Post 7 or post 15?

Post 15, leaving the triggering cap's polarity as is shown in the drawing.

EDIT: You may also use post 7 circuit on the right, which is configured so as to better protect and stabilize the 555, but post 15 should work fine too. IF your circuit ever fails (I doubt it) and if you have to rebuild it from scratch, then you may use post 7 instead.

 

post 15's configuration works on breadboard as suggested, now to the veroboard, I have the cap as in the drawing of 15! so all I have to do is connect R2 to positive end, and not the negative end as it is now. thanks, now makes sense about the floating cap, onwards to building it (the power is back on)

 

post 15's configuration works on breadboard as suggested, now to the veroboard, I have the cap as in the drawing of 15! so all I have to do is connect R2 to positive end, and not the negative end as it is now. thanks, now makes sense about the floating cap, onwards to building it (the power is back on)

Good to hear.... now push the "like" button... ha ha ha...

 

Good to hear.... now push the "like" button... ha ha ha...

I did ;-) hahaha; now the wait for the first false trigger... or never hopefully

 

I did ;-) hahaha; now the wait for the first false trigger... or never hopefully

hey... if it doesn't work as expected you can always "unlike" my comment...

 

I did ;-) hahaha; now the wait for the first false trigger... or never hopefully

I did notice however that the switch doesn't need to close, anything conducting touch ground and it triggers. Is there any way around that? Or will post 7 fix that? No false triggers yet though.

 

Something to try. As drawn in post #15 I don't think it is correct. When the switch is open you have VCC on the switch. When the switch closes the junction of the switch and cap get pulled to ground and remain there. That isn't what you want. The cap can be a .1uF non polarized cap. R2 can be a 10K resistor. You need the cap and R2 to form a differentiator so all you get on pin 2 off the 555 is a negative spike to trigger the 555 and return high.

I believe what you want is for VCC through R2 to pin 2 of the 555. One side of the cap to R2 and pin 2 junction. Your switch to ground to the other side of the cap. When the gate opens and the switch closes all you will get on the 555 trigger pin is a negative spike to trigger the 555. If that is not what you ended up with I suggest you give it a try as what I see back in post #15 I don't believe is what you want. I can do a drawing and run a sim if you would like.

Ron

 

Something to try. As drawn in post #15 I don't think it is correct. When the switch is open you have VCC on the switch. When the switch closes the junction of the switch and cap get pulled to ground and remain there. That isn't what you want. The cap can be a .1uF non polarized cap. R2 can be a 10K resistor. You need the cap and R2 to form a differentiator so all you get on pin 2 off the 555 is a negative spike to trigger the 555 and return high.

I believe what you want is for VCC through R2 to pin 2 of the 555. One side of the cap to R2 and pin 2 junction. Your switch to ground to the other side of the cap. When the gate opens and the switch closes all you will get on the 555 trigger pin is a negative spike to trigger the 555. If that is not what you ended up with I suggest you give it a try as what I see back in post #15 I don't believe is what you want. I can do a drawing and run a sim if you would like.

Ron

I'm not sure I follow, I need a cap to stop the never ending buzz of a continuously closed circuit, just 6 seconds of buzz and then the gate can stay open for as long as it likes, keeping the switch closed. I use a normally closed reed with an exceptionally strong magnet to keep it open when the gate is closed, I rocked the gate vigorously and no false trigger. And because it may pose a problem in rare cases, why does anything conducting that touch ground trigger the buzzer?

 

Something to try. As drawn in post #15 I don't think it is correct. When the switch is open you have VCC on the switch. When the switch closes the junction of the switch and cap get pulled to ground and remain there. That isn't what you want. The cap can be a .1uF non polarized cap. R2 can be a 10K resistor. You need the cap and R2 to form a differentiator so all you get on pin 2 off the 555 is a negative spike to trigger the 555 and return high.

I believe what you want is for VCC through R2 to pin 2 of the 555. One side of the cap to R2 and pin 2 junction. Your switch to ground to the other side of the cap. When the gate opens and the switch closes all you will get on the 555 trigger pin is a negative spike to trigger the 555. If that is not what you ended up with I suggest you give it a try as what I see back in post #15 I don't believe is what you want. I can do a drawing and run a sim if you would like.

Ron

if your suggestion still gives me a static duration of buzzing then a drawing please, maybe I'll see it then, I'm very interested!

 

Still false triggers, damn

 

Still false triggers, damn

back to the drawing board... at least for me... calling @#12 we need your help!

 

Are you calling him or should I?

Lets state what we have
1 555 circuit that produces 7s worth of buzzing on reed closing when gate opens, and at closing because of switch bounce (which doesn't matter)
circuit is unstable and produces false triggers
any conducting material touch ground, we get a trigger
as far as I can see, we never have floating ends at all of the capacitors

How can it be so difficult to make a simple stable gate buzzer?

 

back to the drawing board... at least for me... calling @#12 we need your help!

so I assume we're not going with #7 right circuit just yet?

 

Are you calling him or should I?

Lets state what we have
1 555 circuit that produces 7s worth of buzzing on reed closing when gate opens, and at closing because of switch bounce (which doesn't matter)
circuit is unstable and produces false triggers
any conducting material touch ground, we get a trigger
as far as I can see, we never have floating ends at all of the capacitors

Question, what battery are you using on the circuit?

 

A 12v switching PSU, cheapie got it for R30 (R22 for 2l of milk R-South Africa RAND) If you think it's the PSU, then I can use a 9v PP3 see if that makes a difference, or maybe I should replace the 22uF with 1000uF, if it's the psu giving problems. I'm guessing that you're suggesting that my power supply's ripple could cause these intermittent faults?

 

A 12v switching PSU, cheapie got it for R30 (R22 for 2l of milk R-South Africa RAND) If you think it's the PSU, then I can use a 9v PP3 see if that makes a difference, or maybe I should replace the 22uF with 1000uF, if it's the psu giving problems. I'm guessing that you're suggesting that my power supply's ripple could cause these intermittent faults?

That's one possibility. To test it, you can replace the PSU with a 9V battery, see what happens. On the other hand, you could tie the ground of your circuit to the gate (it's a metal gate, right?) again, see what happens...

 

@MaxHeadRoom, #12 is not here right now, could you please take a look at post #15 and tell us why the OP is getting spurious triggering on that circuit?

 

@MaxHeadRoom, #12 is not here right now, could you please take a look at post #15 and tell us why the OP is getting spurious triggering on that circuit?

what does OP stand for? it's night now, will be getting to bed, so I'll give the 9v a go tomorrow

 

what does OP stand for? it's night now, will be getting to bed, so I'll give the 9v a go tomorrow

"Original Poster" ... it used to also be called TS, for "Thread Starter" ... sweet dreams...

 

still have 30mins left before bed, wanna know what MaxHeadRoom says

NOW it's bedtime, will continue tomorrow, thanks for all your effort!