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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

Topic by Ed69    |  last reply

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.

Topic by Knip.    |  last reply

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.

Topic by pless84    |  last reply

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

Topic by gungfudan    |  last reply

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)

Topic by Kiteman    |  last reply

Led voltages

I have a small pile of salvaged LEDs from various burned up electronics (flashlights, old stereos, etc) and I am wondering if there is any way to figure out what the voltage requirements are for the led. if anyone has an idea how to find this out it would be of great help.

Topic by danlab    |  last reply

Voltage boost

I'm trying to make a remote shutter release for my large format lenses. I found a solenoid that will do the trick. It's 12v / 36 ohm push solenoid with 3/8" travel. I prefer to drive this thing with a single AA battery. Is there a simple way to boost 1.5v?

Topic by JonLoder    |  last reply

5 voltages?

What are the top 5 voltages we deal with in the U.S.?

Question by erik30    |  last reply

Voltage regulator? Answered

Does a voltage regulator IC (e.g 7805, LM317 etc) still draw current when there is no load?

Question by .Unknown.    |  last reply

voltage measurements

I need to make several voltage measurements simultaneously.  I am looking to troubleshoot a intermittent problem with my truck. Has anyone any experience with this challenge ?   I would like to be able to store these measurements to be analyzed at a later time. Thanks, Dave Sender.  

Topic by davesender    |  last reply

Voltage Divider?

I will need to convert 5v to 1.2v... I chose 10k and 2k because 10k/(10k+2k)=1.2v. Would these resistors work for this?

Question by lorogan    |  last reply

Voltage Drop

I have a 12v led bulb, I need to connect the led bulb to 12V rechargeable battery  and connect bulb for  long distance from battery and i connect the bulb i won't  work, i think the voltage drop would be the  answer and how can i solve that????

Topic by rshan    |  last reply

laser voltage?

I have a laser diode that needs between 3.7v  and 4.2v to run, and i plan to run it of an arduino (5v). to reduse the voltage i have calculated that i need a resistance of aproximately 1.333ohm. is this necessary/is there a bether way to do this? thank you in advance for any answer!

Question by ludvig.risan    |  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

Voltage question

I'm building a electric anchor for my boat. I'm using an electric actuator thats rated at 24v to 36v. I need to step up the power. my boat is only 12v. I was going to use a stepup converter. Found one  12v in and 48v out. Is there a way to control the voltage so i can tune it down to 36v. Also would there be a big difference running it 24v verus 36V?

Question by kurt1968    |  last reply

Voltage reducer

I have a solar charger that outputs a minimum of 6V. I also have an iriver H300 that has an input of 5V. Does anyone know how I can make a voltage reducer, the link to any instructions or if I can buy one, so that I can recharge the H300 with the solar charger?The link for the solar charger is this: .The link for the H300 is this: .Thank you. :-)

Topic by zedascouves    |  last reply

Voltage for NiChrome?

Will 2.5 volts be enough to heat a small segment of NiChrome wire up to/over 100 C? If it helps, the power is coming from a 8.1 kJ 2.5v 2600 F super capacitor which can unload very quickly.

Question by LiquidLightning    |  last reply

LED Voltage? Answered

So recently I had an idea to make a steam gun by heating steam with a NiChrome wire driven by a 9v battery, anyway, to keep it safe and so i knew when it was on, i decided to add an LED to the circuit. I went to to see which resistor i needed. From what i understand, the resistor limits the CURRENT across the circuit. So, what i want to know is whether the Led will work with the first attached circuit and not bun out from the voltage, and whether the nichrome wire and led will work in circuit 2. EDIITTT: Well, after a few answers, i'm realising i cant run this off of a 9volt, so, what small powersupply could i use?

Question by LiquidLightning    |  last reply

Voltage Regulator

EDIT: Anyone Interested please check below posts, this is one is obsoleteHello!I need a voltage smoother and regulator on my circuit(attached below)it is a modified shunt charge controller circuit.It converts the Tri phase alternating current to DC and feeds it into the circuit.The regulator will have to be attachable to the BATTERIES wire in the circuit.It should not consume more than 1v power on its own.My Vout to the battery currently is fluctuating.I will need the to be a stable 12v to charge the batteries. A potentiometer will have to adjust current.I will calibrate current according to my battery bank needs.Led 1 indicates 'charging' Led 2 indicates 'Dump'And Please forgive my circuit diagram design(it looks like crap)but works like gold.Also do NOT suggest huge changes to my controller for the regulator to work. Small suggestions to make it more effective,useful like change the zener diode power rating will be welcome.P.S- Its for my hydro project.Check it out at

Topic by mhkabir    |  last reply

High voltage DC voltage doubler? Answered

Is there any kind of high voltage voltage doubler that uses pulsed DC? (Solid state not anything like a Marx)

Question by The MadScientist    |  last reply

will this really regulate voltage?

Will this really regulate voltage?I would think that voltage could just flow arround the caps

Topic by kendallickes    |  last reply

LED Voltage Help Answered

I recently purchased 10 led's from but I cant seem to figure out their voltage. I am not good with electrical terms (I am a noob with electronics) so the led's detail page just confuses me. If anyone could figur out the voltage of them by going to this page here it would be a lot of help. Thanks!

Question by DBMods    |  last reply

voltage multiplier bath

I saw the voltage multiplier Instructable 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.

Topic by guyfrom7up    |  last reply

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. 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

Topic by cjr187    |  last reply

voltage vs uf?

If you were building something, say a coil gun, would it be best to use a bank of higher voltage (300+V), lower uf (80-120uf), or a few capacitors of say, 1000uf 50V or lower?  

Question by Spaazztik    |  last reply

Low Voltage Disconnect?

Hi, I would just like to seek your assistance and idea for the observation below on my experiment: I have a gadget that is being charge by a 2w 9v solar panel, the problem is I haven't place a blocking diode and I observed that when I tested the charging slot there is about 0.16v output. To clear it that was supposed to be my input voltage. 1. Question is why does it produce an output voltage even though it is imy input voltage? 2. Would the 0.16volts output have a significant effect on my system during night time and or bad weather? Please give facts and computation if possible. 3. If I want to step down my input voltage of 9volts to 4.5 volts can you give me the idea how to do it. Well, I am asking you this because your insights and helps for me in the past are very helpful for my science project. Thank you teachers

Question by mitchiko    |  last reply

Voltage Regulator Question? Answered

Hi Guys, Looking a bit into voltage regulators. When I'm looking at the wiring diagrams on the datasheets, most of them indicate that it requires a 30V+ish input voltage to work. I was hoping to get a small adjustable voltage regulator to run off the 12v range. I really don't need anything over 12volts anyway. Can I get this to work or do I have to find a power supply capable of providing 30V+ for the voltage regulator? I was looking at models such as the lm117 if it helps. Also, If I do need 30v+, where can you suggest I get that kind of power supply? I usually use 12v wall adapters. Thanks!

Question by transistorguy    |  last reply

High Voltage shenanigans

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

Topic by The 4th Doctor    |  last reply

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?

Topic by sabeen557    |  last reply

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?

Topic by guyfrom7up    |  last reply

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...

Topic by lone_viper    |  last reply

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

Topic by frankv6    |  last reply

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.)

Topic by Kiteman    |  last reply

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.

Topic by csharpdeveloper    |  last reply

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?

Topic by guyfrom7up    |  last reply

Voltage quality recorder? Answered

Hello, i am an electronics hobbyist, and want to develop an system which is an voltage quality recorder, i mean it measures the various voltage disturbances like transients, swells, sags, THD, etc, I was comfortable in analyzing the concept and with the software too. but for the hardware implementation i am confused of which kind of TI microcontroller or microprocessor is suitable for my project. i will work on the real time calculations and will use FFT in analyzing the voltage.I am planning on dsp processors of C2000 series of TI. But not able to wisely choose them. On what major parameters should i look upon while choosing them. I would be helped if anyone can suggest me which one would precisely be used for this cause. Any more suggestions on how to proceed with it are welcomed. Thank you.

Question by Tejas Narayan    |  last reply

Resistor Voltage Drop

Is there any way to calculate the voltage drop of a resistor value? For example, if I had a 47 ohm resistor, would its voltage drop equal -30V, -857358V, or -0.5V?

Topic by puffyfluff    |  last reply

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?

Topic by guyfrom7up    |  last reply

Voltage regulator for laptop

Hi there. I have a problem for which I'd like some opinions: I have a PB laptop which has fried its inverter for the LCD due to the input voltage towards the inverter being too high (19v while it should be 12v and can only endure upto 13v). Most PB models have this problem. I looked around and some people suggest making a voltage regulator with a 7812 and some capacitors that gets its power directly from the input of the power adapter on the laptop (19v, 6+ amps). But since I am not really that into electronics, I have no idea if this will work, especially towards the heat that comes with the 7812, will it be high? The inverter needs around 0.5 amps input current. Others suggest a setup with (zener) diodes, but I have no clue how to start on that. Anybody have a suggestion? Many thanks.

Topic by .conne.  

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.

Topic by pennsteve    |  last reply

LED Voltage indicator

I have recently installed a solar panel in my garden to charge a 12volt 21Ah battery. I would like to show it off a bit by using a simple LED display to show it working. What I was thinking was to have a range of about 8V-25V. At the low end would be blue leds (for cold) up to red (hot) at the high end. Does anybody have any idea how I would go about getting something together. I can read circuit diagrams at a push (my Dad's the expert) and would like as much information as possible. Would it be possible to have 1 LED per volt ? Am I being simple? Would this project be self defeating in that it'd use lots of the free power I'm trying to collect? Any help anybody can give I'd be grateful to receive. Share & Enjoy. Zippy.

Topic by bunglesmate    |  last reply

Transistor Swithching Voltage? Answered

Looking at this data sheet: How much voltage has to be applied across the base and emitter to switch on a "TIP 3055" transistor? The V-be row is the only thing that looks like it is telling about that, but I don't think that's what I'm looking for (mabey it is?).

Question by Jaycub    |  last reply

phototransistor for high voltage

Before the begining sorry for bad english I want to make laser tag with electric shock when hits This is circuit of taser what I want to do is remove the switch and replace with wire so that the taser can charge automatically then I want to put a phototransistor(that react to red laser) to the poles(where you get shocked when touch them together) but because the both poles are attached to bodies the taser can't be charged so I tried to block one side of pole with phototransistor but when I touch the two poles phototransistor burned(?) and I got shocked in this case what can i do?

Topic by hyeok205    |  last reply

-5v Voltage Regulator

I want to make a -5v Voltage Regulator... Does anyone know if I replace the 7805 regulator with a 7905 would that be enough, or would the capacitors have to be different values?5v Voltage Regulator Schematics

Topic by mrshow555    |  last reply

USB 2.0 Voltage

Can somebody tell me what voltage a USB 2.0 port puts out, what the cable is capable of transferring and how much voltage an Ipod takes in? Thanks, kidboy

Topic by kidboy    |  last reply

AC Voltage Attenuation?

Hello, All- I am making my second version of the "Tube Lamp." Others have managed to wire in these neat-looking old analog meters on theirs, and I thought that would be something I'd like to try. I bought a couple 1-10VAC meters from The problem is (besides the fact that I am an electronics idiot) that obviously if I try to wire in this particular meter to normal 110 AC, the meter will blow up. Is there a way to attenuate the voltage coming out of the dimmer to "play nice" with the 1-10 VAC meter? I suppose I would need to divide the voltage by a factor of 10. How would I step down the voltage to the meter only, while supplying the bulbs with the proper voltage? Any help would be appreciated!

Topic by 40percentrobot    |  last reply

Transistor Voltage Inverter?

I am a newbie and was hoping someone could assist me. Given the following schematic which takes a voltage of 12v and considers it off and a voltage of 2 volts and considers it on can someone tell me what changes would need to take place regarding capacitors and resistors (if any) to account for 20v instead of 12v? Meaning that when 20v is considered off and 2v is considered on.

Question by TimothyE2    |  last reply

Plasma disc voltage? Answered

Hello! I've seen a few of these plasma discs and was wondering if anyone know what voltage these things generate? I know its some high-frequency ac voltage powering the disc, but does anyone have a rough estimate? Just curious. I've been meaning to take one apart, but I don't think my multimeter could withstand a  shock from it. (Rated for 600v).  Pic of a plasma disc: Thanks!

Question by transistorguy    |  last reply

Transistor Voltage Inverter

I am a newbie and was hoping someone could assist me. Given the following schematic which takes a voltage of 12v and considers it off and a voltage of 2 volts and considers it on can someone tell me what changes would need to take place regarding capacitors and resistors (if any) to account for 20v instead of 12v? Meaning that when 20v is considered off and 2v is considered on.

Topic by TimothyE2    |  last reply

Voltage of iPod Battery

Ah, so I have this iPod Shuffle Gen 2 (which I really dislike, I won it in a contest), and I would like to know what the voltage of the li-ion battery inside is or about is. I don't know if anyone knows, any help would be nice. Thanks!

Topic by Bran    |  last reply