I have already discussed one programmable timer circuit in this blog earlier, the circuit involves the IC 4060 for generating the basic oscillations which is further used for generating the required time intervals, however this cannot be synchronized with an external clock.
The following circuit was requested by Mr.Amit, here the concept makes use of a clock for acquiring the required base timing oscillations and therefore is able to get synchronized with external clocks or watches.
The above procedure of using simple oscillator module for acquiring the oscillations may look quite impressive, but it accompanies a serious disadvantage.
Using an External Clock for Synchronizing Time
The above type of timers cannot be synchronized with a clock and therefore are never accurate.
The article explained here utilizes a clock's second's pulses for acquiring the basic triggering oscillations for the different sections of the corresponding circuit stages which are divided into minutes, hours etc.
These outputs are suitably configured with a set reset latch for obtaining the required programmable timer application needs.
As shown in the figure the circuit basically incorporates many 4017 ICs for dividing the source seconds pulses into minutes and hours.
How it Works
Each IC 4017 consists of 10 output ports which become high and low sequentially in response to the inputs applied at its pin #14.
It means if a pulse of one second duration or 1Hz is applied at the input, the Pulse will become of 10 seconds duration at pin #3 of the IC.
The first IC from left is applied with the seconds pulses derived from a regular digital clock.
As explained above, it's pin#3 now generates 10 seconds of time interval, meaning it goes high after every 10 seconds.
This pin#3 is next connected to the input of the second 4017 IC, which again does the same, increases the time interval *10, that is it generates 10*10 = 100 seconds time, however since its pin number 5 is connected with pin#15, this IC generates 60 seconds time duration at its pin#3.
This 60 sec time interval is further applied to the input of the next 4017 IC, which now in the same way transforms this input into a period of 60*10 = 10 minutes.
The above 10 min time interval is again applied to the input of the next 4017 IC producing an output of 10*6 = 60 minutes. that is equal to 1 hour at its pin #3.
The above procedure may be increased to any number of time interval outputs just by adding more and more 4017 ICs in the array.
Now interestingly, the timing generated at the respective IC's pin outs are all in accordance to the main input acquired from the digital clock's seconds pulse, therefore are perfectly co-ordinated with the clock timing.
If you are interested to achieve a programmable feature from the above set up, you just need to appropriately calculate, assess and integrate the relevant pin outs from the corresponding ICs to the SET Resest Latch circuit input trigger terminals, as explained below:
Using a Set/Reset Latch
The set reset latch circuit shown in the diagram is actually nothing but a simple latching set up, which can be used to activate a relay through one of the inputs (set) and reset it back to deactivate the relay via another input trigger.
The two input triggers are separate and may be individually acquired from the above explained IC 4017 pin outs. How you would like to achieve a particular set of triggering action as per your needs will solely depend how you analyze the above set up and configure the respective pin outs with the set reset latch.
The relay associated with the set reset latch will eventually be responsible for activating and deactivating a particular load discretely as per the assigned timing inputs from the 4017 ICs.
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jason bobis says
Sir.. I don't really fully understand this circuit but can I use it as a 30 second timer?and if yes How?
Swagatam says
jason, for 30 seconds delay you can try the following circuit, the above is far too complicated:
https://homemade-circuits.com/2013/10/simple-adjustable-industrial-timer.html
Aleem Dargah says
Hello Sir,
I'm a student & also an intern at a local factory. Earlier in factory there was a siren (of 1/4 watt motor, 240V AC) connected with a programmable timer clock (ptc). It used to siren for 10 seconds for 12 times a day. Now the 'ptc' is broken, the manager doesn't want to buy a new 'ptc', so ordered me to make a new one as an assignment.
Can this ckt be used for my purpose?
I can read ckt dgm & recognise components & understand how ckt works, but I'm not an expert to design & build a new ckt on my own.
Can you kindly help me out? That would be of great help.
Swagatam says
Hello Aleem,
yes you can use this circuit for your application, you will need to connect the different outputs via individual diodes to the set/reset stage for getting the required outputs.
Idy-In-Yang says
My mentor,kindly help to post a fully automatic 1kva inverter using sg 3524 as oscillator. Thanks
Swagatam says
OK my dear student, I'll try to do it soon….
Idy-In-Yang says
Hello,my mentor kindly explain this set reset circuit and how it's applicable to the timer. How many of the set reset ckt do i need in the timer. Thanks
Swagatam says
Hello my student, the set reset timer shown in the second figure will switch ON the relay and latch it when a positive voltage (momentary) is applied across its "set" and ground points. The relay will remain in latched position until a voltage is applied across its "reset" and ground terminals. The process may be repeated as per ones own preferences. The relay may be connected to a particular load, example an AC, fridge, incubator, lights etc.
The above set/reset pins can be appropriately configured with the first sequential timer for obtaining any desired switching/timing of the relay….
siree says
hello sir…
okayy.. can u please tell me some other applications other than timer circuits plz….
Swagatam says
It is also used for LED decoration, running light, chasing light etc applications.
siree says
thank u sir…
siree says
hello sir…
i have a doubt.. plz give me a detailed explanation why u had connected that pin#5 to pin#15??? initially at the pin#3 we get 10*10=100sec as o/p but if we connect that 15th and 5th pin.. how it can be modified to 60sec??
Swagatam says
Hello Siree,
I have explained everything about the IC 4017 in one of my earlier blogs just type 4017 pin outs in the search box, you will get all the required data about it's configuration.
captain mudassar says
Sir u didn't mention the name of blue transistor!
siree says
hello sir….
yaaa i hav gone through ur earlier blog… its really very gud explanation for the freshers…sir… hav a doubtt.. according to this operation i understood that this can be used only for timer circuits.. are there any otherr applications…?????
Swagatam says
That's not a resistor, that's a relay
Swagatam says
Siree, actually the IC has many applications, just needs to be configured appropriately.