Making a timer on delay and off delay without microcontroller

Thread Starter

fadlianturu6

Joined Feb 20, 2024
5
I am new and want to make a compact circuit without a microcontroller. The idea is when you push the button/switch, it will delay the timer for at least 6 hours. After that, it will activate the motor for 20 seconds and loop forever. I am thinking of using a 555 timer with a 1000uF capacitor here, but it fails miserably. Any ideas? Screenshot_227.png
 

boostbuck

Joined Oct 5, 2017
515
Six hours is a long call for a 555. A common way to achieve extended times using a 555 is to run it at around 1 hertz and feed a divider chain (4040 for example).
 

panic mode

Joined Oct 10, 2011
2,752
RLA is relay...
555 is producing clock which is adjustable between 1.4Hz and 18Hz.
this is then divided by 10 using 4017
then it is divided again by 16384 using 4020
so transistor will turn on/off with frequency that is 555 producing, divided by 163840.
but as soon as transistor turns on, relay is on, and one of relay contacts will cause it to latch on... (and stay on until power is removed)
the other relay contact(s) can be used to drive some load. so this works as timer on.


while this works (and it works very well), setting up desired time accurately is cumbersome.
when accuracy is required, it is better to use oscillator that runs at fixed frequency, followed by counters like shown above.
but the timer preset would be then selected using dip switches tied to outputs of the counters.
this way one can enter code in few seconds and know that this will be spot on.
but today microcontrollers are supper convenient for things like this. i know you don't want them but this is perfect application for something like DigiSpark.
 

panic mode

Joined Oct 10, 2011
2,752
for 6 hours we have half-period of 6h *3600 sec/h = 21600 seconds
so period is twice that or T=42300 seconds
since divider is set to 163840, the 555 oscillator need to run at frequency
f = divider/T = 163840/42300 = 3.8Hz

so if you use above circuit and capacitor is 1uF, you should adjust potentiometer to about 200k
 

Thread Starter

fadlianturu6

Joined Feb 20, 2024
5
Update
I've designed a circuit using the IC CD4060 to count 6 hours and a 555 timer to control a 20-second rotation for the motor. According to the CD4060 datasheet, the formula for calculating the period (T) is:

T=2.2×Rx×Cx

If I want the period to be 2 seconds, and I'm using a 100uF capacitor, then the resistor (R) should be approximately 9.1K Ohms. However, in Proteus simulation software, I find that I need a 12K Ohm resistor to achieve a period close to 12 seconds.

Before I proceed with building a prototype, I'm concerned about potential issues such as reverse voltage across the capacitor, discharging, and leakage. I'm unsure where to start and what factors to consider first.

Can you recommend any books or websites that cover these topics? Additionally, I'm using gates, and since the IC4060 can handle 2^14 bits (16384 pulses), I'm summing them up to achieve a nearly 6-hour count with a T = 2s period. I'm not overly concerned about efficiency, but I aim to keep any inefficiencies below 10%

Screenshot_229.png
 

Thread Starter

fadlianturu6

Joined Feb 20, 2024
5
for 6 hours we have half-period of 6h *3600 sec/h = 21600 seconds
so period is twice that or T=42300 seconds
since divider is set to 163840, the 555 oscillator need to run at frequency
f = divider/T = 163840/42300 = 3.8Hz

so if you use above circuit and capacitor is 1uF, you should adjust potentiometer to about 200k
any ideas ?
 
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