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 9 years ago  |  last reply 9 years ago

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 10 years ago  |  last reply 10 years ago

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 2 years ago  |  last reply 2 years ago

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 11 years ago  |  last reply 10 years ago

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 1 year ago  |  last reply 1 year ago

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 1 year ago  |  last reply 1 year ago

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 3 years ago  |  last reply 3 years ago

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 9 years ago  |  last reply 2 years ago

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 there something i can do with Arduino.. any ideas guys....? Thanks in advance Chuppandi

Topic by chuppandi 7 years ago

Transformer current restriction? Answered

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 5 years ago  |  last reply 5 years ago

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 9 years ago  |  last reply 9 years ago

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 6 years ago  |  last reply 6 years ago

Diode current ratings Answered

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 3 years ago  |  last reply 3 years ago

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 10 years ago  |  last reply 10 years ago

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 1 year ago  |  last reply 1 year ago

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 11 years ago

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 3 years ago  |  last reply 3 years ago

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 5 years ago  |  last reply 5 years ago

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??

Question by 9 years ago  |  last reply 9 years ago

Too much current Answered

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 1 year ago  |  last reply 1 year ago

Current at Maker Faire

I'm sure you know that the Maker Faire is next weekend... and all of us at and Current TV are excited to share with you that we are going to be there! If you are going, please drop by our booth and introduce yourself (you can find us at booth #217-X). We'll have a very special DIY treat to share with you, and a full set of computers if you need a place to blog from (and for those of you interested in embarking in the wild world of vlogging, we'll have webcams too!) If you aren't going to the Maker Faire, then feel free to visit us at If there is something that you are just dying to learn more about or get a closer look at, we have a team of people on the ground with cameras in hand who can be your eyes and ears for you. Just email your questions on the above mentioned page, or email Leah at Videocan not parse options from: classid="clsid:D27CDB6E-AE6D-11cf-96B8-444553540000" width="400" height="400">, {width:425, height:350} And by all means, feel free to introduce you and your DIY blog by clipping your blog comments to the You make all sorts of things. We want to hear about it. PeaceAda

Topic by Ajala 10 years ago  |  last reply 10 years ago

Conventional current. A question about DC current flow. Answered

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 9 years ago  |  last reply 4 years ago

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 8 years ago  |  last reply 9 months ago

Limit DC current from LiPo battery?

Dear Colleagues,  could you please advise if there is a way to limit DC current from LiPo battery?  I need to push the high current (80A) through very low resistance circuit, but do not want to fry LiPo. So need to limit the current at 80A I am not an electronic professional, and all solutions coming to my mind are based on increasing resistance of circuit (by adding resistance manually, or constructing something like FET-regulated limiter). The problem here is that I will generate lots of heat, and need too much space for its dissipation.

Question by SergeyD15 2 years ago  |  last reply 2 years ago

Ac current limiting per light bulb? Answered

Dear all.. Please help me to know: how wattage of light bulb(please see photo) is needed for limiting my circuit 120ac 60 watt maximum Thank you so much.

Question by lam 5 years ago  |  last reply 5 years ago

How to increase AC current without using amplifiers and external power source? Answered

Iam having 12V AC and the current 100mA.When i apply the 12V AC to secondary winding of 5V transformer.The voltage gets boosted up to 64V.I don't want voltage to be boosted,instead i want to increase the AC current without using transistors,external power sources,etc.Like the transformer which is boosting voltage when applying AC voltage at secondary.I need to increase AC current only and not the voltage.I want these to be done without using amplifiers.Because amplifiers uses external power source.Any one tell me how to increase current.Otherwise is there any way to increase AC current by reducing the voltage?

Question by Rajkumar2506 1 year ago  |  last reply 1 year ago

Electronics help

I need an easy way to distribute power 2 way and when the on button is switched the correct goes one way and when off then on again it goes another? Thanks

Question by Camyo 3 years ago  |  last reply 3 years ago

i want online or software about circuit creator ...?

Question by Rehmatullah 6 years ago  |  last reply 6 years ago

can I turn 2A into 5A? Answered

I am makinga hot wire foam cutter and using the hot wire foam calculator from Shawn James and it says that I need a supply of 7.5V 5A, but my transformer only gives 2 A. I've seen voltage multipliers and I don't know if there's a current multiplier. If so, please give me the instructions to make one.

Question by tgferreira184 6 years ago  |  last reply 6 years ago

Low AC to DC conversion

Hi, I'm looking for simple way to convert a low AC into a usable DC, of say 4 - 5 volts for charging batteries. I recently saw one discussed online, specced at costing about a quarter, but couldn't find a way to do it, or a way to purchase something like that. Thanks!

Topic by fafnir665 11 years ago  |  last reply 7 years ago

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 6 years ago  |  last reply 3 years ago

how to make current meter with PIC 16f877?

please help, if anyone knows. tell me what components do i need to make current sensor? and the process to be displayed on LCD 16x2

Question by starda 8 years ago  |  last reply 8 years ago

inrush current make mcb trip

Hi all, i have a problem with my miter saw, it run at 220v and have power 1.8Kw or 1800w my house power can provide 2200Va, the problem is, when i start the miter saw the MCB will trip,  so i must turn off all my electrical home aquipment , than i can use my miter saw. i try to search on g**gle and find that it need some slow start, or soft start so the mcb will not trip again. it cause from inrush current, when the motor start. but the slow start  some forum in indonesia say it can be done by using capacitor bank. to repair the power factor but there is no explanation what size of capacitor bank we can use for any diffrent load...especially a big load like mitter saw for sure, how can i reduce inrush current from the miter saw? what should i do?

Topic by beatobe 7 years ago  |  last reply 7 years ago

How much current can IRF540 MOSFET handle?

Question by raftor 5 years ago  |  last reply 5 years ago

how to make a current meter with microcontrollel PIC 16f877?

I want to make a current meter with microcontroller and LCD 16x2 as display. what components do i need? and what is CT?

Question by starda 8 years ago  |  last reply 8 years ago

What is the current on my foam cutter? Should I be worried?

I built the 5 min. foam factory, but instead of a model train transformer ($45 for the cheapest one they had) I used a regular 12 volt transformer and a rectifier bridge (I had to borrow it from my infinite LED tunnel :'( ) Now when I went to buy a variable resistor/potentiometer for the thing my local electronics shop guy said that the 12 volt transformer put out too much current for the ones he had. Now this has me worried. How much current is currently going through this thing? Should I be worried?

Question by shyguy567 10 years ago  |  last reply 7 years ago

What is the output current (limit) of a typical USB car charger???? Answered

I need to power 2 hard disks in the field. Power requirement: 900 mA each. For the 5V connection, I want to convert the 12V power input with one or more car USB chargers. I need to know if one or more chargers in parallel (how many??) are needed. I have sufficient 12 V juice (small lead acid battery). Additional: for surges in power consumption, do I need to add a capacitor? What would be the rating? Do I have to wire it in series or across? (Sorry I'm a layman in electronics...)

Question by BobS 9 years ago  |  last reply 2 years ago

Procedure to getting Voltage and current of an LED without knowing ANYTHING else?

Good day good people. I got batches upon batches of various surface mount and dip leds. Not a single god damn seller wrote the specs on neither the website, nor the package and there are so many that I can't tell which one's from who. Regardless, however the ridiculously low price you get these things for, you can't really complain. So I need to know if there is a procedure to finding out the current and voltage of an led and that is without knowing a single rating about it. It it guesswork or is there a proper testing procedure? It can be a 1,5v can be a 2.5 or a 3v led I don't know. What should be tested first, what should be second? All I have is a basic multi-meter and besides checking batteries voltage I have't been using it for anything else. Thank you, folks.

Question by MilesT9 2 years ago  |  last reply 2 years ago

Please help! How do I lower the current strength (Amps) in a parallel circuit so I don't fry my LEDs? Answered

I have a AC/DC adapter that gives out 4.5V and 500mA, how could I lower the strength of the current so that I can connect four LEDs (4.5V, 20mA) in parallel and not fry them? Sorry if I ask the impossible, I'm a total electric beginner. Thank you in advance!

Question by dark_boshkarin 9 years ago  |  last reply 9 years ago

Current Free E-Books? Answered

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

Question by schoonovermr 8 years ago  |  last reply 8 years ago

Fan needs 12 volts at .44 amps. How can I limit the current to .44 amps from 2 amps, without losing the 12 volts? Answered

I am trying to power a fan that needs 12 volts at 440 milliamps. I have a wall-wart transformer that is 12 volts, 2.0 amps, and I many components. I have thermal compound,  heat sinks, resistors, 12 volt and lm317 voltage regulators. So, how can I limit the current to 440 milliamps from 2.0 amps, without losing the 12 volts? Also, I tried a resistor at 33 ohms and it burnt out. Thank you, Jeremy (Please note: I am teaching myself electrical engineering, I have not taken physics yet. My knowledge is based on sever books, web resources, and hundreds upon hundreds of youtube videos)

Question by JBronen 6 years ago  |  last reply 7 months ago

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 5 years ago  |  last reply 5 years ago

Voltage regulator? Answered

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

Question by .Unknown. 8 years ago  |  last reply 8 years ago

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 7 years ago  |  last reply 7 years ago

how to amplify a dc power of 7v and 130mA to maximum?

I know that i could do that using transistors, but how , what type and what rating of components should i use? should i supply transistors a separate current in order to power it? if i have to supply, is it profitable even after giving that current? Becuz we are wasting a power to increase another power!!

Question by SRI HARIH 4 years ago  |  last reply 4 years ago

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 5 years ago  |  last reply 5 years ago

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 9 years ago  |  last reply 9 years ago

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 3 years ago  |  last reply 3 years ago

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 8 years ago  |  last reply 8 years ago