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. 😎👍
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!
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.
You are incorrect. The two 10k resistor voltage divider tied to 2 and 6 holds the 555 in and indeterminate state between 1/3 and 2/3 Vcc. As long as there is power it will stay latched in one state or the the other.
@@jp040759 Yup he is incorrect, this circuit was originally designed to power 12volt relays for car stereos back in the 1970s, in this circuits current configuration switching it on will stay latched on for 32768 hours, which is 1,365 days or 3.7 years and its not even connected as a countdown timer circuit at all, the 10k resistiive loads keep the IC latched ON or OFF The circuit was originally enclosed in an aluminium can as its sensitive to capacitive coupling (touch) It will only deactivate itself with the wrong value resistors
Not easily. When the push-switch is open and the capacitor has charged, the capacitor is either at the positive rail or at ground, while the other side of the switch is at half the supply voltage. A mosfet has a body diode that will conduct in one direction or the other, depending on whether it's p-channel or n-channel, so it will short out one of the two conditions as soon as the voltage across it is more than around 0.6V.
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.
The circuit is missing a decoupling capacitor between the supply and ground - use 100nF close to pins 1 and 8, Without that the LM555 is very hit-and-miss when switching because of current spikes as it switches. The CMOS versions don't have this problem, but can't supply so much output current.
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.
Waht will the state of output when power is applied?? Does it rest on power on or not And i think if we press and hold the push button output will resonate (keep changing it's state from on state to off and vise Versa)
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.
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?
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?
There could be noise picked up on switch-on that triggers the 'on' state. It's difficult to know as it depends on layout, stray capacitance, etc. The 555 should always have a 100nF capacitor between pins 1 and 8 to ensure stable operation. To ensure a consistent start-up connect the reset pin (4) to the supply via a resistor (not critical but around 47K will be fine) and also via a small capacitor (not critical but around 100nF will be fine). That will give a "soft-start" at switch on, keeping the reset low for a few milliseconds and ensuring the circuit starts up in the 'off' state.
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.
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.
It worked fine with just one LED, but when I set a resistance value to flow 40mA to the LED, I was able to turn it on from off, but I couldn't turn it off from on.
@@johnm2012 TI (for example) manufactures both the LM555 and the NE555, but they are pretty much the same. However, those are bipolar devices. CMOS versions also exist, e.g. LMC555, ICM7555, and others. These have much lower quiescent currents, but cannot supply as much output current, so may not always be suitable substitutes.
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!
This is important: if you are using bipolar 555 timers, like the NE555 or LM555, you *must* decouple the supply close to the supply pins 1 and 8 with a 100nF capacitor. The bipolar 555 timer 'crowbars' the supply as the device switches, drawing around 400mA for around 100ns. Without a decoupling capacitor, that can drop the supply down to ground, whereas a 100nF capacitor will limit the supply voltage drop to less than 0.4V. In other words, if you don't decouple the supply, using a bipolar 555 timer is very hit-and-miss, and that is probably the reason for many of the questions here in the comments section. HTH.
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.
Worked awesomely! 1 question though.. 😅 I want this on off to work as a start stop for the Casper electronics sequencer. Would I plug the square wave LFO(clock) into the button? And I’d have to take it back out somewhere to go back into the 4040 😅😅 Ahh I wish I had latching buttons.
"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.
@@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 !!!!
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.
The visuals here are amazing. Very well done sir. Thanks for sharing.
Thank you, this is an amazing video with a good & clear explanation. Keep up the good work !
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.
Nice work. Thank you for making and posting this video. Thank you for the schematic and explanation of function. 🙂
Great explanation, and also a very useful circuit.
Another cool circuit with the 555 timer chip. THANX
Very well presented and explained, thank-you... I've subscribed.👍
Where can i buy such readymade module and what is it called????
Really informative, thanks alot!
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.
You are incorrect. The two 10k resistor voltage divider tied to 2 and 6 holds the 555 in and indeterminate state between 1/3 and 2/3 Vcc. As long as there is power it will stay latched in one state or the the other.
@@jp040759 Yup, this circuit was designed to permanently off and on latch 12volt relays.
@@jp040759 Yup he is incorrect, this circuit was originally designed to power 12volt relays for car stereos back in the 1970s, in this circuits current configuration switching it on will stay latched on for 32768 hours, which is 1,365 days or 3.7 years and its not even connected as a countdown timer circuit at all, the 10k resistiive loads keep the IC latched ON or OFF
The circuit was originally enclosed in an aluminium can as its sensitive to capacitive coupling (touch)
It will only deactivate itself with the wrong value resistors
Nice video. Very succinct!
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 ?
Not easily. When the push-switch is open and the capacitor has charged, the capacitor is either at the positive rail or at ground, while the other side of the switch is at half the supply voltage. A mosfet has a body diode that will conduct in one direction or the other, depending on whether it's p-channel or n-channel, so it will short out one of the two conditions as soon as the voltage across it is more than around 0.6V.
Sweet circuit. Thank you!!
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.
The circuit is missing a decoupling capacitor between the supply and ground - use 100nF close to pins 1 and 8, Without that the LM555 is very hit-and-miss when switching because of current spikes as it switches. The CMOS versions don't have this problem, but can't supply so much output current.
Awesome effort sir. 🎉
Thank you, great explanation
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.
what happens if C1 was a 10 or 100uf cap.?
Lovely work
Hi
Can somebody confirm is that push button or a switch(on/off).
Thanks.
Waht will the state of output when power is applied??
Does it rest on power on or not
And i think if we press and hold the push button output will resonate (keep changing it's state from on state to off and vise Versa)
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.
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?
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?
There could be noise picked up on switch-on that triggers the 'on' state. It's difficult to know as it depends on layout, stray capacitance, etc. The 555 should always have a 100nF capacitor between pins 1 and 8 to ensure stable operation.
To ensure a consistent start-up connect the reset pin (4) to the supply via a resistor (not critical but around 47K will be fine) and also via a small capacitor (not critical but around 100nF will be fine). That will give a "soft-start" at switch on, keeping the reset low for a few milliseconds and ensuring the circuit starts up in the 'off' state.
Could this work with 12v input ?
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.
At 9V the LM555 typically uses around 6mA, but samples vary, and it could be twice that.
Wow worked for me after some serious tinkering 😅
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
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.
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.
It worked fine with just one LED, but when I set a resistance value to flow 40mA to the LED, I was able to turn it on from off, but I couldn't turn it off from on.
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.
@@johnm2012 TI (for example) manufactures both the LM555 and the NE555, but they are pretty much the same. However, those are bipolar devices. CMOS versions also exist, e.g. LMC555, ICM7555, and others. These have much lower quiescent currents, but cannot supply as much output current, so may not always be suitable substitutes.
This IC is iconic 555=Public release 5/5/75
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!
Please make circuit hold 3s to on and hold 3s to off. Thanks. 🙏🙏
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.
please make lathicng hold 3 second to on and off. Thanks
Nice.
Great vid, keep it up. Ask the wife about a manicure... it has MAN in the word, can't be that bad :)
And I guess if you hold the switch you get oscillation?
This is important: if you are using bipolar 555 timers, like the NE555 or LM555, you *must* decouple the supply close to the supply pins 1 and 8 with a 100nF capacitor.
The bipolar 555 timer 'crowbars' the supply as the device switches, drawing around 400mA for around 100ns. Without a decoupling capacitor, that can drop the supply down to ground, whereas a 100nF capacitor will limit the supply voltage drop to less than 0.4V.
In other words, if you don't decouple the supply, using a bipolar 555 timer is very hit-and-miss, and that is probably the reason for many of the questions here in the comments section. HTH.
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?
Put a 100nF capacitor between pins 1 and 8 to decouple the supply and you'll have much more stable operation.
its NE555P. not LM555.
Thanks for catching that Kerim. I've updated the title.
They are the same
🎉
Worked awesomely!
1 question though.. 😅
I want this on off to work as a start stop for the Casper electronics sequencer.
Would I plug the square wave LFO(clock) into the button? And I’d have to take it back out somewhere to go back into the 4040 😅😅
Ahh I wish I had latching buttons.
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 !!!!