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Computer Nerd Kev
Guest

Sun Jul 10, 2016 8:38 am   



THE SHORT STORY:
^^^^^^^^^^^^^^^^
I want to know what sort of microphone would be suitable for
picking up the sound of a car horn from around 10-20m away.
It would be mounted outdoors and the signal used to detect
the sound of the horn and turn on/off an exterior light.

THE LONG STORY:
^^^^^^^^^^^^^^^
I'm hopefully soon to receive a new headlight to replace the
cracked one that's in my car currently, and I had the thought
yesterday that it might be handy to set it up inside a box. Then
locate it where it can illuminate a part of my driveway which
can be difficult to reverse down at night.

That should be easy enough, though I will be assuming that halogen
car headlight bulbs work OK on 12VAC, unless someone here wishes to
advise me otherwise. The issue is having the light turn off once
I have reached the point of the drive where my car can be returned
to it's rightful forward orientation.

To this end I looked for some radio control circuits, and happened
across a circuit to trigger an action upon receiving a certain
audio tone, with theoretically good scope for relatively fine
adjustment and stability (ETI Circuits Cookbook #5, pg. 80 "Tone
Operated Switch). I'm now thinking of using this to detect the
sound of the car horn, and control the light (perhaps with a small
addition so that two toots are required within a period of time).

This leaves me with the problem of what kind of microphone I should
use to detect the sound of the car horn, and unfortunately this is
an area where I am not very knowledgeable.

To use, I have some cheap Electret microphones, and the head of a
Dynamic microphone I got with some other electronics parts (if it
works). I'm not against buying something if it's fairly Cheap.

Should I simply put an Electret mic at the end of a large cone
pointed in the direction I would be approaching from? Or would
I be better off using something with a bigger diaphragm, even a
speaker? Any advise appreciated.

P.S.
For those worried about me disturbing the peace of my
neighbours, the nearest other residence is over half a
Kilometer away.

--
__ __
#_ < |\| |< _#

Computer Nerd Kev
Guest

Sun Jul 10, 2016 10:19 am   



Sylvia Else <sylvia_at_not.at.this.address> wrote:
Quote:
On 10/07/2016 4:38 PM, Computer Nerd Kev wrote:
THE SHORT STORY:
^^^^^^^^^^^^^^^^
I want to know what sort of microphone would be suitable for
picking up the sound of a car horn from around 10-20m away.
It would be mounted outdoors and the signal used to detect
the sound of the horn and turn on/off an exterior light.

THE LONG STORY:
^^^^^^^^^^^^^^^
I'm hopefully soon to receive a new headlight to replace the
cracked one that's in my car currently, and I had the thought
yesterday that it might be handy to set it up inside a box. Then
locate it where it can illuminate a part of my driveway which
can be difficult to reverse down at night.

That should be easy enough, though I will be assuming that halogen
car headlight bulbs work OK on 12VAC, unless someone here wishes to
advise me otherwise. The issue is having the light turn off once
I have reached the point of the drive where my car can be returned
to it's rightful forward orientation.

Not liking the horn solution, (though I note your comment about the
neighbour's distance), I'm wondering whether a sensor to detect your
headlights while you're reversing would do the job. While headlights
detected, illuminate driveway.


Nice idea, but unfortunately the driveway has a bend in it, which is
the main reason I would like the extra light to make sure I don't
find myself against the power pole that the bend is placed to avoid.

It's possible that my ignorance of microphone capabilities is the
reason I think the horn idea will work. Do you have any reason
to suggest it wouldn't?


Actually, a light sensor and a time delay might work. I dismissed
a manually triggered time delay because I'm not very consistent
in the time it takes for me to go from leaving the house to begining
down the drive. But the headlights would enevitably be pointed at
the sensor until the bend, and the time taken to negotiate the bend
is much easier to determine. There will have to be an ambient light
sensor as well, to disable it during the day.

I might stay with the horn idea for the moment unless someone
educates on why it won't work. My worry with the light sensor is
that I'd have to fiddle with it to make sure light from the house
and reflected light from the driveway light itself didn't trigger
it. It would probably also mean that I couldn't leave the carport
light on for when I got back, if desired.

In any case, many thanks for the suggestion. I might end up going
with it.

--
__ __
#_ < |\| |< _#

Computer Nerd Kev
Guest

Sun Jul 10, 2016 12:04 pm   



F Murtz <haggisz_at_hotmail.com> wrote:
Quote:

One of the problems is legality, unless on private property, there are
laws on use of horns which do not include turning on lights. Smile


Oh it's very much on private property. What I'm calling the drive is
really just the drive to the carport. I reverse out of that, past the
house, then begin the drive proper (facing the right way 'round).

The road (lane technically) at the end gets one car an hour on a busy
day, and probably hasn't seen a policeman in many a year.

Still, I'd be happy to petition for an ammendment to the road rules
if my idea catches on. :)

--
__ __
#_ < |\| |< _#

Sylvia Else
Guest

Sun Jul 10, 2016 1:12 pm   



On 10/07/2016 4:38 PM, Computer Nerd Kev wrote:
Quote:
THE SHORT STORY:
^^^^^^^^^^^^^^^^
I want to know what sort of microphone would be suitable for
picking up the sound of a car horn from around 10-20m away.
It would be mounted outdoors and the signal used to detect
the sound of the horn and turn on/off an exterior light.

THE LONG STORY:
^^^^^^^^^^^^^^^
I'm hopefully soon to receive a new headlight to replace the
cracked one that's in my car currently, and I had the thought
yesterday that it might be handy to set it up inside a box. Then
locate it where it can illuminate a part of my driveway which
can be difficult to reverse down at night.

That should be easy enough, though I will be assuming that halogen
car headlight bulbs work OK on 12VAC, unless someone here wishes to
advise me otherwise. The issue is having the light turn off once
I have reached the point of the drive where my car can be returned
to it's rightful forward orientation.


Not liking the horn solution, (though I note your comment about the
neighbour's distance), I'm wondering whether a sensor to detect your
headlights while you're reversing would do the job. While headlights
detected, illuminate driveway.

Sylvia.

Computer Nerd Kev
Guest

Sun Jul 10, 2016 1:26 pm   



Sylvia Else <sylvia_at_not.at.this.address> wrote:
Quote:
On 10/07/2016 6:19 PM, Computer Nerd Kev wrote:
Sylvia Else <sylvia_at_not.at.this.address> wrote:
On 10/07/2016 4:38 PM, Computer Nerd Kev wrote:
THE SHORT STORY:
^^^^^^^^^^^^^^^^
I want to know what sort of microphone would be suitable for
picking up the sound of a car horn from around 10-20m away.
It would be mounted outdoors and the signal used to detect
the sound of the horn and turn on/off an exterior light.

THE LONG STORY:
^^^^^^^^^^^^^^^
I'm hopefully soon to receive a new headlight to replace the
cracked one that's in my car currently, and I had the thought
yesterday that it might be handy to set it up inside a box. Then
locate it where it can illuminate a part of my driveway which
can be difficult to reverse down at night.

That should be easy enough, though I will be assuming that halogen
car headlight bulbs work OK on 12VAC, unless someone here wishes to
advise me otherwise. The issue is having the light turn off once
I have reached the point of the drive where my car can be returned
to it's rightful forward orientation.

Not liking the horn solution, (though I note your comment about the
neighbour's distance), I'm wondering whether a sensor to detect your
headlights while you're reversing would do the job. While headlights
detected, illuminate driveway.

Nice idea, but unfortunately the driveway has a bend in it, which is
the main reason I would like the extra light to make sure I don't
find myself against the power pole that the bend is placed to avoid.

It's possible that my ignorance of microphone capabilities is the
reason I think the horn idea will work. Do you have any reason
to suggest it wouldn't?

Not really, but you'd need an amplifier and a filter to separate the
horn from other noises (unless spurious triggering doesn't bother you).
If you want to use the horn to turn it off, you'd also need to implement
a toggle.


The circuit from ETI should take the place of a filter, and be more
adjustable. It detects peaks in the sound wave and measures the period
between them to determine the frequency. If the frequency is within a
certain range, it produces a constant HIGH output.

Quote:
You might find that it triggers in heavy rain (the noise of which has a
wide spectrum). If you're using the horn to turn off as well, then heavy
rain might cause spurious turn-offs. No doubt some effort could be
expended to detect the wide spectrum, and ignore it, but you'd then want
to make sure it still responds to the horn even in heavy rain - it all
starts to get rather complicated.


Yes, perhaps. I hadn't thought of rain, but one other issue will be
wind. There aren't many wind breaks around and, looking at the local
forcast, it would have to work in winds at (very) least up to 50Km/h.
You'd have both the wind noise and the effect of the wind blowing
away the sound of the horn (although it would be rare for a strong
wind to be blowing from the bearing directly behind the microphone).
I wouldn't be surprised if I had trouble myself hearing a car horn
15m away while standing in a 100+Km/h wind gust, and there are a lot
of other noises introduced by surrounding structures in those
conditions as well.

The wind, if it were to blow near parallel with the line between the
car and the microphone would also distort the frequency due to the
doppler effect. Well I think that's right anyway...

Quote:
Actually, a light sensor and a time delay might work. I dismissed
a manually triggered time delay because I'm not very consistent
in the time it takes for me to go from leaving the house to begining
down the drive. But the headlights would enevitably be pointed at
the sensor until the bend, and the time taken to negotiate the bend
is much easier to determine. There will have to be an ambient light
sensor as well, to disable it during the day.


I might stay with the horn idea for the moment unless someone
educates on why it won't work. My worry with the light sensor is
that I'd have to fiddle with it to make sure light from the house
and reflected light from the driveway light itself didn't trigger
it. It would probably also mean that I couldn't leave the carport
light on for when I got back, if desired.

Putting the sensor inside a tube (painted matt black inside) pointed
down the driveway should eliminate spurious operation - headlights are
pretty bright, so the sensor need not be so sensitive. You may even find
that you don't need daytime suppression.


The problem is that the drive isn't very level (it's gravel), so
the headlight beam will move vertically as pot-holes and pot-hole
repairs are encountered. There should be a middle ground where a
tube or box will allow enough light in, I just fear it might take
a fair bit of tinkering in the dark of night.

Once set up perfectly, it sounds like it might be more reliable
than the horn though. Yes, I'll go gather up what light sensors
I've got.

Comments on microphones still appreciated though, both is always
an option!

--
__ __
#_ < |\| |< _#

F Murtz
Guest

Sun Jul 10, 2016 3:13 pm   



Computer Nerd Kev wrote:
Quote:
Sylvia Else <sylvia_at_not.at.this.address> wrote:
On 10/07/2016 4:38 PM, Computer Nerd Kev wrote:
THE SHORT STORY:
^^^^^^^^^^^^^^^^
I want to know what sort of microphone would be suitable for
picking up the sound of a car horn from around 10-20m away.
It would be mounted outdoors and the signal used to detect
the sound of the horn and turn on/off an exterior light.

THE LONG STORY:
^^^^^^^^^^^^^^^
I'm hopefully soon to receive a new headlight to replace the
cracked one that's in my car currently, and I had the thought
yesterday that it might be handy to set it up inside a box. Then
locate it where it can illuminate a part of my driveway which
can be difficult to reverse down at night.

That should be easy enough, though I will be assuming that halogen
car headlight bulbs work OK on 12VAC, unless someone here wishes to
advise me otherwise. The issue is having the light turn off once
I have reached the point of the drive where my car can be returned
to it's rightful forward orientation.

Not liking the horn solution, (though I note your comment about the
neighbour's distance), I'm wondering whether a sensor to detect your
headlights while you're reversing would do the job. While headlights
detected, illuminate driveway.

Nice idea, but unfortunately the driveway has a bend in it, which is
the main reason I would like the extra light to make sure I don't
find myself against the power pole that the bend is placed to avoid.

It's possible that my ignorance of microphone capabilities is the
reason I think the horn idea will work. Do you have any reason
to suggest it wouldn't?


Actually, a light sensor and a time delay might work. I dismissed
a manually triggered time delay because I'm not very consistent
in the time it takes for me to go from leaving the house to begining
down the drive. But the headlights would enevitably be pointed at
the sensor until the bend, and the time taken to negotiate the bend
is much easier to determine. There will have to be an ambient light
sensor as well, to disable it during the day.

I might stay with the horn idea for the moment unless someone
educates on why it won't work. My worry with the light sensor is
that I'd have to fiddle with it to make sure light from the house
and reflected light from the driveway light itself didn't trigger
it. It would probably also mean that I couldn't leave the carport
light on for when I got back, if desired.

In any case, many thanks for the suggestion. I might end up going
with it.

One of the problems is legality, unless on private property, there are
laws on use of horns which do not include turning on lights. Smile

Computer Nerd Kev
Guest

Sun Jul 10, 2016 3:18 pm   



Sylvia Else <sylvia_at_not.at.this.address> wrote:
Quote:
On 10/07/2016 9:26 PM, Computer Nerd Kev wrote:
Sylvia Else <sylvia_at_not.at.this.address> wrote:
On 10/07/2016 6:19 PM, Computer Nerd Kev wrote:
Sylvia Else <sylvia_at_not.at.this.address> wrote:
On 10/07/2016 4:38 PM, Computer Nerd Kev wrote:
THE SHORT STORY:
^^^^^^^^^^^^^^^^
I want to know what sort of microphone would be suitable for
picking up the sound of a car horn from around 10-20m away.
It would be mounted outdoors and the signal used to detect
the sound of the horn and turn on/off an exterior light.

THE LONG STORY:
^^^^^^^^^^^^^^^
I'm hopefully soon to receive a new headlight to replace the
cracked one that's in my car currently, and I had the thought
yesterday that it might be handy to set it up inside a box. Then
locate it where it can illuminate a part of my driveway which
can be difficult to reverse down at night.

That should be easy enough, though I will be assuming that halogen
car headlight bulbs work OK on 12VAC, unless someone here wishes to
advise me otherwise. The issue is having the light turn off once
I have reached the point of the drive where my car can be returned
to it's rightful forward orientation.

Not liking the horn solution, (though I note your comment about the
neighbour's distance), I'm wondering whether a sensor to detect your
headlights while you're reversing would do the job. While headlights
detected, illuminate driveway.

Nice idea, but unfortunately the driveway has a bend in it, which is
the main reason I would like the extra light to make sure I don't
find myself against the power pole that the bend is placed to avoid.

It's possible that my ignorance of microphone capabilities is the
reason I think the horn idea will work. Do you have any reason
to suggest it wouldn't?

Not really, but you'd need an amplifier and a filter to separate the
horn from other noises (unless spurious triggering doesn't bother you).
If you want to use the horn to turn it off, you'd also need to implement
a toggle.

The circuit from ETI should take the place of a filter, and be more
adjustable. It detects peaks in the sound wave and measures the period
between them to determine the frequency. If the frequency is within a
certain range, it produces a constant HIGH output.

You might find that it triggers in heavy rain (the noise of which has a
wide spectrum). If you're using the horn to turn off as well, then heavy
rain might cause spurious turn-offs. No doubt some effort could be
expended to detect the wide spectrum, and ignore it, but you'd then want
to make sure it still responds to the horn even in heavy rain - it all
starts to get rather complicated.

Yes, perhaps. I hadn't thought of rain, but one other issue will be
wind. There aren't many wind breaks around and, looking at the local
forcast, it would have to work in winds at (very) least up to 50Km/h.
You'd have both the wind noise and the effect of the wind blowing
away the sound of the horn (although it would be rare for a strong
wind to be blowing from the bearing directly behind the microphone).
I wouldn't be surprised if I had trouble myself hearing a car horn
15m away while standing in a 100+Km/h wind gust, and there are a lot
of other noises introduced by surrounding structures in those
conditions as well.

The wind, if it were to blow near parallel with the line between the
car and the microphone would also distort the frequency due to the
doppler effect. Well I think that's right anyway...

No, the Doppler effect only depends on the difference in speed between
the sender and the receiver - the effects of the wind speed cancel out.
The speed of the vehicle has an effect, but I gather you'll not be going
very fast at that point.


Ah, I understand. Thanks for that.

Quote:
Actually, a light sensor and a time delay might work. I dismissed
a manually triggered time delay because I'm not very consistent
in the time it takes for me to go from leaving the house to begining
down the drive. But the headlights would enevitably be pointed at
the sensor until the bend, and the time taken to negotiate the bend
is much easier to determine. There will have to be an ambient light
sensor as well, to disable it during the day.


I might stay with the horn idea for the moment unless someone
educates on why it won't work. My worry with the light sensor is
that I'd have to fiddle with it to make sure light from the house
and reflected light from the driveway light itself didn't trigger
it. It would probably also mean that I couldn't leave the carport
light on for when I got back, if desired.

Putting the sensor inside a tube (painted matt black inside) pointed
down the driveway should eliminate spurious operation - headlights are
pretty bright, so the sensor need not be so sensitive. You may even find
that you don't need daytime suppression.

The problem is that the drive isn't very level (it's gravel), so
the headlight beam will move vertically as pot-holes and pot-hole
repairs are encountered. There should be a middle ground where a
tube or box will allow enough light in, I just fear it might take
a fair bit of tinkering in the dark of night.

From what I gathered, this solution requires a delay timer anyway, to
deal with the bend in the driveway. Just be sure that it gets reset
every time the sensor detects the headlights. Then as long as the sensor
is not outside the beam for a very extended period, it will work.


Yes, that's true. I'll probably set a decent time of three minutes or
so as there's no great rush to turn the light off, so it should be
fine even if it's only triggered when the vehicle first takes off.

OK, I'll go with this solution unless someone convinces me that most
of your and my worries about the microphone are false.

Thanks for the advise.

--
__ __
#_ < |\| |< _#

Sylvia Else
Guest

Sun Jul 10, 2016 3:51 pm   



On 10/07/2016 6:19 PM, Computer Nerd Kev wrote:
Quote:
Sylvia Else <sylvia_at_not.at.this.address> wrote:
On 10/07/2016 4:38 PM, Computer Nerd Kev wrote:
THE SHORT STORY:
^^^^^^^^^^^^^^^^
I want to know what sort of microphone would be suitable for
picking up the sound of a car horn from around 10-20m away.
It would be mounted outdoors and the signal used to detect
the sound of the horn and turn on/off an exterior light.

THE LONG STORY:
^^^^^^^^^^^^^^^
I'm hopefully soon to receive a new headlight to replace the
cracked one that's in my car currently, and I had the thought
yesterday that it might be handy to set it up inside a box. Then
locate it where it can illuminate a part of my driveway which
can be difficult to reverse down at night.

That should be easy enough, though I will be assuming that halogen
car headlight bulbs work OK on 12VAC, unless someone here wishes to
advise me otherwise. The issue is having the light turn off once
I have reached the point of the drive where my car can be returned
to it's rightful forward orientation.

Not liking the horn solution, (though I note your comment about the
neighbour's distance), I'm wondering whether a sensor to detect your
headlights while you're reversing would do the job. While headlights
detected, illuminate driveway.

Nice idea, but unfortunately the driveway has a bend in it, which is
the main reason I would like the extra light to make sure I don't
find myself against the power pole that the bend is placed to avoid.

It's possible that my ignorance of microphone capabilities is the
reason I think the horn idea will work. Do you have any reason
to suggest it wouldn't?


Not really, but you'd need an amplifier and a filter to separate the
horn from other noises (unless spurious triggering doesn't bother you).
If you want to use the horn to turn it off, you'd also need to implement
a toggle.

You might find that it triggers in heavy rain (the noise of which has a
wide spectrum). If you're using the horn to turn off as well, then heavy
rain might cause spurious turn-offs. No doubt some effort could be
expended to detect the wide spectrum, and ignore it, but you'd then want
to make sure it still responds to the horn even in heavy rain - it all
starts to get rather complicated.

Quote:


Actually, a light sensor and a time delay might work. I dismissed
a manually triggered time delay because I'm not very consistent
in the time it takes for me to go from leaving the house to begining
down the drive. But the headlights would enevitably be pointed at
the sensor until the bend, and the time taken to negotiate the bend
is much easier to determine. There will have to be an ambient light
sensor as well, to disable it during the day.


I might stay with the horn idea for the moment unless someone
educates on why it won't work. My worry with the light sensor is
that I'd have to fiddle with it to make sure light from the house
and reflected light from the driveway light itself didn't trigger
it. It would probably also mean that I couldn't leave the carport
light on for when I got back, if desired.


Putting the sensor inside a tube (painted matt black inside) pointed
down the driveway should eliminate spurious operation - headlights are
pretty bright, so the sensor need not be so sensitive. You may even find
that you don't need daytime suppression.

Sylvia.

Phil Allison
Guest

Sun Jul 10, 2016 4:01 pm   



Computer Nerd Kev wrote:
Quote:


.


The circuit from ETI should take the place of a filter, and be more
adjustable. It detects peaks in the sound wave and measures the period
between them to determine the frequency. If the frequency is within a
certain range, it produces a constant HIGH output.


** Most cars have two horns with slightly different frequencies - so the combined sound is a dual tone chord with rapid amplitude modulation.

I have no info on that old ETI circuit so cannot say if it is compatible with a car horn sound.

Electret mics have more output than dynamic capsules so that would be my pic for the task - with some pre-amplification and filtering of low frequencies by careful choice of coupling caps.

Good luck.


..... Phil

Sylvia Else
Guest

Sun Jul 10, 2016 6:06 pm   



On 10/07/2016 9:26 PM, Computer Nerd Kev wrote:
Quote:
Sylvia Else <sylvia_at_not.at.this.address> wrote:
On 10/07/2016 6:19 PM, Computer Nerd Kev wrote:
Sylvia Else <sylvia_at_not.at.this.address> wrote:
On 10/07/2016 4:38 PM, Computer Nerd Kev wrote:
THE SHORT STORY:
^^^^^^^^^^^^^^^^
I want to know what sort of microphone would be suitable for
picking up the sound of a car horn from around 10-20m away.
It would be mounted outdoors and the signal used to detect
the sound of the horn and turn on/off an exterior light.

THE LONG STORY:
^^^^^^^^^^^^^^^
I'm hopefully soon to receive a new headlight to replace the
cracked one that's in my car currently, and I had the thought
yesterday that it might be handy to set it up inside a box. Then
locate it where it can illuminate a part of my driveway which
can be difficult to reverse down at night.

That should be easy enough, though I will be assuming that halogen
car headlight bulbs work OK on 12VAC, unless someone here wishes to
advise me otherwise. The issue is having the light turn off once
I have reached the point of the drive where my car can be returned
to it's rightful forward orientation.

Not liking the horn solution, (though I note your comment about the
neighbour's distance), I'm wondering whether a sensor to detect your
headlights while you're reversing would do the job. While headlights
detected, illuminate driveway.

Nice idea, but unfortunately the driveway has a bend in it, which is
the main reason I would like the extra light to make sure I don't
find myself against the power pole that the bend is placed to avoid.

It's possible that my ignorance of microphone capabilities is the
reason I think the horn idea will work. Do you have any reason
to suggest it wouldn't?

Not really, but you'd need an amplifier and a filter to separate the
horn from other noises (unless spurious triggering doesn't bother you).
If you want to use the horn to turn it off, you'd also need to implement
a toggle.

The circuit from ETI should take the place of a filter, and be more
adjustable. It detects peaks in the sound wave and measures the period
between them to determine the frequency. If the frequency is within a
certain range, it produces a constant HIGH output.

You might find that it triggers in heavy rain (the noise of which has a
wide spectrum). If you're using the horn to turn off as well, then heavy
rain might cause spurious turn-offs. No doubt some effort could be
expended to detect the wide spectrum, and ignore it, but you'd then want
to make sure it still responds to the horn even in heavy rain - it all
starts to get rather complicated.

Yes, perhaps. I hadn't thought of rain, but one other issue will be
wind. There aren't many wind breaks around and, looking at the local
forcast, it would have to work in winds at (very) least up to 50Km/h.
You'd have both the wind noise and the effect of the wind blowing
away the sound of the horn (although it would be rare for a strong
wind to be blowing from the bearing directly behind the microphone).
I wouldn't be surprised if I had trouble myself hearing a car horn
15m away while standing in a 100+Km/h wind gust, and there are a lot
of other noises introduced by surrounding structures in those
conditions as well.

The wind, if it were to blow near parallel with the line between the
car and the microphone would also distort the frequency due to the
doppler effect. Well I think that's right anyway...


No, the Doppler effect only depends on the difference in speed between
the sender and the receiver - the effects of the wind speed cancel out.
The speed of the vehicle has an effect, but I gather you'll not be going
very fast at that point.

Quote:

Actually, a light sensor and a time delay might work. I dismissed
a manually triggered time delay because I'm not very consistent
in the time it takes for me to go from leaving the house to begining
down the drive. But the headlights would enevitably be pointed at
the sensor until the bend, and the time taken to negotiate the bend
is much easier to determine. There will have to be an ambient light
sensor as well, to disable it during the day.


I might stay with the horn idea for the moment unless someone
educates on why it won't work. My worry with the light sensor is
that I'd have to fiddle with it to make sure light from the house
and reflected light from the driveway light itself didn't trigger
it. It would probably also mean that I couldn't leave the carport
light on for when I got back, if desired.

Putting the sensor inside a tube (painted matt black inside) pointed
down the driveway should eliminate spurious operation - headlights are
pretty bright, so the sensor need not be so sensitive. You may even find
that you don't need daytime suppression.

The problem is that the drive isn't very level (it's gravel), so
the headlight beam will move vertically as pot-holes and pot-hole
repairs are encountered. There should be a middle ground where a
tube or box will allow enough light in, I just fear it might take
a fair bit of tinkering in the dark of night.


From what I gathered, this solution requires a delay timer anyway, to
deal with the bend in the driveway. Just be sure that it gets reset
every time the sensor detects the headlights. Then as long as the sensor
is not outside the beam for a very extended period, it will work.

Sylvia.

Fred Smith
Guest

Mon Jul 11, 2016 12:36 am   



Wait till the lyre birds start copying your car horn...

Trevor Wilson
Guest

Mon Jul 11, 2016 2:55 am   



On 10/07/2016 4:38 PM, Computer Nerd Kev wrote:
Quote:
THE SHORT STORY:
^^^^^^^^^^^^^^^^
I want to know what sort of microphone would be suitable for
picking up the sound of a car horn from around 10-20m away.
It would be mounted outdoors and the signal used to detect
the sound of the horn and turn on/off an exterior light.

THE LONG STORY:
^^^^^^^^^^^^^^^
I'm hopefully soon to receive a new headlight to replace the
cracked one that's in my car currently, and I had the thought
yesterday that it might be handy to set it up inside a box. Then
locate it where it can illuminate a part of my driveway which
can be difficult to reverse down at night.

That should be easy enough, though I will be assuming that halogen
car headlight bulbs work OK on 12VAC, unless someone here wishes to
advise me otherwise. The issue is having the light turn off once
I have reached the point of the drive where my car can be returned
to it's rightful forward orientation.

To this end I looked for some radio control circuits, and happened
across a circuit to trigger an action upon receiving a certain
audio tone, with theoretically good scope for relatively fine
adjustment and stability (ETI Circuits Cookbook #5, pg. 80 "Tone
Operated Switch). I'm now thinking of using this to detect the
sound of the car horn, and control the light (perhaps with a small
addition so that two toots are required within a period of time).

This leaves me with the problem of what kind of microphone I should
use to detect the sound of the car horn, and unfortunately this is
an area where I am not very knowledgeable.

To use, I have some cheap Electret microphones, and the head of a
Dynamic microphone I got with some other electronics parts (if it
works). I'm not against buying something if it's fairly Cheap.

Should I simply put an Electret mic at the end of a large cone
pointed in the direction I would be approaching from? Or would
I be better off using something with a bigger diaphragm, even a
speaker? Any advise appreciated.

P.S.
For those worried about me disturbing the peace of my
neighbours, the nearest other residence is over half a
Kilometer away.


**There are a large number of far better schemes which can be employed,
very inexpensively. AT the low end, you could buy a movement sensor lamp
assembly. These things are pretty much plug and play. There is usually
an adjustment for sensitivity, ambient light level and length of time
for illumination. Buy one. Less than 50 Bucks.

--
Trevor Wilson
www.rageaudio.com.au

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Tony
Guest

Mon Jul 11, 2016 6:25 am   



On 11-Jul-16 4:55 AM, Trevor Wilson wrote:
Quote:
On 10/07/2016 4:38 PM, Computer Nerd Kev wrote:
THE SHORT STORY:
^^^^^^^^^^^^^^^^
I want to know what sort of microphone would be suitable for
picking up the sound of a car horn from around 10-20m away.
It would be mounted outdoors and the signal used to detect
the sound of the horn and turn on/off an exterior light.

THE LONG STORY:
^^^^^^^^^^^^^^^
I'm hopefully soon to receive a new headlight to replace the
cracked one that's in my car currently, and I had the thought
yesterday that it might be handy to set it up inside a box. Then
locate it where it can illuminate a part of my driveway which
can be difficult to reverse down at night.

That should be easy enough, though I will be assuming that halogen
car headlight bulbs work OK on 12VAC, unless someone here wishes to
advise me otherwise. The issue is having the light turn off once
I have reached the point of the drive where my car can be returned
to it's rightful forward orientation.

To this end I looked for some radio control circuits, and happened
across a circuit to trigger an action upon receiving a certain
audio tone, with theoretically good scope for relatively fine
adjustment and stability (ETI Circuits Cookbook #5, pg. 80 "Tone
Operated Switch). I'm now thinking of using this to detect the
sound of the car horn, and control the light (perhaps with a small
addition so that two toots are required within a period of time).

This leaves me with the problem of what kind of microphone I should
use to detect the sound of the car horn, and unfortunately this is
an area where I am not very knowledgeable.

To use, I have some cheap Electret microphones, and the head of a
Dynamic microphone I got with some other electronics parts (if it
works). I'm not against buying something if it's fairly Cheap.

Should I simply put an Electret mic at the end of a large cone
pointed in the direction I would be approaching from? Or would
I be better off using something with a bigger diaphragm, even a
speaker? Any advise appreciated.

P.S.
For those worried about me disturbing the peace of my
neighbours, the nearest other residence is over half a
Kilometer away.


**There are a large number of far better schemes which can be employed,
very inexpensively. AT the low end, you could buy a movement sensor lamp
assembly. These things are pretty much plug and play. There is usually
an adjustment for sensitivity, ambient light level and length of time
for illumination. Buy one. Less than 50 Bucks.


Like this one, $6.29 delivered and available in 12V:

http://r.ebay.com/ddOSeF

Tony

Phil Allison
Guest

Mon Jul 11, 2016 6:25 am   



Trevor Wilson wrote:

Quote:


**There are a large number of far better schemes which can be employed,
very inexpensively. AT the low end, you could buy a movement sensor lamp
assembly. These things are pretty much plug and play.



** The OP has asked for a light switch system that works over a 20m range and without necessarily a direct line of sight and preferably only when he operates his car horn.

A PIR detector unit will fail on all counts - cos its lacks range and the ability to see around corners plus triggers any time of day to any moving object, like a tree blowing in the wind.

His idea can work well, a car horn is a loud and distinctive sound particularly in a rural environment.

But designing and building it will take a tad more engineering than he presently imagines.


..... Phil

Trevor Wilson
Guest

Mon Jul 11, 2016 6:43 am   



On 10/07/2016 11:18 PM, Computer Nerd Kev wrote:
Quote:
Sylvia Else <sylvia_at_not.at.this.address> wrote:
On 10/07/2016 9:26 PM, Computer Nerd Kev wrote:
Sylvia Else <sylvia_at_not.at.this.address> wrote:
On 10/07/2016 6:19 PM, Computer Nerd Kev wrote:
Sylvia Else <sylvia_at_not.at.this.address> wrote:
On 10/07/2016 4:38 PM, Computer Nerd Kev wrote:
THE SHORT STORY:
^^^^^^^^^^^^^^^^
I want to know what sort of microphone would be suitable for
picking up the sound of a car horn from around 10-20m away.
It would be mounted outdoors and the signal used to detect
the sound of the horn and turn on/off an exterior light.

THE LONG STORY:
^^^^^^^^^^^^^^^
I'm hopefully soon to receive a new headlight to replace the
cracked one that's in my car currently, and I had the thought
yesterday that it might be handy to set it up inside a box. Then
locate it where it can illuminate a part of my driveway which
can be difficult to reverse down at night.

That should be easy enough, though I will be assuming that halogen
car headlight bulbs work OK on 12VAC, unless someone here wishes to
advise me otherwise. The issue is having the light turn off once
I have reached the point of the drive where my car can be returned
to it's rightful forward orientation.

Not liking the horn solution, (though I note your comment about the
neighbour's distance), I'm wondering whether a sensor to detect your
headlights while you're reversing would do the job. While headlights
detected, illuminate driveway.

Nice idea, but unfortunately the driveway has a bend in it, which is
the main reason I would like the extra light to make sure I don't
find myself against the power pole that the bend is placed to avoid.

It's possible that my ignorance of microphone capabilities is the
reason I think the horn idea will work. Do you have any reason
to suggest it wouldn't?

Not really, but you'd need an amplifier and a filter to separate the
horn from other noises (unless spurious triggering doesn't bother you).
If you want to use the horn to turn it off, you'd also need to implement
a toggle.

The circuit from ETI should take the place of a filter, and be more
adjustable. It detects peaks in the sound wave and measures the period
between them to determine the frequency. If the frequency is within a
certain range, it produces a constant HIGH output.

You might find that it triggers in heavy rain (the noise of which has a
wide spectrum). If you're using the horn to turn off as well, then heavy
rain might cause spurious turn-offs. No doubt some effort could be
expended to detect the wide spectrum, and ignore it, but you'd then want
to make sure it still responds to the horn even in heavy rain - it all
starts to get rather complicated.

Yes, perhaps. I hadn't thought of rain, but one other issue will be
wind. There aren't many wind breaks around and, looking at the local
forcast, it would have to work in winds at (very) least up to 50Km/h.
You'd have both the wind noise and the effect of the wind blowing
away the sound of the horn (although it would be rare for a strong
wind to be blowing from the bearing directly behind the microphone).
I wouldn't be surprised if I had trouble myself hearing a car horn
15m away while standing in a 100+Km/h wind gust, and there are a lot
of other noises introduced by surrounding structures in those
conditions as well.

The wind, if it were to blow near parallel with the line between the
car and the microphone would also distort the frequency due to the
doppler effect. Well I think that's right anyway...

No, the Doppler effect only depends on the difference in speed between
the sender and the receiver - the effects of the wind speed cancel out.
The speed of the vehicle has an effect, but I gather you'll not be going
very fast at that point.

Ah, I understand. Thanks for that.

Actually, a light sensor and a time delay might work. I dismissed
a manually triggered time delay because I'm not very consistent
in the time it takes for me to go from leaving the house to begining
down the drive. But the headlights would enevitably be pointed at
the sensor until the bend, and the time taken to negotiate the bend
is much easier to determine. There will have to be an ambient light
sensor as well, to disable it during the day.


I might stay with the horn idea for the moment unless someone
educates on why it won't work. My worry with the light sensor is
that I'd have to fiddle with it to make sure light from the house
and reflected light from the driveway light itself didn't trigger
it. It would probably also mean that I couldn't leave the carport
light on for when I got back, if desired.

Putting the sensor inside a tube (painted matt black inside) pointed
down the driveway should eliminate spurious operation - headlights are
pretty bright, so the sensor need not be so sensitive. You may even find
that you don't need daytime suppression.

The problem is that the drive isn't very level (it's gravel), so
the headlight beam will move vertically as pot-holes and pot-hole
repairs are encountered. There should be a middle ground where a
tube or box will allow enough light in, I just fear it might take
a fair bit of tinkering in the dark of night.

From what I gathered, this solution requires a delay timer anyway, to
deal with the bend in the driveway. Just be sure that it gets reset
every time the sensor detects the headlights. Then as long as the sensor
is not outside the beam for a very extended period, it will work.

Yes, that's true. I'll probably set a decent time of three minutes or
so as there's no great rush to turn the light off, so it should be
fine even if it's only triggered when the vehicle first takes off.

OK, I'll go with this solution unless someone convinces me that most
of your and my worries about the microphone are false.

Thanks for the advise.


**Even better, would be some of these:

http://www.ebay.com/itm/Waterproof-14LED-Dual-Head-Solar-Powered-Yard-Lights-PIR-Motion-Sensor-Spotlight-/121957783746?hash=item1c654018c2:g:2iQAAOSwubRXEbBU

No wiring, no hassle. I use one for my driveway.

--
Trevor Wilson
www.rageaudio.com.au

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