automatic room light

[ceredigion]

A lot of you have already probably seen this circuit and given advice or reviews, but i am really interested on building this circuit for my electronic project. trouble is, I am not very experienced therefore need help and won't be able to redesign circuit alone. I was wondering if anyone had a similar circuit or a redesign that i could have. thanks a lot. any help will be much appreciated.

https://www.electronic-circuits-diagrams.com/lightsimages/lightsckt4.shtml

**broken link removed**

 

[audioguru]

What help do you need?
What redesign needs to be done to that circuit?

 

[Madhouse]

Maybe he wants it to detect whether two people entered the room together, and left "side by side"! There's a challenge.

A PIR solution could be good - the lights go off when the activity stops......And then come on again briefly when they are ready to leave!

Mods, please delete this if you think I'm pushing it, but the real problem is how do you do it? Multiple LDR's spaced at distances won't work!

I do it with dogs(see below) - each dog has a microchip, and two sensors placed in suitable positions around the kennels tell me which dog is where by serial number. I guess the day when all humans are tagged electronically can't be far off now, but it will certainly solve this problem!

Ooops - had to edit that bit - I don't do it with dogs - just track where they are. Cheers!

 

[ceredigion]

well i wud like to do this circuit but apparently it doesn't work...does anyone have an altenative circuit? thanks a lot.

 

[audioguru]

That circuit is missing parts in places. Like a resistor at pin 14, the Clock input of the 4017 counters.

 

[ceredigion]

would someone be able to rebuild this circuit for me as i have little experience would much appreciate this. or even a similar circuit. thanks

 

[gunsmoker]

That circuit is missing parts in places. Like a resistor at pin 14, the Clock input of the 4017 counters.

What else is missing or wrong?
I am a beginner. I built this circuit and it was very iffy, sometimes it would work and sometimes not. I never got it hooked up to the room lights because it wouldn't work reliably. I checked everything many times and even replaced the light sensors with infrared emitters and transistor type sensors, wiring the infrared in three different configurations. The results of my labors have been fruitless and I had to give up, which is something I don't usually do. I have searched in vain for answers, so if anyone can tell me more I would appreciate it very much.

 

[audioguru]

What else is missing or wrong?

That circuit is missing a resistor to ground at the clock input of each CD4017 to provide a low clock voltage of 0V. Try 100k to ground at pin 14, or short C8 and C10.

The CD4017 needs a minimum high clock voltage level of +6.3V with a +9V supply.

The clock high voltage won't be high enough to reach the +6.3V minimum so many CD4017 ICs won't work:
1) The output high voltage of a 555 is about 7.8V with a +9V supply.
2) The voltage drops of D1, T1 and T2 for the upper part of the circuit total about 1.8V.
3) Then the high clock voltage to pin 14 of the CD4017 is only 7.8-1.8= 6.0V which is too low. It would work properly if each 555 is replaced by a Cmos 555.

I wonder why the circuit uses old TTL logic ICs.
I see the problem: The old SL100 transistor was made in India a long time ago, when and where this circuit was designed.

 

[gunsmoker]

Thank you very much for your informative reply, audioguru.
I did a little reading about the resistor between pin 14 and ground. Am I to understand correctly this is to prevent the entrance of external noise?
Concerning the 555 timer, would this one be a good choice?
**broken link removed**
From the data I think a tlc555cp would be a good drop in replacement, correct me if I'm wrong please. Apparently this line of timer works up to 15V and retains very nearly all it's voltage at output according to page 7, the chart here assuming operational voltage of 15.
Mouser has it in part # 595-TLC555CP for $0.88 each.

 

[audioguru]

I did a little reading about the resistor between pin 14 and ground. Am I to understand correctly this is to prevent the entrance of external noise?

No. Pin 14 needs a DC voltage near 0V as a logic low, and a DC voltage near the supply voltage as a logic high. The coupling capacitors C8 and C10 prevent DC voltages so the resistor to ground makes a logic low DC voltage.

Concerning the 555 timer, would this one be a good choice?

Yes, a TLC555 is a Cmos 555 and its output goes to the supply voltage if the load's current is low. An LMC555 is the same.

 

[gunsmoker]

Thank you, audioguru.
I will get two of these and put in the two 100k resistors between pins 14 and ground, I'll let you all know how it turns out.

 

[philba]

OK, after looking at that circuit and reading the guy's text (don't people believe in paragraphs any more?), I'm convinced that circuit is nuts, beyond the errors that were pointed out.

Using LDRs will be problematic. This is because it's assuming that a person entering will cause enough light drop to run the circuit. not always true - sensor placement is critical and it will take some tweaking to handle all ranges of light. In addition, people sometimes bunch up when they enter or leave a room so the circuit could easily get confused. what if some one enters halfway, swings their arm when turning around and leaves? Again placement is critical. Also, this circuit needs light to function. Where's that light coming from if the purpose is to turn on the lights??? In general, this is simply the wrong way to do it. As was pointed out, a PIR is a better way, though not fool proof either.

 

[gunsmoker]

OK, after looking at that circuit and reading the guy's text (don't people believe in paragraphs any more?), I'm convinced that circuit is nuts, beyond the errors that were pointed out.

Using LDRs will be problematic. This is because it's assuming that a person entering will cause enough light drop to run the circuit. not always true - sensor placement is critical and it will take some tweaking to handle all ranges of light. In addition, people sometimes bunch up when they enter or leave a room so the circuit could easily get confused. what if some one enters halfway, swings their arm when turning around and leaves? Again placement is critical. Also, this circuit needs light to function. Where's that light coming from if the purpose is to turn on the lights??? In general, this is simply the wrong way to do it. As was pointed out, a PIR is a better way, though not fool proof either.

Thank you, philba for your comments. They are well placed and quite right.
I'm doing this for the experience, I believe trying to solve problems will help me to incorporate components better in future projects. Whether the circuit becomes a useful and permanent fixture remains to be seen.

 

[ertiexd125]

HI! ITS BEEN A LONG TIME SINCE THIS THREAD HAS TALK ABOUT. I am also working with the circuit and until know we can't get it to work.. any reply from the thread starter would be great for me.. the deadline is very near!

 

[microtexan]

".. the deadline is very near! " Surely since last march it must be really near

 

[ertiexd125]

".. the deadline is very near! " Surely since last march it must be really near

what?

any reaction from the thread starter or anyone here? does this circuit work?

 

[gary350]

You can buy pressure pads and pressure tape to put on the floor at each room entrance so it turns the light on when you enter. You use motion detectors to keep the lights on as long as someone is moving around in the room. When someone leaves the room the lights go off. If the person in the room falls asleep and stops moving the lights go off. My wife turns every light in the house on and will not turn them off I had to figure ways to make the lights go off on their own.