How to Keep LED On for 1 Hour with Switch Activation—Simple Timer Circuit Ideas

Not an EE but an Industrial Designer. I need a LED to be turned on via a switch and remain on for 1 hour. What would be the best approach to accomplish this? Thanks in advance

Jason, sorry, not enough information here.  What power do you have available?  When you say an hour, do you want precisely one hour or would something that does within a few minutes be OK?There's an integrated circuit called a 555 that would do this for you, but not very precisely, even if you put in an adjustment.If you have mains power available, you could time it more precisely by counting the cycles of the mains 50/60 Hz power.Which approach you would take depends on your requirements and resources....

Hi Jason-I'd start by taking a look at TI's TPL5111 system timer.  It can generate delays between 100 milliseconds and 7200 seconds, and it's pretty easy to use.  It operates on 1.8 to 5 volts, so you'll need a source of voltage to run the chip and if the LED needs to be very bright you'll need to add an interface circuit (probably a single transistor) to increase the chip's output capability.If you want to provide more information about what you want to do we can offer more help.Edit:  You might also take a look at the  74HCT555 chip.
-Rick

Here is more info. The space this needs to occupy is small, imagine an area 2.5" diameter and hopefully no more than 0.5" tall. It will need to be battery operated and the LED will be the source for a light pipe that will illuminate the outer edge of a 2.5" acrylic disc. 
Exactly an hour would be nice in order to make that claim on the product (don't want to run into the whole Subway  foot long sub not being actually 12" lawsuit) but if its easier to get within a few minutes that should be acceptable

I created this circuit to show a proof of concept. The LED will fade away after about 2 minutes . Could this approach be used to stay on for an hour? Parts list include BC 547 Transistor, 2200uF Capacitor and 47 and 150k Ohm resistors

Jason
There are quite a few details omitted from your question. How accurate do you want the time period? Do you want it to be retriggerable? What is the operating voltage? Is it a freestanding LED and is it configured with a resistor etc. Where do you want to use it? Do you want to make it yourself, and have you got the experience.I am going to take a different tack to my colleagues above, and assume that you want it for a process outside of a hobby interest and that you are not interested in producing a simple prototype. You can get timer relays which can solve your problem without too much concern about the internal workings. There are many such devices and suppliers- you might want to start at Digikey, which is where many designers do- see this page

Hi Jason -- I agree with the earlier answers -- we need a bit more information -- you say "I need a LED to be turned on via a switch and remain on for 1 hour. What would be the best approach to accomplish this?"When you say "switch," do you mean a toggle switch -- something like a light switch in a house -- or do you mean a momentary push-button switch?Assuming a toggle switch, starting from an OFF condition, does flicking the switch ON cause the LED to come ON? When does the 1 hour delay start? I mean, does it start when the toggle switch is turned ON, or when it's turned OFF again.Suppose someone turns the toggle switch on and leaves it on for 2 hours -- does the LED also stay on for 2 hours, or does it turn off after 1 hour, or does it stay in for 1 hour after the switch has turned off?Suppose someone turns the toggle switch On and Off again and the LED turns On -- now suppose that after 30 minutes the switch is again turned On and Off -- does the LED still go off in 30 minutes time, or does the 1 hour count restart from the second toggle of the switch?How accurate do you need the 1 hour delay? Would +/- 10 seconds be OK, or +/- 1 second, or does it have to be accurate to a millionth of a second?
Sorry -- I R an Engineer LOL

I would suggest using one of those 8 pin super cheap micros, Microchip comes to mind. Depending on you battery voltage and capacity you could get away with just the 8 pin IC. One decoupling capacitor is the only extra component (plus of course the LED and resistor). Time is then set up via software based on the internal oscillator so there is no issue with getting to 1 hour.
Thinking about it you may need a voltage regulator to keep the intensity of the LED constant.

You can use a mechanical switch (like a relay) - the one that springs back to its original position after an hour. Quite inaccurate, but it's the simplest implementation for inexact purposes. Hehehe...

I don't think this approach will work for an hour. At least not without a much bigger capacitor that won't fir in your size constraint.Your circuit works by having the switch charge the capacitor then the capacitor is discharged by the LED.
It looks like you have 3V to work with. If you have an LED that requires 2.5V (check the data sheet), the LED will go out when the capacitor voltage drops 0.5V (actually less due to the resistor). If the current through the LED (set by the resistor) is 10mA, we can get a rough estimate of the capacitor size needed by C = 10mA * (3600 sec) / (0.5V) which gives me 72 Farads if I did that right.I think a timer relay or small 8-pin super cheap micro as Aubrey suggested is probably the best bet.

I was thinking about this after my post above and while a 555 is quick and easy and does not involve any programming, getting a reliable 1 hour delay would need a very high resistor (22Meg) and capacitor (up to 1000 uF) and any leakage in the capacitor would render the results erratic or unusable.So I came to the same conclusion as Aubrey above (he is a smart guy and beat me to it!).  The only thing I would add is that if you can't program in C or assembler you could consider the PICAXE chips.  They are programmed in BASIC which you may already know, are cheap and easy to use.  Their smallest chip, the 8-pin 08M2, would easily do what you need. I've played with these chips and they are really easy to use.You can get a kit with a PICAXE 08m2, PCB, LEDs and switches, battery box, that would get you started for a proof-of-concept, and you could then fit the result into your case using a smaller PCB or even veroboard.  The only other thing you'd need is a programming lead.I wrote some articles some time ago on my journey with the PICAXE chips:Part 1 ,  Part 2 ,  Part 3 ,  Part 4 .  

Having to program a PIC seems like overkill. Here's a circuit I found by putting "counter timer IC 1 hour" into Google:
http://www.electronicecircuits.com/electronic...uits/cd4060-timer-circuit-1-minute-to-2-hours

Nice call Sean...the circuit as shown would need some mods to act as a monostable I think, but should be doable.

Thanks everyone, your help has been much appreciated.

CD4541 can be used as well, cheers,Richard