Little help please

[Andi]

i'm trying to design a circuit for a project, i have 2 LED's, one red and one green, once a toggle switch is turned on then the green LED will stay on for about 5 seconds, then the red LED too light up and the green to go out. so far all i have been able to do is make the green LED lit at all times and the red LED goes on almost instantly and stays lit for 5 seconds. the mostimportant part of the design is the delay between the switch being pressed and the red LED lighting up.

any circuit designs or adivse or links would be brilliant

cheers everyone

andi

 

[RadioRon]

Hi Andi

If you post the circuit that you tried already we could suggest improvements. Alternatively, if I was starting from scratch, I would first figure out how to make the green one come on for 5 seconds then go out. Once you have this working, you can use the output of this circuit to trigger another circuit that makes the red one come on.

To make a green one come on for 5 seconds, you might consider using a timer IC like the 555. You would design one 555 to trigger from the toggle switch in monostable mode. The 555 output would drive the green LED and would also drive a transistor switch. The transistor switch would turn on the red LED when the green LED turns off.

I actually prefer to use the 4060 CMOS counter (or a 74HC4060) for this kind of application but its a bit more complicated to explain. You wire the clock terminals as an RC oscillator clock, and you choose the divider output that divides your clock frequency down to 0.1Hz and wire this divider output back to the reset input. You will need on additional flip flop ic that also toggles from this divider output. The toggle switch must be wired to this flip flop also so that the flip flop controls when the 4060 runs or when it resets. The green LED will be driven by one of the flip flop outputs, while the red LED is driven by the other flip flop output. Like I said, its hard to explain in words but simple in a schematic.

 

[Andi]

i currently have three different circuits that all do the same thing in a different way, unfortunatly they are in school with the rest of my project so i can not access them at to moment,
two of them opperate on 555timers and i found the most efficient way to get the switch between diodes was to use a relay.

your first idea of the transistor switch would be better for my design, i am trying to keep it as simple as possible as i have very little time left to complete the project and this is a "finishing touch" circuit so to speak

thank you for your ideas and suggestions, again, once i get a chance i will post the current circuits and the specification

andi

 

[Roff]

Do they have to fade on and off, or does the green one go off abruptly at the same time the red one goes on abruptly?
And does the green light go on again when the red light goes out?

 

[kchriste]

So, are you using a toggle switch (Like a light switch etc):

once a toggle switch is turned on

Or a momentary push button (Like on a button on a phone):

delay between the switch being pressed

Below is a circuit which will work with a toggle switch:

 

[Roff]

So, are you using a toggle switch (Like a light switch etc):

Or a momentary push button (Like on a button on a phone):


Below is a circuit which will work with a toggle switch:

Errrmm...
That needs a little help. You left the discharge pin floating. It won't oscillate.

 

[kchriste]

You left the discharge pin floating. It won't oscillate.

It's not supposed to.
Read the original posts by Andi.

 

[Roff]

It's not supposed to.
Read the original posts by Andi.

OK, I get it. I had asked if it was supposed to oscillate. I guess that, in the back of my mind, I assumed it was supposed to.

 

[Andi]

So, are you using a toggle switch (Like a light switch etc):

Or a momentary push button (Like on a button on a phone):


Below is a circuit which will work with a toggle switch:

yeah, sorry for being unclear, i am using a toggel switch, (but they are push toggle switches, like the push down buttons on the end of some biro pens)


and thank you for the circuit, i will try it and get back to you