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Old 09-10-2017, 05:10 PM   #1
Chuffchuff
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Default Random on/off switching for LEDs in buildings

Has anyone seen or used a circuit for randomly switching on and off for random periods.

Sort of spec I have in mind is 12v (or under?) , switching one amp, or less (for a bunch of LEDs) say, off for 5 to 10 minutes, then on for 5 to 10 minutes.

The circuits would be used for lighting buildings, so that LEDs would come on and off, mimicking people moving around from room to room or building to building.

I have looked on the web, but most circuits seem to flash, rather than switch. My first look into electronics for many a year, so has to be simple ;-)

Rgds
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Old 09-10-2017, 05:19 PM   #2
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been looking myself, i did find a circuit where changing the resistor values can increase/decrease the on/off periods, i have it saved somewhere will have a look for it,
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Old 09-10-2017, 05:29 PM   #3
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here's a link to the one that i have, https://www.rapidonline.com/pdf/70-1051_v2.pdf
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Old 09-10-2017, 05:37 PM   #4
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ChuffChuff........this may work, looks fairly simple......it shows just 2 LEDs but could probably do 3 or 4 with different value resistors.......but you'd need several of these circuits to accomodate several buildings........could be worth making one to experiment first.......HB
555 timer circuit leds.jpg
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Old 09-10-2017, 06:15 PM   #5
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Quote:
Originally Posted by Chuffchuff View Post
randomly switching on and off for random periods.
The circuit shown is a very accurate repeating flashing of one LED on and one LED off - then vice versa. There is never a time with both LEDs on or both off or change the flashing rate ...
The building fitted with one of these circuits will look like a road pedstrian crossing.

Taking a second look , it appears that the circuit doesn't work. The RC network has errors , pins 2 and 6 are shown connected to the 9V battery supply - (Check it against the recommended circuits for astable circuit)

Last edited by scratchbuilt; 09-10-2017 at 07:07 PM.
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Old 09-10-2017, 06:26 PM   #6
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an astable multivibrator circuit is close to what you'll need.
It forms the basis of simple synth electronics.
You could have something quite effective using a decade counter (4017 IC)
That will give ten outputs sequentially. So you could have ten lights per chip or banks of lights.

On cadmans link,
The 47k and the capacitor control the timing, (a potentiometer in place of the 47k will allow timing control)
The pair of 470R basically controls led brightness.

Edit, link to
(555 astable with cd4017 ic)
Timing set fast for musical rhythms but easy to change to very slow, one or two components only to alter speed, really just one electrolytic cap will do it!)

https://flic.kr/p/YiKgRz
My sequencer based on the baby 8 circuit.
(It was one of my first circuits, and the first I developed from various sources, I mean I didn't copy the design.)

I could work something out for you?
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Old 09-10-2017, 07:42 PM   #7
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So cadmans circuit works like this.
I built it as shown.
https://flic.kr/p/CbrefY
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Old 09-10-2017, 08:01 PM   #8
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Well that's no good, exactly what the OP doesn't want.........I thought the 555 timer could be configured to switch over longer periods..........maybe Arduino will solve the problem......HB
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Old 09-10-2017, 08:07 PM   #9
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It can be, the green wires take you to the 47k.
Changing this will either speed up or slow down the function.
As will changing the electrolytic.......
But with this circuit all you will ever get is the alternating sequence.

Arduino is out of my league! (Includes all other similar type chips)

Totally random is difficult to acheive with electronics........
(At least with my knowledge!)
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Old 09-10-2017, 08:26 PM   #10
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https://flic.kr/p/ZeMs15
Same circuit with 47k resistor changed to B100k pot
Shows effect of resistance change in the timing section of the circuit.
0R=fast 100k=slow (slower than the original 47k)
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