stardustsailor
Well-Known Member
I was afraid that the large capacitor C1 and resistor R1 I'm using would cause issues (like the timer never finishing and being stuck from leakage current in C1 being greater than R1 value), but in practice the delay has been "a few minutes" and never got stuck.
I had a design based on decade counters, binary counters, and some combinational logic. The simulations showed it to work as expected, but I never implemented it like I did this one. I have all the chips needed to, but it seemed to be more complicated than it needed to be. This new one is also a bit overcomplicated, and requires that big capacitor.
I just realized how silly it sounds that I was opening a box when the main lights were out in the first place. The reason i was doing that is because the main timer wasn't programmed right (set it last night with a new digital timer)... The main light was supposed to be on when I checked, but wasn't. That's why I was opening a box with the lights off in the first place. Sorry, that was very unclear. I guess in normal operation, a user would not open a dark box in the first place.
Anyway ,here's another timing option for the previous " block " schematic ...
Yes,kinda complicated but not so ,at it seems to be ...
The pcb needed is very small ,in case of etched pcb and 1206 SMD caps & resistors are used ...
First of all it needs an input timing signal from a LM 555 timer circuit at ASTABLE mode ...
A continuous-square -timing signal ...
For the described circuit ,of 100 times (10x10 ) smaller period than the desired delay FR LEDs ON time .
So say ,you want the FR light to switch ON after the COBs are OFF and stay ON for 20 min ...
Then you will need to program the 555 astable signal to be of 12 seconds period ..
(12 sec period x 100 = 1200 sec ...1200 sec / 60 sec/min = 20 min ) ...
The circuit ...
Red: +12VDC
Purple : timing signal
black : COM GND
green : self-locking x100 ( x81 actually ) output
Intro : When the COB driver(s) will switch OFF relay #1 (NC ) will trip back to NC position .
So via AC power the +12 VDC power source will power the 555 astable timer (not shown )
and the two 4017 ICs....
How it works :
The timing signal enters the CLK input of the first (left ) 4017 counter .
The 22K resistor is connected prior to CLK input to ensure that ,when there's no HIGH signal the
CLK input is lowered to GND and not floating (noise contamination =false triggering ).
The electrolytic cap and the two 100 n ceramics-at 12 VDC powering line - are for noise bypassing.
(More than just one cap used here ,
in order to decrease the total ESR ,
while increasing the total capacitance ,
thus increasing the overall noise filtering - )
Notice that both the RESET & CLOCK INHIBIT inputs of the first counter , are brought down to GND .
Then each output ( 0 to 9 ) can be connected to 10 corresponding DIP switches .
The other end of their single pole ,is connected parallel ( 22K res here for non-floating signal ) and
be the incoming timing signal to the second 4017 ....
The second 4017 differs from first as the CLOCK INHIBIT input is connected to the output of the second
x10 DIP switch array ...And a transistor is connected ther also ...
What happens actually :
Say ,that you flip the 10th switch of the first DIP switch array and
also the 10th switch of the second DIP switch array... ( 10x10 =100 ,9x9 =81 actually as output #0 is high since 4017 is powered up .. )
The 555 timer outputs a 12 sec period signal ...
first 4017 :
it will take 9x12 secs until output #9 ,gets to be HIGH ....
second 4017 :
output #0 is ON from power ON ...
Output #1 goes high after 9x12=108 secs ....
first 4017 :
it will take 9x12 secs until output #9 ,gets to be HIGH ..Again ....
second 4017 :
Output #2 goes high after 9x12=108 secs ....
that is total time of 108+108 sec= 216 secs ...
repeat .....
first 4017 :
it will take 9x12 secs until output #9 ,gets to be HIGH ..
second 4017 :
Output #3 goes high after 9x12=108 secs ....
that is total time of 108+108=108 sec= 324 secs ...
and so on until #9 -of the second 4017 IC (right at pic ) - goes high ...
( 9x9x12 sec = 972 sec = 16,2 min ...
Adjust the 555 timer signal, to reach the desired 20 min period )
Then-after 16,2 min- two things happen :
1 ) CLOCK INHIBIT input goes HIGH ,and second timer "locks" its #9 output to HIGH state ...
No matter what happens to the rest of the DC circuit ...
2 ) Transistor conducts and the NC relay#2 ,trips to open state ..
FR leds switch OFF ...And stay OFF....
Uuntil DC timing circuit is switched OFF
( COB driver ON = NC relay #1 opens =DC timing circuit & FR LED driver have no AC power ,thus no matter if RELAY #2 is closed ,the FR LED driver is OFF .)
and powered again / once more
( COB driver OFF =- NC relay #1 closes =DC timing circuit & FR LED driver power up ,( FR LED driver will remain ON until NC relay #2 opens .Then it will switch OFF .)-
....No matter what ....
( Diode is there to protect the transistor from inductive current spikes from the relay coil.
Returns spikes to coil .. called "freewheeling diode or flyback diode " )
Combining the -adjastable via pot - 555 time signal period and different switch position combinations between the two DIP switch arrays ,period of FR leds operation can be quite precisely adjusted / preset ,while 555 operation is kept pretty stable and accurate-for long service time .
-Using three 4017 ICs and three x10 DIP switch arrays likewise ,
then you can have a max period of "FR ON " = 555 timer signal period x 729 ( 9x9x9 ).
or ... whatever ...
i.e. 12 sec x 9 x 4 x 7 = 3024 sec = ~ 50 min ..
or
i.e. 500 ms x 9 x 9 x 9 = 364,5 sec = ~ 6 min ...
Fully analog circuit ,fully programmable ,cheap and service -friendly ..
No MCU to ....fuck up ..ever ...
( microcontrollers have their own "blue screen of death " moments at some cases ...
And not so rarely ...)
Cheers
(EDIT: updated )
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