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Push button requiring a minimum pressing time to be activated

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chris99

New Member
Hi experts,

I need to have a panic button for my alarm system. Since I have little kids around, I need some sort of security mechanism to prevent them from pressing it accidentally or just for fun. I was thinking of making a simple push button that could be activated by pressing it for a number of seconds (kids don't have patience!). Do you know if something like that already exists? I looked everywhere, but I'm afraid I don't know the exact terminology to find it.

Thanks a lot for the help!
Chris
 

cowboybob

Well-Known Member
Most Helpful Member
I googled "push-button switch with time delay" and was presented with a array of delayed output devices.

Variations on the query might fine tune your search.

More specific info on what the panic switch is triggering would help.
 

Tony Stewart

Well-Known Member
Most Helpful Member
Series R, large Shunt C gives T=RC delay, such that R <<internal Pullup res.
Use a pot across switch to determine max R needed to trip alarm, then compute C and shunt output.
Pullup must >=100K for reasonably largest C = 1000 uF then R= 50k for 0.5 second.

This is a passive solution. Active transistor solutions can use smaller RC values but more parts, if you prefer.
 

Misterbenn

Active Member
When I was at university, a fair while back, the most common and annoying drunken prank was to set off the fire alarm at the night clubs or in the dorm at 1am.

To get around this new alarms were installed which activated an internal siren for ~30 seconds. This was loud enough and convincing enough to send the prankster running (or more likely drunkenly stumbling). However the main alarm would only go off if either two break-glass points had been activated or immediately on smoke detection. A single break-glass event would alert security so they could check it out but it wouldn't set off the full alarm or alert the fire brigade. False alarms were massively reduced to just the odd slice of burnt toast.

anyway back to the OPs predicament ...I think you underestimate the curiosity of children. When a switch doesn't do anything press it harder and longer! It may be better to have a small alarm that goes off immediately with a cancel button and a delayed signal to the main alarm.

you could use a 555 time delay circuit like this one. http://www.electronics-project-design.com/timedelaycircuit.html with a pull down on the input.
 

alec_t

Well-Known Member
Most Helpful Member
Since I have little kids around, I need some sort of security mechanism to prevent them from pressing it accidentally or just for fun.
Handcuffs? :).
 

chris99

New Member
Thanks to everybody!

I googled "push-button switch with time delay" and was presented with a array of delayed output devices.
That was one of my first queries, but the results are all buttons with timers which start with the push and stop after the programmable amount of time. What I need is almost the opposite: the button needs to be pressed for n seconds before activation occurs.

Series R, large Shunt C gives T=RC delay
Thanks for the formula. I have no idea on how to implement it, but it might come handy if I can't find a ready-made product!

you could use a 555 time delay circuit
Good tip. Again, I hope to find an existing product but I'll keep this one in mind.

Handcuffs?
Tried without success!!


I find it almost incredible that it's so hard to find an existing product like that... am I the only one needing it?
 

Tony Stewart

Well-Known Member
Most Helpful Member
because there are millions of values for both C and R which are application ".specific" and such a small function, it is pointless to make a product for this. They do make expensive timer relays which are industrial overkill though.

What you MIGHT be able to do is use a 16 pin socket and wire it with AWG magnet wire or wire wrap and put the 555 in the 8 pins and use the other 8 pins for Passive components. then fit it into the clock using its internal supply.
 
Last edited:

BobW

Active Member
I find it almost incredible that it's so hard to find an existing product like that... am I the only one needing it?
No, but as soon as you add the time delay requirement, it's no longer a simple mechanical pushbutton. It now requires internal electronics and a power supply. Since almost all electronic devices manufactured today already have some central processor, that processor can handle all of the necessary conditioning of inputs, including time delays.

Simple solution: find out how high the kids can reach, and mount the pushbutton one foot higher.
 

Mikebits

Well-Known Member
Simple solution: find out how high the kids can reach, and mount the pushbutton one foot higher.
I thought of that then remembered myself at that age. I would have grabbed a chair to get taller :)
 

atferrari

Well-Known Member
Hi experts,

I need to have a panic button for my alarm system. Since I have little kids around, I need some sort of security mechanism to prevent them from pressing it accidentally or just for fun. I was thinking of making a simple push button that could be activated by pressing it for a number of seconds (kids don't have patience!). Do you know if something like that already exists? I looked everywhere, but I'm afraid I don't know the exact terminology to find it.

Thanks a lot for the help!
Chris
Sorry for this: in case of really old people I would worry for the possibility of them not being able to press it for too long or the x many times needed. What I learnt from emergencies mostly experienced on board: mind tends to narrow to the basic for lot of people. But, as usual, I could be dead wrong.
 

alec_t

Well-Known Member
Most Helpful Member
Dire warnings about withdrawal of privileges might persuade the kids to leave the button alone.
 

Misterbenn

Active Member
Sorry for this: in case of really old people I would worry for the possibility of them not being able to press it for too long or the x many times needed. What I learnt from emergencies mostly experienced on board: mind tends to narrow to the basic for lot of people. But, as usual, I could be dead wrong.
to be clear, with my idea you would only need to press the button once quickly. The delay would be on the output signal to the main alarm while a smaller local alarms scares the kids off. after 30 seconds or so if someone hasn't cancelled it then it sets off the main big panic alarms.
 

Misterbenn

Active Member
could you use this: http://uk.rs-online.com/web/p/time-delay-relays/0160262/ . A time delay relay.

I'm thinking you could use it on the "ON delay with control input (Es)" range. Once the control button had been pressed this would wait a set time before triggering the relay and setting off the alarm. The relay would be reset as soon as the button is not-pressed. So if you stop pressing the button before the set time has elapsed it wont trigger the alarm.

The relay can work of 12V DC.
 
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