The forums are retiring and are now closed for new topics and comments. The existing content will remain online and accessible through 2020 to provide everyone the opportunity to save any relevant information. In the spring of 2021, these Community forums will be taken offline.

# Search for current in Topics

I have some solar panels that produce 3v at 175ma. I was wondering if i could somehow make a switch to have it turn on when the panels are producing at least 100ma. Maybe also a switch for 150ma too :) Any ideas?? If additional voltage is needed it shouldn't be a problem :) Thanks!

Question by astroboy907    |  last reply

### free current

I have a current source of 50 v from a phone line can i reduce it into 12 volt to make a 12 v bulb glow?

Question by faintedbrain_007    |  last reply

### Volts and current ? Answered

I'm confused what's the difference between voltage and current ? also what's the difference if I power a 1.5v motor with 3 1.5 battery's in parallel and same motor in 3 1.5 battery's in series

Question by Robinson ruiz    |  last reply

### Limiting current?

Good day, I am interested in an effective way of limiting current for a TEC application. This application involves using the TEC's (12V @ 1A) to reduce the incoming air temperature in a noise isolating enclosure from ambient temp to about  5-10 deg C cooler. In doing some research on implementing the TEC's I have found that these units operate at their greatest efficiency around 1/3 of max amp input and lower when you do not have a large heat load to "pump" away. So all of this being said I would like to operate a number of TEC's at  this low amperage range, and to be able to cap their maximum current draw between .1 and .3 amp.  Any input would be greatly appreciated, thanks

Question by MatthewSternbauer    |  last reply

### Current Artwork

I am doing this for a friend's wedding. The medium is acrylic paints. The photo is fuzzy and doesn't do it justice. You can't see the skin tone changes and highlights, :( This is my first time painting something like this, it's all mainly guess work (The hair, the skin, etc.) Work in progress. What are you working on?

Topic by Spl1nt3rC3ll    |  last reply

### how to decrease current??

I have 12volt 8.5amps battery with me i want the output of 12v & 4amp  i dont knw how plz anyone suggest me

Question by SrinidhiS5    |  last reply

### What is an Alternating current? Answered

It is always easy to understand the working of Direct current, but I need to know about Alternating current right from the basics till advance. I would be grateful if you could help me understand about Alternating current better.

Question by DeeptiR3    |  last reply

### how to reduce current ?

We designed a circuit . But it is drawing 70mA of current. I want tot reduce it for atleast 30-40mA.

Question by SunnyJ1    |  last reply

### Current in IC chip

Hello, It's a bit stupid to ask (I think), but essential to me. From all schematic I readed over intructables I never saw anything or anybody that cared for that. If a IC have a maximum and minimum current to respect ie: 6mA to 10mA, do we even care? Do I need to limit the current somehow? As I said, every schematic I readed never added any resistor or talked about anything relate to limiting the current on the VCC for the integrated circuit. I'm currently building a device that use one 555 timer IC in astable and a few others IC and they are all connected in parralel to the power suply. Thanks

Topic by sxdemon    |  last reply

### High Current measurement

I need to measure Current from a welding machine to make a alarm if it goes down below some level for ensuring better quality of welding. The current normally set is of the order of 200A max with around 100V DC.Not sure if i could use some clamp-on meters and pass those values out to Arduino for switching circuit. Shunt resistors may be a better option. But to make a signal conditioner to convert the ma output will be a problem i guess..is there something i can do with Arduino.. any ideas guys....? Thanks in advance Chuppandi

Topic by chuppandi

I am aware mostly how transformers (AC - AC) work, but I am lest informed on a few key parts.  I know there is a direct relationship between windings and voltage as well as an inverse relationship between voltage and amperage. The thing I don't understand is what limits the current produced by the transformer.  I know you can keep droping the secondary windings to increase amperage, but eventually you get to a point you can no longer do that.  To overcome this one can use three sets of windings wired in parallel which will retain voltage but increase amperage.  The amount of amperage is still limited to the maximum throughput of the primary, but how do you actually find this out.  If one wanted to make a variable current AC welder, it would be relatively easy to predict the voltage, but establishing a potential amperage is more difficult.  What actually establishes the maximum output of a transformer because in some cases the max current is reached long before the actual failure, and is there a way to predict the end product.  P.S. I am not looking for the answer they use voltage/current limiting circuts ect...  I am looking at something like a pole pig which maxes out output before internal failure and contains no additional circutry, not a wall wart

Question by jj.inc    |  last reply

### Current Problems with speakers...

Hey guys, I've uploaded some pictures of my problem. What I have here is an attempt to add bass to my speakers - I'm a newb, so this isn't going so well. The music is comeing from an iDock, and is being routed in parallel to a set of computer speakers. The right speaker has volume & tone knob, the left is simply plugged into the right. I unplugged the left speaker, took the circuitry out, and connected its input & output to a larger bass speaker - quickly was I suprised with a smoking capacitor (lol how healthy!) so... what should I do, simply add a resistor? Edit: Note the resistor (brown red red = 12k? or 1.2k?) is only in series with the LED and is not affecting the bass speaker. I am just wondering how a bass speaker could draw MORE amperage than the small speaker without any circuitry?

Topic by GreenD    |  last reply

### Specific output of current? Answered

I'm getting a little more knowledge about current measured in mA, but it's still all confusing. From my understanding, your project draws the current needed out of your battery. If my LED uses 25 mA, then the LED will be sucking 25 mA from the battery. If I have two LEDs, then it would be sucking 50mA from the battery, thus reducing its life. So, based on that, how can wall warts have a specific output of amps? How can a wall wart put out 1000 mA? If you use a project that only takes 700mA what happens to the other 300 mA? What if your project use 1,500 mA? And. . . How do you measure the current being pulled through a basic circuit and your average 555 circuit? Thanks,

Question by HavocRC    |  last reply

### led current problems?

Im running some leds off a 12v sealed lead acid battery and i need to know the best way to keep it from drawing to much current. Perhaps a fuse or large resistor?

Question by DELETED_cdousley    |  last reply

How can I determine the current rating of a diode  A forward current of 2 amps is needed and the reverse voltage is 12v                                                                hopefully   Gordon                                                                                                   Thank you

Question by GordonT3    |  last reply

### Varialbe current regulator?

Have you ever seen a variable current regulator? i googled it but i keep getting standard voltage regulators Any help would be appreciated!

Topic by Sandisk1duo    |  last reply

### How much will be the current?

If i use a transformer of 2A to make a 12v dc power supply, what will be the output current? Will it be same or some variance will come?

Question by Naveedm15    |  last reply

### BLACKROD's Current K'nexWorkshop

I thought some of you K'nex people might find this fun to look at. I just finished the Cyclone. Currently I'm putting on different rubber bands, as you can see in the picture. Enjoy.

Topic by BLACKROD

### Current measurement with arduino

Hey I try to measure current with hall-sensor amploc 25A, it sense magnetic-fields, offset voltage is 2.5V and I use arduino uno. I get 519 value from analog pin and 37mV/A is hall sensor sensitivity. My formula is outputValue = ((((sensorValue*5000.0)/1023.0)-2500)/37 multimeter shows 0.112amps when I put load but I dont gett correct value on LCD Is my formula OK?

Topic by mattilaniko    |  last reply

### Reducing current to drill

Hey everyone. I'm building a potters wheel for my girlfriend for Christmas, and for the motor I'm using a corded drill. I want to use something like a sewing pedal to control the speed, rather than the trigger of the drill. I've looked it up (on here) and it sounds easy enough, but the problem is that most corded drills are 4 amps and over, and the highest amperage I've found on a sewing pedal is 1.5A, I'm assuming this would blow up the pedal. Is there some way I could use a resistor to reduce the current drawn by the drill? Would the drill still operate on 1/3 the current? It won't need even close to full power. Where would this resistor go? Thanks in advance.

Topic by checkmyusename    |  last reply

### Is it a current limiter or what???

when rebuilding a battery pack for a Sears cordless drill,I encountered a tiny diode or fuse or thermistor of sorts,in the wire coming from the negative pole.It appears this is only active during charging. At any rate,what is it and where do you find a new one??

I built a hotwire device to cut foam insulation. If I connect it directly to a 12 volt battery, it gets 'way too hot very quickly--the hotwire turns red almost immediately. However, if I connect the device to a wall charger rated at 5 volt/2amps, it works fine,if a little too cool for a good cutting speed. What's happening here?

Question by suncoaster    |  last reply

### Current at Maker Faire

Topic by Ajala    |  last reply

I just started reading electronics for dummies and it tells me that DC current flows from negative to positive.  It later states that in the early days of electronics it was assumed that current flowed from positive to negative.  Later they discovered that it flows from negative to positive.  Some schematics will have an arrow for current flow going from positive to negative (conventional flow).   Why do they still do this if they know the current flows from negative to positive?  This is confusing.  Thanks.

Question by pennsteve    |  last reply

### Trouble out putting a DC current to AC current?

Im looking for a way to use a 9v DC current to regulate an AC current.  I have a set up a diagram of my problem: I thought of using a relay but i would like the light to be able to dim not just either be on or off, then i thought of a transistor but im not sure if that will work with both ac and dc at the same time.  I could really use some help here.

Question by keeperrico    |  last reply

### how to make a dc current from ac current?

I m making a power supply project which works on dc. but i don't wan't a battery, so i wanna connect it direct to ac to dc convertor i don't know how to make it :[...... Anyone who answer plzz give detail summary with a perfect diagram of the circuit

Question by arihant    |  last reply

### what makes collector current to be beeta(current amplification factor) times base current?

What makes collector current to be beeta(current amplification factor) times base current? Is it because of shape of the transistor or doping? or Why it is acting as constant current source? or Why the collector current is independent on collector resistor and Vcc(voltage across collector and emitter)?

Question by deepakmurali    |  last reply

### Current Consumtion by a DC Motor?

I am asking few questions EV related, more current related. Let a consider a dc motor rated 4hp at 24v and 2hp at 12v. So is there a way to calculate ampere draw of the motor at various loads.(like no load, full load, or any load). And if we know the full load current of the dc motor then can we calculate the max load for the dc motor. Next as the dc motor is 2hp at 12v then will this value be constant or will the motor be able to produce 4hp at 12v even rather than at 24v. And will a battery eg 50ah be able to supply more then 50amp.

Topic by flyingdutchmen1659    |  last reply

Anyone know where I can download CURRENT free e-books? Current like Rick Riordan, James Dashner, etc.

Question by schoonovermr    |  last reply

### Arduino maximum current draw? Answered

What would the maximum current draw through an Arduino be? (ATMEGA328) - I'm planning on running 16 LEDs from it and I need to know if I should be powering them separately somehow.I have the appropriate resistors (100ohm and 180ohm LED dependent).

Question by jonrb    |  last reply

### Charging capacitors with different currents? Answered

How does charging a big capacitor with a high current affect it rather than a low current? Certainly time taken decreased. What are other effects, and is it as safe as using a low current?

Question by ARJOON    |  last reply

### current limiting for phone battery? Answered

I have a very old phone and its battery is outdated, I am replacing the battery with a new one but that is rated differently Phone ratings: 3.7V DC ; 350mA New battery rating: 3.7V DC ; 860mAh ; 3.2Wh >what is the difference in "mA" & "mAh"? >My main question is ; do I need to put some resistor in between the battery and phone input to limit the current or the current flow depends upon the load ?, do I need to put resistor in series b/w the phone and battery or in parallel. Try to provide a schematic to make answers more clear NOTE: I dont want to replace the phone and am working on it as a restoration project. Thanks in advance!

Question by MYawar    |  last reply

### reducing current on a power supply

So I am trying to reduce the on the current power supply I have from an old router. The out put is 12v DC 800mA (.8A). I want to use it to run a man 12v .3AI just wanted to make sure I did my math right and to make sure I didnt miss anything.Ohms LawI = V/RR= V/I V = 12 I = .812/.8 = 15 ohms resistance in theroy_Current on the fan is .3 A, I am assuming that is the max. So desired current is .25I = .25 V = 12 R is current resistance, X is additional resistance Q=(R+X)I = V/QQ= V/IR+X = V/IX = (V/I) - R V = 12 I = .25 R = 15(12/.25) - 15 = 33 ohm resistance neededSo I would need a minimum of 33 ohm resistor. Am I correct?Sorry for the explicitness of the math, its been drilled into me to show every step.

Topic by dragonkeeper117    |  last reply

### Reduce current but maintain voltage?

Do resistors reduce voltage or amprage? It's amprage as far as i know. I've got a power supply thag outputs 9kV at 300mA and I need to get it to 9kV at 0.2mA, someone suggested a 450kOhm resistor. When I phoned go get one they asked if I want a quarter watt resistor, what does that mean (1/4, 1/2 watt). I need to reduce the current comingfrom the power supply because I'm using it to power a fusion reactor and the diodes I have to comvert the AC to DC can only handle 0.02mA

Question by JunaidA44    |  last reply

### how is ac current generated? Answered

Ok, so I was under the impression that brushless motors were AC motors (and therefore conducted AC current), until recent internet searches proved me wrong. I am curious how AC current is conducted, is it conducted using brushless motors? Or is it a different type of motor that will generate such electricity?

Question by A-Nony-Mus    |  last reply

### Wall outlet current draw

I have built a transformer, that will take 120v, and step it down to 2.5v. I used all the right parts, and the correct rated wire for this. My only issue, is that when i connect the primary coil, to a call outlet, at 120v, it draws more current then my 5A fuse can handle, and the power goes out in my home. I need to get 1.5 amps, @120v going through my primary coil, in order to get the desired output on the secondary. I was wondering, how things "draw" current from the wall, as well as if i where to use a resistor, wouldn't it still draw too much amperage, and just dissipate it in heat, to give the desired output (i cannot use, because it draws more than 5 amps). i could not find a resistor out their, that could handle over 100 watts, so i was also wondering how things like vacuum cleaners only draw a small amount of current. Would i need some sort of current regulator (if that's even a thing)? if you had a light-bulb, and a battery, would the circuit the light-bulb is attached to drain less current, if their was a resistor, and thus having the battery last longer, or would it draw the same amount, and just dissipate energy through the resistor in the form of heat, to give the light-bulb its self less current?

Topic by merlinj    |  last reply

### High Current Power Supply

For a project totally nonrelated to my tesla coil I need a way of regulating a voltage down to 36 Volts at 8 amps. My transformer (or a bunch of transformers hooked together) is suppose to have an output of about 38 volts at 8 amps, yet the voltage (with no load) is actually around 60 volts... Basically I need a way of regulating this voltage. For saftey, lets say the max input is 70 volts and it should be able to handle 10 Amps. The output voltage should be 36.

Topic by guyfrom7up    |  last reply

### constant current or constant voltage?

Hello, I'm looking into driving about five separate piezo ultrasonic water misters and one of them have the rough requirement of 24 volts. my question is if i wanted to drive all five at the same time I'm thinking I would want a 24 volt constant voltage source, is this accurate? Bonus question: what dictates whether a constant current or a constant voltage source is needed?

Question by waldosan    |  last reply

### Increasing current for hho cell?

What is the simplest method for someone like me who has very little experience in electronics and a low budget, to achieve a high current output for a hho cell? This is for a hho cell and torch so the voltage must be low and the current must be high. Basically what Im looking for is a cheap and easy way to create 3v -5v together with 10-100 amps. Are there any specific household appliances that can put out this current? Not car batteries, car battery chargers or wall sockets. Also is this enough to kill you or just give you a bad shock?

Question by mitchells    |  last reply

### How to pulse dc current? Answered

Hi! I was just wondering if people could give me some different ways to pulse dc current. I am trying to power a transformer with dc. Thank you in advanced.

Question by tesla man    |  last reply

### VFD voltage and current needed

I've a Futaba 4-LT-16 9L big VFD display. Unfortunately I'm not able to find the datasheet or exact details about it. Maybe I could contact Futaba... The only informations I found are these two schematics https://revspace.nl/old/IMG_2239.JPG (but it doesn't match with the 4-LT-16 display) https://revspace.nl/old/IMG_2240.JPG (not very useful to me) from this page and this video from the same page. Could someone help me? Are there typical voltage and current for the filament (I think it depends from the length and the display dimension)? What about the grid voltage? Thanks!

Question by andrea biffi    |  last reply

### Low Voltage Higher Current?

Topic by edy    |  last reply

### Measure current and voltage with arduino? Answered

How would I measure the voltage and current of this circuit with an arduino?

Question by flybye22    |  last reply

### What is a constant current source?

I had some questions: What is a constant current source? How does a constant current source work? Do i need a cc supply for an led or would a cv supply work? Thanks :)

Question by qwerty156    |  last reply

### Constant voltage AND constant current? Answered

Hi, smart people of the internet :) Is there a power supply or a converter that can be set on a specific voltage and current, and keep both constant at the same time? I looked at ebay converters like B3606, DPS5015, BST400 and the like. They all have constant voltage (CV) and constant current (CC) settings, but they can't do both at the same time. If for example the current being drawn is too high, the unit switches from CV to CC and drops the voltage as much as needed to keep the current constant. Is a simultaneous CC CV power supply even a thing? Thanks!

Question by Morgantao    |  last reply

### Building a current booster circuit

Need to understand whats going on in this circuit which is a class project.

Question by ighalo_joshua    |  last reply

### Current challenges not visible on iPad

Until last week I was able to pull/view the current challenge on the home page (using my iPad).  Now it seems the only way I can view them is if I log onto my PC and click on "contests". Is there a way to view the current contests (that are still open) conveniently on my iPad?  Thanks!

Topic by kcli    |  last reply

### how to calculate battery current ?

i want to make a ps2 battery, but it is must be up to 5.65 A

Question by Rendydevara    |  last reply

### Bridge rectifier max current

I have 12V 1,8A transformer and few 1N4007 diodes that should rectify only 1A. But if i connect them in Bridge configuration will current pass through 2 diodes at each cycle and be Safe to use Up to 2A?

Question by AnotherD1    |  last reply

### how to limit to current to led's? Answered

Hi all I have a diy led project.  My batteries are dying really fast, I did a litte bit a research and find out that my led are drawing alot of current from my 3 AA's I wire my 36 led's in a parallel fashion voltage supply 4.5v vf = 3.4 per each led If = 20 ma  currently Not running any resistor through the leds.  What is the best way to make the battery last longer or to limit the current that is being supply led's? thanks in advance!!!!!

Question by incogn    |  last reply