Voltage help

Hello I am new to electronics I am having trouble designing a circuit that lowers VDC as ground resistance increases and raises as ground decreases every circuit I've built works backwards. I am working with 5vdc any help would be much appreciated thanks

Posted by Ed69 1 year ago


Question about voltage

I am brand new here and have a question about voltage. I was reading the Instructable about how to run battery operated devices with ac power. https://www.instructables.com/id/Run-any-battery-powered-item-through-AC-power./ If I have a device that uses, for example three 1.5v batteries ill need to find an adapter that will push 4.5v. Is that correct? If that is correct, what would I do in this case? I have 20 of the same device, each of the devices take three 1.5v batteries. I want all 20 of these devices to be run on one wall plug(if possible). Does this mean that I need to get a wall plug that will push 90v? If thats the case, is that even possible? Thanks in advance

Posted by cjr187 7 years ago


How to cut down the Voltage???

Hello guys it's electricnewbie again, I have another newbie question that I think you can help me out with. OK so go easy with me since I'm a beginner. . . So, I have a laser/light (from walmart) that takes three 1.5 volt batteries that gives it a total of 4.5 volts. So, I want to hook it up to USB cable. Now, a USB cable supplies about 5.1 volts. How do I drop the current from 5.1 volts down the 4.5? How could I use the same principle in my other projects? Say I have a 9v battery and a 3.4v buzzer. I know how to use resistors with an LED. [R=V1-V2/mAH] Since I know the mAH of the LED, then I know what resistor to use. But how use that equation if at all on other things?? Thanks guys,

Posted by HavocRC 5 years ago


will this really regulate voltage?

Will this really regulate voltage?I would think that voltage could just flow arround the capshttp://electronics.howstuffworks.com/digital-electronics4.htm

Posted by kendallickes 9 years ago


anyway increase voltage without using ac ?

Anyway to increase voltage using only dc input and using low voltage batteries (1.5 ~ 9 V ) ? and without making big or with loads of parts circuit ? ( I need simple circuit) any more taughts than joule thief ?

Posted by chosenone3 10 years ago


Voltage regulation

I have a solar charge controller (Velleman SOL4UCN2) that outputs 12v, 6v and 3v. But I need 9v and I'm not sure how to get that.

Posted by pless84 10 years ago


Voltage Relays

Hello, I'm new to this board, and well, making things in general, and am particularly stumped about voltage relays. I know in theory how they work, a small voltage triggers a circuit to close and let a larger voltage through, but practically have no idea what the terminology used in the data sheets mean. What I'm looking for is to have 120VAC be triggered by a 5VDC. The 120VAC would only be on as long as there was 5VDC triggering it. Can anyone out there tell me what I should be looking for, in particular, what the voltage that causes the circuit to close is called? Thanks. --D.K.

Posted by Knip. 10 years ago


voltage level monitor circuit ?

Hello, So for my application, i need to have a circuit that can monitor the input voltage until it reach 5V (usually from 0V ) then switch on and allow the 5V to flow into another circuit.  The problem is i have no idea where to start. Can anyone help me ?  Thank you very much

Posted by ChuongV1 1 year ago


Voltage regulator?

I need to know how to build a 12v-5v pulse regulator for my fuel level sending unit/gauge in my truck. I would like to know what parts to buy and the order of everything. Thank you in advance. Daniel

Posted by gungfudan 6 years ago


Using a recycled switch -- Question about voltage

I'm building a simple solder fume extractor using a 12v fan from an old appliance. I will wire in a 12v power supply. The switch I want to use is rated 125v AC at 13 amps. Is there any reason I couldn't use this switch? Or do I need to match the switch's voltage with the fan's?

Posted by Boy Genius 6 years ago


Traffic signal input voltage help

I have recently bought this traffic arrow from a surplus store and i cannot find the input voltage anywhere on the net. it has a built in switch mode power supply from what i can tell and i think it is 120V AC but am not sure. the arrow is a GE Gelcore LED Traffic Signal. ANY help would be appreciated.  thanks

Posted by devicemodder 5 years ago


Help with Voltage Regulator

Hi, I have put one of these together for an ATX power supply and have come across something that I might be getting wrong.... In mocking up the LM317 circuit in breadboard (standar one found everywhere on line and on the LM317 pages), I have got the thing metering -11v to +11v??? I am using one of the black ground wires of the PSU on the black side of the volt meter, but cant figure out why I am not just getting positive voltages??? Could the diode be faulty? Or is this in fact correct? Any help appreciated...

Posted by lone_viper 6 years ago


Bench power supply build from ATX power supply acceptable voltage

Hi, I built a bench  power supply from an ATX power supply and I am not sure if the voltage is correct. I am getting 5.74 volts off of the 5 volt supply and 12.7 volts from the 12 volt supply. Is that too high to use or should I try to bring it down a little? When I built the supply I didn't have a 10 ohm power resistor so I used a 6 ohm 10 watt resistor. Could this be the reason for the higher voltage? Thanks for any help you can give me. Dan

Posted by danridge 7 years ago


Increasing USB voltage? (newb here)

Hey all, I've recently got into learning to solder and learn about electronics. Well, I've been trying to make a few USB toys, but have come to find out that the USB ports don't put out enough power to get most of my stuff going. (an led light strip requiring 12 volts for instance). I was wondering if there was something simple I could put together to get some more power.

Posted by Soniku 9 years ago


RGB LED Voltage indicator for 15 - 10 volts

I would like to make a one RGB LED DC voltage indicator, 15 – 10 volts in half volt changes.  At first I thought I would use a bunch of zener diodes, but it seems a bit more complicated than that as on my chart how I want the colors indicated.  Any ideas how I can accomplish the circuit?  There are probably new fancy things I could use but am not aware of since it’s been a very long time since I’ve made a circuit.  I am currently just using an analog panel meter.  It would be nice have a colored light indicator.  If it could be done.

Posted by K00kie 4 years ago


1/8W 39ohms resistors

How many 0.6W 39ohms resistors will I need to fulfil a 1/8W 39ohms resistors place?

Posted by scribble73 2 years ago


Quick coilgun Capacitor question

Im using chargers to rank 330V or even 370V. Heres my options. 400V 330uF Capacitor 450V 150uF Capacitor Im guessing the 330uF, But what's better for a coilgun? (using 4 of them in parallel, yet buying 10.)

Posted by Killa-X 10 years ago


Scientific Theory

I am working on a scientific theory and I need a little help. I have 2 car batteries in series to create 24v need to power an electric motor. The motor is 14.5 amps and I need a way to control the amperage from the car batteries to the motor. Any help would be greatly appreciated.

Posted by Ice Dragon 5 years ago


too many volts to an LED

I have an LED that is supposed to take about 2.8 to 3.4 volts.  A single 3v coin cell works great.  However, if I use two or three of those batteries, it gets ULTRA bright.  My question is, what harm is this doing?  Risk of burning out the light, causing heat, other bad things???  What exactly would happen over prolonged use?

Posted by aliasjanedoe 8 years ago


Help with voltage/resistor

Hello.  I bought some Christmas LED replacement bulbs but they have no specs with them.  I decided to wire one up.   I figured I would go with 1 . 5 volts at 7 1/2 mA.   Using a 9 volt battery, I have a 1K ohm resistor.   9 - 1.5 = 7/ .0075.  My problem is, when I put my meter on it, the one side of the resistor is showing 9 volts, correct, but the other side is showing 3.5 volts.   Shouldn't it only be reading 1.5 volts?  What is wrong?  *I've had the LED lit up for over 25 minutes so far and it hasnt burned out yet. Thank You. EDIT:   I just added  a 10K resistor, so now I have 11K (in series), yet I am still getting a reading of 3.5 volts.   I'm missing something here. lol   I'm also getting a reading of about 9mA with 1K and 11K ohms.   I'm lost.

Posted by pennsteve 8 years ago


Will a 240 Volt AC Motor Operate on 120 Volts AC

I need to know if a 240 volt ac squirrel cage fan motor can be safely run on 120 volts ac. An quick internet search reveals several sources that all say no, but I am concerned that the people answering the question don't know what they are talking about - as is often the case on the internet. I know there are a lot of want-to-be engineers out there ready to answer any question posed even when they have no experience or knowledge of the issue. Please do not guess at this or offer some unsubstantiated opinion.  I need a real answer to this question. Here is what I do know about this issue from researching a couple of electrical engineering sites. Lowering the motor input voltage by 50 % does several things. 1) The motor will run slower. 2) The torque developed will drop to about 25% of its full voltage rating.  3) This decrease in torque can make the motor stall when trying to start under a heavy load. 4) There may be drastic speed fluctuations due to load variations.  5) The motor current will double if the load remains constant. I can understand how these issues could cause severe problems in some applications, but perhaps not in the application I am looking at. I want to use a squirrel cage motor rated at 1/20 HP, 240 volts, 0.5 amp in a direct drive fan application. Here is how I am looking at this issue: - I need to reduce the fan speed so the speed reduction is a good thing in my application. - I have test run the motor on 120 volts for about an hour and there is plenty of torque to operate the fan. I figure at the lower speed there is less air load on the fan blades so less torque is required. Again a good thing for this application. The is no heavy load at start up and the motor seems to have plenty of starting torque for the fan. The fan does not reach full speed as fast as it does on 240 volts, but it still does so in about 4 to 5 seconds so this shouldn't be an issue either. Since it is a fan moving air and not some machine moving gears and levers the load is constant so the speed does not fluctuate at all. Again this should not be a problem. The possibility of the motor current increasing is my only concern so far and apparently it is not an issue since a test run showed the current decreased from 0.5 amps at 240 volts to 0.4 amps at 120 volts.That is a significant current drop instead of the predicted increase. Since this is a fan, I think the current decreases because the load decreases with the lower speed. For these reasons and based on my apparently successful test run I think the motor will operate fine on the decreased voltage. However, I am not sure how to factor the motor slip into this. Slip is the difference between the synchronous and asynchronous speed of an induction motor. From what I have read the slip will increase dramatically when the voltage is cut in half, but I am not sure what physical affect that will have on the motor. If you know what effect that will have or know of some other factor I am not catching please let me know.         

Posted by biochemtronics 5 years ago


voltage multiplier bath

I saw the voltage multiplier Instructablehttps://www.instructables.com/id/High-Voltage-Multiplier/and I'm wondering if it's necessary to put it in oil.My capacitors would be severely under volted (that should be a word, the past tense of volt, LOL) and the diodes wouldn't even be challenged.

Posted by guyfrom7up 10 years ago


High Voltage shenanigans

I thought it was about time to post these videos ive made so i did! my very first forum post!

Posted by The 4th Doctor 9 years ago


Green Led voltage?

I picked up some green leds at a surplus store today. I've been assuming that they run on 1.7 volts, is this about right?

Posted by sabeen557 10 years ago


How to make voltage rise sharply from 0v to 5V ?

Hello, So i am designing a circuit board using microhard pDDL2450. So after a few trial and contact help from them, I figured out the reason the board didnt work.  The input voltage after pass through a voltage regulator doesnt rise fast enough, hence the chip wont turn on. So the next logical step would be designing an independent add-on circuit that can make the voltage rise faster.  Any idea on how to do that ? 

Posted by ChuongV1 1 year ago


High voltage suggestion

Anybody have any suggestions for what I should do with some high voltages. I don't want to make a taser, cause it could kill and I have no need for it. I don't want to make a jakob's ladder. anyone have any cool ideas?

Posted by guyfrom7up 10 years ago


Can I Limit Current Without Dropping The Voltage?

This kind of a noob question. I have a power source that supply 12V, 500mA. And the device I'm powering takes 12V, 140mA. How can I drop just the current (from 500mA to 140mA) without dropping the voltage? Since using a resistor would cause the voltage to drop as well. (Right?) Any help is greatly appreciated. Thanks.

Posted by gyromild 10 years ago


Small Voltage Regulator

I am looking to buy or build a small voltage regulator that can fit in an O gauge electric train engine. It needs to have a 18-20 volt AC input and 10-12 Volt AC 1 amp output. I would like to buy one already built, buy a schematic or a schematic with the parts to build. Thank You

Posted by frankv6 3 years ago


Voltage regulator circuit design

Hi, I'm trying to make a DC - DC voltage converter. The real purpose is to power an old USB hub in a car. This is because so many of my electronics these days use USB to power them and rather than have a nasty mess of car power adapters I want to use a single 12V supply for the hub and then plug all of my goodies into it. Now for the meat of the question..... What is the best circuit design for using a voltage regulator. I have looked at some stuff in data-sheets and it just seems way too simple. The part I'm looking at using is a National Semiconductor LM1085-5.0. Input voltage 6.5 - 20V output 5V max of 3A

Posted by Sailing_Nut 9 years ago


Increasing DC voltage

I need to increase the voltage of a battery from ~30v to ~230v, the only way i can think of doing this is somehow pulsing the DC rapidly to create a sort of "pseudo AC" then using a standard transformer to increase the voltage, followed by the standard rectification process. My problem is how to pulse the DC (bearing in mind the pulse will probably need to be in the order of kHz, and the device being powered at 230v has a power rating of 400W) and how to after the rectification process implement a pwm system. In addition, the method of increasing the voltage strikes me as extremely inefficient, so if anyone has any other ideas I would be very great full. Thank you for any help you can provide.

Posted by csharpdeveloper 10 years ago


High voltage beer

Whilst browsing the net doing some research, I came across this video.Watch the fluid currents created by the electrical currents.Cool.(And, please, no comments about wasting beer - it looks like it's only a lager.)

Posted by Kiteman 9 years ago


Violet Voltage?

Every so often, I see "violet ray" electrotherapy devices come up on ebay. They often sell for silly money, but occasionally one will sell for only a few pounds.Originally quack medical devices, they seem to operate in a similar manner to a plasma globe (gas discharges, high voltages). Does anybody know how they work? Is it worth getting hold of one to rip the innards out to get at the high-voltage supply?(Yes, I know they have "adult uses", but, really, it is the innards I'm talking about)

Posted by Kiteman 10 years ago


Micro High Voltage

I'm going to attempt to make a super micro tesla coil that is 100% contained (unless it runs off of like 12 volts dc, then I'll use a wallwart). Of course, one of the i biggest problem is the power supply. So this is what I'm asking, what's the best way of ramping up the voltage? A tiny toroid transformer? An inductor that gets pulsed? Voltage Multiplier? Something with static electricity? Some type of Inverter? Using Greinacher Cascades? A marx generator hybrid? Other stuff I havn't heard of?

Posted by guyfrom7up 10 years ago


What's the best way to lower 6 volts to 5 volts?

Hey friends!  I have a question. I want to be able to use 4 AAA batteries (6v) to power an IC. The IC's max voltage is 5.5. Is there any kind of way I can use two resistors as a voltage divider to lower the voltage 1 volt or should I just use a diode(which would lower it by 1.4v)? Thanks!

Posted by HavocRC 5 years ago


Voltage Control: 20v DC

I am trying to find an electronic part that will take in anywhere between 12-36v and put out a consistent 20v. What could do this? And how can I get one? If amperage matters, I'll probably be putting between 1 and 4 amps through it.

Posted by V-Man737 10 years ago


How do I transform a power supply to other voltage value?

Hi! I need a 9.0 V AC  1.0 A power supply but despite I have a lot of power supplies around, no one has this values. The most I have are 12 V DC I suppose there must be some method to lower or rise the voltage of a power supply to meet the required voltage. Also, the resulting power supply must be AC (I also have a 20V AC power supply if this is easier than converting from DC to AC) Please, tell me what do I have to do.

Posted by jedikalimero 7 years ago


volatage booster

Hi every one . i need to know if its possible to boost DC voltage from 0.1V source to 3.8V DC output and how to do it  thx for answer :)

Posted by insurgent 2 years ago


High Voltage shenanigans back with avengence

I threw together some more vids with significantly moar powah, enjoy! interesting note about the cd explosion according to my science the edge of the cd was traveling around 420mph i also have another cd explosion vid on my channel but this ones much more impressive

Posted by The 4th Doctor 8 years ago


How to reduce current without reducing voltage

Hi, I'm working on a sign that basically has LEDs as letters. I have 140 LEDs that I'm planning to put in series of 4 each and then 35 in parallel. My problem is that I was mailed a transformer that outputs DC 12v 1.25 A (Actually 12.3V 1.4A). The current is too large for what I need for the LEDs and I don't want them to burn out too quickly so how would I drop the current without affecting the voltage? Any advice would be appreciated, thank you!

Posted by ytan10 4 years ago


High Voltage Ground

I'm starting to work with high voltages again, but for real this time. I just built an ignition coil driver, using a 555 (and I got an ignition coil), but my 555 broke (the texas instruments ones can only drive 15mA, oppose to the normal 200mA, oops) so I have to go buy one today. My main question is what to use for ground, whether it be for an old screwdriver for arcing sparks or the secondary of a tesla coil. I was originall just going to use the 3rd prong of an outlet, but somewhere on the internet I heard this could destroy all surge protected power strips and destroy all plugged in electronics at your house. I, of course, do not want this cause... well... I'd be screwed. Is this true or not? Can I use the 3rd prong?

Posted by guyfrom7up 10 years ago


How Can I Reduce Current Without Dropping The Voltage?

Hello friends,                       i am making home automation with IR sensor , The problem is that the IR sensor sends random garbage values to arduino's serial monitor when connected to external power supply. The external power supply has output of 5v DC voltage and 2000mA current. The whole system worked perfectly when I take power from computer's USB port . The problem is how to reduce the current to 0 -500 mA of external power supply. thank you !

Posted by RakeshL1 1 year ago


undervoltage LED

If you undervoltage and LED (by like .05 volts) you don't need a resistor, right?

Posted by guyfrom7up 11 years ago


12 volt stabilizer/regulator (high current)

Hi, I need something that's able to regulate the car voltage that vary from 10.2 to 14.7 (with lower voltages at startup that's not relevant)  to a stable 12v with a tolerance of 1-2% at high current (need at least 35A but I don't want to full load it too often then 40A would be better). I saw something like a lm317 with some external transistor that's able to put out something like 15A but it required a 30V input and it was a too much low current. can you link me an image of a circuit that's able to do what I want?

Posted by andry08 2 years ago


Need help. How to ground high voltage.

Hello, I am in need of a little help. I recently purchased a small Holmes fan with filter as I had a coupon, it was normally 15 dollars, but the coupon was $10 off. When I first bought it I intended to convert it into a electrostatic precipitator, then when I got it home I realized it already had a built in ionizer, which simplified my idea as I can use that as the hv power supply. I am going to use alternating high and grounded metal plates in place of the filter. I was wondering what is the best way to ground the plates? The fan doesn't have a grounding wire.

Posted by rbneville 6 years ago


Need to step down a lead acid battery from 12vdc to 10vdc 350mA

I would like to run a 6pcs 1W white led lights from a lead acid battery. A Single bulb input voltage is 3.2-3.6V & 350ma. I connected every 3 led's in Series (2 Groups) . Can I use 7810 IC or how can I do it. Sir Please send me a diagram . lead acid are in full-charge 14.5v. , in normal 12v, low 10v

Posted by Goldensathiya 4 years ago


Need help with LED lights

Hey, I'm making an infinity tunnel/mirror based off an instructable on this site. https://www.instructables.com/id/cool-DIY-infinite-LED-tunnel/?&sort;=NEWEST&limit;=40 But the instructions are crystal clear and I'm running into a few road blocks. What kind of LED should I buy? They all have to be the same voltage correct? Does it matter if I connect it to a battery pack or the wall? What kind of battery should I use? Basically I know nothing about electronics and I don't want to create a fire hazard. Any help is appreciated.

Posted by changsta3 8 years ago


High Energy shenanigans

Blowin up small fruits with my capacitor bank, and a little look at my homemade plasma globe hopefully ill add more of a description at some point, feel free to comment and ask questions

Posted by The 4th Doctor 8 years ago


N2 TEA Laser Challenge!

CHALLENGE: To build a functional N2 TEA laser with readily available parts. There are plenty of websites where people describe the laser that they built, but I have never seen anyone on instructables who has done this. Please, just make something! Good luck!

Posted by Xellers 9 years ago


USB generator

I am building a small crank-powered generator for a college electronics class that will power a USB port. I know a USB port supplies 5V DC, and that my generator will obviously produce AC current, but I'm not sure the best way to convert AC to DC, then how to step my voltage up to 5 volts. My generator uses 6 wire coils in a circular pattern. 12 neodymium magnet rotate over the coils. This doesn't seem like the most efficient design ever, but that part is a stock university kit, the wiring is up to me. I've only been able to test each coil at a time, and each one produces .5-.7 VAC. Do any electricians out there have some tips? When all is said and done, I'll definitely be posting an instructable on this.

Posted by fortneja 10 years ago


basic electronics question - series circuit

Hi i have a device which normally uses a transformer rated at 2 amps outputting 5 volts.  i want to put together a battery pack to power this device.  it's easy enough to put together the batteries and get a 6 volt output, but i'm worried about burning out the device w/a 6-volt power source.  i'm thinking putting a resistor in the circuit should be enough to lower the voltage to 5.  if i remember my high school physics right, i'd need a resistor whose resistance is r = (v1 - v0) / i = (6 - 5) / 2 = 1/2 ohm ...but this seems strange.  1/2 ohm??  my approach must be too naïve.  can anybody point me in the right direction? thanks doug

Posted by dielan123 7 years ago