What audio potentiometer to use?

I am building small Bluetooth speakers for Christmas presents. I am using a 5v 2*3w Bluetooth Amplifier with a PAM8403 chip. I am wanting to add a dual potentiometer to control the output of the speaker, not the power going into the amplifier. I am going to use a logarithmic potentiometer but I cannot figure out the resistance I am needing. I have found A5k and A10k resistors, would these work for the project? Is there an equation or guide that would help me out?

Question by MitchellD30   |  last reply


is there any way i can make lava? Answered

In my earth science class if i bring in a cup of lava i get an automatic 100 for my grade for the entire year PLEASE HELP MEEE

Question by scotchtape110   |  last reply


connect usb cable to usb keyboard

I have a usb keyboard. somehow the usb cable is disconnected from the keyboard. I opened the keyboard. USB cable has 4 wires (1 blue, 1 orange, 1 white and 1 green). The circuit board has code like C, V, D and G. Now which one is for which wire? out of C,V,D and G which is for ground, which is for VCC and which is for Data+ and data- the color code of USB cable I know. But cannot understand which wire to connect which code (C,V,D,G) of circuit board?

Question by jpsarkar   |  last reply


Photoelectric sensors sending a text

What I'd like to achieve: Multiple motion sensors that will send a text message to my phone when any have been triggered. Once I get the hang of that, I'd like for it to specify a zone (ex: Zone 1 - Front of house, Zone 2 - Back of house, etc...)First things first, I'd like to just understand what components would be needed to complete this in the lightest way possible and for someone who is very new to any of this. I have found sensors, but I need them to send a signal somehow so that something like an alarm.com can send a text to my phone.I'm open to this being a learning experience, but am definitely at a beginner level.Here are two sensors I'm looking at:http://www.seco-larm.com/E-931-S35RRQhttps://www.amazon.com/Infrared-Waterproof-Photoel...Any guidance will be appreciated. Thanks!

Question by hazenbenjamin   |  last reply


where to get wine corks? Answered

I need wine corks for a project i'm working on, and have not been able to find them. I have tried asking a friend who is a caterer, no luck. I have asked other people, but no one has any. please write any suggestions that you have. I have no money, so it would be best if they where free.

Question by Mr. tony stark   |  last reply


How to make exact size svg fiels for eleksCam software?

I bought this DIY Chinese laser machine. After some trials. I got it all fixed and yes it cut and engraved. They gave me 2 softwares. One is Engraver Master which i found useless as non of my dxf files show up properly. it's always warped. Then I tried EleksMaster. This software is great. But there is a major problem. It cuts only texts and engraves. But when i insert a new image and ask it to cut outlines, the image does not load up. I even checked this instructable and asked help. So to cut I found SVG files work. But there I encountered another problem. I cannot resize the images. All SVG files opened through PicCarve Appears way larger. Sizing is very important for me. Sometimes the size is way larger than my cutting area. It's really frustrating and annoying. It's more than a month now, and I'm still unable to cut custom cake toppers cause I can't seem to get a single software right for me. Someone said to try laseraxe but that does not connect to my laser. I have no clue why. So please help me so that i can cut the exact size of an image using PicCarve . Ther is a place that says input G Code. I'm not sure what that is. Currently I'm reserching that too. But if Anyone knows...Plese Please help.Thanks

Question by shazni   |  last reply


Building an ultrasonic soldering station ?

I have some strage projects coming up that will require me to solder things together that usually don't really like this.In my past job this was quite easy as we had an ultrasonic soldering bath and several ultrasonic soldering stations.Well, the access to those is gone :(At first I thought "How hard can it be to build one?"Not really too hard for a half decent soldering bath but a lot harder for a soldering iron...The soldering stations we used operated in the range of 50-60kHz.Commonly available transducers and their drivers however you find for 28 and 40kHz.Finding small ones in the range of 10 to 20W is also not easy.I can deal with a soldering iron that ends up in the size of a 500W wood burning iron as long as the tip is replacable.But what are the frequencies really required to solder for example on ceramic, titanium or lab grade glass?Does anyone have experience with doing this on lower frequencies than what the professional stations use?Last but not least:Is there any software available (preferably free or as an online tool) to simulate the quite long feed horn that is required with a soldering tip?Going with 1/4 wavelenghts is logical but how could I get the info on the actual shape required without simulating it first?I was thinking of using a heater cartridge like used for the hotend on a 3D printer to heat the tip.However, tests on my ultrasonic actuator showed the entire thing disintegrates within a few minutes, at least the filler and "glue" used to hold it all together.Would a free standing heating coil around the tip work?Heat transfer would be a pain and losses high, but should be possible?In case you wonder why: I just don't ave the thausands of dollars at hand required to buy one of these soldering stations....

Question by Downunder35m   |  last reply


ntc thermistor for auto rpm pc fans

I have 470 ohm thermistors and i want to auto control my pc fans ie when the temperature is low the fans are off or low speed,when temperature go high the fans rpm follow up.is there a scematic how to do a pcb?

Question by napoleonis   |  last reply


How do I make an actual power-generating minaturized Arc Reactor?

What materials do I need? What designs do I use? Any chemicals or magnets? How much power do you think it holds?

Question by awesomo3000   |  last reply


How do I fix my car stereo ground wire? Answered

I installed my new stereo and it won't work. The fix-it hotline told me to touch the ground wire to the negative batt. terminal, and the red and yellow wires to the positive terminal. The stereo worked, meaning the ground wire coming from the dash is probably bad.?

Question by robjob1918   |  last reply


How to connect google map app to arduino ?

How may I connect google map app to arduino so if i press a button connected to arduino it will turn on the google map app assistant. Then the instructions of google map will bass to speaker connected to arduino.

Question by B-D-M 


Please help with qi coils! A chance to inform my ignorance!

Hi! I am working on a small wirelessly powered project and am having considerable trouble with finding a qi coil that is small enough and also has a charging circuit. Specs:1" square at most5v at 500maferrite shieldcharging circuit just as smallMy questions:1) Can I use any prebuilt coil and swap the circuit from a larger one? I feel like there is a reason I can't!2) Recommendations of specific coils?Thank you so much!

Question by Moonman0922   |  last reply


Headphone Jack mini portable speaker

Would I be able to successfully take an OEM phone's loudspeaker and connect it to a 3.5mm Male headphone Jack Plug for use with an mp3 player, like a mini portable speaker? All the options that I have run across are too big for what I'm looking for. I also don't need it to be super loud.

Question by HanzonM   |  last reply


How to recondition 12v lead acid cell battery for a Riding Lawn mower

Battery has never held a full charge very long since it was new, Needs to be recharged a couple of times during the season, only 3 years old. Can this battery be recondition to hold a proper charge or should I replace it. This is on a john deer riding mower.

Question by johnhoening   |  last reply


Need a 1.5-volt(in-voltage) sun-sensing dawn/dust on/off pigtail widget... Help?

Need a 1.5-volt(in-voltage) sun-sensing dawn/dust on/off pigtail widget... Help?

Question by CCinPA 


How powerful of a motor do you need to run an alternator? Answered

From questions I have read and step by step’s I have read a question came to my mind. How powerful of a motor do you need to run an alternator? I checked the Delco Remy alternator series from 10SI in 37 Amps, to the 40SI durable brushless model, in 240, 275, and 300 Amps. All their performance charts show rpm’s at the alternator not the motor. The pulley on the crankshaft is considerably larger than the pulley on the alternator, giving you more rpm’s at the alternator than at the motor. All their performance charts show rpm’s from 1200 to 8000 rpm’s. All their performance charts show at 3000 rpm’s you get 13/16ths of max power. The last 5000 rpm’s only gaining 3/16ths of power. The thing is none of the performance charts say the horsepower to drive the alternator. I decided to approach the problem from a different direction Typical alternator efficiencies are in the 54%-60% range. Brushless alternator efficiencies are in the 60% 70% range. A typical 12v 60 Amp alternator produces 720 watts at 55% efficiency. It needs just 1310 watts to drive it or a little under two horsepower at 1492 watts. This does not account for mechanical efficiency of connecting the alternator to the motor. With this in mind a three horsepower motor should drive a 12v 60 Amp alternator. This is just an educated guess but I would like a horsepower chart. 720 watts would do well at charging a battery bank while you sleep; however I could not run my microwave and charge batteries at the same time.

Question by Josehf Murchison   |  last reply


Best magnet size to coil size ratio for an electromagnetic generator?

What is the best magnet (neodymium - disk shape) size to copper coil size ratio for optimal electron production per one break/pass of flux lines across coil at a 1/2" distance? For instance, if magnet is 2" diameter what is best inner diameter for copper coil? Best number of windings? Best gauge wire? what are the best specs for optimal electron production before you reach "over kill". I know some things are variable like core material and magnet grade. I'm looking for an all things being equal kind of scenario. Also what would be the best thickness of magnet at 2" diameter? If anyone could point me in the direction of any existing tables or ratio information on this subject it would be appreciated. Thank you.

Question by BishopKnight   |  last reply


How to Build combat suit? What materials are needed for bulletproofing? Cheapest materials that can be used safely? Answered

I have some designs I'm mainly looking for recommendations and references for the materials needed. Also need some advice on kinetic energy replacement for high drops and jumps. Frame material needs to be light weight and strong. Outer armor will be interchangeable. Weapons are still in development more posted later. Also all metals must be nonferrous.

Question by DaVinciStein   |  last reply


Can anyone explain RMS vs average? (particularly the math portion, and the intuition)? Answered

My current understanding of RMS (Root Mean Square) is that it is the equivalent AC voltage/current/power necessary to drive a resistive load the same around as the DC voltage/current/power counterpart. However, I am a bit confused about the math involved that can apply to all waveform. I know the conversation factor for sine waves is 1/ sqrt(2), and that the conversion factor for square waves is 1:1 (no difference) On my graphing calculator, if I take the square root of the definite integral (from 0 to pi, integrating the x ) of the sin(x)^2, then divide that by the period, pi, I get the correct answer. However, what is the purpose of the squaring, then square-rooting? is it purely to perform a absolute value mathematically? If so, then I should be able to simply integrate the absolute value of the sine, and divide the result the the period the integration was performed over. If it period it was performed over was 0-pi, then there is no need to even take the absolute value! But this method returnees 0.636619... not 0.707106... Intuitively, it makes much more sense to me to somehow take the mean average of the continues |sin(x)| function. I know this can be done with desecrate numbers (a sequence, perhaps) and by taking the sum of them, and dividing it by the number of 'elements.' (series's, anyone?). I would expect this average is what determined the average power used by a load. EDIT: Wikipedia states that "The true RMS value is actually proportional to the square-root of the average of the square of the curve, and not to the average of the absolute value of the curve." So it appears I have just proven this. But Why???? What is so special about the squaring and rooting??? Please don't bombard me with heavy math, as I am not familiar with calculus, and have barely passed pre-calculus (The class was supposed to touch upon series and sequences, and integrals, derivatives, limits, etc. but due to show days and delays, the class only covered trigonometry --the bare essentials--). I do not yet fully understand single-variable integrals, let alone multi-variable calculus. I really just want a better intuition of RMS. More than likely, there is probably some confusion I have about integrals in general, and how to calculate them on-paper.

Question by -max-   |  last reply


Computer turns on but then monitor goes to sleep. Can aneone tell me what's wrong? Answered

I found this out at the curb with someone's garbage. It turns on and the dvd rom drive opens and closes but when i plug a monitor into it the monitor goes to sleep. Its not a very old computer and i would like to get it working. Can anyone help me fix it or telling what is wrong with it? The model number is T3410 desktop pc its made by emachines and runs on Windows XP

Question by LetsExplodeSomething   |  last reply


To repair Razer Kraken Pro V2 headphone jack

Good morning, I'm a new member of this family:)I'm trying to replace broken jack4 Pole connections / colour of wires on broken headphone jack on Razer Kraken Pro V2. the old one has (Red, Green, yellow and white with shield to solder on new plug.Hopefully, someone provide the correct connection locations with colour of wiresI appreciate your time and efforts.Thanks in advancePardeep

Question by sira123   |  last reply




How to calculate the total time a battery can operate light?

Hi,I am willing to just use solar panels to recharge my batteries and then to power my garden lights.  What I need is how do I know if my battery will be able to power my lights for atleast 24 hours.  How do I choose the solar panels to be able to charge the batteries. IF I know how to calculate for atleast one light and battery that should be enough for me to calculate for my whole system. Thanks

Question by Chamburn   |  last reply


high output metal to metal thermoelectric generator?

I saw this on youtube: http://www.youtube.com/watch?v=gNND2pxvxgU He has like 16 wires in this setup, and it generates enough power to light an LED... how much power could you get with some more wires? Say 1600? Does the thickness of the wire matter? Sorry to make you watch the youtube video, if you don't want to, here's what's going on. This guy, Nyle, uses copper wire lengths which he has heated at one end and cooled to coat each end of each length with copper oxide. He then bends the wire so that two ends of copper oxide-coated wire are touching and another end is about 3 inches from the junction. By heating the loose end, and touching one wire to another, he's able to generate enough current to light an LED... pretty neat!

Question by jmlidea   |  last reply


help me out to get 12V output for battery charging from this UPS transformer (600VA)(240Vac)?

The following images . I'm not able to get 12V output, but is supposed to provide 12V+ to charge the battery(12V). how to find the input to ac 240v  and output of 12volt to charge a battery  plz help me i will tell u primary section 3  wire and colour  one is  (red) ,middle one brown and last one blue and secondary section there is is 6 wires first is yellow wire ,blue wire , third is green wire  4th is brown wire , 5th is red wire and last is black wire plz help me find input 230v wires in primary and find 12volt for battery charging  wires

Question by BrahmadevT   |  last reply


what kind of filter would I need to filter out solder fumes? Answered

Would i need a HEPA filter or could i just make a little thing that fit's on a box fan and holds a bunch of activated charcoal. i live in the great up north so i can't open my windows to let the smoke out and doing it in the shop is out of the question because it's so drafty it can't hold heat at all. I'd like to be able to set up a soldering station in my room but the problem with that is the smoke being too noxious, it'd freak my parents out. do they make actual specific filters that can hold onto all the smoke? or is it more along the lines of getting mostly everything but never quite being able to get it all?

Question by waldosan   |  last reply


Korg em1 customize

Hi i would like customize my korg em1 and add a single output to every part of Drum and synth. Can you help me? Tank you. Sorry for my english

Question by Tirec95 


Guide on making a audio surveillance only device maybe using raspberry pi?

There are tons of video camera surveillance projects using the raspberry pi, but I'm looking for audio only.Ideally, it could be controlled by network, Should be able to save collected recordings with time stamp to attached storage device,A bonus if multiple mics could be attached to it,I checked around and couldn't find a project that dealt with audio only and I apologize if I missed it.

Question by techlearner2020   |  last reply


Battery run bluetooth class d amp - help me fix the noise problem.

Hello, I am designing a small bluetooth battery powered portable speaker enclosure/boombox. At the core of this design is a cctv li-ion battery that has 12v and 5v USB output ports. Its a great start to a boombox, or at least I thought it was. From that battery, I am powering two things. A parts express Stereo Bluetooth Module, (running on the 5v USB) and a Lepai 2020 tripath amp, running on the 12v Perfect you say. Thats what I said. Plug it all together.... huge huge huge garbage noise, with digital clicks and beeps. All three components work fine on their own. The amp plays cleanly with bluetooth modules that have internal lithium batteries, the bluetooth module sends a clean signal to amps not sharing a power source. I had a proficient audio repair man attempt to filter out the noise with resistors placed in numerous places, but it only slightly lessened the noise. Unfortunately I didn't document what he tried. I have attached a photo of the setup (without the speaker attached) I noted one thing... that if one was to connect the bluetooth using the rca input to the amp, if you only touched the internal rod to the inside of the female rca jack on the amp, keeping the outer shielding free from the amp, it would clearly make the noise, with no change in the noise when you pushed the plug all the way on, touching the outer shielding. That seems of interest. Yes? Let me know if I can clarify any more of this. Any help would be most appreciated! Thanks, Tor

Question by torclausen   |  last reply


Quick question regarding car stereos and speakers? Answered

Hi, so I was thinking of buying a new stereo (receiver) for my '97 Mitsubishi Mirage DE, along with some speakers (mine are crap). When I go online (such as autozone.com), I run into some confusing descriptions. The receivers are usually rated as 200W for four channels (it'll then say like 50W x 4), whereas some of the speakers say "100 Watts Peak 50". I think I only have two speakers on the interior of the car (driver and passenger). Does this mean I can buy speakers with a higher wattage? I'm guessing the 50W x 4/ 200W over four channels means that it's 200W of power/audio for four interior speakers. Does having less speakers give me a greater allowance for speaker power, or will less speakers put more strain on the ones that I install (200W getting split over two channels instead of four)? For reference, here is the receiver I'm looking at, along with a pair of speakers I found that fits the "Peak 50": http://www.autozone.com/autozone/accessories/Dual-Electronics-Corp-200-Watts-AM-FM-CD-MP3-WMA-receiver/_/N-2628?counter=6&itemIdentifier;=219598_0_0_ http://www.autozone.com/autozone/accessories/Dual-Electronics-Corp-6-1-2-in-100-Watts-Peak-50-Watts-RMS-2-way-speaker/_/N-2626Z1z114tr?counter=3&itemIdentifier;=219603_0_0_&viewAll;=true

Question by Hadokendude   |  last reply


how can you make your own d/c variable voltage tattoo power supply?

I need it to put out no more than 2 amps. Also can anyone think of a clever household item to use as a footpedal? Thanks.

Question by opiate4themasses   |  last reply


Flc100 magnometer

Hi, can you launched sensor fluxgate flc100 magnetometr with ardunio and conected to pc wiht bleuthos? thack you very much

Question by parisa2000   |  last reply


why won't my parents let me have a cell phone?

Why wont my parents let me have a cell phone that's all i wanna know gosh

Question by craphed   |  last reply


I bought 50W 6Ohm LED Load Resistors for LED Turn Signal Lights and they don't work (2009 impala)

How do I remove them if they're already spliced with my wires? 

Question by josh.plunkett.98   |  last reply


How do i connect old speakers to mobile?

 Ok, so I have a very old speaker surround system (JVC MX-60). It plays only Cassets and cds which we dont use nowadays.However the speakers are huge. The clarity and sound is good enough to listen to heavy metal music. I want to connect these speakers to my mobile. But the thing is, i dont know how to . Now I am a complete noob when it comes to electronics. Based on my knowledge I need to connect these speakers to an amplifier . To do that i need to know the wattage. And I dont Know how to find out. I was going through the main unit(which is destroyed) and it mentioned that the speaker impedance is 6 ohms. Wattage is product of voltage and current. How do I find that? Multimeter perhaps? here is a few things that I want to mention -The speakers have two wires(black and red). Nothing is mentioned on the speakers regarding its power. voltage etC. - I dont have the manual. The device must be older than me. - i have uploaded the pics of the back side of the main unit http://imgur.com/qNBKWst Thanks!!

Question by rockz1991   |  last reply


Wireless DPDT Switch?

How can I make a wireless DPDT Switch for my robot. I'll be using a receiver and transmitter system but have no idea how to control the DPDT Switch using that.

Question by Shantam Sridev 


How to send and receive/read 2 Values LoRa Arduino

Hey, I wanna build a car with Arduino, LoRa and more stuff. But I have a Problem, I need to send 2 Values(one for the Servo, wich turns it right/left and the second is for the motor. Both are controlled by the Servo library) at the same time and when I receive them, the arduino needs to seperate them, and I don't know how to send them right or how to seperate the values. Please help me.

Question by Sergey K 


MT3608 nixie boost

Hello, i am trying to make nixie dc-dc boost from 12v to 100-200V using mt3608 and external mosfet, And my mt3608 won't to generate frequency

Question by kuba.prochazka 


Mt3608 nixie

Hello, i'm trying to use mt3608 as dc-dc boost for nixie 12v to 100-200V and mt3608 look like it doesn't switchingplease help

Question by kuba.prochazka 


Newbie question about DC motor (sorry...a real newbie)

Ive got a dc motor with this type of plugs. How do i connect this to any power source?? what do i have to buy??

Question by WG7   |  last reply


Why is my electro magnet switching on and off!

I've recently built an electromagnet with a DC power supply off 5v 4a but when I turn it on it goes on and off . I'v checked this by downloading a sensor on my phone and surely enough every second the magnetic field goes higher than my phone's range and then returns to normal can you please explain why and how to keep a constant field

Question by charlie30122004   |  last reply


How do i permanently deleted files from my PC?

I wanted to sell my PC but before this i wanted to make sure that my files has permanently deleted from the D partition of my PC. As i was using the D partition for saving my files.

Question by BobT97   |  last reply


Hacking a Liftmaster solar gate controller system

I have a solar powered gate, using a liftmaster system. The main control box cannot have a power input above 12 dc at 30 watts. I need to be able to control the power input to about 25 watts. Due to the environment in which the system was installed, I had to use solar panels and batteries that have a higher output than 30 watts. How can I keep the volts to about 12 volt and keep the watts under 30? I tried to google adjustable amp regulators, and the answers are not clear. How can I find an adjustable amp regulator for my specific needs?

Question by charliemmann1975   |  last reply


Where to get piezo igniters?

I have several lighters that I still like, either for their design or intended purpose. But over the years some failed to produce proper sparks with the piezo. For some I could salvage replacements from cheap lighters but not so much for the longer ones - the type to get your bbq or oven going. Here the wire from the igniter is in ne long piece going all the way from the piezo, through the long neck to the flame outlet. As the wires in those piezo igniters are aluminium it is next to impossible to attach a longer wire as usually there is no room for crimped connections and the isolation is a problem too. I also have one particular lighter that uses a slightly longer and thicker piezo igniter, the common ones don't work here as they are too short. Adding more support underneath is a no go as the shorter ones have less travel when activated. Last but not least is one lighter that requires a piezo with not just the little metal cap at the end but with a full metal body for the stationary part. The lighter in question does not work with standard types even if I add a little metal strip to make proper contact. Problem is simply put that like this the standard ones arch over and no spark comes out of the wire. So big question: Is there any supplier or Ebay shop where one could actuall see the various types of piezo igniters and order them in small or single quantities? So far I already struggled to find a source for the crappy standard ones and the only one I found wanted to charge $ 2.95 US per igniter plus postage. Sounded a bit greedy to me considering I can buy a complete lighter with it for around one single buck...

Question by Downunder35m   |  last reply


My Hydrochloric acid and Hydrogen peroxide etchant goes red without any copper in it. How come?

I recently tried making acid cupric chloride etchant; however, my batch always goes a darkish red colour as soon as i mix the two together even when i haven't added any copper. I've been using 3% hydrogen peroxide from a pharmacist and 30% HCl From Bunnings. All the stuff was fresh and in dark plastic bottles. The container i put it into is plastic. It still etches but it's nearly impossible to see if the copper is etched away without pulling it out. Can anyone tell me what's in the mixture that's making it red and how i can correct it. Thanks

Question by Lost in Translation   |  last reply


My laptop won't connect to our wireless router?but other computers will? Answered

So a few days ago my computer disconnected from our wireless router which im used to this happening so i just let it go i figured it'll connect again just like before...and now a week later it still doesnt connect. So far i have tryed doing a system restore, updated my wireless card drivers, and have done an automatic update from windows. Still doesn't connect to it at all so im lost..any ideas as to what is wrong or what i should do? im running windows 7 intel i7 and a intel wifi link 5100(i believe thats what it is?) and if you need more info let me know.

Question by tubanator-2.0   |  last reply


movie ideas anyone??

Hi I'm a filmmaker (i work for Stop Motion Pictures) and am really looking for movie ideas because right now I have nothing! I have movie making block. Any idea I choose to use you will be credited. It will probably not be made in a while I'm working on getting my camera and tools. Please share any ideas! Even stupid ones!

Question by amakerguy   |  last reply


corrupted rar file? Answered

Hi, I have a rar of which WinRAR says that the CRC is wrong, and the file is corrupted. I allready tried to "keep broken files" when I extract, and I allready tried to repair the file. It doesn't works. What can I do to extract .rar archive? Thanks in advance.

Question by altenabaste   |  last reply


Why is my electro magnet switching on and off?

I've recently built an electromagnet with a DC power supply off 5v 4a but when I turn it on it goes on and off . I'v checked this by downloading a sensor on my phone and surely enough every second the magnetic field goes higher than my phone's range and then returns to normal can you please explain why and how to keep a constant field

Question by charlie30122004