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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

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

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 if you have any ideas

Topic by NathanMenke    |  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

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

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


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://     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: 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? 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: 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  

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

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

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

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

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

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

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


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  

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

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

Help with Solid State relay and Neon Indicator

I have a problem using a neon light to indicate when an SSR has switched on. When the neon is connected across the SSR output it lights even though the SSR output is off. There is about 100v on the output, enough to light it. Is there any solution to this. Photo attached.

Topic by CBBC    |  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

Help with On-Line Indicator for Jabra GN8530e headset

I have a Jabra GN9350e headset that I use at work, both with my desk phone and USB on my workstation. Jabra sells an on-line indicator (, but it's just a plastic stick that lights up at the top. No one will understand what it is, or what it means. I intend to build an LED box that says something to the effect of 'ON A CALL' with a chasing border to get attention and deliver the message that, well, I'm on a call. The tricky part for me is that I can not tell what type of connection is used to connect the device to the base station. I know it is a 2.5mm TRS connection, but am unsure if it is stereo or mono flavor. I am also unsure what the actual signal would be - is the sleeve is ground, tip signal, etc. I have spent a few hours searching the web and found nothing. My end goal would be to build a plastic box to house the indicator assembly, with mirrored plastic on the front so that when the indicator is off it would appear to just be a black box. When active, there would be a chasing light border (two or three LED sequence, just regular chasing lights), and a solid on field in the middle with verbage. I'm good with a soldering iron, but new to this kind of build. If someone could assist / recommend how to proceed in building the circuitry that could connect the LED's together (sure I can find that information on this site elsewhere) that would be nice, but primarily I would need help interfacing the indicator with the headset base station. Thanks!

Question by jon.hazlett  

Dell indicator light? Don't throw it out!

I'm working on a project that will become an 'ible when it's done, and I need a little help from fellow sysadmins. If you come across a Dell-server indicator light, please don't throw it out! Send it to me instead! See, Dell servers all come with an indicator light on a cable (it's really just a blue LED connected to a 4 foot cable, and it ends with very thin barrel plug). The light is intended to be plugged into the server, then clipped to the side of the rack, so you can see if a server is off or on without looking at the back or front of it. Nobody ever uses the light as far as I can tell. Where I work, we generally throw them out. I've been collecting all the ones that I come across for awhile now, and have only gotten together 16. The project I have in mind needs at least 60. You can think of sending them to me as recycling :) Thanks --Kyle

Topic by Kyle_S  

Arduino high voltage capacitor charge indicator?

I made a 330v gauss gun and wanted a way how to know when capacitors charge, at first i took an led and resistor, that worked but is kinda boring. I want to use arduino and lcd to display percentage which should look more cooler. How should I measure the capacitor bank voltage with arduino? Should I use voltage divider? or there is a better way?

Topic by spudziuvelis    |  last reply

Help fitting a low voltage indicator into this circuit?

Hello,I know very little about circuits and electrical components, so please be kind.Attached is a picture of a simple circuit. "A" is a 4,5V AAA alkaline pack, "B" is a latching pushbutton switch and "C" is a nicrome wire.In the simplest and cheapest way possible, this circuit needs to alert the user if the battery pack goes below 3V. The indication signal needs to be a "beep", just like a 9V fire detector. (I can't have a LED signal).After some googling, I found that a 3V "low signal relay" could be one option. I prefer to use wires, and not a PCB in my circuit. My questions follow below:1. Is a low signal relay this the cheapest and simplest way, or are there others?2. What components do I need to achive the "beep" and where in the circuit do these components go?3. Will these components draw any power in standby mode, or do they only consume some power when the "beep" goes off? Because if they draw power continuously, I will need to add an extra (coin cell?) battery, as I need to save my alkaline pack for the nichrome wire. The extra battery shoud last for min 3 years.All help highly appreciated.Thanks!/Karolina

Question by karolina81    |  last reply

Simple (I hope) Treadmill Incline indicator

Hi,  I have an older treadmill that has a button to control the incline, but doesn't display the incline. I have a treadmill program app on my iPhone that guides me through a exercise session by telling me to set the speed and incline many times throughout the 30 minutes I am on the treadmill.  I would like to build something to display the incline as I adjust it.  I have just enough memory from all my childhood Radio Shack projects learning to not be afraid to attempt this and also the vast knowledge of the internet :) I have already calculated and marked the incline differences on the frame of the treadmill near my feet but I can't really see it well. I figure a small LED display would work best. I can visualize running wires up and down the frame to the LED display to an arm that will move with the treadmill while hitting contacts. I am sure I can get this to work but it sure seems like a lot of wires so I feel I am missing something. If anyone has any suggestions about an easy way to do this or can draw me a diagram of what I would need, I would be forever grateful. Thanks, Cindy in Indy

Topic by logock    |  last reply