Good voltmeter ICs? Answered

I would like to make a readout for my knob-controlled DC power supply so I don't always have to use the voltmeter with it.   Web search for "LSI DVM" did not produce useful results. What are some good ICs to use for something like that?

Question by 8bit   |  last reply

How do i build a digital voltmeter without using a programmable ic?

i want to build a digital voltmeter having 3 digit display.but i don't want to use a programmable ic. it is possible to build it or there is an alternative device to replace the programmable ic?

Question by niok_sosa   |  last reply

Help finding an LED voltmeter? (or figuring out how to use a 3 wire one for this)

For my coilgun/railgun/whatever project I want to use one of those all In one LED voltmeters, however, all the ones I can find are either 2 wire and just measure the input voltage, or 3 wire, and require a neutral ground. That's where the problem lies. I want to use it to monitor the capacitor bank's charging, which goes up to 250 volts, I'd be fine splitting the voltage and using two meters, but to measure it the negative connection is high voltage positive, which means I can't measure the capacitor bank's charging. Is there an LED volt meter (that's not super expensive) that will accept power from a separate source and has negative and positive connections for measuring voltage? If not, how can I work around this neutral ground problem?

Question by XOIIO   |  last reply

Is it possible to create a voltmeter to test car batteries with an arduino and 3 leds?

I am trying to figure out how to wire an arduino as a voltage meter to test the voltage on car batteries and lead acid batteries in other things. I want to output the readings in 3 different colors leds (green, yellow, red) that correspond to the voltage range. Im a n00b in this field and Id hate to fry any components trying to figure this out without guidance, my main concern is making the voltage and current safe for the arduino, so I need to know any additional components necessary to make this work. I know  I need to implement a voltage divider, etc to bring the voltage to a range the arduino can handle but do not know if the 1/4w resistors I have on hand will suffice. Id appreciate any feedback on how to hook this up and even more so anyone able to provide sample code and/or urls with hints to get this working.

Question by cwbuckner84   |  last reply

Wiring Digital Voltmeter Ammeter Without Shunt

I have this: They say is can it be used up to 10 amps without a shunt, but I can't find wiring diagram. I am trying to wire into 50 watt led light. I know the small red and black go to power source. I am not sure how to connect 3 thick wires( red, black, yellow) without a shunt. I am only trying to meter 1.5 amp circuit.  Here's what I am trying to wire. Thank you

Topic by flatfish   |  last reply

I'm making a voltmeter for household batteries, what resistor values should I use on the input? Answered

So I've made a voltmeter, a basic outline is it has a different amp as the input, this feeds into an ADC DCA feedback system to find the accurate value. It works fine as it is but the purpose of it is to find the voltage of household batteries. I have heard that for this I will need to use large input resistors on the difference amp so that the voltage measured is more accurate when the battery is near depletion or something like that. Is this true? If so could someone explain it to me or send me a link to somewhere that does because everything I've found so far seems to be vague. I link would be great regardless as I need to show evidence of what I've found. Thanks in advance.

Question by TomV48   |  last reply

How can I use an Arduino to record the voltage of an RC circuit??

Complete noob here.  I would like to lay a simple RC circuit out on a breadboard, and use the Arduino's analog input to look at how the voltage changes across the capacitor as the capacitor charges.  I've studied the theory -- I know the graphs and the how to calculate theoretical results, but I want to see real data so I can work with my own numbers.  (I have already used the analog input to measure voltage from sensors so I feel as if I have a decent understanding of what is required for that)  Of course I could go buy a voltmeter, but where's the fun of that?  Thank you in advance for any help.

Question by Slicklines   |  last reply

How do I to put an mA meter and V meter to my 12v 1.7A regulated power supply with loads that start at 1mA up to 15mA?

I have aregulated power supply 120VAC to 12VDC & 1.7A to operate small coreless motors that start rotating at 1-3mA operating up to 13mA and need to add a mAmeter, trim pot, rheostat and fuse. How?

Question by SirDeClare   |  last reply

Modifications to LED Bar Graph Volt Meter for 12volt batteries(and Battery banks) Answered

Hi I found this LED bar graph voltmeter at want to understand how to build this voltmeter.But please read the solorb website page before posting, for more info.1. What is an offset resistor???2. What is a 'span'(see pic notes)2. For 12v operation,short J2 and J5,but what to do to all the other unconnectd 'J 'wires, just join the wires or what?3.To use without the Blue LEDs, just remove the two LEDs or any other connection/shorting is required????4.What is switch S1 used for ???, I do NOT want to manually push switches while the meter is in operation.5.How to stop the blink-LED mode, I want the constant display mode always.6.There is also two arrows shorting two pins on the IC with words 'Adjust for 12v'?????????7.How to calibrate the circuit accurately???PS:- If you want to know more about a larger part of this project,visit

Question by mhkabir   |  last reply

Q: why does a 220v (down-step) regulator output 300v?

Hi, bought this 220v regulator (see photo). strangely enough the volt-meter shows almost 300v on the output (at zero load). otherwise it works fine. any ideas? gracias

Question by la xerra   |  last reply

Fluctuating voltage?

I am trying to build an ammeter using a 100:5A CT and a pic16F716 and display the value using 7segments. However, The voltage I get from the CT after rectifying it using an OPAMP still fluctuates between 4.8 and 5.4 .  I don't understand what is causing it to fluctuate that way. I will attach a picture of the circuit I am working on.

Question by IndiraK2   |  last reply

test a power wupply without a voltmeter

OK so yesterday i got this broken laptop from someone.  I knew the problem was the ac jack ( it would charge if the the jack was proped up in just the right way) but only if I used a power supply that did not come with the computer.  I have never soldered anything in my life but figured what the heck.  I took the laptop apart and located the AC jack.  Since I do not have the cash flow to buy a new AC jack I decided to experiment and just reflow the solder on each post of the jack. Well things went well.....I think.  The problem is this.  When I plug in the power supply the "charge" led comes on for just a second or two and shuts off right away.  But there is further information about this power supply.  It is putting out 3 volts less then the original power supply.  Could this be the cause?  The think the OEM power supply is dead because I have nver been able to get the computer to do anything with that one.  Is there a way I can test this power supply without a volt meter or any other product to plug it into?

Topic by jcaresheets 

Low voltage AC?

How can I make a simple circuit that will produce alternating current using 1.5 to 9v power supply? This is an experiment for using an AC voltmeter - that is, making the needle move.

Question by brandegor   |  last reply

How do i make a coil? Answered

The might sound a bit childish but i want to know about a coil. I am currently making a voltmeter(analog).I need to make a coil for it. I have a magnetic wire(around1.5 meters).Every time I make a coil out of it and supply it with power the battery shorts. I get no responce from the coil(like it does not attracts or repels a magnet or nail).So how do make a correct coil for my voltmeter and how do i know weather it responces.

Question by flyingdutchmen1659   |  last reply

How do I create/buy a 0-9v LED Voltmeter?

I am doing a school science fair project and I need to create/buy a LED Voltmeter. It will be hooked up to a DC motor that is connected to my bike. This DC motor is producing about 0-9v. This LED Voltmeter will be used to display how much power is going to be made.

Question by 7Chris Crash   |  last reply

Arduino 5x9 led display and 0-10V voltmeter. Answered

Arduino Duemilanove ATmega328 I want to make a 5x9 led display that monitors a 0-9.99VDC source for a huge motor. I would like to display up to a hundredth of a volt. I would like to do this all using 1 board. I plan on having it display the 3 digits using the 5x9 led display. Can I do this with the limited pins I have without using a shift register? (I think thats what it is called) Do I have all that I need? I have some knowledge of electronics but am in the learning stage but this project will help me a lot in my everyday life. This will be used to monitor a DC water turbine for my pool. I have: -tons of LEDS -Arduino -tons of resistors

Question by newrev426   |  last reply

How to build a joule thief? Answered

      I'm building a voltaic cell and a joule thief. I searched on some instructables and followed the one on youtube by MAKE:. When I hook up a 9V for a few seconds (To not burn the LED out), it works. However, a AA doesn't work. Not even a brand new one. So, I presume that I haven't wrapped the toroid around enough to create more voltage and lessen the amperage (If that's what joule thieves do)? I posted some pictures below. Also, I'm looking to buy a voltmeter, I'm around basic level and just need to measure if the joule thief is even increasing voltage (For now at least). Here are some cheap ones I'm looking at on amazon: Some of those have autoranging, is this to automatically find the voltage/amperage? Thanks, please reply

Question by knexpert1700   |  last reply

How can i make a 4 to 9v voltmeter using lm3914 and how to compute the resistors?


Question by JmM1   |  last reply

How do I use the LM3914H bargraph voltmeter circuit to switch 2 amp, 12 VDC loads instead of LED's?

I'm thinking either power transistors or relays instead of the LED's, but designing the actual circuit is a little beyond me. I'd actually like to build two of these and use the second to measure DC current of 0 - 20 amps, I'm thinking measuring the voltage drop across a shunt resistor...

Question by stevekrawcheck   |  last reply

Overvolted multimeter?

Hi.  Simple question. (or maybe not) I have a digital multimeter I bought a while ago that I think I accidentally put too much voltage through. The voltmeter function on it is now broken. Whenever it's turned on, it reads "156 VDC" even though no voltage is being applied. (however, when I do apply voltage, the meter does detect it.) All other functions seem to be working correctly, but I'm bummed because the voltmeter is what I use the most. Is there any way to "reset" a multimeter? if not, is there anything I could try to fix it? Thanks in advance.

Question by tylervitale   |  last reply

What to do with this 'mystery machine' to turn it into an sci-fi monitor/screen/prop that's alive? Ideally, stand-alone? Answered

You're looking at a photo of what I came to call the 'mystery machine', as I've no idea what it's real purpose is exactly. I suspect it's an old, big multi- or voltmeter. As I say in the question, I'm looking to turn it into an sci-fi monitor/screen/prop that's 'alive' somehow; continually generating interesting content. What I'm thinking of is replacing the big, central meter with a monitor/screen of somesort. But, what kind? Ideally, this'll be easy to make, stand-alone and cheap.

Question by Hellwolve   |  last reply

How to rewire from a three phase motor to a 240 volt single phase motor.

I am replacing a  40 year old three phase motor with a 240 volt single phase motor. The three wires are all black and not coded in any way. How do I measure with a voltmeter? I assume one wire is neutral, but which one? Thanks.

Question by beachbum2006   |  last reply

Compaq Presario v2000 Laptop Doesn't Turn On?

Hi y'all! I need a little help. I'm trying to fix my uncle's laptop. It is a Compaq Presario v2000 Laptop. It will not turn on or show any lights on the front(e.g charging, power up, ect.). I have tried blowing out the motherboard, removing and inserting the battery, and testing the DC power jack with a voltmeter. Any help will be appreciated! 

Question by joespicnictables   |  last reply

SLA Battery Charging? Answered

Quick question about charging SLA Batteries, I haven't really dealt with battery charging too much in the past.  I have two 12v 5Ah SLA batteries, in series, and I have built an under/over voltage protection circuit for each of them, but while charging I noticed that testing voltages across each battery, they are different, however, as soon as I remove the charger and test them as is, they have the exact same voltage (+/-0.05 volts, they are very close).  Is this just because the charger is hooked up, or should I be worried at all about that? I am charging them to 14.75 volts each, or would like to, they say they should be charged to 14.5 to 15v right on the front of them.  While charging they both climb, but one climbs faster and stops once the voltmeter reads 15.2v across it.  0.2v over the rated value really doesn't seem to be of major concern, I just find it odd the different voltmeter readings across the batteries are different while the charger is connected and identical when its not.  Does it have something to do with charging them in series?  I did read that you really can't measure batteries while charging, you have to disconnect the charger first, but any insight would be appreciated.

Question by Electric Spectre1   |  last reply

LED Strip connected to car 12v port and isn't lighting up?

So i bought an LED strip which was rated at 12V, i connected it to the wall and they lit up, i then got a car charger which was 12V and wired it up, and they don't light up. The car charger itself has its indicator LED glowing and i checked with a voltmeter that it was supplying the 12V. I cannot seem to figure out for the life of me why they aren't lighting up? Any ideas?

Question by marcelrees   |  last reply

What is a good schematic for a multimeter with an attiny85v and some 7 segment leds?

I want to make a multimeter out of an attiny85v, and some 7segment leds for a 12volt power supply that I made, I would like it to measure from 0.0V to 12.0 volts, with an accuracy of .1 volts. Anyone know any good circuits? EDIT: This is what I am looking for, except the author has not included any code

Question by Michael_Bell   |  last reply

Problem with my variable regualted dc power supply.

I have a used variable voltage regulated power supply that does not work ; when i turn it on, the Volt meter tops, and if I switch to ammeter, it shows 0amp, if i plug a voltmeter on the female banana plugs there's no juice... I've checked the fuse, it is not damaged. i've also checked to potentiometer with my ohm-meter looks like it's working normally. I don't know what is wrong with it... Do anyone have any idea ?

Topic by lordofthedonuts   |  last reply

what does a #131 error mean on an Msntv 2 receiver?

Recently I picked up an Msntv 2 at a local goodwill, and when I took it home and tried to power it up, nothing happened. When I opened it up, I saw that two capacitors, both 470uf 16v low esr, had blown. After ordering the caps on ebay and waiting two weeks, they finally arrived. Today I attempted to replace the capacitors with my 40 watt soldering iron, which turned out to be quite a challenge, so I guess i need a more powerfull one in the future. I thought that I had totally destroyed the board connections on all four holes for both the capacitors by the time I had finished soldering, but nevertheless I plugged it in and this time it powered on but went to a green screen that said there was a problem with my receiver and gave me the error code #131. Because it powers on now, I kn ow that at least one of the capacitors works. I have a couiple of questions now to help determine my next move. First, can i check the capacitors by simply checking for voltage with a voltmeter? second, What does an error code 131 even mean? Third, could the error be because I dont have the msntv service? any help would be appreciated! Edit: I just checked the capacitors with a voltmeter, and they had a voltage on them so i dont think that that is the problem. Could it be a problem with the compact flash card where the files are stored?

Question by danielemur 

How many LEDs rated at 5V can I use on a 6 Watt Radio Amp?

I there, I have a 6 watt radio amp that if I used the Voltmeter correctly is only really using 1.3 watts at it's highest volume on the busiest song.  I want to add LED lights to the dial and I'm wondering how many can I use?  I purchased LED lights rated to a max of 6V and the engineer told me that they can be used for a 5V power supply.  I would like to use as many as I can in series and will like to learn how one comes up with that number.  Thanks

Question by javierdiaz4   |  last reply

Audio signal help? Answered

I was going to build Amplifier with Gain = 20 Minimum Parts From this datasheet But I have no Idea how to put the signal on. I think that the signal is Vin (pin 3)  but that is one cable when a headphone has three cables. I know the red wire is right and the blue is left and the other is comm so I onley need 2. Because there is one input I need to make it one cable. Would this work (I will test what resistor I need with a voltmeter later). If I am wrong about there olny being one input can someone explane to me how to wire it.

Question by David97   |  last reply

Please, help me with this 3_state switch !?

ANSWER : so, at the end, it was a switch. I had to do it the hard way :( have a look at the last picture. Hi, could someone help me with this 3-state switch ??? I would like to remove it from the PCB, solder some wires and make ARDUINO + MOSFETs to control it = instead of me, manipulating the switch, I want the arduino to do that for me. Unfortunately I'm not able to find out which PINs I have to connect together to simulate the switch. I did some measurements and make matrix - if it could help to find out which pins to put together. Thank you in advance. Zholy P.S. : The voltmeter was set to 2000mV, and the RED_positive probe was attached to the NUMBER pins

Question by zholy   |  last reply

Can anyone please tell me how to wire my flyback tranformer up to make a high power source for a tesla coil. Answered

My flyback transformer has 9 pins at the bottem and is a "L40B02510 MSKK SANYO" I was hoping that i couuld just attach the + to one pin and the - to another pin (using one 9 volt battery) then add a ground to another pin.But im sure its not that easy if it is please tell what pins to use. I dont have a voltmeter to find the primary and secondary. I really need help and please dont send me link that will have me searching all over the internet i have spent weeks tyring to get this to work and nothing works.

Question by talbayaty   |  last reply

Building a genertor? Answered

I have a 5sme22nj028a general electric motor and wanted to buld a generator. It is 10 pin (not including earth). I have used a voltmeter to see what generate but there are many combonations and they all seem to generate. Also it is brushless. I have posted this question before but fogort to include that the motor says varable speed on the side. I was thinking that connecting diffrent pins would make the motor go at diffrent speeds. In my other question someone said that it may need a mirco prosser before it. I think that this is probaly the case but wanted to see if anyone knew about this motor. So if it needs or doesnt need a micro prosessor before it, please tell me. I should be able to work it out from there. Thanks

Question by David97   |  last reply

What am I doing wrong ??? Arduino - tachometer !? Answered

Hello ... I would like to ask, what am I doing wrong. I'm trying to create this instructable ... I downloaded the code, created the circuit (photo provided) ... and I'm using these components :  1. IR LED = SFH487-3 (code CY88)  2. Phototransistor = SFH300-3 (code NP64) Resistors are the same value, like in the instructable. Please, could you tell me, what am I doing wrong ??? Thank you very much. Zholy P.S. : IR LED is working, the PhotoTransistor is working as well <- I tried to measure it with my voltmeter - for CONTINUITY ... and as I was getting closer to the IR light, the value was decreasing.

Question by zholy   |  last reply

how can i find out which part of my charger is malfunctioning? Answered

Hello, I am desperate for help. I have a PWR+ charger for my laptop I purchased a few months ago, today it stopped working. What happened? well the charger still has some function, when I checked it with my voltmeter the output varied from 3 to 6 volts, the little LED on the charger was pulsating, not rapidly, but in short 1 second intervals. Could this be a problem with the voltage regulator? The required amount of power that a normal charger for my laptop outputs is a steady 14 volts, not sure about the current. Now my charger is useless and I don't want to spend another 30 bucks to get a new one, please help. Thanks in advance.

Question by nahum45   |  last reply

+Help with Digital PSU+?

Hi everyone after many days of constant tinkering, I finally got the circuit of my Digital Power supply made. However, I am experienced difficulty in the programming side. I am using an Arduino with an LCD (and various other io such as a current sensor, voltage divider, button and rotary encoder). My program is limited to what I could find online for an ammeter/ voltmeter sketch. I wanted help or some guidance in figuring out how to use the rotary encoder to 'set' a voltage (visible on the lcd) and when i press the button, i send a certain signal to my DAC which is connected to my psu circuit. and i wanted to be able to switch over from voltage 'setting' to current 'setting'. Frankly, i have no idea how to do this :s ! here is a video of what i want it to almost look like Thanks  

Question by making9719   |  last reply

Solar panel short reads 28v? yet charge controller reads 14v? Batteries?

I have a solar panel that I picked up on internet for free due to damaged glass(no biggie).  Placing a voltmeter across the output leads has 28.6volts.  I connected this to a PWM charge controller recycled from a junk yard.  I set the CC parameters to 24v and hooked up two 12v car batteries(13.2v good) in series to make my 24v circuit.  Now the CC digital panel reads 14v.  Checked all the connections and retested the panel, two batteries and CC. It checks out ok. But why does the CC readout at 14v in full sunlight? yet the panel reads 28.6v? The only thing is the two batteries are different in AH ratings. One is 96 Ah and the other 115Ah.

Question by JuG2   |  last reply

Charging capacitor from rectified mains? Answered

Recently my father brought 2 6400uf 400v phillips from his work. i want to charge it with rectiried mains. will be using them in paralell for coilgun  1) what is the voltage of 220v mains when rectified?(my voltmeter bunt) 2) when i try to charge them directly from a rectifier it melts my wire due to current. unfortunately i donot have a high power resistor to limit the current. How can i solve this without buying a high power resistor? 3) I want an led to light up when the voltage from the rectified mains is attained. 4)what will be the best. a 55 amp relay or a 75amp switch. i know that the switch can handle much more current but will the switching be quick  enough?   thanks in advance.

Question by ARJOON   |  last reply

Measuring LED Voltage

Greetings... I have quite a few "salvaged" LED's, none of which have I the slightest clue as to their voltage. I have attempted to measure them using the diode setting on my voltmeter with dubious/mixed/questionable results. Although the measurements are momentary (the reading is barely of sufficient length to note), I can usually arrive at a value. Unfortunately, when I repeat the measurement on the same LED the reading is invariably different. For example, I just measured the value of a random LED (green) and came up with the following: 1.3. 1.4, 1.8, 1.6. I've rounded the values to the nearest decimal point. Are these values through voltage? Are the differences between the readings significant or should I use the minimum when calculating resistor values? I'll, no doubt, have a few more question later on. I appreciate your elucidation on this matter... Best to all, hassi

Topic by hassi   |  last reply

Capacitor charging circuit using bd243c. Will it work?? Answered

I recently made a schematic to charge a capacitor bank for my coilgun.D1-D4 are all 1n0007 t1 is a centre tapped transformer which will step up 12v to 330V. WIll it work. r1 and r2 are 10w resistors. Q1 and Q2 are BD243C with a rating of 65 watts.  i found my transformer from a very old cassette player. huge and heavy able to pump about 100W. i don't bother about charging time. I just want to know if it would be good. don't worry about the voltage monitoring i have a small voltmeter(like a watch. chinese product.) i am just want to know if it will work or not UPDATE: I have tried the shematic. It works flawlessly.  

Question by ARJOON   |  last reply

Measuring a Bluetooth modules output? Answered

There is a serial Bluetooth module that I have used before on an Arduino project but now I'm trying to use in a project without the Arduino. Basically I need it to be an electronic trigger, I don't care really what the signal is just how long and the voltage and current. There are 4 pins on the module: Vcc, GND, Tx, and Rx. There are 2 open pads: Key and State. When I send a command from my phone the module sends a signal out the Tx pin, and it is this signal I would like to measure so I can pick a command with an appropriate signal and tailor the rest of the circuit accordingly. I tried a voltmeter between Tx and GND but saw no signal on any level measuring DC. Is there something I'm missing? Is the signal more complex or different, or is that test setup flawed? I tried other combinations, Rx-GND, Tx-Rx, RX-Tx, GND-Tx, GND-Rx but saw nothing.

Question by bwrussell   |  last reply

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   |  last reply

Big battery bank project. Circuit related questions?

Hello everyone! I have a project in my mind and I would love some guidance and some ideas if possible. I already have a lot of 18650 batteries in an “acceptable” state (1800-2100mAh each) and I am planning to make a large battery bank, for use in camping mostly (smartphone charging, led bulbs, electrical air pumps 12v, etc) I did read a lot of articles in here about battery banks, but i didn't find something as complex as my idea. I have already made a 12v battery pack with 12x18650, 3 rows in parallel, of 4 in series in each row. My goal was to operate a 12v air pump for inflatable mattresses. It worked like a charm! (Also created with instructions from here! Thanks for that!) But since my “DIY disease” does not leave me in piece… I want to build a large enough pack that can support the following: 1) 12v car plug 2) 5v/1A + 5v/2.1A USB plugs 3) charge circuit for the battery pack, so I will no longer have to remove the batteries to charge them separately 4) switches in each plug 5) led voltmeter also with switch ?) at some point I would like to add a circuit to charge it with a solar charger or a mini wind turbine that i will create at some point with my 3D printer, but for now let stay with the basic stuff! For the case i will use a modified screw organizer case, with those classic 18650 black holders from ebay. (photo below) The case will fit almost 8 to 10 holders (4x18650), so we are talking for 32 to 40 batteries... My main concern is the circuit design. I have done a few simple things in the past, but this is a bit more complicated and that is why I want your guidance/ideas. How to safely connect all those things together or maybe suggest a different plan/design, cable thickness, etc... Links gathered so far: I am thinking about 4S in a row. Is that too much? Or should i consider 3S? 3S Li-ion Charger PCB with BMS For charger... something like this maybe? 12.6V 5A Charger optional... maybe i could fit sothing like that, for laptop charging? 150W DC-DC Boost Converter for 5v 1/2.1Amp charger i m looking at this. 5A Charger Step down Module for usb/12v plugs/voltmeter i am considering this option. Thanks in advance for your time!

Question by the_phantom_boy   |  last reply


I am going to start building projects from here (instructables).So i need a toolkit but i am unsure what i need.But I think this will do: A voltmeter or multimeter - Digital or analog i am confused A soldering iron - i already have this A screwdriver set A Drilling machine - I think Bosch would be nice but which one impact or regular and wired or wireless. And am i missing anything above......and hey whats a hot glue gun.Bosch has that but do i really need it? I am not going for big projects so i don't need a router or sander. Does any1 know what are the types of blank circuit boards i mean the circuit boards which do not have any components soldered on. I got a PCB yesterday which had all the holes each row connected to each other by copper strip....that makes things very hard.....And how do i get a third hand in INDIA.... I liked rstraugh's Third hand But the thing are not available in India easily.So can anyone suggest me an easy one.

Question by pratyushpmhptr   |  last reply

can i use two pc psu's to get 24v? Answered

Yesterday i had a great thought for getting my macintosh powerbook 190 to power up. If i used two 12v sources in parallel i could get 24v (i think thats what it is, i mean where one power supplies negative is connected to the others positive and the neg of one and the pos of the other are used to create a combined voltage). So i tried it with one pc power supply but then i realized the 12v's are all connected to the same circuit so hooking it up like that would just short it out. I tried with two wall adapters, and on my voltmeter, it gave me around 30v with no load. the only problem is, that it doesn't supply 2 amps worth of power. but the 12v line on a pc psu supplies at least 10 amps, so if i used two pc power supplies (to prevent any shorting out) and hooked them up like described, could i get the 24v @ at least 2 amps that i need for this? Thanks in advance, z247

Question by zack247   |  last reply

Help with Viewfinder Pinout??

Well guys, I've had this viewfinder sitting around in a drawer for TOO long. I ripped if off an old camcorder in the dump like 2-3 months ago, remembering a few different projects I've seen on here (and other sites) such as: (sorry the hyperlink part of instructables never works for me) I know I've seen a project somewhere online too where a guy used one of these TINY crt's for a miniature arcade machine, just to name an example. I've ran into a bit of a wall here though, it would seem as though everyone else's viewfinders have indivigual wires coming off the board for power and video input. Mine doesn't, it has ONE ribbon connection (although mangled a bit, I still have the ribbon cable that goes with it). This is a really simple looking circuit board, but as I don't exactly have lab quality tools sitting around, I don't wanna solder wires onto it until I know for sure which is for power, I'd hate to fry it on the first time! I tried following the traces on the board but I've never been too good at that, is there some way I can probe around with a voltmeter to determine what is for video input and what is power? I've tried googling numbers off the board and tube and that didn't help either. If anyone can help me power this tube, please tell me!!

Topic by Punkguyta   |  last reply

Why does my LED lamp have AC voltage from case to ground and is it dangerous?

Here's the deal:  3-section under-counter LED light strip in an aluminum housing, with a 2 wire AC cable and plug for 220v. I found however, that when I set a voltmeter to AC and measure between the case and a ground (water faucet, natural gas line or the ground from an electrical socket) I get 74 volts with one unit and 89 with another. The seller first pointed out that a grounded cable should be used. I replied with pictures showing the unit is built to accept only two wire and comes with a two wire cord. Then they said using a sink as ground didn't truly represent ground and that the measurement was faulty and that the current is not dangerous regardless.  I took additional measurements using an electrical ground and the metal pipe from the natural gas line. Same result. However, I'm having trouble measuring current. I put the probe into the ten amp side, set the meter to the mA/A position and got nothing, although I did hear a buzzing sound emanating from the lamp housing--that can't be good. I then put the probe into the mA socket and tried again.  Same buzzing, no reading.  My questions: 1. What's wrong with my setup that I see no current measurement.  2. Is this a dangerous lamp? I took the one near the sink down. The other one is not within reach of an accidental grounding, so it is up until I'm ready to return both units. -Bob

Topic by bobcov   |  last reply

Can't get a TLC272IP OP-AMP to work. what am I doing wrong? Answered

Hello I received this week a few TLC272IP op-amp and I wanted to test them. I created a circuit on a breadboard which looks like the attached image From what I read on the net, this is a  typical non inverting amplifier schema where gain should be (1 + R2/R1) I connected PIN 3 of the TLC272 to pin 3 of my arduino uno and using PWM I set the output to roughly 1V ("analogWrite(3, 51);") I used my voltmeter to read the voltage between ground and pin 3 and I could really see 1V  given I used R1 = R2 = 47k, I was expecting to have a gain of x2 and thus read voltage of 2V between pin 1 of the op-amp and ground  I get something that is very unstable, below 1V. I tried with 4 different TLC272IP I just got and get the same behavior. am I doing something wrong there? what do I miss? or do I need to review how op-amp are really working? (I purchased the TLC272IP because it's supposedly single power supply) thanks for any hint. JM PS. in some doc i read that I should not let the second op-amp in the air, so i tried as well by connecting pin 5 to ground and shorting 6 and 7 with a wire or a small 100k resistor but this did not change anything.

Question by jm-l   |  last reply

Help me fix ma zune!

I've got to fix this damn zune, there's no warrenty on it and all in all it's a piece of crap. The guy doesn't care that much if it can't be fixed. I've got shit webcam reference pictures. You'll see that the battery has the terminals connected to a small IC board with 3 solder pads on it, and a voltage regulator of some sort on the bottomside of it. The ribbon cable has 3 little metal spades that solder to those pads on the battery. There's voltage coming out of the pads (I don't have a voltmeter, just a tongue but that works just as good). When I've got the ribbon cable soldered to the battery and I touch the end of it to my tongue I can feel current, so why is it that only once in a while I get power to the zune? Like if I wiggle the cable around sometimes I can get a low battery symbol to come up and then it shuts off. I don't know why it's still showing a low batt symbol because I charged it and it feels like there's a good charge in there so what's the problem? I wanna get this fixed so I can play around with it, no I've never had the pleasure of a zune :p. Thanks guys for anything you can help me with. I was thinking maybe the IC came loose from soldering/desoldering the cable a few times, but it still appears to be stuck on the board pretty good. Well look at the pictures and decide for yourself. It's starting to look like I'll be buying a new battery, which apparently the ipod 30/60 gig batteries are the same size/amperage and can be used in the zune and at a low price of $14, I can probably get a battery that'll last longer than the factory one eh?

Topic by Punkguyta   |  last reply

How can I fix my DSi?

Okay, I have a DSi since 2010 (I don't remember when I bought it, so this could be false. Look, it's old. OK?) And it's been working fine untill one day. I turned it on, and the power light (blue in this case) turned on for a milisecond and then turned off. I tried it multiple times but nope. Plugging in the charger makes the charging light blink non-stop. So I tried opening up the DSi (I opended it up mutliple times before so the warranty is voided already. I also did it correctly the other times so opening it isn't the problem here) to find out what is wrong but I found nothing wrong in it! Sure, the ribbon cable connecting to the SD card is broken but it's been like that for years if I remember correctly. Battery was looking allright, took it out with a voltmeter, wasn't dead (Also, I doubt it static electricity because it wouldn't do ANYTHING). So, I closed it up and opended up the charger. Strangely enough, a piece of the charger's motherboard was cut off! Like someone took a bite! But how could I be using that charger for all this time and it was working. I won't use it again, defenitely. So I went to a store to try out the store's charger, it gets weirder. I plugged it in and the charging light flickered like before BUT, for only a couple of seconds. Anyway, I went home and couldn't figure it out what it is. Only thing I imagine is the charge port (the port where you put the cable to charge it, duh). I'm sorry if you cannot see the pictures very clear but my camera doesn't focus very well, and I'm not a profesional photographer to set the focus etc. So I'm writing now. Please help! Thanks  

Question by MrJason005   |  last reply