This circuit defaults to the "on" state as configured. To default to an "off" state, add one more transistor stage as described at breadboardcircuits.com/transistor-push-on-push-off-switch/

This .... this is amazing. Not just demonstration of a "classic" circuit (which is great, too), but sharing something useful that he thought up on his own. Wow. This is Art. Thank you, please make more videos 🙏

Frankly, I dont think I would have shared this with the world for free. Its not like its world changing or anything, but it did take a lot of thought and effort. And on top of that, it is useful. Think of all the money other people will make using this in their broader designs with no credit whatsoever to Steve. I hope you all are very grateful for someone sharing actual innovation rather than regurgitated and ubiquitous starter nonsense over and over, e.g. arduino jump how high bro.

Just came here for an online page while looking at latch circuits.. like this one for it's simplicity and low number of components. 👍🇮🇪😊

I'm watching from Russia. Well done! Everything is clear, simple and understandable! And most importantly - a very useful device! On high-quality, cheap and common parts! Respect! The author, but would give an idea about a bistable relay (Pulse relay) at 220V. Similar relays are sold by the Chinese for installation on a DIN rail. There is a lot of information on the Internet on how to connect it according to the type of "pass-through switch" from several places (parallel power buttons), but the Chinese sculpt there, mechanical(!) Relay! And recently they opened such a relay made in a case with some kind of semicircular diamond and saw that there was such a microcircuit HCF4013BE and a minimum of strapping, apparently a direct-current chip from 220 V., and a BT136-600E triac is already in the form of a key (if necessary, I can post a photo of that relay). So I would like to come up with something on this very chip or on a domestic and high-quality K1182PM1 or at worst TDA1085 or NE555 (for example). I called it that offhand, maybe there's even something simpler and much better! (I don't really know the element base). And if it is on K1182PM1, it is powered by a 220 V mains, and it does not need any reduction. (By the way, the Chinese have long had analogues of this chip). And so that the key would serve, just like in the video, a simple and powerful triac (BT136-600; BTA41-600), or even preferably their parallel row, if there is a need for a large current!! Well, if you build on TDA1085 or NE555, then to have a minimum of details, so as only to power the master logic through a quenching conder, a bridge and a zener diode of some kind (zenner), but this is only for TDA1085 or NE555. But if you do, then only without controlling any separate power supply (from a separate DC unit). Something simple with a minimum of strapping (like the Chinese, only to be much better!!) and the maximum benefit. But just like that, in an adult way, so that like on a factory relay (which is on a din rail) - the principle of "one button" once pressed-turned on, the second time pressed-turned off. And such a cycle is in a circle, endlessly. This is going to be a breakthrough! No one has done this before and thousands of people will be grateful! they will take it and do it! Because the thing in the household is very necessary and the request for it is large. Sincerely from Russia! /// Смотрю из России. Молодец! Всё понятно, просто и доходчиво! А главное - очень полезное устройство! На качественных, дешёвых и распространённых деталях! Респект! Автор, а вот выдал бы идею, по поводу бистабильного реле (Импульсное реле) на 220В. Подобные, реле продают китайцы для установки на DIN-рейку. В инете много инфы, как подключать её по типу "проходного выключателя" с нескольких мест (параллельные кнопки включения), но лепят китайцы туда, механическое(!) реле! И вот недавно открыли такую релюшку, сделанную в корпусе каким-то полукруглым ромбиком и увидели, что там стоит вот такая микруха HCF4013BE и минимум обвязки, видимо прямоточная микросхема от 220 В., и в виде ключа уже стоит симистор BT136-600E (если нужно, могу выложить фото той релюшки). Так вот и придумать бы, что-нить на вот этой самой микросхеме или на отечественной и качественной К1182ПМ1 или на худой конец TDA1085 иль NE555 (к примеру). Это я назвал, так навскидку, может даже есть что-нить проще и в разы лучше! (я не особо знаю элементную базу). А если на К1182ПМ1, так она и питается от сети 220 В, и никакое понижение ей не нужно. (У китайцев кстати, давно есть аналоги этой микросхемы). И чтоб ключом служил бы, так-же как и в ролике простой и мощной симистор (BT136-600; BTA41-600), иль даже желательно их параллельный ряд, при нужде в большом токе!! Ну а если строить на TDA1085 иль NE555 , то чтоб минимум деталей, чтоб только запитать задающую логику через гасящий кондёр, мостик и стабилитрон какой-нить (зеннер), но это только для TDA1085 иль NE555. Но если и делать, то чтоб только без управления всяким там отдельным питанием (от отдельного блока DC). Что-то простое с минимум обвязки (как у китайцев, только чтоб намного качественней!!) и максимум пользы. Но только прям вот по-взрослому, чтоб как на заводском реле (которое на дин-рейке) - принцип "одной кнопки" раз нажал-ключил, второй раз нажал-выключил. И такой цикл по кругу, бесконечно. Вот это будет прорыв! Такое ещё никто не делал и тысячи людей будут благодарны! возьмут и сделают! Потому как вещь в хозяйстве очень нужная и запрос на неё большой. С уважением из России!

Guys like this is why I luv KZread 😁

I`ve been looking for a circuit with that purpose for a couple months. And this approach is so simple. I used BC547 (plan on using BC847 on PCB) for the transistors with a 12V power supply I designed and it works perfectly! Thank you very much! 🇧🇷🇧🇷

Oh, thats a very useful circuit....especially in conjunction with an optocoppler and a power mosfet instead of the "good old relais".... subscribed and Greets from Germany

@BBCircuitsbySteveMorrison

2 жыл бұрын

Good idea.

Thanks for the great video and circuits. I've been waiting awhile for this quality

Hi... I believe this is exactly what I have been looking for the last week. I want to build a power output switch for my Bench PSU. This will be done by 12V relay as in your example. In my case the coil has 400 ohms resistance. I must say this was one of the best explained videos I saw. you really provided all information. showing the schematics and breadboard build was a highlight for me! thanks a lot for the great work and sharing your knowledge.

@BBCircuitsbySteveMorrison

Жыл бұрын

Glad to help. Thank you for the feedback!

Excellent, I'm using this. Thanks

I'm also going to subscribe. Like the stuff you have on this channel 😊🇮🇪👍

The Best Explanation Dear❤

Very cool circuit !

Steve, thanks to your prior reply with ideas for ways to use a Hall Effect sensor I successfully build an SPST NO relay-driven Hall Effect sensor circuit using only 6 parts, 2 of which are a 1K R1 & LED to know that the circuit was working. I intended to replace the Inverted Soft Latch pushbutton switch so I could operate the circuit with a magnet, but when I added the RT334012 ( a 2nd & separate relay in the Hall circuit ) to the pushbutton breadboard pins by connecting jumpers of the two relay pins (1 & 14) to the corresponding pushbutton pins when I powered up the Breadboard the Latch Circuit went to an "on-state". Sometimes I could press the push button to turn the circuit off, but most of the time it stayed in the on-state. Removing the new Hall Sensor circuit didn't change the effect of having the latch Circuit go on at power-up on several times I tried. I tested all components to see if any had failed, but everything seems OK. With the power off, I shorted C1 to see if any residual charge occurred, but no change. The only way I could clear the on-state at powerup was by shorting the + & - breadboard bus lines while powered off. Then the circuit worked fine. Further investigation by many trials & errors found that anytime anything touched the Q1 Base caused the circuit to go on. Even the addition of one end of a glass NO reed switch triggered the circuit to go on. I pulled the pushbutton and tried using a jumper in its place and when shorting the connection from C1 to Q1 Base the circuit stayed on. I could not turn it off. Reinstalling the pushbutton and everything is fine. Any ideas or comments?

@BBCircuitsbySteveMorrison

Жыл бұрын

I am wondering if you ever got a chance to try the improved version of the circuit that I published. I think I mentioned the 5 V version, but I’m not sure if that works with your configuration. The 5 V version is much improved and is more stable. I believe that you’ might be getting some bounce in the relay contacts which can cause problems. If anything, you might try increasing the value of c1 to try and mitigate that.

You got another subscriber ☺️

Nice circuit.

Thanku u for good circuit

cam on anh chia se

on the breadboard I swapped the 68K for a 22K and ran it on 5v with almost no bounce. I suspect different loads might have an effect, and a better switch might help. I'm going for the "Off" state next, this will give the encoders more functionality by latching.

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! ~~~~~~~~~~~~~~~~~~~~~ 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!

Does the switch stay in the off state when you apply power the first time? I'm assuming yes?

Hello Steve, Happy New Year. I am nearing the end of my project. I have two working and very stable optional inverted (normally off) circuits. One operates a 12VDC brush-style motor turning in the forward direction and the other circuit has a simple 555 IC circuit that causes a 2-second time delay just before the relay so there is no conflict when power is applied to make the motor go into the reverse direction. I'm using 2 reed switches in place of the push buttons so that 2 magnets spread apart will control when the motor changes directions. It works great as planned, but the reed switches occasionally stick and are not 100% reliable. My research finds that a Hall Effect sensor (3144) would be a reliable replacement, but I've never used one so I'm looking for advice on a simple solution to use the 3144 in place of the pushbuttons. I realize it requires a little power to operate and it is polarity sensitive. The question is how to adapt the output signal lead of the 3144. Any thoughts on that or other recommendations?

@BBCircuitsbySteveMorrison

Жыл бұрын

The output of the 3144 is a current sink, so you can use that to sink a relay to trigger that latch - or use it to drive form of solid state relay (a bilateral switch) such as the cd4016. The 4016 has active high inputs, so you will probably need to invert the output of the 3144 before driving the 4016. For example, the momentary output of the 3144 can be inverted with a CD4009 then outputted to pin 6 of the 4066 which would effectively close pins 8 and 9 (the switch). I think the 3144 will need a pull-up resistor since it is an open collector output. Seems roundabout, but you may be able to envision a more streamlined approach.

@jimetherington

Жыл бұрын

@@BBCircuitsbySteveMorrison Thank you for the fast reply and excellent comments. I'll do my best to try your suggestions and hopefully, I can get it working before my deadline for prototype testing. If I run out of time it's not the end of the world as the Reed Switches will work knowing there may be a chance of one sticking...

Do you have any idea how long I've been looking for a latching circuit like this? Thank you.

@BBCircuitsbySteveMorrison

Жыл бұрын

Glad you like it. A little history behind it. I spent the last part of the senior year in high school and the first year of college trying to figure this thing out. Finally got it working and it was a hit in the electronics lab in college. The 5 V / USB version of this which is another video on my channel is about three to four iterations from that college circuit..

Hi ,actually I was trying to make a gsm motor control using your circuit to turn on and off relay by connecting the phone's vibration signal the problem is that the signal is not continuous so Could you modify the circuit for an off - on time delay .Any help would be great

Has anyone noticed that the Breadboard image for the LED & Relay versions of this circuit are not correct for the placement of the LED & R5? Comparing the breadboard to the schematic, these two parts are in the reverse locations. I am going to build this to see what happens. Outside of that at this point, I like everything about this post and related links… Thank you

@stueyanderton

Жыл бұрын

you can connect a current limiting resistor to anode or cathode, it matters not.

@jimetherington

Жыл бұрын

@@stueyanderton Thank you for taking time to reply. I'll give that a try after I get the circuit to work. No luck so far as the LED is always ON even after pressing switch Pushbutton-1. A work in progress...

How is the button debouncing on this?

Are there any circuitboards available on Aliexpress or Amazon that have this function?

How much does it draw current in an idle state?

Hi I am a high school student learning circuits. Sorry if it is a dumb question. Why doesn't the LED turn on through R4 even when Q2 is off?

@BBCircuitsbySteveMorrison

2 жыл бұрын

It's a good question. Since R4 is 220k ohms, the current through it (and thus the LED) is very low. You can neglect the tiny impact of R2 on this current. If you subtract the LED voltage drop and the Q1 Vbe drop, you are left with 12v-2v(led)-0.7v(Q1Vbe)= 9.3v across R4. The current is then 9.3/220000 or 42uA, which isn't enough to light the LED (unless maybe if you are looking at it in the dark). Most importantly, if you use a relay or more substantial load instead, it won't be energized or affected by that low quiescent current.

Hi, I'm an electronics noob and I've been struggling a while now trying to understand these toggling circuits. I've followed various diagrams and attempted building my own, but I can't get the correct behavior. I do notice tho that changing resistor values has a big impact on the circuit behavior. So I was wondering if you could explain to me how to go about calculating resistor values for such a circuit at a given voltage?

@BBCircuitsbySteveMorrison

Жыл бұрын

There is a detailed description of how this works at the link below. Please go to the "How the Soft-Latch Circuit Works" section. It goes into detail about how the latch works and how the high and low states are maintained between toggles. I hope this is helpful. breadboardcircuits.com/5v-usb-transistor-soft-latch/

It seems that there is always a path for current from V+ to gnd through R5, R4 and R2. Why doesn’t the LED always remain on?

@BBCircuitsbySteveMorrison

2 жыл бұрын

R4 is used to provide a small amount of feedback current to latch Q1. This does cause about 30uA to flow through the load (LED) when it is switched off, but not enough to illuminate it (or energize the relay if using that). A full explanation of the design rationale is at breadboardcircuits.com/transistor-push-on-push-off-switch/ . If you want zero current flowing through the load when off, you can add an inverting common emitter "clean-up" stage with the emitter tied to ground, a 1K ohm load from collector to V+, and a 56K base resistor (connected to Q2 collector). The load resistance/impedance can be adjusted as needed, if maintaining the base resistance at about 50x the (collector) load resistance.

is it possible with a working voltage of 3.7 volts?

@BBCircuitsbySteveMorrison

2 жыл бұрын

Not with the present component values since it's not a linear circuit. At minimum, the resistor and state storage capacitor values would need to be reevaluated.

0:45 - "Q2 in cutoff" - why? R3 provides enough base current to saturate it, Q1 is off so it cannot shunt the base of Q2.

Hey can I use 1uf

How can i use this circuit for my pcb turning off and on? 5volts

@BBCircuitsbySteveMorrison

Жыл бұрын

Look a the 5v version which is at kzread.info/dash/bejne/mJWH17iHc8_WYM4.html or breadboardcircuits.com/5v-usb-transistor-soft-latch/ . That circuit may be more suitable for your needs.

The issue with this design becomes apparent when you press and hold the button for a couple of seconds. Also you don't need additional transistor to default to off state.

Can I use 470nf ceramic capacitor instead of electrolytic?

@marcisberzins

22 күн бұрын

Sure

Will it turn on automatically if you remove and return the supply? Thanks...

@BBCircuitsbySteveMorrison

2 жыл бұрын

Very good question. It defaults to the "on" state. If you add a simple common emitter switch at the output, you'll invert that default to "off". That can be done using the concept in the video titled "Simple Transistor Switch Circuit" on this channel.

@jomhartayaben93

2 жыл бұрын

@@BBCircuitsbySteveMorrison I will check it, but I ask for a favor, can you make a working circuit that defaults to the "off" state epecially if you remove and return the supply.. thanks sir..

@BBCircuitsbySteveMorrison

2 жыл бұрын

@@jomhartayaben93 I will try to do that and post it on the website breadboardcircuits.com and let you know when it's done.

@jomhartayaben93

2 жыл бұрын

@@BBCircuitsbySteveMorrison thanks, really appreciate it...

@BBCircuitsbySteveMorrison

2 жыл бұрын

@@jomhartayaben93 I have modified the circuit and placed it on the web page. You can find it in the section titled: "Optional Inverted Output" on the page at: breadboardcircuits.com/transistor-push-on-push-off-switch/

Why does the collector of first transistor is low, even though its base is high?

@marcisberzins

22 күн бұрын

That's the very point of a transistor...

Hi, Respectfully can somebody help me how to recalculate the part’s values to use the circuit for 5V? I Would like to use it with USB power. Thanks in advance

@BBCircuitsbySteveMorrison

2 жыл бұрын

The time constant for the latching state cap C1 and R1 will need to be recalculated, as well as R3, R4, and R2, because Q1 biasing will need to be adjusted. I may just go ahead and make another video for a USB/5v version of this circuit.

@lorantkovacs5827

2 жыл бұрын

Thank You very much it is very nice of You 😁

@BBCircuitsbySteveMorrison

2 жыл бұрын

@@lorantkovacs5827 I just finished the video you requested and posted it shortly ago. It is video #22.

does the circuit consume zero current while in off state?

@jim9930

4 ай бұрын

Use cmos invertor gates for the lowest quiescent current. 10meg resistors and an HC14 will last years with two AAA cells.

Update: After watching the video kzread.info/dash/bejne/Z5N72NqOhNLZj7g.html and seeing the Breadboard circuit working correctly, I will revise my earlier statement and conclude that the Schematic is incorrect.

@BBCircuitsbySteveMorrison

Жыл бұрын

You might try this version here. It is an updated circuit that also runs on 5v. It defaults to the off state, and can drive a low voltage relay in place of You can drive a low voltage relay in place of R7/LED1. Or you can still drive a 12v load if you use 12v to supply Q3's collector. breadboardcircuits.com/5v-usb-transistor-soft-latch/

@jimetherington

Жыл бұрын

@@BBCircuitsbySteveMorrison Steve, I am unable to get the original 12V two transistor circuit (Default On) to work. The LED is always ON. I have matched the schematic and a screenshot of your breadboard part per part, but pushing the switch does not cause the LED to go out. I have checked all parts with a digital and analog meter and replaced the transistors just in case, but no joy. All part kits purchased new from Amazon as recommended.I have not tried adding the 3rd transistor Q3 and 10k Resistor R6 to make the (Optional Inverted Output Default Off). That was my next attempt before seeing your reply of an improved 5V/USB circuit.I will try your 5V circuit to see if I can make that work, but I had originally needed a 12V circuit to run the relay U1 (RT334012). I see a note: (Or you can still drive a 12v load if you use 12v to supply Q3's collector.) Not sure how to make that happen just yet. At 68 I'm enjoying this challenge while clearing the cobwebs from my High School electronics classes. Thank you for taking time to do this, Jim

@BBCircuitsbySteveMorrison

Жыл бұрын

@@jimetherington I updated the circuit because there was a small amount of current flowing through the LED in the circuit's "off" state. The improved version can be found at the link below near the end of the blog in the "Option Inverted Output section. It also defaults to "off", which may be more user-friendly. breadboardcircuits.com/transistor-push-on-push-off-switch/

@jimetherington

Жыл бұрын

@@BBCircuitsbySteveMorrison Steve, Success, at last, your 12V Push-on, Push-off Latching Switch circuit with Relay (normally on state at power-up) works great! NOTE: Before adding the diode & relay, I noticed the LED was dim in the "Off" state and bright in the "On" state. After adding the relay circuitry, the LED is now “On” or totally “Off” operating with the relay. I am a little embarrassed to say that I made a rookie mistake reading the color code on R2 & R4. I used 470 ohms & 330 ohms instead of (K) ohms. Funny what 50+ years can do to your memory and eyes? However, I did enjoy the challenge and exercise of finding the problem on my own. Now I am off to building the Optional Inverter Output version with a relay so we will start with the "Off" state at power-up. Wish me luck.

@BBCircuitsbySteveMorrison

Жыл бұрын

@@jimetherington Thanks for the update! Please let me know how the next circuit works out and whatever application you use. Thanks for participating in my channel.

at timestamp 2:13 when you push button for the first time, base(Q1) is high and capacitor C1 is low,,,,, after you push the button, why does C1 bring base of Q1 to low;; is it not possible that base of Q1 drives C1 into high value;;

@BBCircuitsbySteveMorrison

2 жыл бұрын

Because when Q1 is on, Vce is almost 0 volts. C1 then discharges through R1 and Q1 to ground. The voltage at the top of C1 is thus lower than that needed to forward bias Q1 Vbe. When you press the switch, as the voltage at Q1 base tries to charge Q1, it drops below the minimum needed to keep Q1 Vbe forward biased and Q1 turns "off".

i would love to know how you pic your resistors in your curcuit designing ?

when switch wire sue circuit is not good working

it's unstable

@BBCircuitsbySteveMorrison

2 жыл бұрын

The demo circuit has a feedback resistor and state storage capacitor that demos well for both the relay load and the LED type of load. You can adjust the values of both R3 and/or C1 to accommodate the load impedance. A lower R3 value provides a time constant that is more appropriate for the relay or lower impedance load, and for improved stability for that load.

@user-ry2qs7xf9k

2 жыл бұрын

@@BBCircuitsbySteveMorrison THANKS

Not good

HEY PAL, IM NOT SURE OF THE VALUE OF THE CAPACITOR, IS IT NOT 4.7 UF? LOOKS LIKE IT BY THE SIZE ETC