Toggle On Off with Momentary Switch
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- เผยแพร่เมื่อ 22 มี.ค. 2022
- Toggle On Off with Momentary Switch
In this video we use a 555 timer's internal SR latch as the basis for a latching switch with a momentary tac button.
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I've been using the 555 quite a bit recently, and as a bit of a novice I've been referring back to many of your 555 vids. All excellent stuff. Keep up the good work. Thank you Sir!!
Man, you're great. The way you drew that circuit let me understand it better. Thanks a lot for all the knowledge you're always sharing with all of us.
As a beginner, I enjoy these circuits a lot. Thx!
Excellent classic circuit! Need to see more of these. Teach the kids how to DIY Paul!
Loved it Paul !!! The circuit i've been searching for!!!
Neat little circuit. Good to get to grips with the basics! 🤣
An interesting exercise is to convert this into a bòot strap circuit, so that the circuit is truly off, when off. That means drawing zero current in the off state. ( The latch circuit unpowered in the off state).
It is also worth considering how to make it proof against accidentally supply polarity reversal when dc powered, and how to make it work when a.c. powered.
Consider the first problem, how to make it bootstrap.
The principle is easy to explain, the details are more difficult without the ability to show the circuit diagram.
The trick is to use both edges of the momentary button push, and its on state. The circuit to be powered is switched either by a power transistor (mosfet or bipolar) or a relay. The latter works with a.c. as well as dc.. When the button is pressed it allows the relay or pass transistor to power the circuit to be controlled, including the latch. But pressing the button also toggles the latch being powered via the pass transistor or relay. The output of the latch is wired OR with the button. So when the circuit is off, (unpowered), pressing the button switches it on, it also changes the latch status so that it holds the circuit in the on state, even when the button is released.
When the circuit is on, held on by the latch, pressing the button changes the status of the latch, removing its ability to hold the circuit on. This when the button is released, the circuit returns to the truly off state. (Note, depending on the implementation, in order to avoid logic race conditions, it is some times nessary to ensure the latch powers up in the switching on state as the default condition. )
The advantage of this arrangement is that it does not matter if the latch is run from a regulator after the pass transistor. So the latch can run from a regulated 5 volts or 3.3 volts supply, while controlling the raw 12 volts supply powering the input to the regulator, as might be the case in car electronics.
While the circuit can be implemented with just latch logic. It really is most often used when powering a micro controller, such as in a mobile phone. The first thing the micro does at power up, is to hold its own supply on, while monitoring the state of the push button on switch, that allowed it to receive the initial power to turn on in the first place.
Pressing the button while the micro is powered, instructs it to remove the signal that is holding its power on. Then when the button is released the circuit turns truly off. In the off state the only current consumed is the leakage current through the transistor, usually micro or pico amps.
If a relay is used as the power switching device, the off current is effectively zero.
That's a 555 favorite nicely done Paul
You're awesome. Thank you for the videos.
This circuit has been on my desk for about a week now. lol
Yesterday I attached a 3V relay opto-isolator board to it.
More circuits you should know! Bravo!
There is a transistor only version of this type of toggle switch with 2 NPNs and 1 PNP and a few 100k and 50k, I found it on Evan Kale's channel about 5-6 years ago but the video is removed but I somehow remembered the working so I tried recreating it on sim and it worked.
Edit: Also a 50uf cap
Finally got them 555 timer! Going to try this one out! Hope you are doing well sir!
New to the channel. I’m training to be an Electronic Tech and I’ve found your videos very helpful with reading schematics and correlating it to learning the actual function of the circuits. So thank you for that! I just bought my own kit and was wondering where you get your components from? The kit came with a very limited number of components to work with, as I’m sure you can imagine.. Thank you in advance!
Problem with these is there’s a constant current draw even when off. But I love 555’s going all the way back to when I was a kid with my Forest Mims Engineers Mini-Notebooks!
Neat! Creative way to do in software too but hardware nice to.
Thanks!
Nice 👍
How would it go with a mosfet in there instead of an LED? Would the mosfet get fully switched on?
Is there a way this could be done with relays and no timer? something a little more Hardy and useable in my car
Debounce circuit next. You may already have a debounce video, I’ll have to look.
Thanks
I made lots of these last year. No idea why, I have no use for them. LOL.
Trying to use factory momentary buttons in a truck for a project. This is exactly what I need but is it available to purchase? I don't know anything about circuits so making this is out of the question
Do you know of a way to make a momentary switch stay on for 10 or 15 seconds after it is pressed once? Thanks!
I have a situation where i need to take a momentary switch and control 2 circuits in a way where i press the momentary switch and one circut comes on and press it again and they both come on is there a way to do this?
I need to get a giant LED to go with my evil mad scientist 555 so I can build this circuit. Are there any basic circuits that use a LM741 and 555? I'd like to use both my kits in a single circuit.
This time it`s works😊
Cool...
Would the circuit still have the same result no matter what toggle switch you use?
Switch has no bearing as long as it's momentary
Mei Gutster, des RC-Glied muss aufn Ausgang statt auf Plus. Sonst funzt des net!
Dear Learnelectronics, kindly, ¿is the switch in your circuit, a toggle on/off type or true momentary, please? Just asking, please. Thank you for making and posting this video. td\.
Momentary tac button
@@learnelectronics Thank you Learnelectronics. td\.
Hey Paul, there's a mistake in the schematic you drawn. The 100k should be connected to the output (3) of 555 not to Vcc.
Didn't work in my simulator until I followed your comment, thanks
Been scratching my head trying to figure out what I had done wrong, apparently nothing compared to the schematic. I'll try the fix tomorrow.
yes and the led is connected to + while the realization is connected to -.
so in the diagram the LED lights up as soon as the power is turned on.
🧡🧡🧡🧡🧡🧡🧡🧡🤍🤍🤍🤍🧡🧡سال نوبر شما وخانواده محترم مبارک باد🧡🧡🧡🧡🧡🧡
🧡🧡🧡🧡🧡🧡🧡🧡سلام پلی لیست درست کنید تشششششکر🧡🧡🧡🧡🧡🧡
Silly question . . . Why not simply use a toggle switch instead of all the extra bits?
Sometimes you just want a single button.
Please make it a practice to explain the path of the operations of your circuits... Ex: 555 Switch = Power passes through the switch and goes to X comparator, then to x transistor... Etc. You did not teach us anything about how this switch works. You only showed us how to set it up. This leaves us frustrated and drives us to other channels to find the answer. Driving us to other channels drops your viewership. Offered as a friendly, helpful business hint.
Correct me if I'm wrong: The voltage at the node is 2.5 volts, the voltage at the 100k side of the momentary switch is 5 volts. When you close the switch, the voltage on the 555 side of the momentary switch increases for a moment causing the 555 to latch???
😬☮️
Yep
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Foist.
Could you explain the purpose for each component in these simple circuits, new students are always asking why!!