What determines a low leakage capacitor?

[AK]

I am trying to find info about what a low leakage capacitor is.

I read that aluminum electrolytic caps have a higher leakage rate than most other types.

How do you determine if a capacitor is low leakage?

I was looking at this one.

0.1ÂľF 250 Volt 10% Metallized Film Capacitor Axial
Specifications

Capacitance: 100000 pF / 100 nF / 0.1ÂľF
Voltage rating: 250 VDC
Tolerance: Âą10%
Size: 14mm x 8.5mm x 4.5mm (W x H x D)
Axial leads

 

[default]

On Sat, 18 May 2019 09:52:29 -0700 (PDT), AK
<scientist77017@gmail.com> wrote:

I am trying to find info about what a low leakage capacitor is.

I read that aluminum electrolytic caps have a higher leakage rate than most other types.

How do you determine if a capacitor is low leakage?

How fast does it lose it's charge just sitting there?

I was looking at this one.

0.1ľF 250 Volt 10% Metallized Film Capacitor Axial
Specifications

Capacitance: 100000 pF / 100 nF / 0.1ľF
Voltage rating: 250 VDC
Tolerance: ą10%
Size: 14mm x 8.5mm x 4.5mm (W x H x D)
Axial leads

Metal film caps are all low leakage compared to electrolytics. There's
something else call "dissipation factor" that only comes into play at
some AC frequencies (how much power the dielectric wastes as heat).

What you are doing is low frequency and the capacitors aren't
critical.

 

[AK]

On Saturday, May 18, 2019 at 12:18:45 PM UTC-5, default wrote:

On Sat, 18 May 2019 09:52:29 -0700 (PDT), AK
scientist77017@gmail.com> wrote:

I am trying to find info about what a low leakage capacitor is.

I read that aluminum electrolytic caps have a higher leakage rate than most other types.

How do you determine if a capacitor is low leakage?

How fast does it lose it's charge just sitting there?

I was looking at this one.

0.1礔 250 Volt 10% Metallized Film Capacitor Axial
Specifications

Capacitance: 100000 pF / 100 nF / 0.1礔
Voltage rating: 250 VDC
Tolerance: ďż˝
Size: 14mm x 8.5mm x 4.5mm (W x H x D)
Axial leads

Metal film caps are all low leakage compared to electrolytics. There's
something else call "dissipation factor" that only comes into play at
some AC frequencies (how much power the dielectric wastes as heat).

What you are doing is low frequency and the capacitors aren't
critical.

Ok.

Thanks. I field tested my circuit on my patio.

Without the laser, ambient light is enough to keep buzzer off.

I passed my hand over the LDR from about a foot away and it sounded.

But it won't work from about 6 feet away which is about the range I need.

So it looks like even with a laser shining and someone breaks the beam, it may not sound if the light level is high enough.

 

[Cursitor Doom]

On Sat, 18 May 2019 10:50:16 -0700, AK wrote:

So it looks like even with a laser shining and someone breaks the beam,
it may not sound if the light level is high enough.

Dump the LDR and use a photodiode instead.





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[AK]

On Saturday, May 18, 2019 at 1:03:05 PM UTC-5, Cursitor Doom wrote:

On Sat, 18 May 2019 10:50:16 -0700, AK wrote:

So it looks like even with a laser shining and someone breaks the beam,
it may not sound if the light level is high enough.

Dump the LDR and use a photodiode instead.





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This message may be freely reproduced without limit or charge only via
the Usenet protocol. Reproduction in whole or part through other
protocols, whether for profit or not, is conditional upon a charge of
GBP10.00 per reproduction. Publication in this manner via non-Usenet
protocols constitutes acceptance of this condition.

Would this work?

Silicon Photodiode with Daylight Filter
PIN Photodiode Chip, BPW34
Features
Photocurrent: 80 ÂľA (? 50 ÂľA)
Reverse voltage: 32V
Forward voltage @ current: 1.3V @ 80uA
Total power dissipation: 150mW
Spectral sensitivity: 0.62 A/W
Wavelength of max. sensitivity: 850nm
Radiant sensitive area: 7.0mm²
Half angle: Âą60 degrees
Short switching time: 20ns typ.

 

[whit3rd]

On Saturday, May 18, 2019 at 11:51:29 AM UTC-7, AK wrote:

Would this work?

Silicon Photodiode with Daylight Filter
PIN Photodiode Chip, BPW34....

For a 'laser alarm', i.e. detecting a light beam, the
presence of anbient light (generally white-ish and not modulated)
is a guaranteed interfering signal.

If you use a photodiode (instead of LDR) your receiver can pick up
any frequency from zero (direct current output) to 1 MHz,
as opposed to zero to 1 kHz (for CdS, which has a storage time).

If you start with a laser, you can use a long black-painted tube to
aim the receiver in one and only one direction. Alignment will be fiddly, though.

Laser or LED light also has a characteristic color, not common in nature,
so some kinds of filtering will reject interference while passing the
whole intended signal.

The best ( easiest) way to make it all work, might be to make the laser
flicker at some frequency, and use a LM567 'tone decoder' that can
pick up on one-and-only-one frequency of light-brightness-oscillation.
Because both the laser and receiver require power, it could be
good to package them together, and use retroreflective tape or
other backscatter optics at the 'target'.

 

[Sjouke Burry]

On 18.05.19 19:50, AK wrote:

On Saturday, May 18, 2019 at 12:18:45 PM UTC-5, default wrote:
On Sat, 18 May 2019 09:52:29 -0700 (PDT), AK
scientist77017@gmail.com> wrote:

I am trying to find info about what a low leakage capacitor is.

I read that aluminum electrolytic caps have a higher leakage rate than most other types.

How do you determine if a capacitor is low leakage?

How fast does it lose it's charge just sitting there?

I was looking at this one.

0.1礔 250 Volt 10% Metallized Film Capacitor Axial
Specifications

Capacitance: 100000 pF / 100 nF / 0.1礔
Voltage rating: 250 VDC
Tolerance: ďż˝
Size: 14mm x 8.5mm x 4.5mm (W x H x D)
Axial leads

Metal film caps are all low leakage compared to electrolytics. There's
something else call "dissipation factor" that only comes into play at
some AC frequencies (how much power the dielectric wastes as heat).

What you are doing is low frequency and the capacitors aren't
critical.

Ok.

Thanks. I field tested my circuit on my patio.

Without the laser, ambient light is enough to keep buzzer off.

I passed my hand over the LDR from about a foot away and it sounded.

But it won't work from about 6 feet away which is about the range I need.

So it looks like even with a laser shining and someone breaks the beam, it may not sound if the light level is high enough.

Put the LDR in a 1 inch plastic tube,20 inch long and paint the tube inside
with black flat paint(used for school boards).
That will keep the ambient light out, and does not inhibit the laser
beam.

 

[Cursitor Doom]

On Sat, 18 May 2019 22:35:09 +0200, Sjouke Burry wrote:

Put the LDR in a 1 inch plastic tube,20 inch long and paint the tube
inside with black flat paint(used for school boards).
That will keep the ambient light out, and does not inhibit the laser
beam.

LDR is too slow. He wants something that *briefly* interrupts the beam to
produce a 'meaningful' output from the detector. The 'burglar' is not
going to stand in front of the beam until the LDR has time to change
resistance.



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the Usenet protocol. Reproduction in whole or part through other
protocols, whether for profit or not, is conditional upon a charge of
GBP10.00 per reproduction. Publication in this manner via non-Usenet
protocols constitutes acceptance of this condition.

 

[default]

On Sat, 18 May 2019 11:51:26 -0700 (PDT), AK
<scientist77017@gmail.com> wrote:

On Saturday, May 18, 2019 at 1:03:05 PM UTC-5, Cursitor Doom wrote:
On Sat, 18 May 2019 10:50:16 -0700, AK wrote:

So it looks like even with a laser shining and someone breaks the beam,
it may not sound if the light level is high enough.

Dump the LDR and use a photodiode instead.





--
This message may be freely reproduced without limit or charge only via
the Usenet protocol. Reproduction in whole or part through other
protocols, whether for profit or not, is conditional upon a charge of
GBP10.00 per reproduction. Publication in this manner via non-Usenet
protocols constitutes acceptance of this condition.

Would this work?

Silicon Photodiode with Daylight Filter
PIN Photodiode Chip, BPW34
Features
Photocurrent: 80 ľA (? 50 ľA)
Reverse voltage: 32V
Forward voltage @ current: 1.3V @ 80uA
Total power dissipation: 150mW
Spectral sensitivity: 0.62 A/W
Wavelength of max. sensitivity: 850nm
Radiant sensitive area: 7.0mm˛
Half angle: ą60 degrees
Short switching time: 20ns typ.

You might try adding a potentiometer so you can adjust the
sensitivity, then take some time and effort and install the detector
in a light-tight tube with a non-reflective black inside coating, and
position the detector so the only light it sees is the emitter (laser
in this case).

6' should be doable even with your simple system.

You are using a laser for a light source. It should work the way it
is, but if you think about it, wouldn't it make more sense to use a
narrow very bright laser beam on a small area like a photodiode or
photo-transistor? Concentrate the light on a small target then any
extraneous light will be much weaker by comparison.

 

[default]

On Sat, 18 May 2019 21:08:12 -0000 (UTC), Cursitor Doom
<curd@notformail.com> wrote:

On Sat, 18 May 2019 22:35:09 +0200, Sjouke Burry wrote:


Put the LDR in a 1 inch plastic tube,20 inch long and paint the tube
inside with black flat paint(used for school boards).
That will keep the ambient light out, and does not inhibit the laser
beam.

LDR is too slow. He wants something that *briefly* interrupts the beam to
produce a 'meaningful' output from the detector. The 'burglar' is not
going to stand in front of the beam until the LDR has time to change
resistance.

LDRs are used at audio frequencies and work very well. They aren't
fast if you are talking about data transmission rates, but in human
terms they are very very fast.

His circuit just needs to drop below a reference voltage to trigger,
speed isn't important.

 

[AK]

On Saturday, May 18, 2019 at 4:28:40 PM UTC-5, default wrote:

On Sat, 18 May 2019 11:51:26 -0700 (PDT), AK
scientist77017@gmail.com> wrote:

On Saturday, May 18, 2019 at 1:03:05 PM UTC-5, Cursitor Doom wrote:
On Sat, 18 May 2019 10:50:16 -0700, AK wrote:

So it looks like even with a laser shining and someone breaks the beam,
it may not sound if the light level is high enough.

Dump the LDR and use a photodiode instead.





--
This message may be freely reproduced without limit or charge only via
the Usenet protocol. Reproduction in whole or part through other
protocols, whether for profit or not, is conditional upon a charge of
GBP10.00 per reproduction. Publication in this manner via non-Usenet
protocols constitutes acceptance of this condition.

Would this work?

Silicon Photodiode with Daylight Filter
PIN Photodiode Chip, BPW34
Features
Photocurrent: 80 ÂľA (? 50 ÂľA)
Reverse voltage: 32V
Forward voltage @ current: 1.3V @ 80uA
Total power dissipation: 150mW
Spectral sensitivity: 0.62 A/W
Wavelength of max. sensitivity: 850nm
Radiant sensitive area: 7.0mm²
Half angle: Âą60 degrees
Short switching time: 20ns typ.

You might try adding a potentiometer so you can adjust the
sensitivity, then take some time and effort and install the detector
in a light-tight tube with a non-reflective black inside coating, and
position the detector so the only light it sees is the emitter (laser
in this case).

6' should be doable even with your simple system.

You are using a laser for a light source. It should work the way it
is, but if you think about it, wouldn't it make more sense to use a
narrow very bright laser beam on a small area like a photodiode or
photo-transistor? Concentrate the light on a small target then any
extraneous light will be much weaker by comparison.

I put it in a 3 inch tube.

It worked but then it was overcast.

I will try again when I have full sun.

The photo diode might work as I can adjust the laser beam to be wider.

Andy

 

[default]

On Sat, 18 May 2019 16:06:43 -0700 (PDT), AK
<scientist77017@gmail.com> wrote:

On Saturday, May 18, 2019 at 4:28:40 PM UTC-5, default wrote:
On Sat, 18 May 2019 11:51:26 -0700 (PDT), AK
scientist77017@gmail.com> wrote:

On Saturday, May 18, 2019 at 1:03:05 PM UTC-5, Cursitor Doom wrote:
On Sat, 18 May 2019 10:50:16 -0700, AK wrote:

So it looks like even with a laser shining and someone breaks the beam,
it may not sound if the light level is high enough.

Dump the LDR and use a photodiode instead.





--
This message may be freely reproduced without limit or charge only via
the Usenet protocol. Reproduction in whole or part through other
protocols, whether for profit or not, is conditional upon a charge of
GBP10.00 per reproduction. Publication in this manner via non-Usenet
protocols constitutes acceptance of this condition.

Would this work?

Silicon Photodiode with Daylight Filter
PIN Photodiode Chip, BPW34
Features
Photocurrent: 80 ľA (? 50 ľA)
Reverse voltage: 32V
Forward voltage @ current: 1.3V @ 80uA
Total power dissipation: 150mW
Spectral sensitivity: 0.62 A/W
Wavelength of max. sensitivity: 850nm
Radiant sensitive area: 7.0mm˛
Half angle: ą60 degrees
Short switching time: 20ns typ.

You might try adding a potentiometer so you can adjust the
sensitivity, then take some time and effort and install the detector
in a light-tight tube with a non-reflective black inside coating, and
position the detector so the only light it sees is the emitter (laser
in this case).

6' should be doable even with your simple system.

You are using a laser for a light source. It should work the way it
is, but if you think about it, wouldn't it make more sense to use a
narrow very bright laser beam on a small area like a photodiode or
photo-transistor? Concentrate the light on a small target then any
extraneous light will be much weaker by comparison.

I put it in a 3 inch tube.

It worked but then it was overcast.

I will try again when I have full sun.

The photo diode might work as I can adjust the laser beam to be wider.

Andy

I'm suggesting you keep the beam width narrow - unless it becomes
impossible to aim. The sensitive area for a photo transistor or diode
is less than a millimeter square. So keeping the beam narrow and
bright will help.

But go ahead with the photocell I believe it can work too. The photo
alarm I built for my motorcycle parking area was easily 6 feet. Across
the whole carport ~8 feet and into a small laundry alcove. (down in
Puerto Rico where pipes never freeze the laundry can be done outdoors)
The carport provided shade from the sun so I didn't need a baffle to
keep sunlight out of the detector.

 

[John Larkin]

On Sat, 18 May 2019 09:52:29 -0700 (PDT), AK
<scientist77017@gmail.com> wrote:

I am trying to find info about what a low leakage capacitor is.

I read that aluminum electrolytic caps have a higher leakage rate than most other types.

How do you determine if a capacitor is low leakage?

I was looking at this one.

0.1ľF 250 Volt 10% Metallized Film Capacitor Axial
Specifications

Capacitance: 100000 pF / 100 nF / 0.1ľF
Voltage rating: 250 VDC
Tolerance: ą10%
Size: 14mm x 8.5mm x 4.5mm (W x H x D)
Axial leads

Cap leakage is sometimes defined as a time, the self-discharge time
constant. That's how long a charged cap, connected to nothing, takes
to discharge itself to 37% of its original voltage. It can range from
minutes to years. Good film caps can be many years. Electrolytics vary
a lot, minutes to weeks maybe.

Sometimes caps are rated for megaohm-microfarads, which is exactly
this same time constant. Namely Rl * C, where Rl is the equivalent
leakage resistance.

Film caps are usually way, way better than the circuit they are used
in.


--

John Larkin Highland Technology, Inc

lunatic fringe electronics

 

[Cursitor Doom]

On Sat, 18 May 2019 18:06:07 -0700, John Larkin wrote:

Cap leakage is sometimes defined as a time, the self-discharge time
constant. That's how long a charged cap, connected to nothing, takes to
discharge itself to 37% of its original voltage. It can range from
minutes to years. Good film caps can be many years. Electrolytics vary a
lot, minutes to weeks maybe.

Thank god for bleeder resistors.

 

[John Larkin]

On Sun, 19 May 2019 14:39:47 -0000 (UTC), Cursitor Doom
<curd@notformail.com> wrote:

On Sat, 18 May 2019 18:06:07 -0700, John Larkin wrote:

Cap leakage is sometimes defined as a time, the self-discharge time
constant. That's how long a charged cap, connected to nothing, takes to
discharge itself to 37% of its original voltage. It can range from
minutes to years. Good film caps can be many years. Electrolytics vary a
lot, minutes to weeks maybe.

Thank god for bleeder resistors.

Big oil or film metal-can energy-storage caps are usually shipped with
a bunch of bare wire shorting the screw terminals. This prevents
killing customers.


--

John Larkin Highland Technology, Inc

lunatic fringe electronics

 

[Cursitor Doom]

On Sun, 19 May 2019 14:01:19 -0700, John Larkin wrote:

Big oil or film metal-can energy-storage caps are usually shipped with a
bunch of bare wire shorting the screw terminals. This prevents killing
customers.

Those are typically quite low F value caps, though. Not much energy can
be stored in them. In any case, why not just send them out uncharged?
Seems the obvious thing. :-/



--
This message may be freely reproduced without limit or charge only via
the Usenet protocol. Reproduction in whole or part through other
protocols, whether for profit or not, is conditional upon a charge of
GBP10.00 per reproduction. Publication in this manner via non-Usenet
protocols constitutes acceptance of this condition.

 

[Jasen Betts]

On 2019-05-19, Cursitor Doom <curd@notformail.com> wrote:

On Sun, 19 May 2019 14:01:19 -0700, John Larkin wrote:

Big oil or film metal-can energy-storage caps are usually shipped with a
bunch of bare wire shorting the screw terminals. This prevents killing
customers.

Those are typically quite low F value caps, though. Not much energy can
be stored in them. In any case, why not just send them out uncharged?
Seems the obvious thing. :-/

That would take too long. Dielectric absorbtion.

--
When I tried casting out nines I made a hash of it.

 

[Look165]

Basically a parasistic parallel resistance that drive some current
inside the cap.
For electrolytics, there are ionic recombination too.
Also thermal shocks can affect the auto-discharge rate.
For electrolytics,, those parameters merely affect the nominal value.
The tolerance (+/10...20%) has no relation with auto-decharge.

The more you put caps in //, the more you put these resistor in // and
the less the resulting value is and ESR  to
With caps in series, it is the opposite.

I think tantalum ones are the worst.
And as already written above, mica and plastic films the best, and of
course, air ones for low values.
Oil and glass caps are rather good too but uncommon (UHT voltages).
The auto-healing once "holed" lower their // resistance.

The main drama is that electrons love protons  and protons love
electrons and the // resistance is a matrimonial agency !
In any case, they try to jump over  the gap between the electrodes !

The ideal cap, though unreal, is the vacuum cap.

AK a Êcrit le 18/05/2019 à 18:52 :

I am trying to find info about what a low leakage capacitor is.

I read that aluminum electrolytic caps have a higher leakage rate than most other types.

How do you determine if a capacitor is low leakage?

I was looking at this one.

0.1ÂľF 250 Volt 10% Metallized Film Capacitor Axial
Specifications

Capacitance: 100000 pF / 100 nF / 0.1ÂľF
Voltage rating: 250 VDC
Tolerance: Âą10%
Size: 14mm x 8.5mm x 4.5mm (W x H x D)
Axial leads

 

[John Larkin]

On Sun, 19 May 2019 22:33:00 -0000 (UTC), Cursitor Doom
<curd@notformail.com> wrote:

On Sun, 19 May 2019 14:01:19 -0700, John Larkin wrote:

Big oil or film metal-can energy-storage caps are usually shipped with a
bunch of bare wire shorting the screw terminals. This prevents killing
customers.

Those are typically quite low F value caps, though. Not much energy can
be stored in them. In any case, why not just send them out uncharged?
Seems the obvious thing. :-/

A serious energy storage cap can store kilojoules, or 10s of kJ. 10
joules is considered to be leathally dangerous in some places.

Discharging 100 joules is an impressive event.


--

John Larkin Highland Technology, Inc

lunatic fringe electronics

 

[Jeroen Belleman]

John Larkin wrote:

On Sun, 19 May 2019 22:33:00 -0000 (UTC), Cursitor Doom
curd@notformail.com> wrote:

On Sun, 19 May 2019 14:01:19 -0700, John Larkin wrote:

Big oil or film metal-can energy-storage caps are usually shipped with a
bunch of bare wire shorting the screw terminals. This prevents killing
customers.
Those are typically quite low F value caps, though. Not much energy can
be stored in them. In any case, why not just send them out uncharged?
Seems the obvious thing. :-/

A serious energy storage cap can store kilojoules, or 10s of kJ. 10
joules is considered to be leathally dangerous in some places.

Discharging 100 joules is an impressive event.

There are some effects that cause capacitors to develop
bothersome charge even after having been discharged.
One is dielectric absorption, sort of like charge hiding
away in nooks and crannies for a while, before coming out
again when you least want it. Another is the slow
accumulation of stray free charge. That's probably self-
limiting.

Anyway, it's safer to ship big capacitors shorted. I've
had some nasty surprises in cases where this wasn't done.

Jeroen Belleman