Placing noise on mains?

T

Terry Pinnell

Guest
Some of the household circuits gadgets I made decades ago have
recently been getting activated spuriously. I suspect some sort of
interference or spikes or whatever on the 240 V mains supply.

One example is a buzzer in the shed that's normally triggered from a
push button in the house - primarily my wife's 'come in for dinner'
call. (It's essentially a CMOS monostable, NPN transistor and a
bistable feeding a small earpiece speaker). But sometimes it gets
triggered unexpectedly, perhaps by an appliance in the house (boiler,
washing machine, etc). Or maybe by an external source nearby. And it
always gets triggered when I switch on the fluorescent lights in the
adjacent garage. There are other gadgets which suffer similarly too.

So in order to experiment with fixing this, I'm seeking a reliable way
of generating mains noise myself. Any practical circuit ideas would be
appreciated please.

--
Terry, East Grinstead, UK
 
On 10/2/2015 1:41 AM, Terry Pinnell wrote:
Some of the household circuits gadgets I made decades ago have
recently been getting activated spuriously. I suspect some sort of
interference or spikes or whatever on the 240 V mains supply.

One example is a buzzer in the shed that's normally triggered from a
push button in the house - primarily my wife's 'come in for dinner'
call. (It's essentially a CMOS monostable, NPN transistor and a
bistable feeding a small earpiece speaker). But sometimes it gets
triggered unexpectedly, perhaps by an appliance in the house (boiler,
washing machine, etc). Or maybe by an external source nearby. And it
always gets triggered when I switch on the fluorescent lights in the
adjacent garage. There are other gadgets which suffer similarly too.

So in order to experiment with fixing this, I'm seeking a reliable way
of generating mains noise myself. Any practical circuit ideas would be
appreciated please.

AC motor with brushes.
Click to expand...
 
On Fri, 02 Oct 2015 06:41:57 +0100, Terry Pinnell wrote:

Some of the household circuits gadgets I made decades ago have recently
been getting activated spuriously. I suspect some sort of interference
or spikes or whatever on the 240 V mains supply.

One example is a buzzer in the shed that's normally triggered from a
push button in the house - primarily my wife's 'come in for dinner'
call. (It's essentially a CMOS monostable, NPN transistor and a bistable
feeding a small earpiece speaker). But sometimes it gets triggered
unexpectedly, perhaps by an appliance in the house (boiler, washing
machine, etc). Or maybe by an external source nearby. And it always gets
triggered when I switch on the fluorescent lights in the adjacent
garage. There are other gadgets which suffer similarly too.

So in order to experiment with fixing this, I'm seeking a reliable way
of generating mains noise myself. Any practical circuit ideas would be
appreciated please.
Click to expand...

A suggestion: have you considered rebuilding the gadgets? 20 or 30 years
sounds like it will degrade the component parts enough that they won't
behave like they used to.
 
On Fri, 02 Oct 2015 06:41:57 +0100, Terry Pinnell wrote:

Some of the household circuits gadgets I made decades ago have recently
been getting activated spuriously. I suspect some sort of interference
or spikes or whatever on the 240 V mains supply.

One example is a buzzer in the shed that's normally triggered from a
push button in the house - primarily my wife's 'come in for dinner'
call. (It's essentially a CMOS monostable, NPN transistor and a bistable
feeding a small earpiece speaker). But sometimes it gets triggered
unexpectedly, perhaps by an appliance in the house (boiler, washing
machine, etc). Or maybe by an external source nearby. And it always gets
triggered when I switch on the fluorescent lights in the adjacent
garage. There are other gadgets which suffer similarly too.

So in order to experiment with fixing this, I'm seeking a reliable way
of generating mains noise myself. Any practical circuit ideas would be
appreciated please.
Click to expand...

Use a relay (in the shed) to turn on the buzzer. The low impedance, slow
speed of the relay will ignore short term noise that a high impedance
circuit will react to.

An ounce of prevention at the source of the noise is worth a pound of
circuitry at the sensitive end -

You can also lower the impedance with a resistor across the line, and put
a filter cap across the signal and ground too to slow the response. But
a relay is cheap dirty and works. (short of a lightening strike on the
line)

Old Magnetic style fluorescent ballasts, are really bad for turn on/off
transient noise. I had to add filters on each and every one - years ago
when I still used them.

Snubbers work good too - 100 ohm flameproof resistor in series with a .1
UF (200+ VAC rated cap) across the switch that turns on the light.
 
Terry Pinnell <me@somewhere.invalid> wrote:
Some of the household circuits gadgets I made decades ago have
recently been getting activated spuriously. I suspect some sort of
interference or spikes or whatever on the 240 V mains supply.
Click to expand...

One thing to keep in mind is that there's a lot more RF in the world
than there was 20 or 30 years ago, particularly at mobile phone and
WiFi frequencies. This could be getting into your circuits and causing
false activations.

One example is a buzzer in the shed that's normally triggered from a
push button in the house - primarily my wife's 'come in for dinner'
call.
Click to expand...

If there are a couple of long wires running from the buzzer in the shed
to the button in the house, they might be acting as an antenna.

If your gadgets are powered from the mains, and you think noise is
getting in that way, you might try a prepackaged filter module. They
have "in" and "out" connections, and (usually) all the safety approvals
you need for connecting to the mains. They are available new, but also
often available cheaply as surplus. Corcom and Delta are a couple of
popular makes but there are several. This is an example of a Corcom
one from Digikey:
http://www.digikey.com/product-detail/en/1-6609008-8/CCM2062-ND/4896522

Standard disclaimers apply: I don't get money or other consideration
from any companies mentioned.

Matt Roberds
 
In article <525s0bhkgut5tliem7v655s3ej4l720s4p@4ax.com>,
me@somewhere.invalid says...
Some of the household circuits gadgets I made decades ago have
recently been getting activated spuriously. I suspect some sort of
interference or spikes or whatever on the 240 V mains supply.

One example is a buzzer in the shed that's normally triggered from a
push button in the house - primarily my wife's 'come in for dinner'
call. (It's essentially a CMOS monostable, NPN transistor and a
bistable feeding a small earpiece speaker). But sometimes it gets
triggered unexpectedly, perhaps by an appliance in the house (boiler,
washing machine, etc). Or maybe by an external source nearby. And it
always gets triggered when I switch on the fluorescent lights in the
adjacent garage. There are other gadgets which suffer similarly too.

So in order to experiment with fixing this, I'm seeking a reliable way
of generating mains noise myself. Any practical circuit ideas would be
appreciated please.
Click to expand...

Dont know about generating noise but I think I can figure out how
to remove it.

Replace your capacitor on the power supply, it sounds like its not
holding charge anymore and will cause a ripple in the supply..


Also, put a pull up R on the input line to lower the impedance or
pull down, depending on which way you designed it.

Jamie
 
On Fri, 02 Oct 2015 06:08:37 -0400, Tom Biasi wrote:

On 10/2/2015 1:41 AM, Terry Pinnell wrote:
Some of the household circuits gadgets I made decades ago have recently
been getting activated spuriously. I suspect some sort of interference
or spikes or whatever on the 240 V mains supply.

One example is a buzzer in the shed that's normally triggered from a
push button in the house - primarily my wife's 'come in for dinner'
call. (It's essentially a CMOS monostable, NPN transistor and a
bistable feeding a small earpiece speaker). But sometimes it gets
triggered unexpectedly, perhaps by an appliance in the house (boiler,
washing machine, etc). Or maybe by an external source nearby. And it
always gets triggered when I switch on the fluorescent lights in the
adjacent garage. There are other gadgets which suffer similarly too.

So in order to experiment with fixing this, I'm seeking a reliable way
of generating mains noise myself. Any practical circuit ideas would be
appreciated please.

AC motor with brushes.
Click to expand...

Electric drills (with cords) work well for this.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com
 
On 10/2/2015 12:41 AM, Terry Pinnell wrote:
Some of the household circuits gadgets I made decades ago have
recently been getting activated spuriously. I suspect some sort of
interference or spikes or whatever on the 240 V mains supply.

One example is a buzzer in the shed that's normally triggered from a
push button in the house - primarily my wife's 'come in for dinner'
call. (It's essentially a CMOS monostable, NPN transistor and a
bistable feeding a small earpiece speaker).
Click to expand...

Your wife is just f%$#ing with you!

Mikek :)
 
On 10/3/2015 3:39 PM, amdx wrote:
On 10/2/2015 12:41 AM, Terry Pinnell wrote:
Some of the household circuits gadgets I made decades ago have
recently been getting activated spuriously. I suspect some sort of
interference or spikes or whatever on the 240 V mains supply.

One example is a buzzer in the shed that's normally triggered from a
push button in the house - primarily my wife's 'come in for dinner'
call. (It's essentially a CMOS monostable, NPN transistor and a
bistable feeding a small earpiece speaker).


Your wife is just f%$#ing with you!

Mikek :)
Click to expand...

It's within the realm of possibility. :)
 
M Philbrook <jamie_ka1lpa@charter.net> wrote:

In article <525s0bhkgut5tliem7v655s3ej4l720s4p@4ax.com>,
me@somewhere.invalid says...

Some of the household circuits gadgets I made decades ago have
recently been getting activated spuriously. I suspect some sort of
interference or spikes or whatever on the 240 V mains supply.

One example is a buzzer in the shed that's normally triggered from a
push button in the house - primarily my wife's 'come in for dinner'
call. (It's essentially a CMOS monostable, NPN transistor and a
bistable feeding a small earpiece speaker). But sometimes it gets
triggered unexpectedly, perhaps by an appliance in the house (boiler,
washing machine, etc). Or maybe by an external source nearby. And it
always gets triggered when I switch on the fluorescent lights in the
adjacent garage. There are other gadgets which suffer similarly too.

So in order to experiment with fixing this, I'm seeking a reliable way
of generating mains noise myself. Any practical circuit ideas would be
appreciated please.

Dont know about generating noise but I think I can figure out how
to remove it.

Replace your capacitor on the power supply, it sounds like its not
holding charge anymore and will cause a ripple in the supply..


Also, put a pull up R on the input line to lower the impedance or
pull down, depending on which way you designed it.

Jamie
Click to expand...

Thanks all, appreciate the helpful suggestions and will experiment
along those lines.

--
Terry, East Grinstead, UK
 
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