Making a latching relay with 555 timer
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- čas přidán 24. 02. 2023
- I explain how the NE555P integrated circuit works, and how to make a latching relay switch with it. This will work with an LM555 as well. #breadboard #circuit
Link to schematic: cruciallab.com/electronics/lat... - Jak na to + styl
This circuit is featured on page 48 of the Engineer's Notebook II: A Handbook Of Integrated Circuit Applications by Forrest Mims (1982). It is not a latch but a countdown timer and shouldn't be relied upon to stay in the 'On' state indefinitely. Leave it with the LED on for a few minutes and you will see that it turns off by itself without the button being pressed.
Cool and simple design. I’ve built a similar circuit before with a 555, but had timer function set by the value of a capacitor/resistor combination that powered a small relay.
For a latching switch that uses a relay to power a heavier load using a low current type push switch, one could use two momentary push switches, one a normally open, one a normally closed.
These two push switches would be in circuit in this manner:
Press the N.O. switch and a + battery coil voltage flows through the push switch to a D.P.D.T relay coil and to the ground through the N.C. push switch , and it clamps. To make it latch you also feed + batt coil from the out side of N.O. push switch voltage to one of the two N.O. relay contacts, you then connect a wire between the other contact of the relay to the momentary N.O. Push switches “always hot side.” When you push the norm open (N.O.) switch, relay coil voltage flows and goes through the other N.C. push switch to batt negative & relay latches.
Summery: When the relay clamps, the one contact of the relay hooked to + then resupplies the relay coil continuously. If one then presses the norm closed (N.C) switch, the relay looses its - Neg connection to the battery and the relay drops out, “opens up.” The other N.O. relay contact of the relay can then be used to switch the hot lead or + DC of another power source to whatever load or device you are wanting to power up. There are also other relays such as T.P.T.T. Triple pole triple throw and more. Except these relays with many poles then become expensive. The resting contact state of each contact can be purchased different, with some contacts being N.C (normally closed) in unpowered state as well.
Your circuit can do the same and with only one switch if you hook your output that powers the LED instead to a relay coil. I’m not sure how much current a 555 timer chip can supply for a relay coil, I think 0.100A (100mA)? The relay coils operating voltage and resistance would need to be selected accordingly with LED & current limiting resistor removed to operate a relay directly instead. I suppose as an alternative, one could pop in a opto isolator in place of your LED, then power a relay coil through the opto isolator’s switch side “collector” hooked direct to the positive & then through the relay coil to - Neg source of the project if the 555 cannot provide enough voltage and/or current to power the chosen relay directly. Of course Opto-Isolator’s also have max voltage and current ratings for their switch side that one would need to observe. SCR’s are also fun to use for latching circuits. 😎👍
Great explanation, appreciate the thorough schematics.
Thank you, this is an amazing video with a good & clear explanation. Keep up the good work !
Sweet circuit. Thank you!!
Nice work. Thank you for making and posting this video. Thank you for the schematic and explanation of function. 🙂
Really informative, thanks alot!
Nice video. Very succinct!
Great explanation, and also a very useful circuit.
Very well presented and explained, thank-you... I've subscribed.👍
Awesome effort sir. 🎉
Love it. You should make some more interesting videos on the LM505, as I see it everywhere in all sorts of different hacking videos but never understood what was so special about it!
Versatility. It's special because it can be made to do so many useful things beyond what it was designed to do.
Lovely work
Nice video, thanks for sharing it with us, well done :)
Nice circuit, how much power does it draw when it is turned off ? I'm considering it for battery operation.
Wow worked for me after some serious tinkering 😅
This was exactly what I was looking for. Only in my project the momentary switch is connected to ground on one side, which I cannot change. I therefore tried to control a relay with my switch. This relay replaces your switch in the schematic. Unfortunately the logic is not stable anymore after replacing the switch with a relay? Any tips? I used the NO and C pole. Maybe the capacitor does not work with the relay?
Would it be possible to replace the push switch with a mosfet so that a switch to one of the power supply rails could be used ?
Great circuit i did it & it works perfectly,but sometimes when i turn the supply off & on again the circuit turns on by itself! How to illuminate that please?
tandy, radio shack publication 62-510 by forrest m mims iii. engineer's mini-notebook, 555 timer ic circuits cover this with some basic theory
I loved those books as a kid and still wish I had them. Forrest Mimms had some of the best material for beginners.
Where can i buy such readymade module and what is it called????
Nice.
I'm watching from Russia.
Well done! Simple and clear!
The author, is it possible to make a similar circuit for 220 V?
To get a pulse relay with one-button control?
And instead of a mechanical relay, you can use a triac. After all, as a key, a triac is much more reliable than a mechanical relay!
And if you use a MOSFET or a microchip, then power can be supplied through a low-capacity quenching capacitor, a bridge, a smoothing capacitor and a Zener diode at the desired voltage.
And yet, there should always be a scheme! Preferably laid out separately or in the video itself, at least for 5-6 seconds. Then it will be considered a full-time job, and this is already professional and high-quality! And then, you will want to watch something else on Your channel again!
Sincerely from Russia!
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Смотрю из России.
Хорошо сделано! Просто и понятно!
Автор, а можно сделать подобную схему на 220 В?
Чтобы получилось импульсное реле с управлением от одной кнопки?
И вместо механического реле можно использовать симистор. Ведь как ключ, симистор намного надёжнее, чем механическое реле!
И если использовать МОСФЕТ или микросхему, то питание можно сделать через гасящий конденсатор малой ёмкости, моста, сглаживающего конденсатора и диода Зенера на нужное напряжение.
И ещё, всегда должна быть схема! Желательно отдельно выложенная или в самом ролике, хотя бы на 5-6 секунд. Тогда это будет считаться полной работой, а это уже профессионально и качественно! И тогда, захочется снова и ещё что-то смотреть на Вашем канале!
С уважением из России!
I tried to use this circuit in practice to control a lamp from two separate switches that are 60ft apart. The circuit is so unstable it either turns on by itself or it refuses to latch and I look like an idiot trying to press the switch multiple times. I was advised to put a small cap between 5pin and ground and one in parallel to S1 to filter high frequencies. Did anyone try this and how did you fix it. Mine latches after the cap hack but not from the first try.
Great vid, keep it up. Ask the wife about a manicure... it has MAN in the word, can't be that bad :)
Great work, brother, but I have a question: Does the circuit maintain its last state when the source current is cut off?
No it doesn’t. When you turn it on it always starts at 0 even if it’s turned off while 1
Could this work with 12v input ?
Hello, greetings. I'm from Indonesia. I want to ask how many volts the LED is? and for the load on the LED, for example if I replace it with a relay, is that possible? because I will use it on 220v AC voltage.
🎉
would someone please explain why this is more advantageous over using an appropriate resistor and a switch (without the 555 timer)- what is the benefit of adding the 555 & capacitor? cheers
The switch is momentary. It is only closed while it is being pressed. The 555 timer adds the toggling/latching action that causes it to stay on after the button is released.
In many cases it isn't more advantageous, which is why many appliances, such as table lamps, use a mechanical toggle switch. But the purpose of the circuit is to add a toggling action to the simple momentary switch.
will this work with 5 volts DC?
Sure, the 555 operates at 4.5 to 16v.
Why is resistor connected to ground?
Isn't it supposed to come before the LED?
It doesn't make any difference.
I'll assume you are referring to R4 for both questions since you didn't specify.
1. The output of pin 3 is either at ground potential when "off" or at Vcc potential when "on". When it is at ground potential, there is no potential across R4 and the diode. When it is at Vcc potential, there is potential between Vcc and ground distributed between R4 and the diode. Therefore current flows from pin 3 through R4 and the diode to ground. If they were not connected to ground, the R4/diode circuit would be open and no current would flow through them regardless of the output of pin 3.
In a different circuit, it might be possible to reverse the diode and connect it to Vcc. Then, no current would flow when pin 3 was "on," at Vcc potential. When pin 3 was "off," at ground potential, current would then flow from Vcc, through R4 and the diode, to pin 3. That however would not work in this circuit since it would interfere with the function of C1.
2. The order of R4 and the diode is irrelevant. The same current that flows through one must flow through the other.
Doesn't matter what type of 555 circuit we use? Because I'm using it ne555 timers.
No. Different manufacturers simply use their own prefix. It's the three fives that matter.
mine doesn't work. it can turn on but can't turn off. what's the problem ?
You can test the voltage at pin 6 with a multimeter to make sure the it is getting more than the 2/3 the supply voltage, which comes from the capacitor in the upper left hand corner of the diagram.
I haven’t tried this circuit yet, but it looks like it should work. The LED turns on in your circuit, so that works. Now just make sure the switch sends >2/3 voltage to pin 6.
This can get a little complicated, so, watch the video a few times to make sure you see how it works. This is a good way to learn how the 555 chip works, so, it’s worth your time.
@@thetooginator153 great explanation!
But i already used other circuit for my project. It has two push buttons instead of one (one for on and the other for off). It less efficient but at least it works.
its NE555P. not LM555.
Thanks for catching that Kerim. I've updated the title.
I tried making the latching circuit but used an..... 10uF capacitor and 5 volts. the led took like 5 presses to turn off but like one press to turn on dont know why i tried many different capacitors didnt work.
What value resistors did you use?
A relay and a switch would have been easier !!!!
It's not as cool though :)
And how would say, a transistor operate such a switch?
"How does a transistor...?" A transistor IS a switch. 🤦
As for why use this instead of just a switch, this provides a toggling, debounced on/off signal with a temporary pushbutton switch and common components. It's unlikely your load would actually be a relay if you were to use this, but it provides a satisfying click sound for demonstration purposes.
You’re missing the point
@@jjhack3r I did not miss the point, this project was just another way to re-event the wheel... that is all. no bad intent on my part. Thanks for jumping out of the Croud for such a small comment !!!!