countdown timer

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RoyalMaster

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I'm trying to make a circuit to do the following:
When 2.5V is applied, it start some sort of countdown timer (30-60 min). When that timer is over, it triggers another circuit which opens a circuit for a minute. During that minute, another 2.5V will be applied and the process will start over again. Could someone point me in the right direction?
 
You could look into a 555 timer IC. You could use a quad (I think it's the 556) for multiple timers to support your multiple time values. There are more components and calculations involved, such as resistors and capacitors to set the timing.

You might also be able to use some time-delayed relays to simplify it.
 
Hero999 said:
You could also use a PIC to simplfy the circuit even further.
Click to expand...


What kind of supporting circuitry does a pic need? If none, then it would simplify a lot of projects I have going, too.
 
I don't think a 555 was meant to do 30-60 minute delays...

Microcontrollers are great, not sure about PIC, guess it could be made to work , just kidding. Kind of depends on what you power supply will be. I use AVR, and they work from 1.8 volts up to 5.5. In real use, a single 1.2 NiMH AA battery to a 6 volt SLA, directly to the chip. You would usually use a 7805 voltage regulator, and a small bypass capacitor. Depending on your input, pull up/down resistors. Some kind of driver for the output.

And of course you'll need a programmer, learn to program the device, maybe learn to program in general...
 
Ratch said:
What kind of supporting circuitry does a pic need? If none, then it would simplify a lot of projects I have going, too.
Click to expand...

Very, very, little! - it simplifies most circuits massively! - in your case to a single chip (could be as small as 8 or even 6 pin), a power supply for it (could be a battery), and your input and output interfaces - that's it!.

As suggested, you don't need to use a PIC, they are just the most popular and best supported ones - but ANY micro-controller could easily do it, it's a very trivial application.
 
Yes, PICs are also great. I don't use any additional IC for my project of course some components.
 
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