Transistor switching problem

I am having trouble using transistors to switch a some LEDs, I have 5 LEDs in parallel being switched by one transistor but each LED is indervidually switched by another transistor. I have given each LED its own resistor and the problem I am having is that when all LEDs are on each LED gets dimmer then if only one was on. I don't really understand why this is happening but I'm not 100% comfortable with transistors and I have probably done something stupid. I have attached a image of how I have wired it up with only two LEDs

Posted by camlv 8 years ago

Stupidly simple circuit question - answered.

OK, so I accidentally volunteered to make an X-factor type buzzer board for a school event. Three switches.  Throw each switch, in any order, a light comes on. Throw the third switch, in any order, and a buzzer and/or fourth light comes on. It's a simple circuit.  Must be.  Just a few transistors, LEDs and batteries. But, I just cannot work it out! I should be able to sketch it out in my sleep, but my brain will simply not cooperate. I'd prefer to use a single DC power supply, up to 12V (multiple LEDs to make the lights brighter), but I have several I can use if required. Dimensions are not important, I'll just change the lengths of wires. But, can you help with the circuit? >K Thank you, Lemonie!

Posted by Kiteman 8 years ago

I need help with arduino

Hi everyone,  I am playing around with arduino, and I got in trouble with the push button. Is there any possibilities to switch in between the LED patterns. I got the coding for three difference LED pattern here. I want to switch from 1st to the 2nd , and from the 2nd to the third by pressing the button. Thank you so much, I really appreciate your help. These are my LED patterns

Posted by tompham89 3 years ago

URGENT!!!Reply fast!!!BC 547 switching? Answered

My school exhibition's tomorrow and I need to do something urgent.There's a 7 VDC supply which is converted to 5 VDC by a voltage regulator(both have a common negative terminal).I need a BC 547 to act as a switch and complete the circuit of a device connected to the 7 volt circuit when the 5 volts is used as a signal and sent to the transistor.To put it in another way-The device needs to run on 7 volts when a 5 volt signal is sent to the BC547.I've got about 4 hours of time before I go to sleep(actually forced to!)and the exhibition's tomorrow morning!!!

Asked by Adarsh_tronix 5 years ago

When should my sister switch to baritone saxophone?

My sister started playing saxophone, and she wants to switch to bari sax. The problem is, she's way too small. She can barely play my tenor! She really wants to play it, but she'll have to wait until she's slightly taller and better at sax. When could she play the bari and what should she know before playing it?

Posted by robin.howell.56 3 years ago


I have five existing wall lights that are hard wired to a single switch, running on 230v a/c It's impossible to run alternate wiring as it's all embedded in the walls (which are three feet thick.)   I am going to convert each light to be dual-function, with (a) background candle-LEDs and (b) a couple of 5w LED spotlights Already I have acquired 12v LED drivers and step-down transformers (12v to 5V) for the candle LEDs.   What I wanted to figure out was some electronincs to allow me to control them all by using the existing in-wall wires and perhaps replacing the wall switch with a push-button switch. What I had in mind was to be able to achieve different functions sequentially, possibly using an IC like a 4017. However, I'm only a beginner at electronics, and I haven't been able to figure out a way to do it.   One sequencing that would be effective, commencing with an all-off situation, would be:   1st press = candle lights only on   2nd press = LED spotlights on (Candle bulbs remain on)   3rd press =  All off   Cycle then repeats.   If this proves to be impossible, I also considered the idea of short and long presses, which could trigger a timer for the long press to acomplish some switching   The power of 230v a/c will also be travelling down the same wires to give power to the 12v LED drivers in each lamp, so I'm actually talking about sequential presses on a 230v a/c circuit.

Posted by colinstcharles 1 year ago

Should I Stay or Should I Go?

Oh boy, Instructables.... It's happened again. My Mom asked me if I want to change schools next year. I have no idea on this one. Usually one school sticks out above the rest, but this is tough. At the school I'm going to right now, I'm all settled in, it's a decent school, and I've got friends here. My only complaint is that there's no band. The school my mom wants me to go to is the 60th best school in the US, plus it's a public school, so that saves us a bunch of money by not having to pay tuition. If I go to this school, Mom said we'd have enough to get me a new computer and a decent car, both of which I could really use. Also, there's a band, and let's face it, school just sucks more without band. This potential school sounds like a dream school to me, band, great academics, small class sizes, but I'm not sure if I'm willing to leave a place where I've got friends. I mean, it's not like I've never done this before (5 schools since middle school, FTW), but that doesn't make it suck any less. So, thoughts? Anyone else been in a fix like this before? Help me out, here, guys ;-)

Posted by Labot2001 9 years ago

How to tell what current-limiting resistor to use Answered

I'm having my Arduino Leonardo substitute a few buttons in a device. In the buttons, one pin connects to ground with the other going to a microcontroller. I figured I could connect an NPN transistor in parallel, with the emitter to ground, the collector to the microcontroller, and the base to a resistor and my Arduino. How do I choose this resistor? Every guide I found involves getting the current load, and I don't know how to do that. I'm thinking I can just put in a 10k resistor and be fine, but I want to make sure. Thanks for any help

Asked by 4lifenerdfighter 6 years ago

Modifying a DC-DC boost circuit

I'm building a circuit that would run off roughly 7v and convert it to 12v using the LM2577 (LINK). the datasheet (LINK) provides an example circuit that will output 12v @ 800mA. I need a little more power than that. around 1.25 A. my question is that if the 100mH inductor was replaced with a larger one. say a 150mH one, would that increase the current output? i would also replace the 680uF cap with a bigger one to reduce ripple. FYI the LM2577 is rated to convert 3.5v-40v to 12v. any information or direction would be appreciated picture is from the national semiconductor datasheet page 3

Asked by stapler117 7 years ago

illuminated ball - remote switching and charging

I'm working on making an illuminated ball for playing bike polo with at night time. A couple of high output red LEDs are sufficient for light to get through a normal street-hockey ball. The problems I'm currently facing are switching the lights on or off, and charging the batteries. Ideally both of these could be done remotely - i.e. without having to open the ball up. For switching I was thinking of using a magnetic reed switch - when a magnet is attached, the lights switch off. The only problem is that reed switches seem to be (a) made of glass (not ideal when the ball gets hit really hard), and (b) in a normally-open configuration - I'd need a normally closed one for this. As for charging, I have two ideas - one is to have two small metal pads on the surface of the ball to connect to the charger. This could be problematic due to forces on the ball during gameplay. The other more fun idea would be inductive charging. Like what you get in those fancy electric toothbrushes. One coil inside the ball, one outside. How practical is this? can it supply the necessary voltage and current to charge either a pair of NiMH batteries or a Li-ion cell? vik

Posted by askvictor 10 years ago

is it possible to use a low voltage controller at higher voltage?

I want to make a isolated switching power supply intended to drop and convert 220VAC to 12VDC, but the only available controllers in my area can only handle 100VDC at maximum. is there a way where i can use those switching controllers at 220VAC?

Asked by codestroy7 6 years ago

How do I design a Step Down Switching Circuit from a 12V 3A lead acid battery to a 5V 1A Load?

I am designing a solar panel charger for usb devices, I have a 12V 3A lead acid battery and I want that reduced to 5V 1A to comply with most portable devices, Help is much appreciated and diagrams would be ideal

Asked by EmptyCoffin92 4 years ago

Hig Voltage transistor switching 230V Arduino PWM Control Hig frequency

Hi all :)  My name is Karlo Kasupovic and ay come from Croatia. I need a way, to control a microwawe transformer whit a arduino and a mosfet ay wona use a 230v AC input and rectifier to 200-230V DC then whit a opto isolator control a POWER Mosfet (the signal generator its a Arduino.) I wanna play with different frequencies Code for the Arduino signal genergenerator already hawe. Ay need  schematic and explanations. thanx a lot all :D

Asked by karlok1 3 years ago

Parts info please

Hi all: Does anyone know of a part that will swith  240v AC current on & off for short periods of time like a pulse effect ?. Thanks.

Posted by tezza1 6 years ago

led selection circut

I am building a 500 DVD library shelf.  I'd like to be able to select a number, on maybe a keypad etc, and have just one led turn on on one location of one of the shelves, indicting the location of that DVD.  As usual and understandable, I would like said system to be as inexpensive as possible.  I'd like to run it off of a battery.  I can do it with three selection switches and an individual set of wires to each LED.. Just seems like some IC would work if I knew a little more, and maybe reduce some of the wiring.  Like maybe an IC under each shelf that could select which led on that shelf to turn on.  I intend to drill small holes into the face of the shelves and insert each led about 5/8" apart with the wiring run back through and then under each shelf.  Lots of tiny wires and lots of LEDs but if I could make it inexpensive enough it would not only help in finding a movie to watch but it would aid in putting it away later.  Since to some extent, each DVD is variable in size, the location of any DVD is a little dynamic, but any one LED should be close enough to guide me. If you don't have time to fill in all the knowledge I am missing, any place that you can point me would be appreciated... It seems to me like it may take a number of IC to make several selection to power up just one LED>   thanks Dave

Posted by oneofsharp 6 years ago

RF remote Microcontroller etc?

So I found this remote control deal For the past few months I've bounced around the idea of using a hacked remote to turn the lights in my room on and off. This, however, makes hacking stuff a non issue. However, I still don't know how to make the remote communicate with a microcontroller. The one I linked appears to have an antenna, which is undesirable, but could become an option if nothing else. I also would like to see if I can find a similar control that uses infrared. Right, so, Basically I want a remote that sends a single signal to some kind of Microcontroller. When this signal is received, I want the microcontroller to emit a single pulse to toggle a latching relay to turn my lights on and off. Where should I look to find ideas or buy parts? I already have an Arduino, but I think I'd rather build a knockoff for a permanent circuit. So thanks in advance.

Asked by mrmerino 5 years ago

Power Supply Question? Answered

I want to build a switching Power Supply, without the use of IC's with everything already inside. I only want to use op amps and passive components. Below are my goals on what to achieve. I would like to make this PSU current limited, or at least shut off when the current goes too high. I basically took the concept of the linear voltage regulator and expanded on it, turning it into a 'proof of concept' switchmode supply. Input Voltage range: . . . .7-24 Volts Voltage: . . . . . . . . . . . . . . 5-24 Volts Max Current: . . . . . . . . . .10 Amps Price: . . . . . . . . . . . . . . . . $5 -- $10         Instead of feeding a voltage reference into an op amp, I modulated it with a few components. (A triangle wave generator, and a array of resistors to lower the amplitude and introduce a DC bias.) The DC bias is controlled by the current protection module, which is simply an op-amp that reads the voltage on a small resistor and multiplies it by 5. This finalized current controlled, DC reference biased triangle wave is fed into a comparator, which will then switch a rather large MOSFET on and off at about 200 Hz, with varying PWM, depending on how much 'droop' there is on the output. Here is a rundown of what the components will do: OK, I refined my plan to this general specs: Input Voltage range: . . . .7-24 Volts Voltage: . . . . . . . . . . . . . . 5-12 Volts Max Current: . . . . . . . . . .10 Amps Price: . . . . . . . . . . . . . . . . $5 -- $10        I basically took the concept of the linear voltage regulator and expanded on it, turning it into a 'proof of concept' switchmode supply. I don't want to use any prebuilt chips where you have a magic black box with inductors, capacitors and resistors connected to it. I want this to be entirely raw, basic, cheap parts. Maybe later, I will replace many of the op amps with a single programmable chip (like an Atmega328P)         Instead of feeding a voltage reference into an op amp, I modulated it with a few components. (A triangle wave generator, and a array of resistors to lower the amplitude and introduce a DC bias.) The DC bias is controlled by the current protection module, which is simply an op-amp that reads the voltage on a small resistor and multiplies it by 5. This finalized current controlled, DC reference biased triangle wave is fed into a comparator, which will then switch a rather large MOSFET on and off at about 200 Hz, with varying PWM, depending on how much 'droop' there is on the output. Here is a rundown of what the components will do: Green field: This contains a voltage regulator which acts as both a 5V power source and a voltage reference. Not only will this module produce a 5V output, but also produce a triangle wave. Blue field: This module will be fed the triangle wave, decrease it's amplitude, and inject it with a bias voltage, controled by the current limiter (red field). Red field: This basic module simply measures current flowing through a 0.1 Ω resistor, and multiply that reading by a factor of 10, and inert it (the circuitry is probably wrong, and I am not sure how this will work, if it even will do what I want it to Will this work?) Yellow field: The final modulated triangle wave is then fed into the last comparator, which will switch a MOSFET on and off at a fixed frequency of 200Hz. The output of this last comparator is now PWM. As the output voltage sags, the pulse width will increase, and cause the final voltage to stabilize at either the peak value of the triangle wave (with little to no load), or near the bottom end of the wave (with a heavy load) ------------------------------------------------------------------------------------------------------------------------------------ My questions:  I try to run this in LTspice simulator but some reason the output of the last comparator is a distorted triangle wave. I think this has to do with my filtering capacitor and MOSFET gate capacitance. Can anyone give suggestions about this design?  I'm sure the current limiting function is not going to work as intended until I finalize it's design (I hope I don't need more than 4 op amps altogether, It would be nice to use a single chip I already have) Any suggestions? I might just omit this part entirely, as it is not necessary.

Asked by -max- 5 years ago

Best way to switch multiple circuits?

Hi, all - first time posting. I have limited knowledge with electronics and have come across a scenario where I basically need a kill-switch for a cable with 9 ends. I can't find any sort of toggle switch (SPST, DPDT, etc..) that would accommodate that many wires. I started reading up on digital bus switch IC's. It seems a 10-digit one like this would work, leaving one unused.,118/568-8418-1-ND/2765135 My question: is this the easiest solution? I simply don't know what all options exist, so any advice from someone more experienced would be greatly appreciated. Thank you for your time. -Caleb

Posted by calebpaul 3 years ago

Transistor Swithching Voltage? Answered

Looking at this data sheet: How much voltage has to be applied across the base and emitter to switch on a "TIP 3055" transistor? The V-be row is the only thing that looks like it is telling about that, but I don't think that's what I'm looking for (mabey it is?).

Asked by Jaycub 7 years ago

Can I run 10w 12v leds directly form a switching power supply? Answered

Hi, I have a regulated switching power supply with 12vdc 400w output (similar item pictured below) and I need to power around 20 10W LEDs which are rated at 900mA. Can I wire these in parallel directly from my power supply since I know the voltage can't change meaning that the current (and heat) shouldn't really change? Thanks in advance.

Asked by reducingmyconsumption 4 years ago

Will this 'switching' circuit work for cabinet lights? Any comments?

Im making cabinet lights using LEDs. I use a transformer to power it off AC mains, but I want it to run on batteries too... So Im making a circuit that would automatically change the source of the power from the mains to battery when the power goes out, and back again when it comes on. Im using an NPN and a PNP transistor to do the switching. When mains (S1) is on, the NPN is on and current flows from the transformer, when S1 is off, NPN is off and PNP is on and current flows from the batteries. What I am worried about is that (I think) the transistors need a Gnd on the emitter. Is that right? If I connect the +ve of LEDs to [OUT] and -ve to GND will it work as expected? Can someone try please?

Asked by pro2xy 6 years ago

A self switching switch? Answered

Does any one know a switch that switches or toggles to another output after each one has had 1 turn  

Asked by techxpert 6 years ago

LT Spice Switches?

I have a simple question... If anyone here knows about the program LTSpice, is it possible to create switches that are manual, like pushbutton switches, spdt/dpst/etc., not automatic switches?

Asked by 101yummYYummy101 8 years ago

Latching switch to a momentary switch?

Basically I want to make a toggle switch to trigger a circuit from on or off. its hard to explain but when the switch is in the on position it triggers a circuit momentarily. When I switch the switch off i need it to trigger the circuit again. Its for a 4 wheel drive module for my bronco and its momentary push buttons that I want t o convert to a toggle switch.

Asked by catsnw 6 years ago

what's this programming code language? Answered

i found a code for a pic16f28A it's simple: main:  lablel0:   switch off 3   switch on 0   pause 1000   switch on 1   switch off 0   pause 1000   switch on 2   switch off 1   pause 1000   switch on 3   switch off 2   goto label0

Asked by top.boy 6 years ago

Momentary switches

Hi, Just wanted to know if a momentary switch (normally open) could be used as a on/off switch with out using a relay.  thanks in advance :D

Posted by Nanow 6 years ago

USB to switch?

I am building a backlit keyboard, and I wanted to hook it up to a switch. How would I make it from the USB, or the default connector, to a switch?

Posted by Exploitation 4 years ago

Infinite Rotary Switch? Answered

I'm looking for the search term I need to find a "Rotary Switch" That spins very smooth and will keep spinning indefinitely like a volume control switch.

Asked by bradleynelson102 2 years ago

painting switch sensor?

How a painting switch sensor works

Asked by AshutoshS94 7 months ago

Remotely activated switch? Answered

Howdy, I'm workin on a project with LEDs and I wanna know if there is a switch I can remotely activate?

Asked by sf49ers 4 years ago

USB Light Switch

I have a spare light switch and I want to convert it to play a song when I flip the switch. How could I do that?

Posted by wisconsinrules88 4 years ago

infra red light switch?

Has anybody got any ideas on how to make a switch with an infra red light and a receiver, like when you interrupt the beams it switches on?

Asked by freerunnin1 8 years ago

What can I use for an oven switch? I want a switch to turn "eyes" on and off on my child's play oven.

What can I use for an oven switch? I want a switch to turn "eyes" on and off on my child's play oven.

Asked by commercial free 5 years ago

how to convert SPDT switch to DPDT switch ? Answered

Question Body: give us more detail on your question...

Asked by gobigas 1 year ago

Need help with switches.

II have two switches. One momentary and one latching. Both have leds and want to wire them so that the LEDs turn on or off when the latching switch is activated. Please see pictures as they are not regular 2 or 3 poled switches. Thanks.

Posted by bastafari 5 years ago

k and a slide switch

I got a k and a slide switch and i dont know how to use it to connect the wires to it.

Posted by southautomatic 10 years ago

I need some help an an ignitor box (loook in details)? {REMADE}

Alrighti posted this before but it seemed like people didnt understand what was going on. Altight, we have a box and our first switch is a rolling switch (SWITCH 0) that is used to make sure that it only works if the box is closed. Then we have a series of 5 switches that are basic on off switches {SWITCH 2, 3, 4, 5, 6) and the switches are used for how many ignition we wish to do at one time but these switches have to be switched in order so example we cant turn on switch 3 without first flipping switch 2 and etc but these switches will light a light a soon as there flipped on still with the rule that the previous switch must be switched first also the switches run a positve current throu our first alligator clips of the ignition cords. then we have a main switch (SWITCH 7) that has a cover as a safety and this will also turn on a light and this switch will run current to our last switch (SWITCH 1) which is a momentary push switch that will run the negative current to the second alligator clips of the ignition cords thus setting off what was wished to be ignited. but we have the problem of the current bypassing (LOOK AT THE PICTURE) so therefore switch 7 isnt needeed bet yet it only is used to light up our (LIGHT 6) so we need to figure out how can we prevent this from happening without completely rendering our circut.

Asked by bluejuice 8 years ago

led switch

My dad is redoing his basement and he wants to have a panel of switches with leds above them.  so that when the switch is on the led above it is on to.  does anyone know how to do this?

Posted by tic tac man 8 years ago

DPDT Switch? Answered

1. Why 2 units of (DPDT) switches are listed on the materials for the project?

Asked by pablorovira 1 year ago

Is there a switch that reverses polarites? Answered

 Is there or do I need to get complicated?

Asked by Chromatica 8 years ago

help needed to wire a series of toggle switches

Can anybody please show me how to wire a series of 7 toggle switches. The switches are 3 amp 2 or 3 pole, a diagram would be very helpfull with an explanation. Or a video

Posted by Woodycrafts 8 years ago


I have a triple switch which connects fan and 2 lights. I want to install a remote control switch (picture attached) and make the process remote as well as switch. How can i do this? 

Posted by SafarM 2 years ago

How do I switch a Push button Switch to a toggle switch?

I bought EL wire and the power is a push button switch and would like to know how i could change it to a toggle switch also if anyone knows how to change it from battery powered to powered by the car ild greatly appreciate it for that I was thinking of using a fuse tap though

Asked by alphashark45 5 years ago

USB cable with On/off Switch

Anyone know how to make USB cable with On/off Switch, not just to off the power, but to completely switch off the data flowing on a usb cable.  Thanks!

Posted by dimension_55 8 years ago

Sending more than rated amps through a switch?

I know that if you use a switch or a relay and send more amps through it than rated, it can cause the contacts in the switch to melt. My question is what if you only open and close the switch when the amps being sent is less than the rated max and then send more than the rated amps but don't touch the switch? Will this still cause the contacts to melt/explode the switch? I'm asking because I currently have a circuit that works as described above and the switch still works even after many uses. Is this because I only operate the switch when the amps are less than the rated max for the switch or is the switch going to die soon?  Thanks in advance :)

Asked by WilfredS3 2 years ago

Cat5 Changeover Switch?

Is there anyway to make a switch that switches between cat5 connections? For example, if I have 5 wires running to a rack with some switches in it, and wire one goes bad, I want to be able to turn the switch and then it will start using wire number two instead. How would I go about doing this? Any help would be appreciated :) -Tyler

Posted by tyler9613 8 years ago