A wall-wart alternative
 

I finally got tired of replacing the 2 C-cells in a clock with a moving
pendulum, so I measured the current (3 volts at 340 microamps) and built
a charge pump like this, viewed in a fixed font:

0.047 uF @400 V
|| |
-----------||---------------------|------------
|| | | |
| | 3V
120 VAC --- --- to clock
^ _
0.047 uF @400 V | |
|| | |
-----------||-----------------------------------
||

I used two caps in case one shorts and for some ground isolation. The diodes
are 5.1 V zeners ($1.29 for 2 at Radio Shack) to limit the clock voltage if
someone unplugs the batteries. This circuit supplies 390 microamps. I hope
to avoid replacing the batteries until their shelf life runs out in 2012 :-)

This could be useful for lots of low-power stuff, eg smoke detectors.

Nick

A wall-wart alternative
 

wrote:
I finally got tired of replacing the 2 C-cells in a clock with a moving
pendulum, so I measured the current (3 volts at 340 microamps) and built
a charge pump

We used to use a similar circuit for powering electronic thermostats
when I worked for Potterton Boilers here in Blighty. We used just one
Class X capacitor feeding a 24V zener and smoothing capacitor.

I also used to use one for charging the NiCads in my caving lamp. Of
course I made the classic mistake of plugging it in then picking up the
crocodile clips to connect onto the battery (rather than connecting
onto the battery then plugging in). Rectified 240V doesn't half hurt.

--
Malc

A wall-wart alternative
 

I used a ac adapter of the proper voltage to charge a bunch of D sixed
nicads to run my answering machine during power failures. it was like a
UPS uninterruptiple power supply.

my old machine would spaz with any power failu(

The batteries went bad after 6 years, my new machine a different
voltage with a battery backup of memory, so I dont use this anymore

A wall-wart alternative
 

I hope you are using rechargable batteries!

Regulart alkaline or others may dry out, overheat and start a fire!

USE ONLY RECHARGABLE BATTERIES IN THIS APPLICATION!

A wall-wart alternative
 

I like the concept, but it's hardly worth doing if you value the
portability of the object and batteries can be had so cheaply.

A wall-wart alternative
 

wrote:

I hope you are using rechargable batteries!

NO!

Regulart alkaline or others may dry out, overheat and start a fire!

How much will they overheat if overchaged at 3Vx50uA = 150 microwatts? :-)

USE ONLY RECHARGABLE BATTERIES IN THIS APPLICATION!

NO!

Happy new year,

Nick

A wall-wart alternative
 

A wall-wart alternative
 

Clark wrote:
Looks like a shock hazard to me.



wrote in message
oups.com...

wrote:


I finally got tired of replacing the 2 C-cells in a clock with a moving
pendulum, so I measured the current (3 volts at 340 microamps) and built
a charge pump like this, viewed in a fixed font:

0.047 uF @400 V
|| |
-----------||---------------------|------------
|| | | |
| | 3V
120 VAC --- --- to clock
^ _
0.047 uF @400 V | |
|| | |
-----------||-----------------------------------
||

I used two caps in case one shorts and for some ground isolation. The
diodes
are 5.1 V zeners ($1.29 for 2 at Radio Shack) to limit the clock voltage
if
someone unplugs the batteries. This circuit supplies 390 microamps. I
hope
to avoid replacing the batteries until their shelf life runs out in 2012
:-)

This could be useful for lots of low-power stuff, eg smoke detectors.

Nick

Caps do have a failure mode, so a series safety R is normally included
with these type circuits.

And at that low a current, why not ferget the caps and just use a couple
of 150K resistors? The additional power loss will hardly spin your
meter off the wall and you'll avoid the possible cap failure problem.

Jeff (Ducking and slinking off...)

--
Jeffry Wisnia

(W1BSV + Brass Rat '57 EE)

"Truth exists; only falsehood has to be invented."


If your ac supply is polarised, you'd be a bit safer putting one cap in
the live than one in each pole, as the output will then be at apx earth
potential, though not isolated. As it stands its semi-live.


NT

A wall-wart alternative
 

I...built a charge pump like this, viewed in a fixed font:

0.047 uF @400 V
|| |
-----------||---------------------|------------
|| | | |
| | 3V
120 VAC --- --- to clock
^ _
0.047 uF @400 V | |
|| | |
-----------||-----------------------------------
||

Nick (nicksanspam @ ece.villanova.edu)

Caps do have a failure mode,
so a series safety R is normally included with these type circuits.
NT (meow2222 @ care2.com)

It should be noted that such *series capacitor* devices
were outlawed for commercial products long ago in Europe.
As the Big Cat notes, without a resistor to limit things,
failures are usually dramatic.

A wall-wart alternative
 

wrote in message ...
I finally got tired of replacing the 2 C-cells in a clock with a moving
pendulum, so I measured the current (3 volts at 340 microamps) and built
a charge pump like this, viewed in a fixed font:

0.047 uF @400 V
|| |
-----------||---------------------|------------
|| | | |
| | 3V
120 VAC --- --- to clock
^ _
0.047 uF @400 V | |
|| | |
-----------||-----------------------------------
||

I used two caps in case one shorts and for some ground isolation. The diodes
are 5.1 V zeners ($1.29 for 2 at Radio Shack) to limit the clock voltage if
someone unplugs the batteries. This circuit supplies 390 microamps. I hope
to avoid replacing the batteries until their shelf life runs out in 2012 :-)

This could be useful for lots of low-power stuff, eg smoke detectors.

Nick

It seems counter-productive to build booby-traps into smoke detectors
and the like.

Unlike a wall-wart, it will require special precautions not to accidentally
touch anything when you go to change the battery or maybe even set the time
on a clock. You will never know whether a capacitor has shorted and whether
you might be killed the next time you provide a path to earth ground.

There's nothing to limit the current when capacitors fail, so that failure
will cause a fire. There's no transient voltage protection, so the odds
of capacitor over-voltage failure is pretty high.

Don

A wall-wart alternative
 

What is your child's life worth when they need to steal
a battery for their latest toy?

That's just idiotic.

"Al Bundy" wrote in message
oups.com...
I like the concept, but it's hardly worth doing if
you value the
portability of the object and batteries can be had so
cheaply.

A wall-wart alternative
 

2 Lithium batteries would be safer, cheaper, less work,
last longer and much more reliable.

Just a moronic idea

"JeffM" wrote in message
oups.com...
I...built a charge pump like this, viewed in a
fixed font:

0.047 uF @400 V
|| |
-----------||---------------------|------------
|| | | |
| | 3V
120 VAC --- --- to
clock
^ _
0.047 uF @400 V | |
|| | |
-----------||-----------------------------------
||

Nick (nicksanspam @ ece.villanova.edu)

Caps do have a failure mode,
so a series safety R is normally included with these
type circuits.
NT (meow2222 @ care2.com)

It should be noted that such *series capacitor*
devices
were outlawed for commercial products long ago in
Europe.
As the Big Cat notes, without a resistor to limit
things,
failures are usually dramatic.

A wall-wart alternative
 

Don K wrote:

wrote:

0.047 uF @400 V
1K || |
----www----||---------------------|------------
|| | | |
| | 3V
120 VAC --- --- to clock
^ _
0.047 uF @400 V | |
|| | |
-----------||-----------------------------------
||

Unlike a wall-wart, it will require special precautions not to accidentally
touch anything when you go to change the battery...

And it has battery backup :-)

There's nothing to limit the current when capacitors fail, so that failure
will cause a fire.

I doubt that. The diodes will probably open, and I used really skinny wire.

There's no transient voltage protection, so the odds of capacitor over-voltage
failure is pretty high.

Or diode damage. So... I added a 1K series resistor. This would also work:

0.022 uF @400 V*
|| |
-----------||---------------------|------------
|| | | |
| | 3V
120 VAC --- --- to clock
^ _
| |
10K | |
-----------www----------------------------------

*Digikey's $29.95 M400-KIT-ND 400 V capacitor assortment contains
10 of these, along with 10 of 14 other values from 0.001 to 0.1 uF.

Nick

A wall-wart alternative
 

A wall-wart alternative
 

Looks like a shock hazard to me.



wrote in message
oups.com...
wrote:

I finally got tired of replacing the 2 C-cells in a clock with a moving
pendulum, so I measured the current (3 volts at 340 microamps) and built
a charge pump like this, viewed in a fixed font:

0.047 uF @400 V
|| |
-----------||---------------------|------------
|| | | |
| | 3V
120 VAC --- --- to clock
^ _
0.047 uF @400 V | |
|| | |
-----------||-----------------------------------
||

I used two caps in case one shorts and for some ground isolation. The
diodes
are 5.1 V zeners ($1.29 for 2 at Radio Shack) to limit the clock voltage
if
someone unplugs the batteries. This circuit supplies 390 microamps. I
hope
to avoid replacing the batteries until their shelf life runs out in 2012
:-)

This could be useful for lots of low-power stuff, eg smoke detectors.

Nick

Caps do have a failure mode, so a series safety R is normally included
with these type circuits.

If your ac supply is polarised, you'd be a bit safer putting one cap in
the live than one in each pole, as the output will then be at apx earth
potential, though not isolated. As it stands its semi-live.


NT

A wall-wart alternative
 

0.022 uF @400 V*
|| |
-----------||---------------------|------------
|| | | |
| | 3V
120 VAC --- --- to clock
^ _
| |
10K | |
-----------www----------------------------------

*Digikey's $29.95 M400-KIT-ND 400 V capacitor assortment contains
10 of these, along with 10 of 14 other values from 0.001 to 0.1 uF.

The rest of this stuff is cheap...

$13.65 for 100 1N5231BD1CTND 5.1V zeners,
$15.86 for 1000 P10KBACTND 10K resistors,
and a line cord cut off an old appliance.

Anyone else want to burn their house down? :-)

Nick

A wall-wart alternative
 

nick pine wrote:

0.022 uF @400 V*
|| |
-----------||---------------------|------------
|| | | |
| | 3V
120 VAC --- --- to clock
^ _
| |
10K | |
-----------www----------------------------------

*Digikey's $29.95 M400-KIT-ND 400 V capacitor assortment contains
10 of these, along with 10 of 14 other values from 0.001 to 0.1 uF.

The rest of this trickle charger is cheap...

$13.65 for 100 1N5231BD1CTND 5.1V zeners,
$15.86 for 1000 P10KBACTND 10K resistors,
and a line cord cut off an old appliance.

My smoke detector draws 7 uA = 60x370C, which makes C = 315 puffs, eg 2
0.001 uF 400 V caps in series, Digikey's P1058-ND, $11.43/100. They also
sell 12 V zeners suitable for 9 V batteries, 1N5242BDICT-ND, $13.65/100.

Nick

A wall-wart alternative
 

wrote in message
...
nick pine wrote:

0.022 uF @400 V*
|| |
-----------||---------------------|------------
|| | | |
| | 3V
120 VAC --- --- to clock
^ _
| |
10K | |
-----------www----------------------------------

*Digikey's $29.95 M400-KIT-ND 400 V capacitor assortment contains
10 of these, along with 10 of 14 other values from 0.001 to 0.1 uF.

The rest of this trickle charger is cheap...

$13.65 for 100 1N5231BD1CTND 5.1V zeners,
$15.86 for 1000 P10KBACTND 10K resistors,
and a line cord cut off an old appliance.

My smoke detector draws 7 uA = 60x370C, which makes C = 315 puffs, eg 2
0.001 uF 400 V caps in series, Digikey's P1058-ND, $11.43/100. They also
sell 12 V zeners suitable for 9 V batteries, 1N5242BDICT-ND, $13.65/100.

Nick


Of course you don't have enough current for the audible device so your smoke
detector should sit quietly by while you toast!

A wall-wart alternative
 

A wall-wart alternative
 

Bill_M wrote:

0.001 0.001 uF @400 V*
|| || |
----||-----||---------------------|------------
|| || | | |
| | 9V
120 VAC --- --- to smoke detector
^ _
| |
10K | |
-----------www----------------------------------

My smoke detector draws 7 uA = 60Hzx2xsqrt(2)x120VxC, which makes C = 344 pF,
eg 2 0.001 uF 400 V caps in series, Digikey's P1058-ND, $11.43/100. They also
sell 12 V zeners suitable for 9 V batteries, 1N5242BDICT-ND, $13.65/100.

Of course you don't have enough current for the audible device so your smoke
detector should sit quietly by while you toast!

No. That current would come from the 9 V trickle-charged battery.

We might replace it every 6 years or so, if the alarm
fails to shriek with the test button.

Nick

A wall-wart alternative
 

wrote in message oups.com...
wrote:
Don K wrote:
wrote:

There's nothing to limit the current when capacitors fail, so that failure
will cause a fire.

X rated capacitors use fusible coatings, so a short causes a burn out
of the conductor around the short. The overall capacitance is not
noticeably affectde, IOW its self healing.


I doubt that. The diodes will probably open, and I used really skinny wire.

Very fine wire sounds like effective fusing to me.


You only need 20mA of AC current to cause ventricular fibrillation.
If the capacitor fails, someone could get killed touching whatever
your circuit connects to.

Don

A wall-wart alternative
 

0.0047 uF @400 V*
|| |
-----------||---------------------|------------
|| | | |
| | 1.5V
120 VAC --- --- to clock
^ _
| |
10K | |
-----------www----------------------------------

can trickle-charge a Seth Thomas quartz clock with hands and a AA battery
("Replace every 12 months or in case of suddenly inaccurate timekeeping.")
The trickle-charged battery might last 10 years.

The battery current jumps when the second hand ticks, but a 1K resistor
and a 10K microfarad smoothing capacitor reveal an average 95 microamps
= 60Hzx2xsqrt(2)x120VxC, which makes C = 0.0047 uF, one of the 150 caps
in Digikey's $29.95 M400-KIT-ND. Their P10KBACT-ND 10K resistors cost
$15.86/1000... 1N5231BD1CTND 5.1V zener diodes cost $13.65/100. Their
number is 1-800-344-4539. Most orders are shipped in 12-14 minutes.

This circuit uses about 1.5Vx95uA = 142 microwatts, ie 1.2 Wh/year worth
$0.000125 at 10 cents/kWh. It's probably illegal. Don't try this at home.

Nick

A wall-wart alternative
 

wrote:

My smoke detector draws 7 uA = 60x370C, which makes C = 315 puffs, eg 2
0.001 uF 400 V caps in series, Digikey's P1058-ND, $11.43/100. They also
sell 12 V zeners suitable for 9 V batteries, 1N5242BDICT-ND, $13.65/100.

You have to supply bleeping power, relying on the battery would be
unsatisfactory. In which case it'll draw bleeping power al the time,

Only with constant house fires.

Nick

A wall-wart alternative
 

Don K wrote:
wrote in message oups.com...
wrote:
Don K wrote:
wrote:

There's nothing to limit the current when capacitors fail, so that failure
will cause a fire.

X rated capacitors use fusible coatings, so a short causes a burn out
of the conductor around the short. The overall capacitance is not
noticeably affectde, IOW its self healing.


I doubt that. The diodes will probably open, and I used really skinny wire.

Very fine wire sounds like effective fusing to me.


You only need 20mA of AC current to cause ventricular fibrillation.
If the capacitor fails, someone could get killed touching whatever
your circuit connects to.

Don

It would be a foolish designer that enabled users to touch the output
of one of these, so thats a non issue in a competent design. If for
some reason they did, Y rated caps would be more appropriate than X -
but still, liability like that isnt something I'd want to take on
unnecessarily.

As far as fusing, if a cap shorts, enough i will flow to pop a fine
wire, assuming it really is fine. A single strand of a thin stranded
equipment wire etc. So the fuse concept is good.

I suppose if one wanted to improve the safety of an unsafe device (ie
nonisolated supply with outputs touchable) one could put a cap in both
poles and earth the supply output. Would need to ensure R is
significant to avoid RCD problems.

Note this would work as a 1 cap supply, as the E connection would
effectively short out the neutral capacitor. Ick.


NT

A wall-wart alternative
 

Don K wrote:
wrote in message oups.com...
wrote:
Don K wrote:
wrote:

There's nothing to limit the current when capacitors fail, so that failure
will cause a fire.

X rated capacitors use fusible coatings, so a short causes a burn out
of the conductor around the short. The overall capacitance is not
noticeably affectde, IOW its self healing.


I doubt that. The diodes will probably open, and I used really skinny wire.

Very fine wire sounds like effective fusing to me.


You only need 20mA of AC current to cause ventricular fibrillation.
If the capacitor fails, someone could get killed touching whatever
your circuit connects to.

Don

It would be a foolish designer that enabled users to touch the output
of one of these, so thats a non issue in a competent design. If for
some reason they did, Y rated caps would be more appropriate than X -
but still, liability like that isnt something I'd want to take on
unnecessarily.

As far as fusing, if a cap shorts, enough i will flow to pop a fine
wire, assuming it really is fine. A single strand of a thin stranded
equipment wire etc. So the fuse concept is good.

I suppose if one wanted to improve the safety of an unsafe device (ie
nonisolated supply with outputs touchable) one could put a cap in both
poles and earth the supply output. Would need to ensure R is
significant to avoid RCD problems.


NT

A wall-wart alternative
 

A wall-wart alternative
 

A wall-wart alternative
 

phatty mo wrote:

Why not a small dc-dc converter,from your main 12/24/48V battery bank..

I don't have a battery bank.

Safer,and probably more efficient. (takes the inverter out of the
loop,atleast.)

If your main inverter doesn't run 100% of the time, you might make the cap
larger to charge the battery more when the inverter does run. This circuit
itself is unlikely to make the inverter come out of hibernation.

Nick

A wall-wart alternative
 

These "hot" circuits were always accompanied by safety
devices that disabled them from human contact.
eg.
- polarized plugs
- cheater cords that disconnected when the back was
removed
- all plastic insulated knobs to avoid metal exposure.

wrote in message
...
0.0047 uF @400 V*
|| |
-----------||---------------------|------------
|| | | |
| | 1.5V
120 VAC --- --- to
clock
^ _
| |
10K | |
-----------www----------------------------------

can trickle-charge a Seth Thomas quartz clock with
hands and a AA battery
("Replace every 12 months or in case of suddenly
inaccurate timekeeping.")
The trickle-charged battery might last 10 years.

The battery current jumps when the second hand ticks,
but a 1K resistor
and a 10K microfarad smoothing capacitor reveal an
average 95 microamps
= 60Hzx2xsqrt(2)x120VxC, which makes C = 0.0047 uF,
one of the 150 caps
in Digikey's $29.95 M400-KIT-ND. Their P10KBACT-ND
10K resistors cost
$15.86/1000... 1N5231BD1CTND 5.1V zener diodes cost
$13.65/100. Their
number is 1-800-344-4539. Most orders are shipped in
12-14 minutes.

This circuit uses about 1.5Vx95uA = 142 microwatts,
ie 1.2 Wh/year worth
$0.000125 at 10 cents/kWh. It's probably illegal.
Don't try this at home.

Nick

A wall-wart alternative
 

****. get a small flexible PV panel and use the damn
thing.

wrote in message
...
phatty mo wrote:

Why not a small dc-dc converter,from your main
12/24/48V battery bank..

I don't have a battery bank.

Safer,and probably more efficient. (takes the
inverter out of the
loop,atleast.)

If your main inverter doesn't run 100% of the time,
you might make the cap
larger to charge the battery more when the inverter
does run. This circuit
itself is unlikely to make the inverter come out of
hibernation.

Nick

A wall-wart alternative
 

SolarFlare wrote:
get a small flexible PV panel

glue it to the face of the clock
add a series resistor and schottky diode to charge the
battery.

the frugal will steal the parts from a defunct solar
calculator ;-)

Nick, put equal value cap and resistor in series with each
line and your diodes in a small box with ac plug (gutted
wall wart- there's justice?) then run small cable (like the
old earphone cable) up to clock. Paint red insulator over
any "hot" parts in clock. The "power" cable will be about
as dangerous as any current small appliance "leakage" since
most have .045 mF caps from EACH power lead to chassis. UL
specifies an allowable leakage level. 5 ma sounds familiar
since that's the level that GFI's are supposed to trip at.

There's a thought, wire it any way you want to, then plug it
into a gfi ;-) hook all your clocks, smoke detectors, etc
together and use just one gfi. the gfi will use more power
than you're saving.

have a good new year -larry / dallas

A wall-wart alternative
 

Get an old coil for induction and put a series diode to
the battery. Hang it someplace over wiring with a good
load feed.

voila...self contained clock with no dangerous
connection to high voltage.


"larry" wrote in message
et...
SolarFlare wrote:
get a small flexible PV panel

glue it to the face of the clock
add a series resistor and schottky diode to charge
the
battery.

the frugal will steal the parts from a defunct solar
calculator ;-)

Nick, put equal value cap and resistor in series with
each
line and your diodes in a small box with ac plug
(gutted
wall wart- there's justice?) then run small cable
(like the
old earphone cable) up to clock. Paint red insulator
over
any "hot" parts in clock. The "power" cable will be
about
as dangerous as any current small appliance "leakage"
since
most have .045 mF caps from EACH power lead to
chassis. UL
specifies an allowable leakage level. 5 ma sounds
familiar
since that's the level that GFI's are supposed to
trip at.

There's a thought, wire it any way you want to, then
plug it
into a gfi ;-) hook all your clocks, smoke
detectors, etc
together and use just one gfi. the gfi will use more
power
than you're saving.

have a good new year -larry / dallas

A wall-wart alternative
 

Nick,
All the parts should be in the HOT side for safety. Move thre resistor
from the bottom leg(neutral) to the top (hot) leg. Make the resistor
bigger. Safer would be to use a small transformer to step the voltage
down, then just put a diode in the secondary. That is what most large
manufacturers who don't want to get sued do these days.

Stretch

A wall-wart alternative
 

A wall-wart alternative
 

Stretch wrote:

All the parts should be in the HOT side for safety. Move thre resistor
from the bottom leg(neutral) to the top (hot) leg.

The first old line cord I used was unpolarized...

Make the resistor bigger.

That eats into efficiency, and it might need to change with
the required current. Right now, only the cap needs to change.

Safer would be to use a small transformer to step the voltage down,
then just put a diode in the secondary.

Exactly what I want to avoid, with a thousand times the power consumption :-)

Nick

A wall-wart alternative
 

Nick wants to correct the power factor for the rest of
the house while he is at it...LOL

wrote in message
...
Stretch wrote:

All the parts should be in the HOT side for safety.
Move thre resistor
from the bottom leg(neutral) to the top (hot) leg.

The first old line cord I used was unpolarized...

Make the resistor bigger.

That eats into efficiency, and it might need to
change with
the required current. Right now, only the cap needs
to change.

Safer would be to use a small transformer to step
the voltage down,
then just put a diode in the secondary.

Exactly what I want to avoid, with a thousand times
the power consumption :-)

Nick

A wall-wart alternative
 

wrote:
Stretch wrote:


All the parts should be in the HOT side for safety. Move thre resistor

from the bottom leg(neutral) to the top (hot) leg.

The first old line cord I used was unpolarized...


Make the resistor bigger.


That eats into efficiency, and it might need to change with
the required current. Right now, only the cap needs to change.


Safer would be to use a small transformer to step the voltage down,
then just put a diode in the secondary.


Exactly what I want to avoid, with a thousand times the power consumption :-)

Nick


What we have is a battery powered electric Grandfather clock. That's
stupid enough on it's own. Still, it's too hard to wind up a real
Grandfather clock once a week.

But then Nick in his infinite silliness got tired of replacing the
batteries every year. How tedious it must have been.

Is Nick lazy or just sad?

A wall-wart alternative
 

Nick just likes to reinvent the wheel, whilr ignoring all advances is
safety made along the way. When we are dealing with milliamps or
microamps in the charging circuit, efficiency hardly seems an issue.
Now on a battery only system, efficiency has an effect on battery
life.

He is using a non-rechargible battery that will be ruined by his
recharging scheme. At these current levels, it won't blow up or catch
fire, it just won't work when he needs it. It is a goofy thing to do
for a once a yerar or twice a year battery change.

Strange way to gain efficiency. Reinventing what has already been
invented is rarely cost effective. You can buy something off the shelf
that works for less than you can cobble together some kludge that will
not work reliably. And for a smoke detector, reliability is
EVERYTHING!!!

Now he will have to respond to this. Probably will dig up something
out of NREL :-)

Stretch


Stretch

A wall-wart alternative
 

George Ghio wrote:
wrote:
Stretch wrote:


All the parts should be in the HOT side for safety. Move thre resistor

from the bottom leg(neutral) to the top (hot) leg.

The first old line cord I used was unpolarized...


Make the resistor bigger.


That eats into efficiency, and it might need to change with
the required current. Right now, only the cap needs to change.


Safer would be to use a small transformer to step the voltage down,
then just put a diode in the secondary.


Exactly what I want to avoid, with a thousand times the power consumption :-)

Nick


What we have is a battery powered electric Grandfather clock. That's
stupid enough on it's own. Still, it's too hard to wind up a real
Grandfather clock once a week.

But then Nick in his infinite silliness got tired of replacing the
batteries every year. How tedious it must have been.

Is Nick lazy or just sad?

Dead batteries in smoke detectors are one of the big causes of death in
house fires.

No, the batteries dont jump out and get ya, they just fail to tell you
to get out in time.


NT

A wall-wart alternative
 

Stretch wrote:


Nick just likes to reinvent the wheel, whilr ignoring all advances is
safety made along the way.

How is describing an old CR psu reinventing anything?


When we are dealing with milliamps or
microamps in the charging circuit, efficiency hardly seems an issue.

We know that isnt so. All those household appliances on standby drawing
milliamps nedes a whole power generating station to supply.
The CR supply uses less money and materials in construction too. In
this case it also saves battery replacements
- more material and energy waste
- lives saved as a result of the battery still being available to work


Now on a battery only system, efficiency has an effect on battery
life.

He is using a non-rechargible battery that will be ruined by his
recharging scheme. At these current levels, it won't blow up or catch
fire, it just won't work when he needs it.

I wasnt aware that microamp charging would damage non rc cells. Is this
true, can you offer a reference?


It is a goofy thing to do
for a once a yerar or twice a year battery change.

whats goofy about saving lives?


Strange way to gain efficiency.

in what way is it strange?


Reinventing what has already been
invented is rarely cost effective.

there is no reinvention here


You can buy something off the shelf
that works for less than you can cobble together some kludge that will
not work reliably.

not so. Go ahead and give us a link to one thats cheaper than this.


And for a smoke detector, reliability is
EVERYTHING!!!

Yes, and my one complaint about Nicks application sits here. If either
mains or battery fails, his detector wont sound. Imho if youre going to
the trouble of running mains to the detector it makes more sense to pay
the small extra and ensure it will sound if either mains or battery is
alive.

That issue can be solved simply by making the CR pass enough i to power
the alarm during sounding.


NT