ceengland7(at)gmail.com
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 Posted: Sat Sep 14, 2013 5:56 am Post subject: Looking for a circuit that when you press a button powers |
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To answer your question (instead of trying to change your requirements)  ,
A 555 timer integrated circuit would do what you want, with added components to handle whatever current you need to drive your device. The (momentary contact) switch, when pressed, would supply power to the timer *and* the trigger signal. The timer would be configured to stay on for the specified time. It would drive the high-current driver device (transistor or relay). If you hold the button, the timer runs & then shuts off. If you press the button for less than the preset interval, power is removed from the timer which removes activation from the transistor/relay.
https://www.google.com/search?q=555+timer+circuits&rlz=1C1CHFX_enUS553US553&oq=555+timer&aqs=chrome.2.69i57j5j0l2.7716j0&sourceid=chrome&ie=UTF-8
Look for 'monostable mode':
http://www.555-timer-circuits.com/operating-modes.html
You'd need the switch to both supply power to the timer, and take the signal input 'low' (to ground). This could be done with a 2 pole switch, or with some type of signal inverter (transistor, inverter IC, even another relay).
Remember, the key is to have the switch actually supply power to the 555, so that releasing the switch removes power from the 555 & therefore, the output signal to the power device.
This is just the quickest/dirtiest method that comes to mind.
2nd option: use a 2 pole momentary switch, with one pole supplying the trigger and the other in series with the output of the 555. This is probably a more stable way of doing it, but would mean that the circuit would be powered up all the time instead of only when needed.
If you poke around the search link long enough, you'll probably find a complete circuit already designed that does exactly what you want.
Charlie
On 9/14/2013 2:37 AM, Peter Pengilly wrote:
[quote] So once it is latched on how do you turn it off?
A 3 second press is a long time, assuming the usual operation is to turn it on an leave it on might be best to turn things around.
If device is off:
- Short press (say < 1 second); device turns on.
- Long press (> 1 second); device turns on for 3 seconds, or duration of press if longer, and then turns off.
If device is on:
- Short press (perhaps any press); device turns off
Thinking about this some more, it would be easier if the 3 second requirement is removed, so requirements become:
Button is pressed: device turns on;
Button is released: device turns off;
Ignore button release if within 1 second after button press.
This does mean that button has to be pressed for > 1 sec to turn off, but that prevents inadvertent knocks turning it off.
Hope this helps,
Peter
On 14/09/2013 01:45, Henador Titzoff wrote:
| Quote: | Jeff,
I believe you need a better spec. For example, you say that when the button is pressed, the device is powered on. Then you say if the button is released before the 3 second interval, it should stop powering the device. Or at least that's what I think you said.
I think you need to divide it into the following functions:
- If the button is pressed for less than N seconds, function 1 happens
- If the button is pressed for more than N seconds, function 2 happens
- If the button is held for exactly N seconds, well never mind, there is no such thing unless you have an accuracy spec. If you do, then function 3 happens. These three functions need not be mutually exclusive.
Whatever functionality you want, I believe a microcontroller or CPLD will do the job. If you describe your functionality more accurately, including output voltage, current, etc., then this group can recommend specific products, including boards.
Henador Titzoff
From: Jeffrey Skiba <jskiba(at)icosa.net> (jskiba(at)icosa.net)
To: "aeroelectric-list(at)matronics.com" (aeroelectric-list(at)matronics.com) <aeroelectric-list(at)matronics.com> (aeroelectric-list(at)matronics.com)
Sent: Friday, September 13, 2013 7:27 PM
Subject: Looking for a circuit that when you press a button powers the device but ....
--> AeroElectric-List message posted by: Jeffrey Skiba <jskiba(at)icosa.net (jskiba(at)icosa.net)>
Looking for a circuit that when you press a button powers the device but ....if the button is held on it is only powered for a max setting (say 3 seconds) but this same circuit should stop if the button is released before the 3 seconds.
Hope that makes sense, I bet it exists already and I just am searching under the wrong name.
Thanks in advance for the help
Je= --> http://www.matronics.com/Navigator?AeroElectric-Lista href="http://forums.matronics.com/" target="_blank">http://forums.mat &nbs//www.matronics.com/contribution" target="_blank">http://www.matronics.co==================
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