Mosquito alarm equivalents?


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B

Bob Minchin

Anita said:
I'm talking about the ultrasonic teen repellants. For a gadget that
just generates a high-pitched sound they're astronomically expensive,
around £500.
http://www.personalalarms.com/store/erol.html?743x902#743X0
It must surely be possible to knock something up with bits from
Maplins that will do the same thing for a tenner?
Not for a tenner but a few tenners yes.
Then make is fully waterproof, add a warranty, acquire countless
approvals, market it etc and then only sell a few thousand tops(?)

Maybe you are confusing cost and price in a market place where
organisations are footing the bill, there is no pressure to keep prices
low as there would be selling into a consumer market.


Bob
 
T

T i m

I'm talking about the ultrasonic teen repellants. For a gadget that
just generates a high-pitched sound they're astronomically expensive,
around £500.
http://www.personalalarms.com/store/erol.html?743x902#743X0
It must surely be possible to knock something up with bits from
Maplins that will do the same thing for a tenner?

You could use a hosepipe on them cheaper, [1] assuming we consider
/also/ potentially assaulting innocent people acceptable here (as we
do with such gadgets)?

I say this as the parent of a child who used to 'suffer' cat / pest
repellant's as she innocently walked down the road.

Cheers, T i m

[1] I have an infrared sensing automatic garden sprinkler that you
could adapt. ;-)
 
A

Arfa Daily

Bob Minchin said:
Not for a tenner but a few tenners yes.
Then make is fully waterproof, add a warranty, acquire countless
approvals, market it etc and then only sell a few thousand tops(?)

Maybe you are confusing cost and price in a market place where
organisations are footing the bill, there is no pressure to keep prices
low as there would be selling into a consumer market.


Bob
Of course you could. In fact you could do it for a few pence ... It's a 555
timer IC (pence) , a couple of resistors (pence), a couple of caps (pence),
a pot to adjust the frequency so you can adjust it to match the frequency of
the beating wings of the female (pence), a piezo buzzer element (pence), and
maybe a small driver transistor if you want it to have a good range (pence).
Apart from this, all you are going to need is a box, battery holder and a
switch. Change out of a fiver. I seem to remember Practically Witless
magazine doing one as a project probably 40 years ago.

If you bung "555 based mosquito repellant" into Google, you will get
cartloads of hits. There are also plenty of schematics based around an
astable made up from two transistors and a handful of components, but the
555 is a good reliable and well behaved solution.

Arfa
 
G

Guest

David Hansen said:
On Tue, 03 Aug 2010 15:08:41 +0100 someone who may be T i m
You could use a hosepipe on them cheaper, [1] assuming we consider
/also/ potentially assaulting innocent people acceptable here (as we
do with such gadgets)?
I find being polite to teenagers, as I am to any other group of
people, is far more effective in the long term than some
undiscriminating gadget which understandably makes teenagers resent
old people like me.

They are not alarms, they are indiscriminate weapons.

MEPs have the right idea, "A committee of MEPs voted unanimously for
a Europe-wide ban on the marketing, sale and use of the Mosquito
acoustic youth dispersal devices in all public places."
<http://www.telegraph.co.uk/news/wor...use-they-infringe-childrens-human-rights.html>
--
David Hansen, Edinburgh

Actually the kids are way ahead of us and have been using the high
frequencies on their mobile ring tones for some time.
If you want to know how old you are, this site seems disappointingly
accurate. Try it:

http://www.freemosquitoringtone.org/

S
 
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T

The Natural Philosopher

Jules said:
That's quite nifty... I can sort-of hear the 15.8KHz one (I can hear the
sound, but it's just not as clear as the slower ones), but not the
16.7KHz one - which is slightly better than my age group (assuming the
site's accurate).

My hearing's somewhat shot though (too many rock concerts and pub gigs in
my youth, too many engines and angle grinders as I've got older :) so
it's nice to know that I can at least still hear the expected frequencies
(what I do find extremely difficult are things such as hearing someone
talking when there's a lot of background noise)

cheers

Jules
12Khz but not 14Khz. Damn near 60. So a bit better than average.
 
G

Guest

Jules Richardson said:
That's quite nifty... I can sort-of hear the 15.8KHz one (I can hear the
sound, but it's just not as clear as the slower ones), but not the
16.7KHz one - which is slightly better than my age group (assuming the
site's accurate).

My hearing's somewhat shot though (too many rock concerts and pub gigs in
my youth, too many engines and angle grinders as I've got older :) so
it's nice to know that I can at least still hear the expected frequencies
(what I do find extremely difficult are things such as hearing someone
talking when there's a lot of background noise)

cheers

Jules
Me too - concertwise: but I always thought I had one very good ear because I
can't stand watches ticking in quiet rooms. Sad to say the problem is
really one bad ear, not one good one!

S
 
A

alexander.keys1

That's quite nifty... I can sort-of hear the 15.8KHz one (I can hear the
sound, but it's just not as clear as the slower ones), but not the
16.7KHz one - which is slightly better than my age group (assuming the
site's accurate).

My hearing's somewhat shot though (too many rock concerts and pub gigs in
my youth, too many engines and angle grinders as I've got older :) so
it's nice to know that I can at least still hear the expected frequencies
(what I do find extremely difficult are things such as hearing someone
talking when there's a lot of background noise)

cheers

Jules
Some of the frequencies quoted are wrong, the sounds seem to be 10 kHz
less than they should be. Also, your computer's sound system might be
less sensitive at higher frequencies.

I can hear the '18.8 kHz' sound via the tichy speakers in my flat
monitor, and I'm 40.
 
G

geoff

In message
I'm talking about the ultrasonic teen repellants. For a gadget that
just generates a high-pitched sound they're astronomically expensive,
around £500.
http://www.personalalarms.com/store/erol.html?743x902#743X0
It must surely be possible to knock something up with bits from
Maplins that will do the same thing for a tenner?
I was talking to a malaria expert (tropical diseases doctor at Edinburgh
Uni) and he confirmed that catnip is an effective mosquito repellant. I
read it in NS a couple of years ago
 
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G

Guest

geoff said:
In message


I was talking to a malaria expert (tropical diseases doctor at Edinburgh
Uni) and he confirmed that catnip is an effective mosquito repellant. I
read it in NS a couple of years ago
Hmm:

Not what the OP was after, but having nuisance youths ripped to pieces by
frenzied moggies has a certain appeal...

S
 
G

geoff

In message
Some of the frequencies quoted are wrong, the sounds seem to be 10 kHz
less than they should be. Also, your computer's sound system might be
less sensitive at higher frequencies.

I can hear the '18.8 kHz' sound via the tichy speakers in my flat
monitor, and I'm 40.

I can hear them all

I'm 92 you know ...
 
G

geoff

Spamlet said:
Hmm:

Not what the OP was after, but having nuisance youths ripped to pieces by
frenzied moggies has a certain appeal...
Yeah - I jumped to the middle bit which, in conjunction with the subject
gave me a senior moment. Everyone else is having one, why can't I ?
 
T

tony sayer

geoff <[email protected]> said:
In message


(what I do find extremely difficult are things such as hearing someone
Thats a symptom of some hearing loss. Try this test on the RNID website.
A sequence of numbers are read out and you enter them on your keyboard.

If your rather good at this they increase the noise along with the
numbers thus making it more difficult.

Have a go...

Might have to copy and paste..


<http://www.rnid.org.uk/howwehelp/hearing_check/take_online_hearing_chec
k/?from=/hearing-check-home-right-bott-panel/>


In a hospital hearing test It might come as a surprise for some to find
that they can be 30 odd dB or more even, down from 400 Hz to around 8
kHz and then might worry about their amp being within a .1 of a dB from
DC to Daylight;!...
 
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A

Andy Dingley

a piezo buzzer element (pence),
Won't work. Last time I looked at this, the squeaker involved (decent
efficiency at the frequency involved, reasonable power capacity) was
around a tenner. You don't just need it to be "a bit annoying", it has
to be heard over background noises, iPods etc.

Also using 555s as an audio oscillator is unlikely to be stable
enough, given the environmental variation (mostly heat) for anything
in an external box on a sunny or icy wall. Really though, just using a
555 as an audio oscillator is enough to make Baby Jesus cry.

If you're trying to install one of these things, a bat detector is
useful too. Or else a calibrated teenager.
 
T

The Medway Handyman

geoff said:
In message


I was talking to a malaria expert (tropical diseases doctor at
Edinburgh Uni) and he confirmed that catnip is an effective mosquito
repellant. I read it in NS a couple of years ago
Is that a Japanese cat?
 
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A

Arfa Daily

Andy Dingley said:
Won't work. Last time I looked at this, the squeaker involved (decent
efficiency at the frequency involved, reasonable power capacity) was
around a tenner. You don't just need it to be "a bit annoying", it has
to be heard over background noises, iPods etc.

Also using 555s as an audio oscillator is unlikely to be stable
enough, given the environmental variation (mostly heat) for anything
in an external box on a sunny or icy wall. Really though, just using a
555 as an audio oscillator is enough to make Baby Jesus cry.

If you're trying to install one of these things, a bat detector is
useful too. Or else a calibrated teenager.
Yeah, ok, maybe you would need a small piezo horn and a driver transistor to
ramp up a genuine mossy repellant into a teen annoyer, but such are
available from Maplin for less than a fiver. And where do you get your 555's
from that they are not stable enough ? I have been using them for the last
40 years at least, and have never had the slightest problem with stability
up to hundreds of kHz in all sorts of temperature-hostile environments. Even
if stability was a problem, it would be simple (and cheap) enough to trade
the 555 for a cheapo crystal with a CMOS divider on the end.

http://www.national.com/mpf/LM/LM555.html#Overview

The one in this spec sheet claims a temperature stability of 0.005% per
degree C. The 'commercial' versions of the IC are specced for operation over
the temperature range of 0 to +70 deg C. Whilst we may see outdoor
temperatures somewhat below zero in the depths of winter, I think it is
unlikely that the other end will be exceeded. Even if this did not prove
stable enough, there are versions specced from -55 deg C to +125 deg C. The
one in that link for instance.

We're hardly talking a precision application here anyway. Even if you did
have to pay a tenner for the horn, you'd still have change out of 15 quid,
even with a box to house it chucked in.

Arfa
 

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