LED indicator

How should I drive an LED from a 38 volts power supply? The led wizard says I need a 1800 ohm, 2 watt resistor, but it also says' it'll disipate excessive heat. I recently took apart a surge protector and found that they drive an LED from a 120volt source by having a diode, LED and what appears to be either a 1 or 2 watt resistor. I need help driving an LED from a 38 volts power supply just as an indicator.

Topic by guyfrom7up   |  last reply


who's on? indicator

A lot of forums seem to have a bar that lists who's online. is there any chance instructables may be getting one? it would eliminate the long half hours when people sit in front of their computers waiting for a reply that not coming. any chance?

Topic by tech-king   |  last reply


Signal Indicator?

I'm trying to make a simple transmitter/receiver setup to use in airsoft to keep track of the distance (not worried about direction right now) between me and whatever the transmitter is planted on. The transmitter can send out a steady signal or pulses, and the only problem I have is how it will show the distance. I have a line of LEDs that I want to set up so that more light up the closer I get to the transmitter, but I don't know how to rig the setup so that it displays signal strength (I would think that the closer you are the stronger the signal). Does anyone have any idea how I can do this or perhaps better alternatives that accomplish the same thing?

Question by pyrorower   |  last reply


LED power indicator?

Just wondering how to to wire up a LED to show when a project is powered. Eg. push button switch doesn't show on/off.

Question by SWIRLYTHINGALERT!   |  last reply


LED Slider Indicator

I don't know very much when it comes to electronics. All I know is how to make a simple circuit. Conect bulb to battery, battery to swich, swich to bulb. I need some help making a circuit bord with an on off swich, 5 LED's & a sliding potentiometer. What I like this curuit to do is, turn on swich, the first led lights up. I push the slide potentiometer up or down & the four other LED's light up or down with the slider.

Topic by elkaddalek   |  last reply


Charge level indicator?

I need a nice, simple charge indicator. I have a battery pack that holds 4 AA NiMH batteries. Normally they charge up to 1.3V per cell or 4X1.3=5.2V total. I have a solar trickle charger on there too and I'd like to have a little charge indicator.   Requirements are: -low part count -under $10 -small (it's on my bike helmet) I was thinking something with a pushbutton an LED or two and a zener diode. Something that turns on the LED at  greater than 5.2 volts. But I don't have experience with zener diodes. Has anyone seen a system like this around? Can you think one up? -Cheers

Question by snotty   |  last reply


Usb eMail indicator?

Hi, I am looking for a no circit( or chippy thing) usb diy eMail indicator. I would like it to light up a led and ring a bell.

Question by Warlrosity 


Battery Level Indicator

Trying to build me a battery status or level indicator, using the LM339 series IC. I am just not that familiar with this IC. I want to make this using 3 red LED's, 3Yellow and 3 green or using a bar graph LED. Any advise on how to hook this LM339 up?Thanks

Topic by dominick.j.pezza   |  last reply


Low battery indicator

Can someone please provide me with a schematic to turn on an LED when a 9v PP3 gets low (~<20%), no microcontrollers, the simpler the better. I am hoping you can do this with a few diodes, transistors, resistors, and maybe some capacitors, but I can't think how this would work.

Topic by andy70707   |  last reply


On a call indicator light

I need to figure out a cost effective way to let people know I'm on a phone call. This solution needs to light an LED automatically when I am actively using the telephone. Is there a way for a simple circuit to sense when a phone line is in use and not cause any line interference? The circuit doesn't need to be powered through the phone line, it just needs to be able to sense that the line is in use.I know how to solder and understand basic electronics concepts but am also very teachable. If someone can point me to a schematic I can build it.There are ready made, but expensive, solutions for sale but the costs are restrictive. Any help is greatly appreciated.

Question by CementTruck   |  last reply


Attitude Indicator...For a car....

How would one make a cheap attitude indicator for a jeep...i go offroading and i just thought it would be cool to make my cockpit look more like a cockpit, im putting up some toggle switches and a couple other cool accents but i thought the coolest would be something that shows me how far my jeep is tipping when i flex it.  So if anyone has any crazy ideas on how to pull one off let me know, ive had some ideas of like pinning a floating compass to an axis so it only tips back and forth...but the real electronic ones for aviation are thousands of dollars and very impractical.  Help me out here people....  email me at artbynathanmenke@gmail.com if you have any ideas

Topic by NathanMenke   |  last reply


shaft direction indicator?

Does anyone know an easy way to get/make a simple device to determine the direction of a spinning shaft?  It must give some logic (5V) signal, NOT encoded in any way.  Just +5 if CW or 0 if CCW (or backwards, or 3.3V, or whatever else, it doesn't really matter).  However, it must not A) require any digital controller (no arduino, ATtiny, PIC, computer, raspi, etc.) B) have an "encoded" output, or gray code C) have a large "dead band" where it still indicates CW but it's actually spun a tiny bit CW (or vis-versa).  Must be under 3-4 degrees D) require  the shaft to spin quickly E) be expensive.  This is a prototype for an ANALOG mill D.R.O., so I don't want to have to spend ten bucks on one part that I have to buy several of, plus the other parts.  Its a 1/4" threaded rod, but can easily be adapted to whatever else it needs to be.  The device needn't be small, and I will have a 3D printer avaliable (or at least a mill). 

Question by jduffy54   |  last reply


LED Voltage indicator

I have recently installed a solar panel in my garden to charge a 12volt 21Ah battery. I would like to show it off a bit by using a simple LED display to show it working. What I was thinking was to have a range of about 8V-25V. At the low end would be blue leds (for cold) up to red (hot) at the high end. Does anybody have any idea how I would go about getting something together. I can read circuit diagrams at a push (my Dad's the expert) and would like as much information as possible. Would it be possible to have 1 LED per volt ? Am I being simple? Would this project be self defeating in that it'd use lots of the free power I'm trying to collect? Any help anybody can give I'd be grateful to receive. Share & Enjoy. Zippy.

Topic by bunglesmate   |  last reply


RGB LED Voltage indicator for 15 - 10 volts

I would like to make a one RGB LED DC voltage indicator, 15 – 10 volts in half volt changes.  At first I thought I would use a bunch of zener diodes, but it seems a bit more complicated than that as on my chart how I want the colors indicated.  Any ideas how I can accomplish the circuit?  There are probably new fancy things I could use but am not aware of since it’s been a very long time since I’ve made a circuit.  I am currently just using an analog panel meter.  It would be nice have a colored light indicator.  If it could be done.

Topic by K00kie   |  last reply


How can I make a low battery indicator for a 7.4 Li ion battery?

I'm hoping somebody can help show me how to make one or help me find a schematic for one as I have no Idea where to look, Google search is overwhelming and none of the results are for a similar battery (and are too complex). I really only need a circuit with one LED that lights up when the voltage drops, nothing fancy.     The battery is 7.4 V as stated and is Li ion.

Question by gravythis28   |  last reply


Problem with low battery indicator

Hi guys, I have built a low battery indicator circuit for a 6V battery source. It will light up a led when the voltage reaches below 5V. The 6V battery source powers a servo motor, which is controlled by a microcontroller. The problem I have is that when the servo motor rotates, the led lights up. And when the servo stops rotating, the led goes off. This happens even when the battery is above 5V. Any idea what is wrong? And how I could rectify the problem? I have attached the circuit of the low battery indicator, if it helps.

Topic by kurtselva   |  last reply


How to make a water level indicator?

I want to make a water level indicator without sensors or ic. I want to make it with switches. I have a switch in which we have to press the switch to turn it on and if we leave it, then it turns off. So i can connect the switches with the leds and power it with a 9v battery. Please can you make the wiring diagram for this.

Question by ckkartik   |  last reply


how too make usb with LED Indicator

Hello people I found long a go something that was a led that flashing on the data transfer from a usb so i can't find it now so can you help me out? i try something todo but its not working i buy a usb hub and made npn with led on it if you Base Volts up than you led goes on. now i add the base on the data line on a usb of that usb hub but there is no effect... can somebody help me?

Topic by W4tc   |  last reply


Large Scale Water Level Indicator

Hey everyone, I hope im posting this in the right spot.  I run a large farming operation and get my water from a well that pumps into a large storage tank about 10 feet deep and 6ft diameter.   Because the well is very old I'm not able to add things like a float that will turn it on or off for me so I'm constantly having to check the well though out the day and if the cows are more thirsty one day they can drink the storage tank dry and that causes me problems with my pump, or if i leave it to long it will overflow and it makes a terrible mess. So im wondering if there is a way that I can wire up a water level indicator in the well-house and have a light board in my house that shows me the level of the well.  So for a 10 ft deep well id have an led light for every 1ft or so and when the water level gets to the top foot a buzzer would go off and when it hits the bottom foot or 2 ft then a buzzer would go off.  Ideally a wireless transmitting to the house would be best but I have no idea how that could work.  And wired would be hard with the well house being a few hundred feet away from my house.  I've done a lot of googling and haven't found anything that would suite a large scale water tank like this.  I purely want to be able to see in my house where the water level is and have it warn me when its too high or too low.  I apologize since i don't have a lot of experience in electronics.  Any help is greatly appreciated as i have no idea where to start or if its even possible.  Thanks guys!

Topic by rpfarm25   |  last reply


Need to make charge indicator for 4 V 1 Ah Lead Acid battery Answered

Hi,  I have made a solar study lamp. I am using 4 volts 1 Ah lead acid battery for the same and 3 Watt solar panel. It charges well with the current circuit. But it does not have a charge indicator. I am looking for a battery charging circuit with charge indicators as follows: 1. Low battery indicator  2. Battery full indicator 3. Charging indicator - to indicate battery is getting charged Trying to keep this simple and inexpensive as this lamp is a part of social initiative for rural areas. Thanks in advance! 

Question by rahuldj   |  last reply


lm3914

So this is what I came up with eagle for the lm3914 can someone please verify if this will work as intended.

Topic by dominick.j.pezza 


Bluetooth Water level for smart phones

I need some help in making a bluetooth water level that uses standard float switches.  Once a float switch is triggered it would close or open a circuit then the data of which circuits are opened or closed can be used to determined the level in the tank. This will be sent via bluetooth to a mobile device were i will develop an app to visualize the data. Please i need info on how to setup the electronic components.

Topic by Higrade   |  last reply


Bluetooth Water level for smart phones

I want to know how this would be accomplished PLEASE. Looking to make a bluetooth system that sends water level of a tank to a smart phone. I would think the most cost effective way to do this is by using a bluetooth module and float switches. The module would send three levels full, half and empty, so say all float switches are triggered it would be full, only one it would be half and if none it would be empty. What do i need to build this.

Topic by Higrade 


LED Turn indicator for Motorbike

Hi Everyone, I'm new to this forum and joined to get some help from all the geniuses here. I'm making  LED turn indicator for my 100cc bike. My present Factory installed flasher rating is 12v 10W X 2bulb. I want to add total of 48 ORANGE LED, 24 in front indcator and 24 in rear indicator. The current drawn would be much less for the flasher to work as the LED would not flash. I want to make 4 parallel set of 6 LED in series. as the total volt would be 2.2v*6 led =13.2. I've achieved the above so far but how to make them blink? Flash would be better then blink !! So can anyone suggest me a simple circuit which I can put in place of factory installed flasher and work the same way. I've 12v 7.2Ah Battery on board. and one thing more If I hook up a 55w/55w headlamp directly to the above battery how long will it last. I'll be grateful for the pain you take for me... Thank You Gurdeep

Topic by gurdeepsyan 


Wireless water level indicator?

I have a tank that's above my 2 story house. I did use a 50 foot Ethernet cable and wire up a level indicator, with 5 levels from empty to full. But the wires always corroded, and it just stopped working. What i'am looking for is a way, to do the same wirelessly. Maybe even automate via ifttt, as my motor is connected to a smart plug the HS100. How can i accomplish this, the tank is open to the elements, so something waterproof, and solar/battery operated would be great. I did think of the Xiaomi Water sensor, which generally checks for dampness,but that needs a Xiaomi gateway, so what does the community suggest? 

Question by TalkingStuffN   |  last reply


H.V. CAPACITOR CHARGE INDICATOR

CAN ANYONE HELP ME ABOUT HOW TO PUT A VOLTAGE/CHARGE INDICATOR on flash/High Voltage capacitors using LEDs - Thank You.....!!!!!!!

Topic by KITKAT69   |  last reply


LM3914 battery level Indicator ?

Https://www.instructables.com/community/LM3914-Battery-Level-Montitor/     I am trying to make a Battery Level Indicator using the LM3914 IC. The problem I am facing is... where you see those 3 LED's my voltage increases on the pot, where as when the LED's are all the way on it decrease across the pot. I am using a 9V Battery where I want the red led to show depletion  of battery life around 5 or so volts  how can I achieve this. Can someone please help me with this?      Which pin can I set to 5v and how?

Question by dominick.j.pezza   |  last reply


indicator lights to show voltage.?

I live in the jungle in Thailand, in the morning the electric supply is only 145 volts till 8 am at that voltage many things do not work mainly the water system. During the day the voltage is adequate and things work, in the evening we are back to 145 ish. I want a light panel system so that my wife and I can easily see whether to use the water system or not. So red, yellow and green indicators to show red 145, yellow 170 and green 185 or round about. The display to be constant, I have Fluke meters but they all time out after a while. I can source most electronic components.

Question by sootybrown   |  last reply


auto delay off indicators ?

I have an old car (1930) with a 6 volts positve earth electrical system. Although it has semaphore arm type turn indicators, I have installed a modern flasher type system . It works fine . The problem is , I often forget to cancel the idicators , I need a simple way to to auto cancel the signal after say 20 seconds. I have tried using electronic devices  based on the 555 timer. These work fine until the engins is started, causing the circuit to become un balanced, so its real hit and miss as to reliabilty. mainly due to the fact that the working voltage of the 555 is 5 -- 18 volts. Can anyone suggest a way around this problem. Thanks Gasper1

Question by gasper1   |  last reply


LED indicator for A/V selector

Hi! A while ago, i made an A/V selector, and it worked quite well. It had a small design issue, which is, having the ports at the front, where the switches are, and I want to upgrade it a little bit. The idea is, put on the front the switches with a LED on each input, and when I switch the selected input, the selected LED will also light. I've been looking around, and the A/V voltages are around 1 volt. The switch I have, it can handle 3 circuits at the same time (Video, Left and Right) but it has 3 rows as a conmutator or something. The thing is, i need your help in order to connect the LED. I've been thinking about using the unused row of the switch, but I don't know how, or, place a transistor when the Video input comes across the switch, but I don't know what kind of transistor will do. Thanks in advance I attach a diagram of what is now, with 5 inputs, showing only 2 of them, to have a brief idea

Topic by jimmytvf   |  last reply


12V car battery indicator

Hi, I have been trying to design a circuit to monitor my 12V leisure car battery, I'm thinking this should be fairly simple, but its been years since I did any real electronics. So the basic idea: Use the circular bargraph to indicate the level of the battery when a momentary push button is pressed the circular LED bar graph: https://www.sparkfun.com/products/11492 So the range of the battery would be something like 10.5V to 13.5V, there are 32 LEDs in pairs, so essentially 16. 1. So if we take the first LED pair, this should illuminate when less than 10.5V, so that should be easy, as long as there is some life in the battery it should illuminate 2. The next LED should only illuminate at the next step, 16 LEDs, 3V range 16/3= steps of 0.2V So at the following steps: 10.5, 10.7, 10.9, 11.1, 11.3, 11.5, 11.7, 11.9, 12.1, 12.3, 12.5, 12.7, 12.9, 13.1, 13.3, 13.5. So for 10.7V I guess I should use resistor before each LED. 3. The LEDs should light up after a momentary push switch is triggered, I would like this to be graceful, so the ring lights up smoothly one LED at a time as the voltage increases, I guess capacitors between the resistors and LEDs? This is the simplest way I can think of doing it, I have seen circuits which use a LM339 chip, but that can only monitor 4 voltages, perhaps 4 of these in series could do the job? http://www.electroschematics.com/7068/lm339-lm239-lm2901-datasheet/ I think this is the way to go rather than using inline resistor/ capacitor pairs? So I am a clear novice when it comes to electronics (but I'm enthusiastic), so if anyone can help me with this I would be more than happy to put together an instructables how to, something similar has been done before: https://www.instructables.com/id/Car-battery-tester/ In that example only one bar is lit, I want the other bars to stay lit. I can use Eagle to make the PCB diagram and get it printed, but I need to figure out what components I need and how to do it! Thanks for any help. Gary

Topic by garynobles   |  last reply


Stoplight Status Indicator Project

I have never attempted a project before and I imagine it maybe be somewhat simple for some of you.  If I could get any advice on this I would really appreciate it. I would like to make a "stoplight" that consists of three lights/signals.  Yellow, Red and Green.  I'd like to be able to switch what color light is activated by pushing one (or three buttons if that's easier) but only one light should ever be on at one time.  If one button is used then the order the lights would cycle in each time the button is pressed is Yellow --> Red --> Green --> Yellow --> Red --> Green etc etc... Additionally, I'd like a timer to start whenever the Red light is lit.  After the timer reaches 2 minutes I would like the Red light to start flashing on and off.  Basically a warning that the red light has been on for 2 minutes.  Ideally the timer length would be changeable to anywhere from 1-4 minutes.  Also, as a bonus if some sort of LED timer could actually should the timer counting up from zero that could at least count up to 9 minutes 59 seconds that would be awesome. I could easily enough just make a 3 buttons that turn on/off a light, but here are the two main things I need help with: 1) How do I make it so that when the Red light comes up the timer starts and flashes the light at 2 minutes? 2) How do I make a single button cycle between turning on each of the three lights in order each time the button is pressed (e.g. Press once it turns on Yellow and Red & Green off, press again it turns off yellow and turns on Red, press again and it turn off Red and turns on Green, etc Thanks in advance!

Topic by jebilbrey 


Adding an indicator led to a multimeter when it is on? Answered

I would like to add an indicator led because I keep leaving it on and draining the power.

Question by hkerr   |  last reply


Battery life indicator for Arduino powered fish feeder

Hi all, So I am basically a noob in electronics and a 1st time arduino user for my project. I need to do an automatic fish feeder and this is what I have in mind: I'm gonna use an arduino UNO R3 to connect it to these following components: - a 16 x 2 LCD Display (connected to RTC chip) - a small DC motor - 2 pushbuttons So these are the main components and I need the arduino to be portable ( So has to be battery powered - Maybe a 9V batt) As such I have 2 questions: 1) Is it possible for ALL the components to run using power from arduino? 2) I need to add a battery life indicator as well.. how do I go abt doing it? Hope you guys could help me

Topic by kurtselva   |  last reply


What is a simple indicator for use inside the house to show if a circuit breaker in my garage has tripped? Answered

The refrigerator in my garage has tripped the circuit breaker several times without my knowledge, spoiling my food. Without actually going into the garage, how can I tell if the breaker has tripped, using something such as an led or buzzer? I could hear a loud buzzer in the garage.

Question by jaxboy   |  last reply


Circuit Help!

Hi, I'm trying to put together a basic circuit for charging a capacitor/s with a built in LED to indicate when it's charged. I've created a draft on Multism but can't seem to get it to work. I'm a complete novice at electronics and have pieced it together from various schematics I've found. Help please! :)

Topic by si_eng   |  last reply


Help in constructing a battery charger

Hi there! I need some help constructing a circuit to charge a lead acid battery. The ratings of the battery are: 12v, 7Ah(Or so). The circuit must have the following features: -> Must be fairly simple (Considering the fact that i don't get all the components easily in the place i live, not even online) -> Must automatically cutoff when the battery is fully charged(Or near full). -> Must also have an indicator, (like the ones we have in a digital camera battery charger, which shows RED LED=Charging, GREEN LED=Full, something like that). -> Charging times can be fairly reasonable (Few hours for a full charge sounds reasonable).  -> Hopefully, some explanation on how the circuit works. ;) Thanks in advance :)

Topic by charmquark   |  last reply


I'd like suggestions to make a shock impact indicator like they did on Mythbusters, but more compact and simpler.

This is to put on a dummy to denote whether a kick or punch could break a bone.?

Question by implaxis   |  last reply


USB "charging done LED" circuit?

Does anyone have a very simple circuit (newb here) that can be used to indicate that a USB-based "charging is complete" or "is charging" (whichever is easiest). In other words, say if it's taking 200ma or more, light up an LED. Not a full charger btw, just something that I can plug in between anything - computer/car/ac-charger - and the device. This would be useful on devices that have no indicator at all or on things like phones that have their LCDs dimmed when charging. Thanks!

Topic by cowtip   |  last reply


LM3914

So I looked up the data for the LM3914 followed the steps and I still cant get this thing to work I tried it two ways. I want to be able to set this up for variances of voltage say from 1.5V to 30 volts. Any advise would be great.

Topic by dominick.j.pezza   |  last reply


Simple battery charge level indicator? Answered

I need to be able to see the charge level of a 12v rechargeable battery and want it to be as simple as possible. Would this setup work: 3 zener diodes (at different breakdown voltages 10, 11 and 12 volts for example) with cathodes connected to positive so that when the battery was above their breakdown voltage an led could light up. Here is a diagram:

Question by Scytheon3   |  last reply


HV capacitor bank charge indicator?

Hello! I have a capacitor bank with three 330v capacitors (from disposable cameras, of course... those things are awesome) connected in parallel, but I'm planning to add more. I'd like to indicate when the device has been charged using an LED, but I'm pretty sure that most LEDs can't handle 330v. The disposable cameras often have indicator lights, so how do they do it, and how can I implement it with more capacitors?

Topic by SirCheez   |  last reply


Pro Member indication on new site?

  I've got a feeling I'm missing something blindingly obvious here, but is there still a way to see if a member has Pro membership?

Topic by AndyGadget   |  last reply


Game turn indicator - how to build?

My family likes to play a particular card game called Phase 10. The way it works is that after each hand, the deck is handed to the next person to deal from.  We're often so busy chatting/having fun we forget exactly whose turn it is to deal. Not a big deal of course, but all our attempts to keep track have failed.  I thought it would be cute to set up a little strip of LEDs and have them be controlled by a button. Push button, next LED lights up, with each LED assigned to a player so we know whose turn it is to deal next.  There's nothing commercial I could find, and I don't know enough about LEDs, controllers, etc, to do so - so I'm looking for someone who can explain what has to be done (and the materials) so I can build it... or if someone wants to take on the project and get paid for it too, that works.  It's meant to be a christmas present for my father (who's the worst one of all about remembering whose turn it is) so - that's the estimated deadline. Anyone got info for me on how to set this up?

Topic by sevendaysky   |  last reply


Battery life indicator for 1.5V battery source

Hi guys, I want to make a simple battery life indicator for a device running from a 1.5V battery source. I would just need a red/green LED to light when the Voltage is above a certain limit (say 1.2 V). and to turn off once the limit is reached.. Is there any simple circuit that enables me to do this?

Topic by kurtselva   |  last reply


What - besides rulers - can I put in my photos to indicate scale? What things are the same size all over the world? Answered

 I'd like to include scale-indicator objects in some of my photos; but rulers are boring, and dollar bills or US coins seem kind of US-centric. What small, preferably common-household-type, objects are the same size all over the world?

Question by Gorfram   |  last reply


Low Battery Indicator for 2x AA Batteries

How would I create a circuit which turns on an LED when the voltage goes below 2.5V? I am using 2x AA batteries

Question by john8369   |  last reply


Looking to replace LEDs with solenoid driven indicators.

I'd really like to replace some LED indicators with physical on/off indicators, like they used on old NASA spacecraft. To see what I'm talking about take a look at this console from Apollo 14 at the little windows above the switches at the center left. The top row is all "barber poll" the bottom row open.My initial thought is that I could possibly replace the LEDs with a solenoid that would shove an "on" indicator into a little window when powered, and retract it when powered down.The problem: I know next to nothing about solenoids and don't know if this is feasible. They'd need at least 1/4" throw and to run at low power if they're going to simply be a drop-in replacement for LEDs. What kind of solenoid am I looking for and does it even exist?

Question by Grathio   |  last reply


Lm3914 battery level indicator 1v - 40volts?

So I looked up peoples ideas off of here and google I set it up the exact same way I must be missing a step can someone please dummy proof this for me.

Question by dominick.j.pezza   |  last reply


Led indicates wallet is empty - Wallet Idea !

I had an idea for a wallet instructable, In the section of the wallet where you put the notes there are two metal connectors that touch when there are no notes but the connection is broken when a note is inserted, when the circuit is completed (wallet empty) a red led on the outside lights up indicating you need to go to a cash point and get some more money. Do you think this is a good idea ? should i make it ? What extra features or improvements would you like to see ?

Topic by =SMART=   |  last reply