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555 trigger delay help

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Virus

New Member
Hi Guys

I have built this 555 circuit and it is working well. It is connected to a set of IR-beams in the garden that switches on a light should someone break the IR-beam as a security measure.

With our winter approaching leaves that fall from the trees tends to trigger the IR-beam.

How can I build/connect a trigger delay between the 555 circuit and the IR-beams, that will ensure that a longer pulse (preferably adjustable) is needed before the 555 switches on the light.

Thank you for your valued response.

Theunis :D
 
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ericgibbs

Well-Known Member
Most Helpful Member
hi,
What the type of output from the IR detector.?
Pulsed or just a level, etc
 

Virus

New Member
Hi

On the IR-beams is just a relay that closes.

I tried to upload an attachment, but does not seem to work, sorry.

Theunis
 

ericgibbs

Well-Known Member
Most Helpful Member
Hi

On the IR-beams is just a relay that closes.

I tried to upload an attachment, but does not seem to work, sorry.

Theunis
I would be possible for the detector relay contacts to drive a delay, something as simple as a 40106 ic, use the delayed output to trigger the 555.

What voltage is the 555 working on.?

EDIT: whats the delay limits you require
 
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Virus

New Member
Hi

I am not that very literate in electronics,

The IR-beams and the 555 circuit is running on 12VDC.

Thanks

Theunis
 

ericgibbs

Well-Known Member
Most Helpful Member
Hi

I am not that very literate in electronics,

The IR-beams and the 555 circuit is running on 12VDC.

Thanks

Theunis
hi,
I would like to see a circuit, in order to check the components you have on the trigger circuit inputs.

What delay range is required.?
 
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Virus

New Member
Hi

I tried to upload a png did not work, any suggestions.

Theunis
 
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Virus

New Member
Hi Eric

look at post 9, got an attachement their.

Thanks for your help.

T
 

ericgibbs

Well-Known Member
Most Helpful Member
Try this one !
hi,
Can you indicate whats connected to J1 and J2 in the non triggered state, Im assuming its the detector relay contacts on J2..
Confirm the state of the relay contacts.

What delays do you want.?
 

Virus

New Member
Hi

J1 is reset,

J2 is trigger, connect to the IR-beam’s on board relay.

Delays . . . , I need your input, maybe if it can be adjustable, ± 0.5 sec, how long does it take for a leave to fall ?

Thanks

T
 

ericgibbs

Well-Known Member
Most Helpful Member
hi,
If you have 555 on the shelf, you could make another 555 monostable, with 0.01s thru 0.5secs delay, before it triggers the existing 555 input.

How long does a leaf take to fall.. good question, I could be a smartie and say it depends upon the height of the tree.!:)

Its how long the leaf is in between the IR path.
 

Virus

New Member
Eric

Have some 555 laying around, but I don’t think it will work !, because it will eventually trigger the light just with a delayed time.

Sorry if my terminology is a bit skew.

I want to prevent a vals trigger of the light, in other words, the relay on the IR-beams must be triggered for longer that X-ms before the 555 circuit switches on the light.

For as long as you hold your hand in front of the IR-beams the onboard relay stays energized, If you would move your hand, fast, with fingers apart in front of the beam (10 meter from the receiver), it will actually detect the gaps between your fingers very quickly. (every time energizing the relay.)

I need a circuit that will eliminate short pulses from the IR-beams relay, to the 555 circuit thus delaying the light from coming on for very short pulses from the IR-beams.

Any ideas ?

Thanks

Theunis
 

ericgibbs

Well-Known Member
Most Helpful Member
By using the relay contact in conjunction with a 555 mono it will work as I
suggested.

If the detector relay de-energises before the mono times out the mono will be cancelled and so will the trigger pulse.

Perhaps others may have a better idea.
 

Virus

New Member
Eric

Maybe I am short sighted here.

Can you supply me with a circuit and quick description, please.

How do I incorporate a delay in the 555 circuit ?

Theunis
 

Virus

New Member
Can actually use the reset on the 555 keep it to ground and it won't trigger, But how ? with a time delay?

Theunis
 
Last edited:

ericgibbs

Well-Known Member
Most Helpful Member
Can actually use the reset on the 555 keep it to ground and it won't trigger, But how ? with a time delay?

Theunis
I'll look see what I can come up with.

Confirm one point, the relay contacrs from the detector relay are closed when the beam is broken.???
 

Virus

New Member
Thanks Eric

I think I got it . . . ,

Make it Circuit-1 (old 555 circuit) and Circuit-2 (new 555 circuit)

Build circuit-2 similar to the one posted (circuit-1), omitting Q1, D1, RL1.
Adjust RV1, R3 and C1 for desired time needed in ms.

Connect J1(reset terminals) of Circuit-1 to (omitted RL1) of Circuit-2.

Use same trigger from the IR-beams to trigger both circuits same time,
Circuit-2 will keep the reset pin of Circuit-1 to ground for X-time ms,

See I do need a memory replacement does take time some times to snap into place.

Will try it this way.

Thanks


Theunis
 
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