Hello everyone . This is my first article on the group, also pushed by one of the site administrators have wanted to participate even those who read the’ article about my experience in the field of timers for long times. As the title that I present and a lighting timer entirely designed by me so I ask already apologized for errors .
We come to the point , since I have a child at home and when it comes to sleep does not want to fall asleep at lights out but only with his lamp lit, and since I can not turn it off once she falls asleep ( I often fall asleep before I), I decided to make a timer that does this for me .
Assuming that after a 20 minutes falls asleep (when she is tired) after a maximum of drowsiness Oretta collapses ( when it still has some power ) what I would need is an adjustable timer that goes from a minimum of 15 min to a maximum of 2 hours and 30 me .
Wandering through the net I came across several types of timers, but one struck me in particular is the CD4060 and with whom, and can realize timer with long waiting times , I immediately thought ” well that's it!!” but instead it was a little more complex than what I thought.
We start from the diagram that I made :
It is a 4060 with a cascade 4017 from which it is possible to withdraw from its 10 outputs via a rotary switch the desired signal which varies from a minimum of about 15 minutes to a maximum of about 2 It is a half hours, so everything is in order as I said idea works . So I have to have a pulse every 15 min in order to advance the 4017 one step at a time up to the maximum (10 step =150 min), So the 4060 It must generate a pulse every 15 minutes or its output signal must be of 7 min is E 7 min OFF for a period of 15 min between one step and another . As you can see from below the external components to 4060 I am a capacitor C1 and two resistors R1 and R2 where R1 and C1 serve to generate the base frequency of our oscillator, while R2 serves to limit the input current to the pin 11 and it is generally comprised between double R1 (2R1) at most ten times R1 ( 10R1).
To have given period we now find the values to assign to the capacitor C1 and the resistor R1 and through the internal oscillator will generate the frequency that serves our purpose , the datasheet can be seen that the frequency depends on :
F = 1/(2,2xR1xC1)
Dove (2,2xR1xC1) represent the period T.
Knowing that our time and 15 min or 900 seconds and the frequency is given by 1 / T turns out that our frequency and 1/900 = 0,0011 Hz , but this is not the frequency that will generate the oscillator, but rather the frequency corresponding to one pulse every 15 minutes, to know how often must create our oscillator , We first need to decide on what we want to take the signal pin, in fact, the CD4060 has in its interior in addition to an oscillator also 14 stages dividers that divide the frequency generated by multiples of 2 or : 16 , 32 , 64 , 128 , 256 , 512 , 1024 , 4096 , 8192 , 16384.
I personally chose the pin number 3 namely the divisor for 16384 so I will have to generate the frequency that will be :
Dark = F x 16384 = 18 Hz around.
So having now found the frequency value that serves there remains nothing that size the external components or C1 and R1 , always from the datasheet it shows that the period is nothing but :
T = 2,2xR1xC1,
Now since we have two unknowns R1 and C1 should fix us a arbitrarily for convenience it is preferable to fix the value of C1 , that is why I chose a value equal to C1 100nF now knowing the period and also knowing the value of C1 is nothing left to calcolarci the resistor R1 by means of the inverse formula or:
R1 = T/(2,2xC1) , Follow;
R 1 = (1/dark)/(2,2xC1) = (1/18)/(2,2 x 0,0000001) = 0,055/0,00000022 = 250000 ohm
It follows that the value for R1 is of 250Kohm value that there is no commercially , I used a resistor of 68kohm (R3) seriously to a trimmer 220kohm (R4) with these values result in a more or less precise timing , but so much for my purpose is just fine.
As for the rest of the components , we find a reset car network formed by capacitor C2 10uF and the resistor R1 10Kohm which serve to reset both counters at the time of ignition (as you may have noticed you are not present no switch that turns on the circuit when desired, this to the fact that the whole circuit and enclosed in a cassette for electrical boards inside with a regenerative power supply of an old portable PC that feeds the circuit , and I need to attack when the plug) , LED1 serves as well as to signal that the oscillator functions ,also to a calibration of the instrument , In fact, to have a more or less precise pulse rotates the R4 trimmer so as to have two flashes of LED1 into a second in such a way as to be more or less sure that the times are those desired , while T1 is a common NPN transistor that is used to operate a relay via which the switching on or off of the lamp .
This is just the beginning of the project , if you want you can connect a start and stop circuit through which once reached the desired time, for example, 1 Now ( pin 5 of the 4017) disable the 4017 via its Enable pin (pin 13) so as not to have an infinite loop , or a parallel button connected to C1 in order to reset both counters when you want to have some extra time .
I hope that my experience can be of help to anyone who engages in this field of electronics , Amilcare I have to thank you for helping me understand better how the 4060 and for having responded to my every question.