I have a question about the wiring a 555 Timer in Monostable Mode?

Hey all I am relatively new to the world of electronics. I have been learning about the different modes of the 555 timer chip because I would like to incorporate it into an upcoming project. I made a circuit and did the calculation so that once a button was pushed, an led would stay on for 5 seconds and then go off (a one shot timer). Everything worked ok accept I noticed that when hooked the battery up to the bread board (my last step of the build) the LED would turn on stay on for 5 seconds then shut off.  Is there a way to wire it so that when power is initially applied to the circuit it doesn’t trigger the timer? In other words the only thing I want to trigger the chip is a push of the button, nothing else! please let me know if this make sense. Thanks!

Asked by Mpc1055 2 years ago


555 monostable sensitivity?

Has anyone built a 555 monostable circuit that was extremely sensitive for no apparent reason? I'm trying to use one in a rube-goldburg machine, and for some reason it's extremely sensitive to any sort of touch! The circuit sometimes comes on for no apparent reason, other times it will stay on for longer than the expected duration after the button is pushed. I'm using non-CMOS 555 on about 5 volts to run a small LED. The capacitor I used was a 0.01 uF on pin 1 to 5, and a 1 uF electrolytic on pin 1 to 6. I used a 1M resistor on pin 7 to 8.  I'm simply baffled by it. I've tried using different breadboards, different PSUs, brand new components, and correct gauge wire, but despite everything being seemingly fine, it's still shows the sensitivity. Anyone have any advice?

Asked by tylervitale 5 years ago


How do I set up a monostable 555? Answered

Ya, i've been searching around and what I don't understand is how to make the pulse for the trigger.  Its has to be less than 1/3 the supply voltage right?  But how do I achieve this?  THANKS  

Asked by junits15 7 years ago


How can I make a siren chime for a few seconds when a laser hits a photo resistor using a 555 timer chip?

I am trying to make a target for my laser for camping trips. I don't know how to create my own arduino codes to program an ATtiny so I was hoping to create a monostable circuit using a 555 timer chip instead (If monostable is the correct circuit). Basically I have a 6-14V siren and want it to chime for at least a second when the laser beam hits a photoresistor during day or night. I have tried but to no avail, since I have not been able to understand the ways of the 555. Any suggestions with or without a 555 timer chip are completely welcome. 

Asked by KevinAlien26 6 years ago




Does solid state relay needs a protecting diode for the pin 3 out of a 555 monostable? Answered

Recently i need some timer for my capacitor charger to be used in a coilgun. i just finished a 555 one shot monostable pcb design.  my charger require about 24 watt of power which is unsufficient for the 555 pin 3 out,. I know that a protecting diode can be put with a relay. but a solid state for a solid state realay. does it need a diode. i just want to know because i will put it in my design 

Asked by ARJOON 7 years ago


555 timer output hight and low? Answered

I just soldered up a 555 monostable circuit following an internet tutorial and for some reason the output seems to be both low and high. it can power a LED connected to the 0V & pin 3 and the 9V & pin 3. any ideas what might have happened?

Asked by DrVonTrap 7 years ago


5v battery backup?

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

Asked by GhengisKhan1981 3 months ago


Push button to toggle servo direction - monostable 555 circuit? Answered

I would like to build a circuit where I push a button once and a servo moves 180 degrees and stays there.  If I push the button again it should move back to the start position. A switch is good alternative, whichever would be easier. I've been looking at circuits to do with 555 timers and servos and have found these two which seem useful: http://www.555-timer-circuits.com/servo-controller.html http://www.dummies.com/how-to/content/electronics-components-555-timer-chip-in-monostabl.html Is that second circuit what I need?  How would I change the direction of the servo each time it runs? I looked into flip-flops such as the 4013 which came up as a suggestion instead of a 555 but quickly got out of my depth.  I'm happy tinkering around with electronics but unfortunately don't know too much of the theory...

Asked by Sparrowhawk 4 years ago


How do i make use of the output of a PIR sensor to toggle a switch?

Currently I had build a board according to this schematic, http://www.massey.ac.nz/~wlxu/reports_pdf/HealthArticle2002.pdf . I was told that a edge triggering monostable 555 timer will allow me to have a stable high/low signal. Problem is how do i make use of the output to generate the switch from the edge triggering 555 timer?

Asked by Acronymm 6 years ago


Astable transistor component calculation Answered

Greeting AllI made a few astable and monostable circuits. The one in the attached picture gives me an output of about 1 second, but i need to know which RC components i need to make it give a mark space ratio of 6 seconds.I'd appreciate if i can get the answer along with the calculation and an explanation of how to do the calculation.Thanks in advance for any assistance.KRGK

Asked by GhengisKhan1981 5 months ago


One shot delay timer switch without a microcontroller?

How do you output a single short pulse in an electronic  circuit after a specific period of time has elapsed after the circuit is powered on such that when the circuit is powered on, the output remains zero for x seconds then it becomes +5 V just once for y seconds then again back to zero for the remaining time much like monostable mode of 555 timer except that the pulse here is output in the middle i.e. 0v-5v-0v. Can this be done without a microcontroller?

Posted by raftor 4 years ago


555 triggered by a switch and thyrister problem!! PLEASE HELP!!

Hi, I have a problem because a switch is working as a reset switch for the solenoid as well as a tension release mechanism for the pulley. The thyristor is also triggering the 555 chip (monostable). Do you guys have a solution, please do not tell me to have 2 switches for the tension release as well as the reset for the solenoid circuit. PLEASE SEE MY ATTACHED PICTURE AND MY VIDEO ON YOUTUBE EXPLAINING MY PROBLEM FURTHER!! http://www.youtube.com/watch?v=akqatPnyV04 Ahmad

Asked by in06khattab 7 years ago


Creating a 10-15 second timer?

Hi All, Here's what I need to try and achieve: - I have a servo that I had modified and have removed the circuit board.  Now it just runs from 3 v - I want to reverse the servo once a momentary switch has been activated for 10-15 seconds - once time is up the servo reverses again I thought about using a 555 monostable circuit which would give me the amount of time, but I am unsure how to achieve everything above. I'd love not to have to use an arduino if possible. Any ideas? Thanks.

Asked by lonesoulsurfer 4 years ago


Replacing the 2N3904 with an SCR

So i made a laser alarm system some time back, it worked good but had one fault, more like a limitation. it made the buzzer ''buzz'' only when the laser was interrupted and the buzzer turned off when the laser was allowed to hit the photo sensor again. i wanted it to stay on until turned off by a switch. someone suggested something called a monostable flip flop but i had no idea what it even meant, then i saw something called silicon controlled rectifier or a thyristor, but i also learned that they have to be made using a pnp and npn transistor, what i cant understand is what transistors should i use to replace the npn transistor on my circuit, the tansistor on my cicuit is 2n3904, input voltage is 5v

Asked by walee 5 months ago