5v battery backup?

Hi, I have a 555 timer circuit running in monostable mode which I need a battery backup for.Anyone have a simple, reliable circuit that can achieve the following results :1. Switch power between the 5v cell phone charger and the battery in the event of a power outage. The "switch" needs to be seemless otherwise it will trigger the monostable as it is set to trigger or re-trigger whenever the power goes off and on again.2. Charge the battery when the power is on.3. Stop charging the battery when it is fully charged.Any other suggestions will be much appreciated. I am not rigid on the design and use of parts, although....the cheaper the better without compromising on reliability (of course).This is for a security system that drives two lasers, a camera and a cell phone. Not sure if the cell phone battery can be used to power the "backup system" as well as run the cell phone.Thanks in advance.GK ;)

Asked by GhengisKhan1981 9 months ago  |  last reply 9 months ago


battery backup

I have a really cool sunstech weather station but when the power goes off it loses time date and weather prediction. I live in Spain and we are prone to daily power cuts. I need a low power 5v back up system to power it. Any ideas welcome

Posted by malchall 4 years ago  |  last reply 4 years ago


Where find 5v regulators?

Hi!Where can i find 5v or 12v voltage regulators?

Asked by ondrikczech 6 years ago  |  last reply 6 years ago


Help! (5V psu problems)

Help!I'm trying to make a 5V psu for programming my new (but not so shiny v_v) ATtiny2313'sI've got the circuit shown below set up, but I'm getting out around 5.6V, when the spec sheets say that I'm supposed to be getting out 5V (+/- .2V) I'm using the LM 340t5, just 'cause I don't have any other regs (except for the MC78M05CT, which is basically the same thing.Any Ideas?!EDITI know what was wrong - it was my meter, it really was 5V all along ;)

Posted by T3h_Muffinator 11 years ago  |  last reply 11 years ago


5v and -5v from 9v? Answered

How can I get +5v and -5v from a single 9v PP3? Not 4.5v, I could do that easily with a voltage divider. Preferably using only passives and discretes (Inc. voltage regulators)?

Asked by andy70707 7 years ago  |  last reply 7 years ago


5v to 12v step up

Hi, I am looking to power some led's by USB. Problem is that the led's are 12v. Here are some example led's: http://www.ebay.co.uk/itm/12V-SMD-1M-60-LED-STRIP-LIGHT-RED-HOME-AQUARIUM-CAR-/290571186666?pt=UK_HomeGarden_Lighting_Lamps_Lighting_SM&hash;=item43a76471ea#ht_3932wt_1396 Would something like this do what i want it to do?:http://www.suntekstore.co.uk/goods.php?id=14002311&utm;_source=gbuk  Also looking at the step up booster i have no idea where i would solder/connect wires to the device? Any help would be appreciated. ItzMar

Posted by ItzMar 6 years ago  |  last reply 6 years ago


will 5v stepper will work on 12v?

In "https://www.instructables.com/id/eWaste-60-3DPrinter/"   the datasheet for pl15s-0120(Stepper of dvd drives) says it operates at 5V , Didn't the a4988 gives 12v out ? , will it gonna work ? (posted comment there but no one replied .....)

Asked by _Boltz_ 3 years ago  |  last reply 3 years ago


4.7uF capacitor 5V or lower????

Do someone know where i can buy a 4.7uF 5V (or lower) in europe????

Asked by Dannne11 8 years ago  |  last reply 8 years ago


5v relay module with tv usb

Hello there! I'm sorry if someone already asked this question but I can't find it! I would like to connect 2m led strip to my tv usb so it turns on and off with tv. Can I use this kind of relay ( http://www.ebay.com/itm/5V-1-Channel-Relay-Module-H-L-Level-Triger-with-Optocoupler-for-Arduino-Raspberr-/390865576871?pt=LH_DefaultDomain_0&hash;=item5b016763a7 ) to do it?  Thank you in advance!

Posted by tosho82 4 years ago  |  last reply 4 years ago


-5v Voltage Regulator

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

Posted by mrshow555 11 years ago  |  last reply 11 years ago


"5 volt limit" circuit? Answered

Is there a circuit that will take a range of voltages and make all of the voltages that are over 5 volts be 5 volts  like so: 3.5 => 3.5  4.2 => 4.2 4.9 => 4.9 5.1 => 5.0 6.3 => 5.0

Asked by flybye22 8 years ago  |  last reply 6 years ago


5v to 12v convert

Hello, I want to connect a portable solar powered rechargeable to 2 DC fans of 12v to cool my car. 1. I have 2 options of portable solar powered: (A) 1500mAh, outputs: 5.5V / 800mA (B) 2000mAh, outputs: 5V 500mA     which one is preffered to connect to those PC fans? 2. most of the PC fans are working at 12v. I don't quite sure if I'll build simple 5v to 12v regulator it will works and produce enough airflow. Thanks.

Posted by ashakif 7 years ago  |  last reply 2 months ago


Pulse circuit?

I need to make the circuit that every time it charges the capacitor to a certain voltage (e.g. 5v or 12v) it discharges it

Asked by Dantex 8 years ago  |  last reply 8 years ago


covert 3V battery source to 1.5 V

Hi Guys, I have a 3V battery source and want to convert it to 1,5V to run a device. How do I go about doing it? Will a voltage divider work accurately?

Posted by kurtselva 5 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!

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


zener diode (limit 9v to 5v)? Answered

Can i use zener diode  to limit voltage from 9v to 5v? ( i would use 5v zener diode ) can this work? what else do i need to use? and  is this way efficient? i was thinking to power my phone with this or to charge my light

Asked by tealk 5 years ago  |  last reply 5 years ago


USB 5v step up to 12v?

Is there any such thing as a device that will step up 5v from usb and convert it to something else like 12v? I say this because I have a solar usb charger that charges a 2600 mah battery and outputs 5 v at 800mah to usb. i wanted to step it up so it could be used for other things.

Asked by XBLmonster 6 years ago  |  last reply 2 years ago


Variable speed on a 5v brushless fan

Hi everyone! I have a 5v DC (0,15A, 50mm x 15mm) computer brushless fan that I want to power with a battery pack (4x AA rechargeables= 4,8v) or the MightyMinty Boost. This small blower is meant to be a part of a woodgas stove, and will bring air to the fire through a small duct. I'm looking for a circuit that would allow me to control the speed of the fan and the airflow. Kinda like a dimmer switch. Is there a readily available switch or devices that I could plug between the batteries and the fan? I guess the RC guys out there know a few thing about variable speed controller. I'm a newbie at this; I don't what to build a circuit from scratch, unless it's really simple. Thanks

Posted by jemor143 7 years ago  |  last reply 7 years ago


convert 5v DC to 3.3v DC?

Hello would somebody help me with this please, I am not much of a "electronic" kind of guy so this is a big problem for me. I lost the power adapter of our office router WRT54GC (linksys) and my boss has his finger cross on me. I only knew of its power which is 3.3volts 2A DC. From my location, it is very unlikely to obtain a replacement or an equivalent adapter. I have salvaged a power supply of and old printer that gives off 5.0V 2A DC but the router would not run with this voltage. I will really appreaciate it if somebody would be able to help with a step by step explaination on how to lower the 5v to 3.3V . Thank you very much.

Posted by gincasty 9 years ago  |  last reply 9 years ago


Looking for a 5V valve to be driven by ARDUINO

Hi everybody, I am working on a project to make an automatic watering system driven by arduino. I am looking for a valve which I could operate without any extra power supply but the 5V from the ARDUINO. It would be perfect if the valve could be in the range of the 6mm for tubes connections. As my project will rely on gravity for water movements, I don't want to use a pump or whatever active device. Just some standard batteries connected to ARDUINO. Do some of you know such a valve? I have looked on the net without any success. I have found loads of watering projects using arduino but none with the same phylosphy. If you know one, please let me know. Regards,

Posted by BaptisteL8 1 year ago  |  last reply 1 year 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

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


What t is the difference between the -12v and +12v, -5v and +5v...in a computer power supply? Answered

 I am building an AC to DC power supply based on several Ibles and I am not sure I understand what the 2 different voltages are (-12v, +12v; -5v, +5v ....) Thank You!

Asked by missplumeau 9 years ago  |  last reply 6 years ago


12v and 5v Power Supply from 240v Answered

I am creating a home automation device that uses an arduino. The devices are connected to a relay. The real problem is I am using a using a DTMF decoder with the relay, while the relay works only with 12v power supply the DTMF decoder works only on 5v input (USB from computer to arduino). The devices that I know of are capable of converting a 240 v to 12v or 5v not both. What should be done so that I am able to get a 12v and a 5v from a normal 240v household power socket?

Asked by NirmalMRaj 2 years ago  |  last reply 2 years ago


How can I convert 12v down to 5v? Answered

Asked by niranj_1994 9 years ago  |  last reply 10 months 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!!  

Posted by sblocc10 1 year ago  |  last reply 1 year 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

Posted by Dread_Neck 8 years ago  |  last reply 8 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  

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


Can I power a monitor from 5 volts?

Even if I have to open it up can I run this on 5v using a buck converter or by modding the screen? The screen is a RCA DRC69702 that came with a dvd player and all I want to is power it freom a two port battery. one port will be hooked up to the monitor and one to the raspberry pi.

Asked by nerd7473 4 years ago  |  last reply 2 years ago


9V-12V from portable battery to usb hub?

I have a portable battery: http://www.xpalpower.com/us/products/xp18000/ I would like to run the output labeled DC9-12V (or DC16-20V) to a 5v/2.1a usb hub that I have.  I was thinking I could strip down a 12v usbhub car charger, but I wouldn't know how to manage the connector.  Has anyone done anything like this? Thanks

Asked by 9zpvwz 8 years ago  |  last reply 8 years ago


What should I power my rc car based robot on? it uses 6 1.5v batteries.

I have an erector rc car and i am using all of the interior components. The system runs on 6 1.5 volt batteries, and i want to reduce the amount of space that takes up. is there any other sort of battery(s) equel to 6 1.5volts?

Asked by remo2 6 years ago  |  last reply 6 years ago


What are possible uses for weak batteries? Answered

A followup on my previous question, sort of... I have about 150 old semi used 1.5v AA batteries that don't have enough juice in them anymore to power anything significant. One can only have so many Joule thief powered LEDs, and it's a shame to dispose of them all.  So the question is, what would YOU do (*Pointing at you!*) with those batteries? Thanks for any and all suggestions! P.S. Please provide an instructable if applicable :D

Asked by Morgantao 5 years ago  |  last reply 5 years ago


How to convert 12V to 5V for incar use ?

I need to create a cable that will run from my car battery into a device that runs on 5V DC power. It needs to look like this: INPUT: 12V car battery Simple bare +ve and -ve wires OUTPUT 5V 1.25A barrel connector 5.5mm (I beleive) like this one: http://sgcdn.startech.com/005329/media/products/gallery_large/USB2TYPEM.C.jpg

Asked by SamC17 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.

Asked by zack247 7 years ago  |  last reply 7 months ago


LED USB light cant run with 5V 1A usb charging adapter?

Hello Friends, I cant understand why USB LED not lit up.  when I insert in to PC usb port, it runs nicely. but when I insert in usb charging adapter and try to run. it cant. does it require few mili amps? cant it take few mili amps form 1Amp?  

Asked by supertechey 3 years ago  |  last reply 3 years ago


How do i make a 1 amp boost converter that converts between 3-5v to 5v?

Hey, so  have been buying pre built boost converters but i wanted to build my own, my question is, how can i make a step up boost coverer circuit that takes between 3 and 5 volts and converts it to 5 volts at 1 amp. In you answer could you explain what each part does? Thank you!!!

Asked by jbdawinna 4 years ago  |  last reply 4 years ago


WHICH IS INPUT AND OUTPUT OF THIS? Answered

Tbd392nr lcd inverter

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


how to reduce 5v dc to 2.5v dc?

I need to reduce a 5v power supply to 2,5 v for a certain application, I've got a converter that can do it, but want to do it using some electronics any ideas?

Asked by fjchorn 7 years ago  |  last reply 10 months ago


How to build a 12v to 5v conversor with a zener?

I'm developing a shield for my Arduino Uno and I want to add in it an external power supply. The power source I want to plug in it has four connectors: 5v, gnd, gnd and 12v. The 5v and the gnd pin goes to their respective pins in Arduino, while the 12v pin goes to a 7805 on the shield or to Vin, and the selection is made with a jumper. The only problem is that the connector can be plugged inverted, swapping 5v and 12, which would damage the AT mega. I know zener diodes are useful for limiting power, but I don't know how to use it. I need a simple circuit in which I can plug my 5v supply and it gets 5v to the chip, and in case I plug the connector inverted, to limit its power to 5v to prevent damage or to shut down the power. I can’t use the 7805 on both pins, because it would deliver something like 4v or less if powered with 5v. And something like a led to indicate that the connector is at a wrong position would be nice too. Thank you.

Asked by senitram 4 years ago  |  last reply 1 year ago


How to power an opamp(with -5v) form USB?

I`m making a dac+amp with usb input and headphone out. I`m powering it from USB. The USB controller and the DAC uses 5v and 3.3V, but the opamp(LM4562) uses +-5v. How could I get this differential voltage form the 5V of the USB, even if i get less current. If you can give me a good IC, it would be great, but if you can give me even a schematic (+IC) would be awesome.

Asked by fmada 6 years ago  |  last reply 6 years ago


Arduino Mega 2560 timeout? Answered

I have tried uploading the simple "Blink" sketch onto a 5v Mega Pro from Spakrfun using their 5v FTDI programmer. Despite my best efforts I have kept getting this error... Binary sketch size: 1,632 bytes (of a 258,048 byte maximum) avrdude: stk500v2_ReceiveMessage(): timeout avrdude: stk500v2_ReceiveMessage(): timeout avrdude: stk500v2_ReceiveMessage(): timeout avrdude: stk500v2_ReceiveMessage(): timeout avrdude: stk500v2_ReceiveMessage(): timeout avrdude: stk500v2_ReceiveMessage(): timeout avrdude: stk500v2_getsync(): timeout communicating with programmer I have know I am using the correct COM port and I have the right board selected. I have tried to re-install the driver but to no avail. Nothing I have found online has worked.

Asked by GenAap 5 years ago  |  last reply 1 year ago


Analog sine wave generator? (0v-5v)?

I am wondering how to create an analog (NOT digital) sine wave from 0 - +5 volts (Not -5 - +5). If you could, post a schematics diagram, or send a link to a page with the schematics. It has to have a variable pitch. Thanks, josh1324

Asked by josh1324 7 years ago  |  last reply 7 years ago


Finding an appropriate heatsink for 5V 3W LED? Answered

Hello, I have bought some 3W 5V leds, and now I have to dissipate the heat they produce. I am thinking of using an xbox 360 GPU heatsink i have laying around ( https://s3.amazonaws.com/assets.overclock.net/7/7b/7bb1229a_vbattach111891.jpeg ), cut in apprpriate size. Then I would glue the led with thermal epoxy to it.  Can somebody suggest an adequate size for the heatsink? I can't find any info around. I have other heatsinks as well, I would rather not buying a LED heatsink if that's not mandatory. Thanks in advance :) Picture of the leds attached, they have no board to screw them with.

Asked by en_rov 4 years ago  |  last reply 4 years ago


Building a 5V or 12V powered in-line preamplifier

I want to build an in-line pre-amplifier with a 3.5mm in and out jack.  What I want, or at least think I want, is a simple booster that provides a small, but relatively even gain boost from an MP3 player into the main amplifier. Something along the lines of this: https://www.instructables.com/id/In-line-headphone-amplifier/ However, I would like to be able to power it off of 5V USB or off of the 12V coming into the cigar lighter. What I'm effectively trying to do is get enough gain on low volume spoken-word audio coming out of my mp3 player so that I don't have to crank the stereo up to max.  Does anyone have any good sources for instructions or advice for this sort of thing? Alternatively, someone can tell me if this is a fools errand to begin with, and that I aught to be taking a different approach altogether.

Posted by wildgunman 7 years ago  |  last reply 7 years ago


Variable USB Power Supply (5V 2A)

I was looking to either build, buy, put together (kit) a Variable USB Power Supply similar to the one that I saw on the EEVBlog (https://www.youtube.com/watch?v=QxWRT4U_I9o). I really liked the compact design of his version, but he never finished it, so I can't buy that kit ;-( Is there a simple way to put together something that is protected (so I don't kill the USB socket I get power from) and has a Variable Volt and Amp adjustments knobs/buttons. I've looked at getting a full size Bench Power Supply, but would love to just have one so that I can power from my laptop or any of my million Micro USB power adapters (5v 500ma through 5v 3A supplies). My first project is something I need to eventually run off of AA batteries, but I didn't wanna keep on re-charging the batteries while I test my circuit design. Would rather have a constant source of 1.25v-1.5v power during the prototype phase. I'm just now getting into Electronics, so please take it easy on my poor little brain. Hopefully this hasn't already been asked, didn't find anything in my quick search through the forums.

Posted by drofnasnhoj 3 years ago  |  last reply 3 years ago


Dual voltage switch, off .5v on 4.5v?

Good day, I have run into a bit of a problem, the original controller has burnt out  for my light controller and i cant find a replacement, but i was able to while it was working find out how much voltage it needs to run. To the light controller is 12Volts,  It requires .5 volts @ 1amp while the system is in the ready phase and when i press the switch it jumps on 4.5volts @ 1amp and the lights turn on. Ideas i had run a crossed was: Running .5 volts straight to the control and having a switch supply the remaining 4.0 volts but i believe that would double the amperage.   Using a relay but i'm not that electrical savvy. Any help would be great. -Davis

Asked by davisar4 7 years ago  |  last reply 7 years ago


Joule Thief Toroid not helping to step up, Why? Answered

Hey fellas..I am having problems with joule thieves especially with the toroid part.... First time I wound my Ferrite Core and the joule thief ran smoothly... But recently I had to unwind it to try other wires which didn't work.. So i again wound up the toroid just like the first time when it used to work but unfortunately this time it didn't work... I have checked everything and found that the only problem is that the toroid is not helping to step up the voltage.. When i applied 9V across it, the LED glowed but for 1.5V it didn't. So there is a problem with the toroid.. But what it is and why is it happening I don't know..I mean for the same core and same style of winding once it worked and now it doesn't, Why ?? Can anyone help me ??

Asked by Arijit Chatterjee 4 years ago  |  last reply 4 years ago


How to step down a 12v DMX LED Controller to 5v?

Hey i currently have an "Abstract MFD-10" DMX controller that i want to run 64 LEDs/2meters of "LPD8806 +5v Strips" off of. DMX Controller= http://www.abstractavr.com/products/dmx-led-drivers/60w-dmx-led-driver/ Led Strips= http://www.adafruit.com/products/306 How do i step down the 12v supply to 5v while maintaining the flow to keep the strips running effectively? If you give me the formula for it i can work it out myself and will post here with what i worked out as i enjoy doing my own workings but i am a bit lost with this. Also I am willing to simply change a component in the controller itself if this would be easier and cleaner (No external boards/components) Need anymore info just ask.

Asked by Pathogenex 4 years ago  |  last reply 4 years ago


How to create dc input to dc 5v and 12v (two outputs) circuit? Answered

I need to create a circuit with two different output voltages but with a single input voltage. The output voltage must be 5v and 12v dc. The input voltage must be max 12v dc (for using 12v dc power adapter from ac mains).

Asked by akki5230 4 years ago  |  last reply 3 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.

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


How it is possible to power up a 12V device using only 5V?

I had a power outage some time ago, and needed to use the internet for university search. i was with my notebook, EEEPC 1000H with 4 hours of batt. my internet is over a cable and it uses 12V for power; i had a cable for my external dvd reader (ad/dc pin to USB)that fitted into the modem, and i plugged it into my usb. it worked very well. however, the notebook started to heat up slowly, and the battery indicator dropped from 4:00 to 2:00; this was safe to do? could it damaged my notebook? how can be possible 12V into 5V?

Asked by Shiron 9 years ago  |  last reply 9 years ago