Light activated circuit

Reloadron said:

So there is no need for an external switch be it transistor of MOSFET.

Ron

Click to expand...

Thanks.

It does work, but it beeps with a much higher rate than it does when wired directly?

I think I will order a plain piezo buzzer.

The beep rate might just be a function of the voltage applied to the beeper. Try a few till you find something you like or just place a resistor in series with the beeper.

Ron

"It beeps with a much higher rate". What is rate?
A piezo beeper has a continuous oscillation: Beeeeeeeeep. Does yours have a discontinuous beep rate: Beep, beep, beep etc?

The frequency of the oscillator in a piezo beeper is set by the acoustic resonance of the piezo disc in the cavity it is in so that its beeping is the loudest.

I put a pot inline to reduce the volume. I am happy with how it is sounding now.

Thanks Gentlemen.

Please post the schematic of your final working circuit with the 555 connected as a 5 minutes timer. The other schematics you posted do not work properly.

The photo does not show the schematic, instead it shows a photo of an intermittent solderless breadboard with messy wires all over the place.
None of the parts or wires are labelled.
The wiring of the pot is not shown.

You see the dimple on the chip or you should.

Then you can tell which pins are which.

The other photo shows where they go to.

I even used different colors to make things easier.

I do not have hours to spend learning a circuit diagram program.

You should spend less time criticizing me and be a cheerful giver.

You are NOT a most helpful member.

One of the key players in this game is the LDR which in this case looks to be a CDS Photocell. Matter of fact based on your image it looks to be very similar to this photocell. Knowing the Light and Dark resistances is sort of important which is why I asked about those numbers in an earlier post. There are hundreds of photocells out there and knowing what you have makes it a heck of a lot easier to help. The Internet is hardly a reliable place to find good functioning circuits, some work fine, some almost work and some never will.

Personally I see the 555 timer as a poor choice for a light/dark detector but obviously it is what you have and decided to run with. You started by mentioning breaking a LASER beam and when I questioned that and gave you a few links it became I just want it to work the way it is. Your first drawings reflected parts installed backwards. If you don't plan to learn and understand data sheets all of this becomes a fruitless exercise in futility which is why most of the early members who wished to help bailed out. To help someone people need a feel for where they are, what level they understand. You have no interest in learning or starting in the shallow end of the pool so just ask by saying I need a light dark sensor circuit. This is not something I wish to pursue. I would have just suggested you buy one of these from Ebay or Amazon for a few bucks and been done with it.

It works, be happy and life is good. I am sure armed with Google you will find other forums and hopefully with more helpful and maybe even Most Helpful members. Just point out you aren't interested in learning, you just want instant results.

Ron

I basically am a happy person.

I have learned even if you think I have not.

And I have and do read data sheets. I have even posted parts of data sheets.

If you expect perfection, then I have some news.

I am not perfect and neither is anyone.

I have been on other forums and they have NO problem with my posts.

They are cheerful to help me far more than here.

I feel you are just making excuses for the unsocial behavior of one individual.

Either help cheerfully or as the others do, do not answer.

Members here have the right to be critical and perfectionist. It's your forum.

Have a great evening.

I do not use a Circuit Diagram Program. Instead I simply copy and paste parts together to make a schematic with Microsoft Paint Program.
Most schematics are already on a datasheet (the 555 timer circuit) or are already posted somewhere. Simply copy and paste it.

That's what did using Gimp. I fix my schematic and changed it in my post.

One problem is the size of the symbols.

I was trying to insert a switch and it was way bigger than other items in the schematic and it looked retarded.

Found this.

Gimp is good as are several other free photo shop programs. There are also other countless free software programs out there designed for doing electrical circuits. Granted some have a steeper learning curve than others but some are really pretty easy to learn. While I haven't a clue where you plan to go with electronics but even at a hobby level it doesn't hurt to learn some new software. Obviously your choice. The circuit you have works so I guess you have what you wanted or needed. Have a good one.

Ron

fixit7 said:

You see the dimple on the chip or you should.

Then you can tell which pins are which.

The other photo shows where they go to.

I even used different colors to make things easier.

I do not have hours to spend learning a circuit diagram program.

You should spend less time criticizing me and be a cheerful giver.

You are NOT a most helpful member.

Click to expand...

Here is a better circuit that triggers when your laser beam is broken. Whether it stays on for 5 minutes depends on the quality of your 1000 uF capacitor - yo need one with low leakage or you mA need to increase the resistance of the 270k to 330k or more.

The "test switch" allows you to trigger as you want.
Cancel button turns of the LED immediately.

I like that circuit but I would replace the 270K with a 500K pot and make sure, as mentioned, a low leakage quality cap.

Ron

Gophert, your timer will not timeout if something blocks the LED (a parked truck?) for time longer than the timeout.
The original circuit has the same problem.

Reloadron said:

Gimp is good as are several other free photo shop programs. There are also other countless free software programs out there designed for doing electrical circuits. Granted some have a steeper learning curve than others but some are really pretty easy to learn. While I haven't a clue where you plan to go with electronics but even at a hobby level it doesn't hurt to learn some new software. Obviously your choice. The circuit you have works so I guess you have what you wanted or needed. Have a good one.

Ron

Click to expand...

I will keep looking at those programs. Ubuntu has a lot to choose from.

gophert said:

Here is a better circuit that triggers when your laser beam is broken. Whether it stays on for 5 minutes depends on the quality of your 1000 uF capacitor - yo need one with low leakage or you mA need to increase the resistance of the 270k to 330k or more.

The "test switch" allows you to trigger as you want.
Cancel button turns of the LED immediately.

View attachment 118346

Click to expand...

thanks, I will try it out.

Is one switch a SPDT switch and the other a momentary on switch?

I will look up what low leakage capacitors are.

I know that capacitors are similar to a battery except with low capacity.

I once shorted one from a long dead analog tv.

Even with heavy gloves on, I got the shock of my life.

I think it even melted part of the screw driver.

fixit7 said:

thanks, I will try it out.

Is one switch a SPDT switch and the other a momentary on switch?

I will look up what low leakage capacitors are.

I know that capacitors are similar to a battery except with low capacity.

I once shorted one from a long dead analog tv.

Even with heavy gloves on, I got the shock of my life.

I think it even melted part of the screw driver.

Click to expand...

Both switches are momentary but you can definitely use toggle switches - just flip and flip back.

Also, low leakage are not "Required", they will just help get the "actual" on time close to the "theoretical" time from the published calculation for 555 timers. I would just use any 1000uF and adjust the resistor.

Thanks. I field tested my circuit on my patio.

Without the laser, ambient light is enough to keep buzzer off.

I passed my hand over the LDR from about a foot away and it sounded.

But it won't work from about 6 feet away which is about the range I need.

So it looks like even with a laser shining and someone breaks the beam, it may not sound if the light level is high enough.