First electronics project - 555 timer?

Psy-Blade · 11 Mar 2013 at 13:04

Hey all,

I've been in need of a timer to remind the house to feed the fish every 24 hours. Instead of buying one I though it'd be fun to get back into some DIY electronics (used to enjoy this as a kid).

I'm looking for a timer circuit which will wait 24 hours, and then continuously beep until a button is pressed. So far I think I've worked out that I'm looking for a monostable 555 timer circuit... but that may not be quite right to last 24 hours on the timer cycle... Anyone here with the knowledge to push me in the right direction?

Thanks!

Makhaira · 11 Mar 2013 at 19:26

How about doing something with a PIC? I's a bit overkill for what you want, but it'll be simple to make your project and more importantly, it will set you up for a lot of future endeavours!

PhillyDee · 11 Mar 2013 at 19:52

Problem is, they are not that accurate, so you may get some issues with the timing.

unrealrocks · 11 Mar 2013 at 21:06

PhillyDee said:
Problem is, they are not that accurate, so you may get some issues with the timing.

Indeed - a 555 can vary pretty wildly, however once you got it right you could probably be safe it will maintain fairly accurate time.

And yes you are correct that a 555 probably won't do 24 hours (not accurately) ... however don't forget you can feed one into another one - so one can trigger another one to time another time, which can then trigger your desired output.

Renton · 13 Mar 2013 at 14:45

Not a clue what a 555 timer is but you can buy a simple rundown timer that will output (alarm) after the set time, in this case 24hrs. You can then use a two pole reset switch with one pole resetting the output and the other pole resetting the timer back to zero so it then starts its count down again.

Im not sure from your OP (as you stated you had electronic back ground) if you wanted to build this yourself at pcb level or use currently available parts. If its the later let me know and I will try and link the parts you will need

d_brennen · 13 Mar 2013 at 15:28

I'd vote Arduino. It's huge overkill for what you need BUT once you have everything working you can port it to very cheap bare chips (£5 ish inc Real Time Clock)

Arduino is massively well documented and supported so great for learning

PhillyDee · 13 Mar 2013 at 15:46

Arduino is good. Especially as you could also then move to a display which tells you when it is due, even add on so it automatically feeds is the alarm is not shut off after so long etc. You can add and develop it as you go!