How to make an BJT astable multivibrator run faster than 30Khz that works?

I am working on a dc to dc converter and it works but it seems to me that when i go higher than that it doesn't work anymore. I am using two C945 transistors. The resistor values for R1 and R4 are 1K and for R2 and R3 are 15k . For the capacitors C1 is 2.2nf and 1nf for C1. i have tried putting in smaler capacitors and increasing the two base resistor values. BTW its for a dc to dc converter that im working on. I also have no idea how much inductance on the inductor is. I am try to step up 6V dc to 15 V. It works put its low on power thats what i want.

Asked by josh1001 9 years ago | last reply 9 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


Why do DC-DC buck-converters not start at 0 volts? Answered

I have been looking into DC-DC converters to build a variable power supply but I've haven't been able to find one which starts at 0 volts. Most of them seem to start at 5-10 volts with the lowest I've seen starting at 0.8 volts. Is there any reason for this? Thanks,

Asked by Smret45 2 years ago | last reply 2 years ago


how to make the dc engine move two ways?

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


DC to DC UPS (Help!)

Hi i am trying to build a sort of DC TO DC ups for my modem/router, please look at the image attached for my project plan. I was able to find many charging circuits online but i cant understand what value relay and capacitor should be used. can any one help me with this project. Thanks in advance. http://i52.tinypic.com/v2v38n.jpg

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


24 V DC servo motor.

I have a 24 V DC servo motor. What do I need to plug it into AC outlet.?

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


dc inductor

Do inductors work with pulsed dc? like would they become more resistive with frequency? Or would they do nothing because it's not ac and the electrons can't "bump" into eachother.

Posted by guyfrom7up 10 years ago | last reply 10 years ago


Measuring Current of 24v dc motor

How to measure the max current of 24v dc motor.. please give me step by step guidance. many thanks

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



How do I convert AC to DC? Answered

I'm running a circuit using 24 volts DC and the power outlet in my country supplies 220 volts AC. What circuit does it?

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


Can anyone help me with an schematic for dc-dc boost converter,from 3.5-3,7V to 5V to charge a phone? Answered

Hello everyone !! I need a schematic for boost converter but with basics components,i need to find them in my country and not very much to cost. I need it for charge my phone from another cell battery with 3,7V. Like an portable charger. Please help !!

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


DC Motor- dead or alive?

I've got a DC motor from a treadmill that when I spin it generates a small voltage then drops off to zero even as the motor continues to spin. Is it shot? Can it be repaired, if so, at what cost.?

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


Connect a DC plug to a Timer?

I have 2 strands of led lights that go up a Flagpole on my rv, I am trying to figure out how to connect a timer through the DC Plug Thanks in advance Mike

Asked by quine9 6 years ago | last reply 6 years ago


how can I convert an ac welder to a dc?

I have a microwave oven transformer welder that I made and it works ok, but I woul like to convert it to dc. Any information will be appreicated. Thanks

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



3-6 volt ac to 12 v dc

Hi, i going to give it a new try, i have a power source of 3-6volt ac , an di want to get 12 volt dc,and i want it to stay 12 volt dc ,if my input is between 2.5 and 6.5 volts.ac

Posted by alex4421 11 years ago | last reply 11 years ago


how to convert ac to pure dc? Answered

I want to convert 5volt ac to 5 or less voltage! i got  a transformer it gives out 5volts dc! i used four diodes bridge ! but the current is still vibrating i came to know this by using a simple white led it vibrates! although the diode bridge converts it to dc but not in pure dc format help me!! can anyone give me a simple circuit to convert it to dc ( i have used diode bridge but it it is still vibrating i need some more out here to make it!!  )

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


50 Watt LED Wired To DC/DC Converter

Hello, I want to wire a 50 watt led to run off of 12 volts.                                                                                                                                   here is info on components:                                                                                                                                                                                    50 watt led                                                                                                                                                                                                           forward voltage:30-36 Vdc                                                                                                                                                                                  forward current: 1750-3000mA                                                                                                                                                                                                                            DC/DC converter:                                                                                                                                                                                                  input volts: 12DC                                                                                                                                                                                                      output volts: 48DC                                                                                                                                                                                              output current:3A                                                                                                                                                                                                Can I use resistors to make this work?                                                    

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


rectifier repair?

How can we repair the rectifire of the dc system

Asked by wasimbari 9 years ago | last reply 5 years ago


DC power electric controls

I have a great idea and looking for a type of DC electric control that can handle a charging system and power release . IS THIS POSSIBLE !! and can there be a program written that can control the amount of dc power released? of course i want to control multiple incoming power sources and release the energy it creates.   ANY AND ALL IDEAS WELCOMED!

Posted by ramonc123 7 years ago | last reply 7 years ago



HELP WITH DC MOTOR CONTROL USING 5 position selector switch Answered

I have to  use a microprocessor MSP430 to  control  speed and direction of aa DC motor using 5  position switch selector.  can somebody help me with how to get started with the hardware

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


To make a 12 volt and 1.5A dc supply which supply power for 1.5-2 hours

I want to make 12volt 1.5A dc inverter which will supply power for 1.5-2 hours for my router. Please tell me how to make it?

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


i want to convert DC to AC supply.and i want the circuit please help!!!!?

I have a dc 6 volts, which i want to convert to AC, so that i can power my plastic core transformer. and also i need an amplifier circuit. PLEASE HELP!!!

Asked by sheetansh 9 years ago | last reply 7 years ago


48vdc conversion to 24vdc is there a simple way

im trying to make a replacement homemade POE for a microwave. i need to convert 48-54vdc from a rectifier down to 24VDC as easily and simple as possible. is there an easy circuit?  ive thought of using a dc/dc converter but it cost about $150. can i build it for less?

Asked by iclymd2hi 8 years ago | last reply 8 years ago


how can i run dc motor with specific criterias as per detail?

1) the motor should move forward for cirtain RPM then STOP when supply is on. 2) the motor should move reverse with exact same RPM then STOP when supply CUT OFF. the supply volage is 230V the motor is 12V DC.

Asked by jdixit89 2 years ago | last reply 2 years ago


How to convert dc to ac? Answered

Hi! Can anybody tell me how to convert dc to ac i actually want to convert 9volts dc to 9 - 7 volts ac cause i need to supply this ac voltage to a step-up transformer so that it will convert it into 200volts the real problem is when i provide 9volts dc to the step-up transformer it only gives out 41volts in output but when i gave it 9volts ac from another transformer it gives out 200volts ac and that's what i need but i need it to be battery powered so i need to convert the 9volts dc supply from the battery to 9 or less volts ac that's all i want to ask how to do it!

Asked by ubdussamad 6 years ago | last reply 1 year ago


Need help choosing a dc motor!!

 Hi, My students are building model cars our of balsa wood that move b/c of a dc motor.  All of the motors I have are burning out - they can't run long, I used to have a dc motor that started out slow, built up speed and then ran fast and for a looooooong time.  Does anyone know what type of motor i'm talking about?  please help.....i gotta get them asap.  thanks! patti:)

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


Is there a way to make ac powered computer speakers to dc ?

I'd like to use a pair of ac powered computer speakers and use them as a portable dc powered "boombox" for mp3 playback. Any detailed ideas out there????

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


Combining AC and DC on the one output?

I have a variable 0-12v DC output which has a maximum output of 1 amp. I have a fixed 16v AC output which has a maximum output of 1 amp. I am looking at how to combine the two so as to power a model with the variable DC output and also power lighting on the AC through a capacitor to filter the DC out. Also, I would rather it was nearer 6v AC at the output. Would this just be a matter of a simple step-down transformer before they are combined? Essentially, I am looking to replicate the functionality of this product for less than £42.95. This is too expensive especially when I need two of them.

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


how i can reduce output current?

I have SMPS  with output ratingd 24v dc and 5A.  The other one is 12v dc motor which has max input current is 200ma with load.  How i can connect these both itoms?

Asked by ParthP14 2 years ago | last reply 2 years ago




how do I energize AC Christmas light with DC power?

I have a set of 50 Christmas lights on a circuit.  120V /  0.17amps.  What can I make to power up this string of lights?  I need to make it mobile so an inverter is out of the question. Thanks, Dewdropin

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


How to switch on a 9-33v DC LED light using 3.3v as the 'trigger'?

I have a difficult entrance into garage and want to use an orange 9-33v DC LED as a marker light when the garage door is opened. I would like to be able to connect the marker LED to the 3.3v LED that comes on when the garage door is opened. This is on a timer, so I envisage both the garage door LED and the marker LED switching on/off when the remote is activated.

Asked by PeteH34 2 years ago | last reply 2 years ago


stock dc motor with 3 switches that spins, stop/lock in place or stay neutral?

I'm trying to build a motorized yarn spooler. The motor is controlled by 3 switches, one to spin it, one to stop or lock it in place and a neutral switch, so the spool can turn freely if it need be. Is there a motor that can be operated that way? Thank you. 

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


DC To AC Converter?

Hello, It Is Now Summer where I live, and it is getting VERY hot. I Want to put in an Air Conditioner, but whenever I do, My electric bill goes through the roof! I have an old car part (Cannot remember what it is called, its the part that uses the turning engine to charge the battery or something like that... I Cant remember) and I would like to use that (made into a mini wind turbine) to charge my spare car battery, and use a DC to AC Power Converter to power the air conditioner... I Have an DC - AC converter, but its not powerful enough... I Need To Build One That Can Power The Air conditioner.... Soon... Its Starting To Get REALLY hot... Thanks...

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


Looking for design help.

I want to build a dc-dc converter with input voltage from 10 to 30 volts and output of 13.5 at 400 watts. This is so I can power a 400 watt inverter from 2 batteries on my camper... I am frustrated with the inverters shutting down at 11 volts saying dead battery, and this way I would be able to drain the 2 down to 5.5 volts each before that happened to me. Hopefully there is a simple answer for this, I am not to keen on the idea of $400.00 to purchase the only one I found on the net.

Asked by jeeper74 6 years ago | last reply 6 years ago


I need help connecting a small wheel to a DC motor, yesh.

Hey all, I'm making a little DC generator for my bike (just to power an LED for now), but I cannot seem to connect a wheel to the motor's shaft. It's not too large of a motor, and I had some toy wheels from some little car, but they don't fit and I can't figure out a good solution. Does anyone have a good way to do such a thing? Or maybe even to make an altogether new wheel?

Posted by Jackhole 10 years ago | last reply 10 years ago



How do I wire a 12V DC motor to micro switches, relay digital timer and battery?

I am wanting to wire up a door to my hen house that will open in the AM and close in the PM. I have a 12V DC powered cordless drill motor and a digital timer. Can you help me on what I need to make this all work as far as switches, relay, etc. and possibly give me some guidance on how to wire it up? Just so you know, I have very limited electrical experience. Thank you. Rod

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


Why do rc cars have capacitors on the motor? Answered

Being a hacker or at least a take-it-apart-er, I have seen what looks like one or more small capacitors (I think) soldered directly onto the motors of radio or remote control vehicles. Are these capacitors? I understand the reason for capacitors on large AC motors. Do they serve the same purpose on small DC motors?

Asked by lancma 8 years ago | last reply 7 years ago


Electric Power DC Generator

I've been toying with the idea of trying to build an electric generator that after receiving initial power to start, could power an electric motor that would in turn somehow power 1 or more generators and would not only produce enough power to continuously power the motor, but also allow it to distribute power for use with an inverter or stored in batteries. Am I crazy that I dont see where anyone has tried this or is it just not possible? Obviously, there would be friction forces from the generator(s) on the motor and it may be difficult to produce enough power to even run the motor, but does anyone know of anyone that has tried this? I've been reading peoples posts and really enjoy looking at other peoples ideas on this site and decided to sign up. Thanks.

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


Inverting 115VDC to 115VAC. 75watts?

What would be the best low cost method for me to invert 115vdc to 115vac for a low 75watts bench experiment?

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


Can I use the same ground line for 2 different DC voltage out puts?

It seemed a bit pointless to me to use an inverter to get mains voltage just to use a transformer to step it back down again to charge a lap top. This in hind sight may be the cheaper option. So I decided to build a power supply from commercially available parts this step up dc to dc device seemed to fit he bill http://www.technobotsonline.com/pololu-adjustabe-step-up-9-30v-5a-max-input-current-2.9v-to-vout-input.html coupled with a replacement charging lead from www.life4laptop.lt. My problem is this, the mains power supply from HP doesn't mention that the central pin is a different voltage to the inside of the plug, as the new cable had 3 wires a stuck a multi meter on the mains adapter to check the outer is indeed negative, and the inner contact 19.5v as shown on the power supply label the unmentioned central pin is at 14.1v . I don't have any worries about running 2 step up devices in parallel from the same 12v supply. I'm a little concerned about using the same ground line for 2 separate devices even though the mains unit does. It has occurred to me that there is probably a simple way to drop the 19.5v to 14.1v for the central pin but I don't know if they run at the same current and if my understanding of electronics was up to that I probably wouldn't need to be asking what I suspect is a fairly basic question. I am pretty adept at assembling and checking out puts of  things others have designed I just don't understand the design bit.

Asked by Stan1y 3 years ago | last reply 3 years ago


Converting Dc to Ac

Ok this is my first post on this site so forgive me if i sound stupid...i like to tinker with things so just to tell a little about things i have done...completely rebuilt a pc..wired up an adapter for an old xbox to work on pc...the easier things....fixing frayed speaker wire....rebuilt/and upgraded a zune 30gb to zune 60gb the usual stuff...my most proud is overclocking my amd 64x2 4000+ to 2.9Ghz.....everyone said it couldnt be done...........anyways on to my question.......i want to know what all i will need to convert Dc to Ac power for a set of old desktop speakers i found in my closet.......i have an idea of what i want to be able to do.......put them in a backpack and make it portable.....currently i have two old 7.2v 1200mah Rc car batteries that i would like to use to power it.....and i also have a charger for them...it can charge and discharge...its old but works....so now my next step is what else am i going to need to complete this project...i dont know a whole lot about electricity but know enough to follow directions...if someone has already done this or knows how to and could walk me through what i need to do i would greatly appreciate it....

Posted by Celestial_Artisian 10 years ago | last reply 10 years ago


electric car

Ok i want to build an electric hybrid system my first question is ac or dc power. i want to build a paralleled drive system. that uses the stock motor to drive on the highway with maybe a little help from the electric motors. here are my thoughts start with a f250 powerstroke diesel crew cab truck, install a divorced t case and new drive shaft, hook the electric motor to the t case front axle output. the goal is to use the space by the tool boxes to fit the batteries and later update the alternator. the goal here is a hybrid that can still haul what a normal truck can but run purely on electricity when in town

Posted by dkeller8 5 years ago | last reply 5 years ago


12V bike battery(with/without battery charger) to regulated 12v 2A circuit for mini computer ? Answered

Hi, I want to make a UPS type of device for my tv box which takes 12V-2A power can anyone suggest how to build one I am not able to find any DIY to work with it and I would like to use that TV box as my little NAS device since it runs on windows. and to make it running even in power outages I need some type of UPS for it. regular UPS would convert 12-v to 230v and then 12v that seems a lot of power wastage. if anyone can suggest a better way to do it it would be a great help Thanks in advance.. Paras

Asked by ParaskumarB 1 year ago | last reply 1 year ago


can we make truck engine starter motor last long time for gokart by rewinding it?

I want to use truck engine starter motor for my gokart or ebike project ? can i rewind it and modify it for long lasting

Asked by Suraj Basnet 4 years ago | last reply 4 years ago


How do I build a 12Dc day night switch?

I've got a 220v day night switch and want to convert it to a 12v one, I've got a 12v relay, a bunch of different resistors and capacitors and diodes I'm looking for a simple diagram or some advice on how to assemble it

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