555 trigger delay help

Virus said:

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

Click to expand...

Thats good!, two heads are always better than one.

See how you go, come back if need be.

Hi guys

Need to know what to do to modify a simple 555 monostable circuit, when a trigger pulse is kept closed/on that the circuit will still time out, and not stay triggered as long as the trigger pulse is kept close.

Thanks

Theunis

Virus said:

Hi guys

Need to know what to do to modify a simple 555 monostable circuit, when a trigger pulse is kept closed/on that the circuit will still time out, and not stay triggered as long as the trigger pulse is kept close.

Thanks

Theunis

Click to expand...

Hi,
Is this the delay 555.?
If yes, then connect the trigger via 2n2, have a 10K pull up from the TRIG input.

So the trig is capacitive coupling, not direct.

Hi Eric,

Yes- for the delay circuit, (need a quick diagram/schematic please. (if possible))

(Pity only have weekends and holiday to actually work on this !)

Thanks again


Theunis

Virus said:

Hi Eric,

Yes- for the delay circuit, (need a quick diagram/schematic please. (if possible))

(Pity only have weekends and holiday to actually work on this !)

Thanks again


Theunis

Click to expand...

hi Theunis,
Since the earlier posts I did some simulation circuits.
Its has to be triggered for a minimum period or number of short periods.

Look at this example.

Eric

Thanks, again much more than I expected.

Please confirm components:
Q2 = BC557
V1= ?
V3= ?

I take it Pin3 of U1 goes to Pin2 of U2.

Can you give me a short explanation of the output ?

Again KISS please.

Thanks for the help.

Theunis

Virus said:

Eric

Thanks, again much more than I expected.

Please confirm components:
Q2 = BC557
V1= ?
V3= ?

I take it Pin3 of U1 goes to Pin2 of U2.

Can you give me a short explanation of the output ?

Again KISS please.

Thanks for the help.

Theunis

Click to expand...

hi,
Q2=BC557
V1 represents your existing 12V supply.
V3 is there for the simulation only, it closes the MWSWitch contacts.
U1/3 >>> U2/2 [trig].
BTW: the U2/3 goes to your relay transistor driver as previously.

I'll post a plot of the waveforms, with an explanation.

hi,
The BLUE trace represents the relay contact closures of the detector relay.

I have shown 3 short pulses, that could be caused by leaves or birds breaking the beam.

You can see, during each pulse the timing capacitor of 555/1 charges a little, on the 3rd pulse the cap voltage is sufficient to allow 555/1 to time out.

The low going output pulse of 555/1 triggers the 555/2 input, as the 555/2 is configured as a mono its output will go high for the time of Res/Cap values.

In the case where the beam is broken for a longer period, the 555/1 cap will charge faster and trigger the 555/2.

When the 555/2 is timing it discharges the timing cap of 555/1, getting ready for any further beam breaks.

If the 555/1 see's say, just one leaf, then the charge on the 555/1 timing cap will be slowly discharged by the resistor in parallel with transistor.

You may have to adjust the timing values on the 555/1 to suit the application.

Do you follow OK.?

EDIT:
added a second waveform, showing when detector relay is closed by intruder.
Longer closure time.

Eric

Again thanks a ton, it is clear enough for a rookie like me.

I understand the principle/concept of the circuit, it is brilliant.

To make 555/1 adjustable/more or less sensitive I can replace R3 with a pot?

Does it need to be TLC 555, ( I only have 1) with the component values you supplied or would other CMOS types do as well?, I noticed they (TLC series) do not trigger the timer when power is applied, like most of the others do.

Attached is a photo of the main board that I have already built with 5 x 555 timers as per attached circuit at post #9 of this thread. (I have omitted the leds + their res, the jumpers with additional caps and resistor for a wider timing from the posted circuit for simplicity)

The idea is to get
Timmer #1 will switch a buzzer for X sec.
Timmer #2 will switch on outside light at night for Y min, at the same time as #1.
Timmer #3 will switch on a siren when set, and will be used as a panic button connected to a wireless remote button.

Is it possible and how to incorporate your trigger circuit with this main board circuit.? As posted in #9.

Otherwise I can rebuild it on your design, it needs to be a stable/flawless system though.

People are voting here this week so not much will happen economically (business wise). Will then make a board and build your design.

Thanks for your time.

Theunis

Virus said:

Eric

To make 555/1 adjustable/more or less sensitive I can replace R3 with a pot?
I would connect a fixed 4K7 in series with say a 50K pot

Does it need to be TLC 555, ( I only have 1) with the component values you supplied or would other CMOS types do as well?, I noticed they (TLC series) do not trigger the timer when power is applied, like most of the others do.
In theory any CMOS version 555 should be OK.

Is it possible and how to incorporate your trigger circuit with this main board circuit.? As posted in #9.
Im not sure what #9 means.???

Otherwise I can rebuild it on your design, it needs to be a stable/flawless system though.
Its been run thru a number of different simulations.

Theunis

Click to expand...

hi,
Its always necessary to prove any design simulation by constructing a working model [prototype].

As they say 'the proof of the pudding is in the eating, not in the simulation'.

The only changes to your original design is the 555/1 delayed triggering circuit.

Sorry I meant post #9

Looking at the circuit you posted, I would then only use U1, taking its output (pin3) to the trigger on my main board (J2) ? ? ? , (as posted in post #9.)

Which of the components can be omitted in your circuit if only U1 is used ?

(I just realize now you would probably have chosen a PIC with much less components to do the same thing ?)

Thanks


Theunis

Virus said:

Sorry I meant post #9

Looking at the circuit you posted, I would then only use U1, taking its output (pin3) to the trigger on my main board (J2) ? ? ? , (as posted in post #9.)

Which of the components can be omitted in your circuit if only U1 is used ?

(I just realize now you would probably have chosen a PIC with much less components to do the same thing ?)

Thanks
Theunis

Click to expand...

hi,
I thought we were trying to modify a one off, existing detector/555 relay driver.??? from being triggered by a falling leaf.

The rightside 555 is your original circuit with a leftside 555 delayed trigger added.
I havn't shown the output relay thats all.

If for a new design I would have chosen a PIC.

Sorry (My bad, you lost me.)

Yes, we are still working on the falling leave delay trigger to a 555 circuit (existing), (would it matter if there are 5 x 555 in stead of 1x 555 using the same delayed trigger from the IR-beam.) ?

Take it then that S2 is the trigger in, coming from the IR-beam ?

Can you indicate the output relay as well, can help to get mind around it.

What software do you use to simulate the circuit ?

Thanks

Theunis

hi,
Look at this edited dwg showing the existing relay and the S2 relay contact.

Sim is LTSpice.

The 5 * 555 trig should be OK.

Eric

Thanks makes more sense now ! ( Pictures makes more sense at my age, still trying to understand the theory)

Can I go-ahead and build this ?

Will give feedback in the week.


Thanks