Frustration

[Cursitor Doom]

On Thu, 16 May 2019 19:53:26 -0700, John Larkin wrote:

I had one engineer who absolutely couldn't tell left from right, and
also couldn't tell logic "0" from logic "1".

I do honestly wonder why on earth you hire the people you do. If I didn't
know you better I'd assume you were trolling.



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[Cursitor Doom]

On Fri, 17 May 2019 07:06:03 -0400, default wrote:

Most of the garden variety of PIR detectors have a wide field of
coverage, but you can apply baffles to narrow the field, or find one
that has a narrow field - usually combined with greater detection range.
Only way to tell is to get one and play with it.

IME they're a total NIGHTMARE. Fine for inside use, but hopeless for
anything out in the open. FAR too many false alarms. Give me the laser/
photodiode combo any day - inside or out.



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[AK]

On Friday, May 17, 2019 at 6:06:04 AM UTC-5, default wrote:

On Thu, 16 May 2019 21:07:22 -0700 (PDT), AK
scientist77017@gmail.com> wrote:

On Thursday, May 16, 2019 at 9:53:32 PM UTC-5, John Larkin wrote:
On Thu, 16 May 2019 16:53:45 -0700 (PDT), George Herold
gherold@teachspin.com> wrote:

On Thursday, May 16, 2019 at 3:08:48 PM UTC-4, John Larkin wrote:
On Thu, 16 May 2019 06:37:19 -0700 (PDT), George Herold
gherold@teachspin.com> wrote:

On Wednesday, May 15, 2019 at 5:31:32 PM UTC-4, AK wrote:
On Wednesday, May 15, 2019 at 2:46:05 PM UTC-5, Rodney Pont wrote:
On Mon, 13 May 2019 19:22:56 -0700 (PDT), AK wrote:

Electronic can be quite frustrating.

I put together a circuit for a laser alarm.

It does not work.

There is no way to tell if a design will be successful even if you follow the authors exact directions.

I will keep plugging away and reading Practical Electronics for Inventors.



Can you post a picture of the assembly so that someone can check that
you have understood how to put the circuit together?

--
Regards - Rodney Pont
The from address exists but is mostly dumped,
please send any emails to the address below
e-mail rpont (at) gmail (dot) com

https://www.dropbox.com/s/leak8ty4dsmw88e/Project2.jpg?dl=0

https://www.dropbox.com/s/edy9xs8p5rfm15q/Project1.jpg?dl=0

The ne555p chip got fried. I got 0 volts at pins 3 and 6.

I have one left.

If someone can step me thru this, I will risk my last chip.

Andy

Hmm, I'm too lazy to check the wires... (and don't know the 555)
How about some capacitance (0.1uF) across the supply rail.
Maybe put some resistance in the power input to limit current..
~ 100 ohms?

How much current does the beeper draw when it's on?

Here's something done with a comparator or opamp.
https://www.dropbox.com/s/gobqe2a4mfqvbuu/light-sens.JPG?dl=0

(the lower circuit scribble)
Comparator could be LM339 or similar.. but then needs a pull up resistor on
the open collector output.

Sign is inverted.
Grin, well that's typical for me. I use circuits to check my
math.
To AK if you build that the output will be low when the light is on.
You can just switch the inputs around.

George H.


I had one engineer who absolutely couldn't tell left from right, and
also couldn't tell logic "0" from logic "1".


--

John Larkin Highland Technology, Inc

lunatic fringe electronics

I just realized some complications of my project.

I want it to notify me when someone crosses the laser path.

I plan on having the switch,led, and buzzer in my apartment

while the rest is outside in a water resistance project box.

But that means I will need wires going from outside to inside.

And I need to figure where to put the photocell so someone does not trip over it etc.

https://www.dropbox.com/s/y4hmrgsm5o7jet2/patio2.jpg?dl=0

https://www.dropbox.com/s/7mp7lgw60m0fgwp/patio1.jpg?dl=0

Would a motion detector or body heat detector be less complicated?

Andy

Less complicated if you buy it ready made, but probably more false
alarms. They are better indoors where there are no pets. They
respond to light, even if it is a wavelength that you can't see. If
you have, for instance, a place that is heated by the sun and a
plant/tree branch that moves in the wind it can give a false positive.

They do sell a combination PIR and "radar" (RF field disturbance)
detector where both must detect something at the same time to cut down
on false alarms.

Passing cars will often trip those from up to ~30 feet away if you are
aiming towards a busy street or nearby driveway.

PIR detectors can also detect people moving through widows both open
and to a lessor extent closed ones.

There's no good way to predict how well it might work unless you have
some prior experience and develop a feel for the application. Then
too, how concerned are you with false alarms?

Most of the garden variety of PIR detectors have a wide field of
coverage, but you can apply baffles to narrow the field, or find one
that has a narrow field - usually combined with greater detection
range. Only way to tell is to get one and play with it.

I was fooling around with an RF field disturbance sensor at work and
it did a pretty good job of alerting me to people walking by my
office/workshop. I just taped it to the wall board inside my office.
The range wasn't fantastic but it did not alert when someone moved
around in a nearby office. I suspect it may have alarmed if someone
in a nearby office was moving something metal around - it was more
sensitive to metal objects than people.

I did make a visible light movement detector. I used two photocells
and a lens along with some op-amps to detect changes in one photocell
that didn't match the other - so it could ignore switching on lights
or the sun rising, but still detect movement. (same principle as PIR
detectors but works in lighted areas only)

I was trying to find a way to protect people from walking into moving
machinery without a physical barrier. We went with a physical barrier
that required the operator to look inside the cage before he pressed
the "start" button. Nothing else was as foolproof.

I will keep working with my laser alarm.



I should be able to set it up.

 

[default]

On Fri, 17 May 2019 17:23:00 -0000 (UTC), Cursitor Doom
<curd@notformail.com> wrote:

On Fri, 17 May 2019 07:06:03 -0400, default wrote:

Most of the garden variety of PIR detectors have a wide field of
coverage, but you can apply baffles to narrow the field, or find one
that has a narrow field - usually combined with greater detection range.
Only way to tell is to get one and play with it.

IME they're a total NIGHTMARE. Fine for inside use, but hopeless for
anything out in the open. FAR too many false alarms. Give me the laser/
photodiode combo any day - inside or out.

I agree. I wouldn't hesitate to use one indoors, preferably up high
by the ceiling and aimed at an area of the floor, and providing no
pets or rodents it would work well.

They are inexpensive. What is an excellent system uses video cameras
and you assign areas of the picture to monitor, but they cost the big
bucks, or did, back when I was messing with that stuff. With video
cameras so cheap today there's probably something that will work with
a cell phone.