Help me to create a timer/clock which toggles after 20 seconds?

[abdulsalam]

i need help in creating a timer /clock which toggles after 20 seconds. I dont want to use any programable chip ( MCU, PLD etc). Thanks in advance

 

[throwaway18]

20 min timer

Google. Books.

A common solution is a 555 timer.

**broken link removed**

 

[abdulsalam]

20 minutes timer

oops sorry i have written 20 seconds. actually i want delay of 20 minutes. i dont think with 555 timer this kind of clock can be created. Thanks.

 

[aibelectronics]

20 minute timer application

check up CD 4022, i think it's a counter with variable timed outputs... not so sure though..

 

[IanP]

4022 555 circuit

555 with 10MΩ resistor and matching cap may do the job, but you can try timer and divider, the 74HC5555
**broken link removed**
Regards,
IanP

 

[throwaway18]

20 minute timer circuit

A 10Mohm resistor in a 555 circuit is not guaranteed to work reliably due to leakage current, paticularly if you try to use an electrolytic cap. It might work on the bench but with an electrolytic cap it could easily not work at all at high temperate or when the device has been turned off for a few month and the cap draws microamps of leakage current.

 

[VVV]

timer 20 sec

How about a 555 folowed by a counter?
That way the resistor/ cap on the 555 will have more manageable values.

 

[shafee001]

555 20 minites delay

the best solution is to use ossilator with short fixed accurate period then use counter to devide the input frequency
555
7490
_ vcc
|-----| |
--11---14-----5-----
| |
| 7490 |-- 12 output = in/10
14 --| |
input | |
--2---3--6--7--10--
|---|--|---|--|
--- gnd
-

shafee

Added after 6 minutes:

sorry text is not clear a image is attached here

 

[echo47]

a timer,20 min

shafee001, here's how to maintain your original text spaces and indenting: Edit your message, highlight the text, and press the "Code" button. You can also press "Preview" to see how it looks before pressing "Submit".

 

[xvibe]

30 minute timer online classroom

The problem for 20 minute clock is where can you find a oscillator low enough to generate the clock for the circuit.
The first and easyest ways is in your home AC plug. You have a stable 50Hz/60Hz sine wave where with the proper circuit you could have a nice TTL square wave.
The problem is that you always need a relative big number of counters to do the divisons.
But, how do you think they do RTCs? They use a 32768kHz oscillator and with that you need a count with at least 7 bits to divive by 32768 and have 1s clock. then this 1s clock is used for the second counters that generates the minutes clocks and so on...
Check here for some tips:
**broken link removed**
http://www.discovercircuits.com/T/timers.htm

 

[desperado1]

20 minutes timer circuit

Mr. Xvibe can you please elaboarate on the use of counters for frequency division. i designed a timer for a period of 5 seconds and i want it for a period of 50 minutes. how could i do so ?

 

[KMoffett]

40 minutes online timer

One of these timers should work.


**broken link removed**


Ken

 

[desperado1]

74hc5555 circuit

One of these timers should work.


**broken link removed**


Ken

But, 555 timer isn't used over here

 

[KMoffett]

a online 20 minute timer

One of these timers should work.


**broken link removed**


Ken

But, 555 timer isn't used over here

desperado1,

Did you look at it? What does the above link have to do with 555 timers?

??????

Ken