### simple 5v regulator?

Today i made a shaking generator for a shaking flashlight.i am using a 5.5v 1F capacitor as storage device.but output of  the generator is 3v~6v DC.how i can regulate the output ≤5v?.i am looking for most simplest and cheapest method. can i use a resistor?

Question by vina1991 3 years ago  |  last reply 3 years ago

### fast and easy way to get 3.3v from 5v without a lm317? Answered

I got a dvd player but the power supply was missing. i can get the 5v and the 12v, but other than a lm317 (which i dont have) i cant get 3.3v. ive looked at all sorts of things to try and find a 3.3v regulator, but everything i have searched up lead to several misleading results. so i was wondering, what value resistor could i use to get 3.3v from 5v or what devices could i look in to find a 3.3v regulator? i have several computer motherboards, a bunch of cd drives, a couple hard drives, etc. please help! thanks in advance,           zack247.

Question by zack247 7 years ago  |  last reply 11 months ago

### can a battery in reverse act as a resistor??? Answered

I was wondering if for example, putting a 1.5 volt battery in a 9 volt circuit, but in reverse would act as a resistor and take the 9v down to 7.5 volts?  I am too scared to try it, and just wanted to know if it has been tried before.

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

I have am writing an arduino sketch for a mini traffic light projects that will require both 220Ω & 330Ω resistors, I ordered them, the problem is that the resistors I received don't add up when looking at the bands. this is the color band  ORANGE+ORANGE+BLACK+ORANGE+BROWN 3 -------------3------------0----------x3------------1%-------- does not this mean 330 x 3 @ 1% so the 330 is actually 3,300 or would it be 330kΩ It's been years since I've looked up color bands , can I even use these ones for simple 5v led projects or should I just re-order the 330Ω resistors now? thanks in advance robert

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

### Resistor for NPN Transistor Base? Answered

Hey all, I need help identifying the value of the resistor I would need for the base of a 2n2222a transistor in this circuit. If you need any additional information, ask and ill try to answer asap. The resistance of the relay coil is 106 ohms and its rated for 6v but I operate it at 5v. The 3.3v is supplied by a step down circuit connected to the same power supply as the 5v used to operate the relay. If you can, please also list the steps you took to calculate the value of the resistor so that it can be useful for future use, I couldn't find a simple answer online. Ty,

Question by SA-DIY 1 year ago  |  last reply 1 year ago

### How to change 5v into 3v using only resistors?

I need to change 5 volts into 3v, using only resistors, to power a LED, I can't use a voltage regulator, because the LED is to see if the current voltage regulator is working, I am happy to reply to questions that would help you answer it. Thanks

Question by alexw2150 8 years ago  |  last reply 8 years ago

### What kind of resistor do I need to turn 9v into 5v? Answered

I'm making a usb charger and can't understand resistors, so can someone tell me what kind of resistor I need to make a usb charger from 9v battery?

Question by Nameless37 9 years ago  |  last reply 1 year ago

### What resistor and method should I use to string 12 led's in parallel from a 5v source?

I'm trying to figure out what resistor I should use to string 12 blue led's in a ring from a 5v source (like this except instead of 8, using 12: http://www.llamma.com/xbox/Mods/xbox_jewel_led_mod.htm). The specs that I have on the packaging of the led's are: MCD 4000~6000 and VF: 3.0v~3.2v. I read 2 different ways to do this, one (the easier way which I was leaning towards) was to use one resistor for the entire parallel series. The other way was to use an individual resistor for each led. What do you recommend. Can I get away with doing it the easy way, and if so, what resistor (ohms, wattage, and tolerance) should I use? Thank you.

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

### How to reduce voltage from 24V to 12V and 5V?

I have a power supply with output of 24V, 1A. I need to reduce the voltage to 12V to power a water pump and to 5V in order to power an Arduino and an air pump.  Can I just create a voltage divider using resistors for this? The water pump has an input of 12V, 5W.

Question by DavidC1165 1 year ago  |  last reply 1 year ago

### Power 30 3mm LEDs (from battery powered string lights) with 5V 140mA wall power block? Answered

I have a string of 30 3mm LEDs attached to a battery pack which holds 3 C-size cells and has a switch, and a 10ohm 10% resistor (brown black black silver). I'm not sure of the exact specs for the individual LEDs, but they look pretty standard (warm-white, 3mm.) I think they are connected in parallel (2 wires in to each, 2 wires out) I also have a power block (wall wart) from an old vacuum which outputs 5V DC 140Ma. Is it possible to power the LED string with the power block, and if so, what kind or resistor should I substitute for the original? (and, for future reference, how did you arrive at your answer?) How does supply wattage matter? Might as well throw this in as well: what resistor would I need to power them with USB?

Question by Vick Jr 9 years ago  |  last reply 9 years ago

### how to convert 12volts 7 ah to 5 v 1ah? Answered

How to convert 12volts 7 ah to 5 v 1ah 12 volts can be connected to 7805 for converting into 5 volts but how to convert current. current could be limited through resistor but which? also give formula of how to found it out

Question by yhdesai 4 years ago  |  last reply 4 years ago

### How to get 5 volts from 4xAA batteries?

Hi all! Whats the best way to get a nice circuit friendly 5 volts from 4xAA batteries? Measuring some brand new AAs, they're about 1.6v when new, which drops under load, I know. So four AAs of course add up to 6.4v, possibly blowing my low current circuit. And isn't a 7805 voltage regulator only good with aroundabouts 7-8 volts source because of how they work? Plus DC-DC converters are expensive, and resistors are wasteful. :-) Thanks!

Question by Heliosphan 8 years ago  |  last reply 6 years ago

### in where do I find and how do I tell if it is a 5v regulator?

I need to find a five v regulator(7805) for a portable 9v battery charger and i cant go out and buy one. can someone tell me in what device i can find a resistor(specifically 5v).  And i need to know how to tell if it is a 5V Regulator. heres one i found.. does it look like a 5v?                                                                                                                                                                                                                                                                       thanks,                                                                                                                              The DoctorOfAwesome

Topic by Dread_Neck 8 years ago  |  last reply 8 years ago

### I have a 6v solar panel. What resistor should I use to get it to 5v? Answered

I purchased a 6 volt output solar panel from radio shack and I need to get it to 5 volt. I have a large assorted pack of resistors but I am fairly new to what is what.

Question by jeoncs 10 years ago  |  last reply 10 years ago

### Calculate Resistor for Heating Wire

Hi there, My Goal is to use a piece of heating wire from an old hair dryer  (1.6 Ohms resistance for the length i want to use.) and heat it red-orange using my old USB power bank. 5V output from an 3.8V lithium ion battery i dont want to mess with the circuitry inside. Problem: The USB Power Bank has short curcuit prevention built in, so when i connect the heating wire the power bank stops supplying electricity. I found a 7.5 ohms resistor and connected it aswell, the wire became a little warm, the resistor incredibly hot but most importantly the power bank continued to supply power - success. I would like to know what resistor i should use to get the wire red-orange hot but at the same time keep the power bank safe and not overwhelm it - i think that would mean not drawing too much current? I also cant check how much current is flowing because my multimeter is too cheap and only goes up to 200ma, which the power bank exceeds. So how would i go about this? What resistor should i use for what wattage should it be rated. And since im a total newb id like to hear your train of thought as to why and how. Thank you so much.

Topic by emiliori 2 years ago  |  last reply 2 years ago

### Converting 12v DC to 5v DC

Greetings, I’m very new in electronics. I would like to connect my analog camera that uses 5v dc to my car battery. So I need your help to make a voltage converter. From what I have understand searching the web, I will be possible and very easy actually. All I would need is an opamp and some resistors?!!! Right? So any diagram or anything that you can help me with will be more than appreciated. Thank you for your time reading this. Best Regards P.S. I hope I’m in the right place writing this topic

Topic by toqilula 8 years ago  |  last reply 7 years ago

### led n00b here, need a little help

Hey guys i am new to electronics and figured id start with leds, my first project will be to make a torth from a penguin caffinated mints tin using some domestic batteries, some Super bright (17000mcd) 3v Green LEDs and 10 resistors only described as "Used to operate a 3.3v LED on a 5v Power Line. " and the same for the 10 12v resistors. now can anyone tell me. when would i need a resistor in my circuit? (i know the one for the 12v line would be perfect for arraching to a car battery and not killing the led.) but the 5v resistors? when would i use them? when i make this torch i will be using 2 or 3 aa batteries, 2 aa batteries make 3v and these leds are meant for 3.3 so im assuming i wont need a resistor however if i used 3 aa (4.5v) would i need the 5v resistor or would it be to much? im sorry im confusing thanks

Topic by Cew27 10 years ago  |  last reply 10 years ago

### How can I multiply/double (or just increase) voltage in a DV 5v curcuit ???

ok i have the following parts to ue for this: (all leftovers from former project..)  :) 1x mosfet IRF510 power transistor 5,6A 100V 9x 2N3904 amplifier transistors 40V 0,2 A .0.625 W ~16x 1uF capacitors 50V ~99x recifier diodes 1A 50V ~35x 2k resistors  0.25 W the idea is to charge a battery pack consisting of 4x 1,2-1,25V = 4,8-5V 3000mah AA nimh batteries using my 5v usb wall charger that has 1A output! i tried connecting the battery pack directly to + and - and 'i think' its starting to charge but after 1-2 hours at full rate (5v 1a) it should be at least 50% charged (3 hours would be full charge -> 5W x 3 = 15W), but if i connect them they last for about 2 -3 minutes and then empty again!! so after this im concerned that i might need at lest 6V-10V to achieve the desired effect !!  -> charge 15W NIMH batterpack with wall charger (nokia ac-60e.. 1-1,5A) i nless than 3 hours (as like a phone would need !!) therefore i need a cuirciut (ONLY DC) to double my 5V OUTPUT to 10V (yiou shouldnt apply more than twice the curent of a batter pack) or ideally 6-7 V but i dont know if thats possible without a swiching IC or more different resistors.. so just doubling would be nice at the moment!!

Topic by sblocc10 1 year ago  |  last reply 1 year ago

### how many ohm resistor do i need to get 5v from a 9v battery? Answered

Hello i am writing up an instructable on setting up a wireless receiver , however i requires both 5v and 9v output, and the whole point of it is that it is simple and cheap, so i need to know, how many ohm resistor do i need to step down 9v down to 5v? i do not wish to use a 5v regulator unless one can be bought for less than \$2, or else the instructable will cost too much.

Question by oldmanbeefjerky 7 years ago  |  last reply 7 years ago

### How can I make an ammeter for ~5V DC up to 3A? I want to connect this ammeter to a microcontroller.

I want to connect this ammeter to a microcontroller ADC and display it on 7-segment displays. I guess a 10W resistor ~0.1ohms or something will be involved. I can obtain them easily. I want to make an inline USB ammeter. I am experienced with PICAXE microcontrollers and surface-mount.

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

### Why does this circuit need these resistors connected to the transistor? Answered

I was following the instructions from the book, "Arduino for Dummies", and worked on this tutorial with a dc motor and it says that I need a 2.2k ohm resistor connected from a digital output pin to the transistor's middle pin. Why does it require a resistor there? Is the transistor not able to handle 5V?

Question by seonghoon52 4 years ago  |  last reply 4 years ago

### Best resistor to lower my current?

Hi everyone, I recently started to get into electronics and now need some assistance. I have a 12v and I believe 1A of power. The component I'm connecting is 3.7v with a 450ma battery that uses 3W. I using a l78m05cp, I built what should be a 5v .5A psu, but I must have calculated something wrong because fried my component. I believe the current is what I'm not getting right. Using P=IV, I found I should be using .8A, but I really am not sure about it. Please help, I'll go broke if I keep frying things!

Topic by ramirez_armando 5 years ago  |  last reply 5 years ago

### 9v to (5v-3v) for pic 16f628a

Problem: I have a 16f627/628 (runs between 3 and 5 volts) that needs to work in tandem with another device (call it D) running at 9, direct current, (active for 1 second in 30 or less frequent). Upon hooking up a number (of descending in size) resistors (without D connected) with the supply and 16f6xx the 6 LED's powered by the 16f6xx do not turn on unless resistance is extremely minimal, and voltage is well above that advised in the datasheet (not to mention making the pic reset itself every 10ms). Can anyone tell me how I might run the 16f6xx from a 9 volt battery, and explain what was going on? This may seem unforgivably dim to anyone who knows but unfortunately I'm more a software guy learning hardware as I go along. Any help would be much appreciated, Thanks Andy

Topic by andy 11 years ago  |  last reply 11 years ago

### Question about opamp, resistor and capacitor? Answered

Hello i have some questions. 1.Im going to build a ROG Tonemender (http://www.runoffgroove.com/tonemender.html).What the 10M resistor do in this schematic ? and its ok if i use a smaller value like 2M or 4M7 ?? 2.If a opamp rated output 10W with 4 Ohms speaker, how many W i can get if i connect it with a 8 Ohms speaker ?? can i have the formula for this please. 3.My amp have output power is 100W , can i connect a 8 Ohms 26W speaker to the amp ? 4.I want to find an opamp like LM386 but use lower supply voltage (5v) can you give me some suggest please. 5.What type of capacitor in the picture bellow ? Thanks for advance. sorry for my bad English!

Question by login721 7 years ago  |  last reply 7 years ago

### Anyone Have experience with Adafruit Square FSR?

I am hoping to create a circuit that will variably control the speed of a motor through pressure. If I were to wire up one of these http://www.adafruit.com/products/1075 , simply as the switch between a small motor and a power source around 5v, would it work to simply turn the motor off at rest and vary the speed with pressure? Is there a way to use this resistor as a "switch" without using an Arduino or  other micro controller? Any help is appreciated. Thanks!

Topic by Flashflint 4 years ago  |  last reply 4 years ago

### How to make it work? USB + 5V rechargeable battery + 12V LED strip!

I want to an LED Strip that works my USB or Battery, I got the battery and the USB working fine, the battery charges up without problems, but I need to light the LED Strip (12V) with a 5V battery. Is there a DIY way to: -Step up the voltage, or -Step down the LED Strip Voltage. I know each SMD LED works around 3V, but I can't make sense of the wiring and resistors on the Strip, to wire the SMDs in parallel.

Topic by RaptorHunter 4 years ago  |  last reply 4 years ago

### What Ohm resistor do i need to turn 9volts into 5volts?

Question by dilydan 10 years ago  |  last reply 10 years ago

### what resistors to pay or what to do ? Answered

OK guys i need help in a simple project i need to make 15 board every board have 5  white LED its 5mm 3.5 v some boards will be connected i when and got 150 LED and 5 test board  but cuz i don't know what resistors i didn't get any so i made my first board connected a Nokia charger to it , it gives DC 5.7 v and 800mA  it burned all 5 LED i used . i will cut the boards down to 15 or 20 small ones OK i will connect 5 boards to gather. how can i calculate what resistor to use . should i use this charger or i get another one. what should i pay to make that work .:update:. i got 150 resistor 150 ohm 2 220v to 5v 1000 mA adapter  and 5 more test boards the first test i got  from a usb cable the lad give me a blue color that is a sign of great power  the with the resistor it gave me white color so i will make the 2nd test with the adapter

Question by hfayed1 7 years ago  |  last reply 7 years ago

### can you u get 12 volts down to 3 volts by using a 5 volt regulator and a 1/4th wat resistor? Answered

I need my car to go from 12 volts to 3 volts for LEDs... please help me!

Question by led235 9 years ago  |  last reply 9 years ago

### 3.7v to 4.5v how ? Answered

I have an wireless game controller which runs on 3xAAA(4.5v) battery... i also have plenty of spare li-ion 3.7v batteries upto 1000mAh.. so what i'd like to do is install that rechargable li-ion battery into my game controller... so i dont hv to buy AAA batteries every time...pls guide me how... and pls tell me as simple as possible... because i live in india..n small electronic parts like resistors,regulators etc. are reallyyyyyyyy hard to find here... thank you in advance...

Question by D3zire 5 years ago  |  last reply 11 months ago

### Connecting a Gameboy to my Mouse.

I got a lot of Gameboys, (I bough em cheap to do some hacks) My Logitec mouse uses 5V ofc. My Gameboy needs his 3V.   So far I have heard that I should therefore use a 200ohm resistor. The question is, can I hook the Gameboy directly into the Mouses powersupply? Or do I have to add a second usb cable for it's power? Also, do I even need the resistor?

Topic by Schoening 6 years ago  |  last reply 6 years ago

### Strangely behaving circuit, why? Answered

I have a circuit with a Lithium battery driving 12 same LEDs in a parallel setup. The circuit looks like this: http://i.imgur.com/FoBT5C0.png (also visible at the bottom of the question) The battery is charged to 3.8V and the LEDs have all around 2.73 forward voltage and they're rated for 20mA. According to my calculations the resistance should be much higher for the circuit to have 240mA (20mA*12) current but even with this low resistance the current is not enough. And that is what I don't understand. I even used this (http://ledz.com/?p=zz.led.resistor.calculator) calculator according to which I should use 4.7Ohm resistor. But even in my circuit with such low resistance I only get about 194mA. The other strange thing is that when I measure current flowing through one of the LEDs it's about 25mA which doesn't add up. 25*12=300 not 194. Where is the current coming from? And why is the current so low when the resistance is only about 1 ohm? Thank you for any suggestions. PS: I also tried using a LM317T in a current regulator setup but it didn't work either. The current was calculated to be 240mA but was much much lower and when I tried to use 5V power supply the current raised (which it shouldn't when using voltage regulator) but still wasn't 240mA.

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

### need some basic help with resistors and arduino

I'm just starting an arduino uno that I got for christmas and I have almost no electronics experience. I have a breadboard that can give me 6 volts, but what type of resistor do I need to get 5 volts out of it, or is it possible to split the 5v pin on the arduino board. What I'm trying to do is recieve an input from 2 buttons. I tried searching for it on google and found nothing. Let me know if I posted in the wrong section too, because I wasn't quite sure if the Tech section is right. Thanks in advance.

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

### How exactly should an LED circuit be properly set up?

I know LEDs need resistors or else they'll die out really fast. The problem is, I'm having trouble figuring out how this needs to be done. Lets say I take this LED: White 70° Diffused 5mm LED: Luminous Intensity: 690mcd typ. @ 20mA Max Forward Current: 30mA Pulse Current: 100mA for <= 10ms, duty <= 1/10 Forward Voltage: 3.6V typ. 4.0V max @ 20mA Max Reverse Voltage: 5V Power Dissipation: 120mW Operating Temp: -30 to +85 C Soldering Temp: 265 C for 10 secs Max Reverse Current: 50uA @ 5V ok so it has a current of 20mA and a forward voltage of 3.6V. Now, If I wanted to power 6 of these with AA or AAA batteries How many would I need and what ohm resistors would I need? It's been a long time since I took a class on electrical currents, and it was pretty basic. Also, looking at the Reverse Voltage, what is that? Is that if I put the batteries in the opposite direction, i.e. Send the voltage INTO the - and out the + ends? I've been researching this but its hard to find the right answer. Lets say I'm making a basic serial circuit with the batteries here (lined up).

Question by joshka89 8 years ago  |  last reply 8 years ago

### Odd Breadboard Question

Hi All  I am brand new to hobby electronics and would love one day to be able to create the endless amount of cool Instructables but I have ran into a problem on my first attempt at putting theory into practice and would really appreciate any help. I have made two diagrams / images showing the circuit I made I have attached them to this post. I am using an Arduino Uno as a power source.... I ran a 5v positive from the 5v pin on the Arduino using solid core jumper to the top of the breadboard onto the positive row / rail and a negative / ground jumper to the bottom of the breadboard. In the middle of the breadboard I placed a 1k ohms resistor bridging the gap / grove/ divide and ran the positive feed through it and on to the anode leg of the LED. The cathode leg of the LED was connected to the negative row / rail completing the circuit. All works as it should because of the high resistance from the resistor the LED barely lights and is green as it should be. So without using a multimeter I know and can see the resistor is clearly working. However if I move the resistor so it's still on the same line / row as it was but no longer bridging the gap the LED goes super bright and turns yellow which means that the resistor is no longer working which I can't figure out why because I know there is definitely current flowing through it given the extreme reaction of the LED. I vaguely remember reading somewhere on these forums that Fritzing is not liked very much so I hope no one minds but to help explain what I mean above I have created two diagrams / pictures using Fritzing. The images diagrams shows the resistor "bridging" and working and the other shows it not bridging and therefore not working. So my question would be why given the resistor has current flowing through it does it not work unless it's bridging this middle divide / gap / grove? It makes me think I am missing something really stupid that everyone should know about breadboards but just seems really odd to me. Many Thanks Rab

Topic by belfastrab 4 years ago  |  last reply 4 years ago

### Is the reverse voltage on all LEDs always 5v or more?

I have a bunch of LEDs (mainly 0603 and 5050 smd, 3mm, and 5mm - all colors).  Most of them don't list a reverse voltage.  Those that do say 5volts.  My question is, do any LEDs have less than 5v reverse voltage?  Is it possible to accidentally kill them by connecting backwards to a 5v power supply?  Should I put resistors on both the positive and negative to protect them (would that even work)?  Thanks.

Topic by aliasjanedoe 5 years ago  |  last reply 5 years ago

### How do I control 2 servos with 1 switch (using 555 timers)?

Currently I am working on a project that requires 2 servos to move in opposing directions; going from 0º to 180º on one and 180º to 0º on the other. After looking at the useless machine instructable, I decided that 2 555 timers attached to 1 DPDT toggle switch (ON-ON) would work best, however I need help with the exact resistance and capacitance values for the resistors. To get the servo to be at 0º (technically -90º) it needs a 1ms pulse every 20ms. To get it to go to 180º (technically 90º) it needs a 2ms pulse every 20ms. The servos run off of a max of 5V, so I am going to be using 3 AA or AAA for 4.5V.  Thanks, -n8

Question by n8man 7 years ago  |  last reply 7 years ago

### Limit current for a circuit using 5V 450mA power supply?

Have a 5V DC power supply that is rated for 450mA +-50mA...want to use it for a 5V circuit with an Attiny85 and a couple of LEDs. I don't think I could use a voltage regulator since that will bring the voltage to lower than 5V, but the current seems high for use in a small circuit. How can I limit it? Using a resistor? Or should I not bother?

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

### joule thief: can i use a cellphone battery charger to power a joule thief? output 5v~ 400-600mah. Answered

What resistor should i use? a 1k resistor,220ohm or a variable resistor/potentiometer B50K is ok?  masters help pls.. im noob

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

### Using Arduino and 8 servos!? What type of power source? Answered

Hey Arduino guys! I got a question. I am using 8 servos with my Arduino. All the servos are hooked up parallel to the 5v and GND on the Arduino. All the control wires are hooked up on pins 2-9. I'm using 6 AA batteries as my pack. Is this OK for my Arduino? With all these servos moving at once, I want to make sure I'm not frying my board. Oh, and, got another question. The 6 AA batteries are too heavy for my robot spider, so I want to use two 9v batteries instead. But, this delivers 18v. Arduino and only go up to 12v. So, what can I use to bring my 18 volts from two 9v batteries down to 9v or 5v? What can I use? A voltage divider with resistors? A voltage regulator (whatever that is :P)? Thanks guys!

Question by HavocRC 6 years ago  |  last reply 1 year ago

### How should I regulate the power for my motors?

Hello, I am planning on building a stepper motor driver using Tom McWire's design. I want to control 3 motors which are rated for 7 volts, 350mA, and 20 ohms. I plan on using a 12 volt 5amp power supply. I am trying to figure out what kind of resistor I should use so that I do not fry my motors. Maybe I am missing something, but this is the way I am looking at it.... If the motor is using 7 volts and the power supply is 12 volts, that means i have 5 volts left to use. 5v over .35amps (the amount the motor uses) is 15ohms. (14.28 rounded up) That also means it uses 1.75 watts (5*.35). Would a 15ohm 2 Watt resistor be sufficient or am I looking at this all wrong? Thank you for your help in advance, folks :-D

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

### How to convert 5V of power to 3V to power a strip of 10 parallel LEDs.

I have a set of 10 parallel LEDs that are designed to be powered off 2 AA batteries. The problem is that they eat through them too quickly, and I wanted to modify them to run off AC power. I want to use an AC to DC power adapter but it outputs 5V of power, when the battery box says it inputs 3V. So I need to turn those 5V to 3V, the easiest way is to use resistors, because they are the easiest to get around here. Which resistors would I need?, I don't fully understand all the data these online calculators give me.

Question by Dandeil 9 months ago

### How do I use a 3.3v micro with 5v signals & transistors?

I need some help with a gap in my electronics knowledge. How do I use a 5v signal as input to a 3.3v micro controller, and inversely how do I switch a transistor with 5v load, from the same micro's output pin? (@3.3v)? Can I just use a suitable resistor on the input pin, and for the output can I simply drive the 5v transistor with 3.3v at the base?

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

### 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 4 years ago  |  last reply 4 years ago

### D-Flip Flop and Clock Alarm

Hey there! I'm trying to hook up one Set Pin of a 74LS74 Double D-Flip Flop to the alarm of my clock. I've already desoldered the annoying buzzer thats been there before and am now measuring the voltage provided to the buzzer. Unfortunately the circuit only provides around 0.1-0.7V (crescendo alert) with each beep, which doesn't seem to be enough to raise the Set Pin to HIGH (0.8V min. I think). So I guess I'm supposed to use some kind of transistor now. Just to make sure I'm asking you guys. Also, if I want to run the clock from a 5V DC wall wart instead of the original 1.5V battery, I suppose the only thing I need to add are some resistors in series. Would that be correct or would there be anything else needed to ensure the clock takes no damage? Would be really nice if someone could help me out with this! Best regards, Philipp

Topic by Christoph680 8 years ago

### How many resistors and what value do I need for building a L.E.D cube Nightlight 3×3×3?

I am using a 5V DC Phone Charger as the power source. In total there are 27 leds, green led 5.0mm.

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

### read external 6V power source via 5V driven arduino?

I need to check external 6V voltage for a servo circuit on my 5V USB driven arduino uno - in order to not waste power & "over-power" the arduino's analog pin reading the external 6Vt: - should i use a voltage divider with high resistor values? i look forward to your advice …

Question by marc_is_curious 4 years ago  |  last reply 4 years ago

### Led Nighttime Light

I wanted to make a red LED flashlight, but wanted to run it with a 9v battery. What resistor would I need? I don't have alot of knowledge about resistors, so what size and color resistor would I need? I'm using a 10mm red LED, with a max forward voltage of 5v, max forward current of 40mA and a 5000mcd intensity.

Topic by John Smith 12 years ago  |  last reply 12 years ago

### 5mm led problem

I want to make a 5mm white led  series and run it by 5v power supply so i want to use 1 resistor is it possible?????

Question by dey suamn 1 year ago  |  last reply 1 year ago

### Will this circuit with 3x LED work? Answered

I'm planning to do a little light with a changeable color and light intensity. I made up this schematic but before I buy a needed parts I'll be glad if somebody checked it after me if it hasn't some flaws I overlooked. Picture of the schematic (don't mind the white box at the bottom): http://i.imgur.com/QsYh1fJ.jpg Notes: -the power source is 3.7V Li-Ion battery -the box right next to the battery is a 5V step-up module (this one) -the resistors are different because the LEDs have different Vf, every one is calculated to limit the current to ~18 mA (with potentiometers at 0) -all potentiometers are the same with 1K max and 0.05W (I'm not sure if the wattage is enough though) -the LEDs are all marked as a 20 mA, that's why I limit the current to a safe 18 mA So what do you think? Will it work? Is there anything that could be made better? Thanks for all replies!

Question by amdlo 4 years ago  |  last reply 4 years ago