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Step 3: Power supply

To make the power supplies I just soldered some wire onto the ends of the batteries I had bought so that I could easily attach the LEDs to them. The 9V battery served as my 9V power supply, one AA battery made a 1.5V power supply and three AA batteries bundled together made a 4.5V (1.5V + 1.5V + 1.5V = 4.5V) power supply. I didn't use alligator clips on the ends of the wire, but they would have been helpful here.
<p>Hello, I would like to connect a computercase HDD LED to two HDD LED headers with two pins (positive and ground) on a computer peripheral (a LSI 9211-8i). Normally such a case LED would connect to just one chanellheader, but since I'm using two channels on this particular peripheral, and I have only one case HDD LED, I would like to split the cable in two parts, and connect each part to a two-pin channelheader (layout of the pins is known).</p><p>Would this be a terrible idea and/or would I risk damage to components, or should this be no problem; could you please help me out?</p>
<p>Hello. I would like to wire 8 LED's in parallel to a 6v (4xAA) power supply. The LED's have a forward current of 3.2V each and a max. current on 20mA. Would I need 8x 140 Ohm resistors?</p>
<p>I need to set up 3 LEDs (white or colors) with either 5mm or 10mm LEDs in parallel with 2 AA 2400mA battery. Want this to last at least 6hrs. Is this possible with the right LED and resistor?</p>
<p>Using one resistor to for two LEDs in parallel you would double the current in the calculation. (9-1.7/.04=182.5 ohm.) Would it be correct if you use one resistor for each LED in parallel to divide only by 20ma (9-1.7/.02=365 ohm). </p>
<p>ALWAYS use 1:1, so yeah, that looks right</p>
<p>what sort of wire would you recommend ?</p>
<p>how many watts? if they're small LEDs, you shouldn't worry (unless it's very thick &gt;5mm/ very thin- hairlike)</p>
<p>Ok, let me see if I've got this straight. </p><p>I want to do 50 LEDs in parallel. They're all 3v, 20mA. Assume they're all pretty well matched.</p><p>If I wanted to use a 5V power supply, and just use 1 resistor, my math would look like this:</p><p>50 * .02A = 1A (total current)</p><p>R = (5Vpower supply - 3Vload) / 1A</p><p>R = 2V / 1A</p><p>R = 2&Omega;</p><p>Also, 3V * 1A = 3Watts, </p><p>so I would need a 3W 2&Omega; resistor, correct? </p>
<p>Nooo. First rule of leds is that they each need a resistor in parallel.</p><p>In parallel, the variance in forward voltages (differences from specification) becomes very exaggerated, so they will all draw different currents. In fact, the majority of the current will travel through the led with the lowest voltage drop, and burn it out. This will occur for every led until eventually none of them work. In series, this problem is more or less solved because there's just one voltage drop (across multiple leds) for one resistor.</p><p>For each parallel circuit, the voltage will be 5V. The voltage after travelling through the led will be approximately 2V(+-variance). </p><p>V=IR</p><p>V=5V input - 2V consumed by loads</p><p>R=V/I</p><p>R = 2Volts/0.02Amps = 100 Ohms</p><p>Each led in parallel will require at least 100 Ohms of resistance.</p><p>You could also do 25 parallel circuits of 2 leds in series. Each pair of leds would then require only a 50 Ohm resistor.</p><p>5V - 4V consumed = 1V, 1V/0.02A = 50 Ohms</p>
<p>I learnt this the hard way when a year or so ago, I bought some flashy new UV LEDs and put them in parallel to make a lamp, then watched them all fry</p>
<p>I never knew you could connect resistors in parallel or series being I was always told it didn't matter which way I orientated it since the polarity was the same on both sides. Could you please help in explaining how I would connect in series or parallel? </p><p>Not trying to be an arse just very curios. Thank you.</p>
<p>fyi, series and parallel have nothing to do with direction</p>
<p>Two resistors connected in series: R total = R1 + R1. Two resistors connected in parallel: R total = R1R2/(R1+R2). This has nothing to do with how your orient the resistors when you connect them. This is for changing to the value of the total resistors to achieve a desired voltage drop or share. </p>
<p>if you saw a groove in a resistor, this will increase the resistance but drop the wattage rating (and your chances of a refund if stuff goes wrong)- just a helpful tip incase wattage isn't a problem and the ohms are just two low</p>
<p>The resistor itself allows electricity to travel in either direction through it, much like a door. Putting 5 doors in 1 hallway slows down people more than spreading 5 doors in 5 different hallways. Resistors are kind of the same idea, so connecting them in parallel increases resistance less than in series.</p>
<p>I need to make lamp battery 3,7V it should be commanded by a momentary switch </p><p>1click 1 led on, 2nd click 2 led on, 3rd click off.<br>Anyone can help me?</p>
<p>I don't understand why people recommend microcontrollers. It's stupid and a waste of money, just get a small electrical switch and solder the power cable to it. Doesn't get much simpler than that.<br>Not sure if these switches are toggle or hold:<br></p>
<p>microcontrollers can easily do what weeks of analog or IC design would struggle with. at &pound;3 a pop for a arduino nano with 13 io ports, ic2, 8 analog ports, serial connections and 6 PWM lines, which will also run many other functions, why not? otherwise, you end up with a huge horrible mess of ANDs, 555s, 4017s, ORs, capacitors, NANDs, resistors, diodes and wires ect. whilst trying in vain to find that ONE dry joint in a million connections- I've been there, and digital is easier trust me.</p>
<p>A microcontroller with 4 outputs can go for as little as 50 cents (if you have the software/hardware to upload). Here's an example[http://electronics.stackexchange.com/questions/74201/is-there-an-ic-chip-to-toggle-through-three-outputs] without microcontrollers. You can also build toggles using simple circuits like JK Flipflops, or buy toggle switches.</p>
<p>so, the most easy way would likely be a microcontroller, but you could (if you're willing to settle for a toggle/slider) just use a single pole triple throw switch:</p><p>one lead unconnected, the other two linked by a diode and each two a LED. both other ends of the LED to ground via an appropriate diode each, and the switch's communicator to +3.7v. </p><p>or if you like a challege and are rich, you could use latching AND gates, a NOT gate and a triple pole momentary switch <strong>but</strong> unless you have custom pcb tools and surface mount soldering gear, it will end up massive. also, trying to describe it with ascii charactors will be near impossible</p><p>a slider may also be more easy to use tho</p>
<p>You're probably better off going to an electrical shop (a decent one) and talking to a member of staff </p>
Youre gonna have to use a microcontroller for that, an arduino should do
<p>I'm a bit confused. I decided to find out why cheap LED torches pop their LED's. Not a resistor in sight. 7 white LED's on 3 rechargeable 1.2 V batteries still pop. They are all wired in parallel. The article states how to connect LED's in parallel with one resistor and further on someone states each LED in parallel must have it's own LED. It does seem that should an LED pop the load on the others will go up if only one resistor is used therefore it would be a good idea to run them at a slightly lower current than maximum. Should an LED pop then the current would still be within tolerance and the batteries / LED's would last longer. The light would degrade slightly though. </p>
<p>&quot;Once I knew that I needed a resistor of 140 ohms to get the correct amount of voltage to the LED&quot;</p><p>I think you mean to say that the resistor ensures that the <strong>CURRENT</strong> flowing through the circuit does not exceed LED's <strong>CURRENT</strong> rating of 20 mA. In your previous step...if you had an LED rated at 1.5 volts and you used a 1.5 volt battery WITHOUT a resistor, your applied voltage would be perfect but you would burn out the LED since the current flowing through it would be extremely large.</p>
<p>I understood your post and like to ask you something:</p><p>If ideally we had a 1.7v input, a 1.7v led that consumes 20ma, which resistor you would need to securely feed the led?</p>
<p>So you need to ensure that only 20mA flows through your LED correct? What size of resistor would permit only 20mA to flow when a voltage of 1.7V is connected across its leads? R = V/I, so R = 1.7 V/ 20 mA = 85 Ohm.</p><p>So 85 Ohms is the resistor you need, choose the closest available resistor higher or equal to this value.</p>
<p>This isn't quite correct... 1.7V(in)-1.7V(f)=0V, 0V/0.02A=0 Ohms. It should be fine without a resistor, though a resistor won't hurt if your voltage source has potential to spike.</p>
<p>I understood your post and like to ask you something:</p><p>If ideally we had a 1.7v input, a 1.7v led that consumes 20ma, which resistor you would need to securely feed the led?</p>
<p>I thought that the LED itself can control the current passed through it when the applied voltage doesn't exceed its forward voltage? My teacher told me resistor only needed when the applied voltage exceed the forward voltage of the LED.</p>
<p>I hope I may ask a question, I have a led light that I recycled from a spot lamp that packed it in. the original unit was 6volt but I do not have a 6 volt power source I do however have a 9 volt one. is there a way to use this power source for that led pack? or would I burn them out. I have basic knowledge of electronics but Im unclear on how much these lights would draw if they would take what they need and disregard the rest </p>
<p>There's a circuit called a voltage divider. It's made by placing two resistors in series, then connecting a wire to the center of this series. Look it up, perform calculations to figure out which resistors will split the voltage into 6V, and use it.</p>
<p>I preface this with, my dad was an electrician and I wanted nothing to do with his long drawn-out lectures on the theory of electricity when i was a kid....</p><p>I'm helping my son with a project. His assignment was to build a 3-story building with 7 rooms. Each room has to have 2 lights and an independent switch but all seven rooms have to be powered by one power source. We bought these battery powered tea lights that come with a CR2032 battery and removed the battery (http://www.hobbylobby.com/Home-Decor-Frames/Candle... and then soldered pairs of two in series (7 pairs in total). I can't find any specifications for the lights as far as voltage so the only information I have is what a CR2032 battery provides. These only have to stay powered for a few minutes while the teacher gives the structure an &quot;earthquake resistance test&quot;. Any help or ideas on an appropriate power source?</p>
<p>I want to create something that uses an LED and is wired into a power cable that you plug into the wall. Can anyone point me to toward instructions on that process to I can ensure I am not missing anything or making any mistakes? Thanks. </p>
<p>just buy LED Christmas lights and implement it into your project. Easy,peasy,lemon,squeezy.</p>
<p>Yes buy a 2 or 3 metre led strip 60 leds per metre and a strip of wood same length. get a 12V converting device and connect to strip. stick strip to wood. place in corner of room from bottom to top then you do not have to worry about fixings. </p>
<p>O the 12 V converter usually comes with the strip but it does pay off looking for them seperate as you can really save a couple of dollars on it that way. Do not buy the strip only if you have not found the converter yet. Do not use longer strips or they will fail after a while. Strips can be cut to length where it has the little scissors on the strip. connect plus to plus and minus to minus on the strip.</p>
<p>What would cause my LED to take a while to reach full brightness?</p>
<p>do you have it connected straight to a power supply? With or without a resistor? If you have it connected straight to a power supply maybe the supply itself is the issue. Try changing to a different one. If you have it connected with a resistor maybe the value are too small or too big. It could also be the led itself. I once used led's from Christmas light who had a chip in them to blink and get brighter and brighter as time went by so you should check where the LED came from or the manufacturer. </p>
<p>You would need a microcontroller for that, and some knowledge of coding, and a adapting resistor.</p>
I think you misunderstood my question. It is doing this on its own. I do not want it to do this.
<p>Sorry then, I don't know.</p>
<p>how many volts do I need to power 40 leds in series and what resistors/how many do I need</p>
<p>see my reply up above </p>
<p>how many volts do I need to power 60 leds in series and what resistors/how many do I need</p>
<p>how many volts is each led and you would need 60 small resistors(one for each led) or one big one(enough resistance to keep the power/voltage stable) for all. Like what you would find in an led light bulb. </p>
<p>I have 3 strings of 10 LEDs each powered by two AA batteries. I believe they are wired in parallel (2 wires in 2 wires out).</p><p>Being green minded, I don't want to add to the trash all the used batteries. I would like to connect them together and power them ( now 30 LEDs) using a DC transformer. I'm thinking a 5V transformer, properly stepped down would do the trick but I'm not sure what current rating it should have. Any advice would be appreciated</p>
<p>Hello, I am looking for directions on how to hook multiple LEDs up to one 9v battery without a breadboard. Can anyone give me a hand?? I am an 8th grade student and this is for my science fair project. Thank you ahead of time</p><p>Emmaruth</p>
<p>you could just wrap the wires around the negative and positive electrodes without soldering to test them, then you can see if it works before you permanently connect them together :)</p><p>Sorry if you haven't gotten this reply in time lol ^_^</p>

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