 Watt Resistor for a 3 Volt Input.Is this really right or have I gotten confused somewhere?Thank you very much if you can help me out,Sincerely Charles.

Question by wccolvin   |  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


18Volt 25watt AC to DC power supply.

I have a 18 volt 25 watt power supply I would like to sell. It converts AC to DC and comes with the power cord. I was going to use it to make an adjustable power supply but ended up getting something I liked better. I'm asking for 10 bucks shipped anywhere in the USA. Paypal is what I would like to use for payment. Thanks for looking. Edit: On the board for the psu it says 18 volt but with my volt meter and no load it is showing 19.24.

Topic by r1dd1ck913   |  last reply


How to make a TDA2003 10W amplifier give less than it's rated output? Answered

I need to power a single 4w speaker, but can't get an amp for it, so I need to use the tda2003. Should I decrease the circuits voltage? Or is it not possible?

Question by DangerousTim   |  last reply


Wiring high power LEDs and need some direction.

Hello all, I am currently trying to design a product, we'll simply call it a light, that requires 6, maybe 7 extremely bright LEDs. I'd like to keep it running off a 3v battery. The LEDs I would like to use are made by Cree (XP-E2) or something similar. The specs can be found on this page:  http://www.cree.com/led-components-and-modules/products/xlamp/discrete-directional/~/media/Files/Cree/LED%20Components%20and%20Modules/XLamp/Data%20and%20Binning/XLampXPE2.pdf My question is, will I even be able  to fully power 6 of these things off 3V or even 6V(I'd rather keep it to 3V)? If so, how long can I expect the battery life to be? I've never had any experience with these high power LEDs before, but all of the other SMD LEDS only light to ~40 lumens. I'd really like to make this work, or find a similar alternative. Thanks in advance.

Question by bodezia   |  last reply


I'm making a lamp...

Hello Instructables community! I'd like to make a desk lamp, and I'd like to plug it into a wall. Now here is my dilemma I have, the lamp would have 9 main lights inside glass globes and I'd like to have small little lights (like LEDs) around the outside like little points of light. Now in my experience LEDs aren't typically plugged into the 120V wall socket. I have a friend who's good with electronics who has tossed around LEDs, fiber optics, etc and it's all just mind boggling to me. He's even suggested using some kind of controller to make the small lights twinkle and I have no experience with that kind of thing. I'd appreciate if I could get some input as in what options I have for lighting this lamp. Right now it sounds like a valid idea is to use "super bright" LEDs for the 9 big lights and just regular LEDs for the multiple points of light around it.  I can provide as much additional details as needed. Thank you for any input.

Topic by hzillmer   |  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


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


using 1 watt LEDs with a 4017

I want to build a chaser type light array using a 4017 counter divider circuit, 555 timer and the ever popular 1 watt luxeon LEDs, but I don't think that the 4017, or the 555 can withstand the current that will be going through them. I know in most cases you can simply toss a heatsink on the component and it will be fine, but I don't know if this will work with the ICs. https://www.jameco.com/webapp/wcs/stores/servlet/ProductDisplay?langId=-1&storeId;=10001&catalogId;=10001&productId;=12749Here is the spec sheet for the 4017. Thanks

Topic by John Culbertson   |  last reply


Generating a Couple of Watts Using Urine?

Hello, I recently came across a paper written by a researcher from a Scottish University about generating electricity directly from urine in a fuel cell and I was wondering if a larger version could be built to generate around 2 watts.  The power per square cm is around 1.5mW so even at 1mW I would need 2000 cm-sq so I think it would be easier to build a stack of cells instead of one or 2 large cells. I'd like to attach the paper but it's one which you need to pay for though I got it for free, could a moderator let me know what to do?  It was written by a Shanwen Tao and called 'A Direct Urea Fuel Cell' DOI: 10.1039/b924786f Another idea I had was to use a small PV setup to generate hydrogen from urine and then store the gas so that it can be used in a hydrogen fuel cell.  I've had some difficulty in trying a to find a cheap fuel cell but then I came across this page: http://www.mtmscientific.com/fuelcell.html Are there any really simple ways of building a fuel cell? I'm posting this here to see if anyone can help me come up with a viable design and maybe even build it for me.  I can pay you for your time and effort; though as a student I do have a tight budget to stick to. Any help, advice and ideas will be very much appreciated. Thank-You

Topic by jezym108   |  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