P
Phil Allison
Guest
"Richard the Dreaded Libertarian"
** Sockpuppet trolling , masturbating fuckwit.
.......... Phil
** Sockpuppet trolling , masturbating fuckwit.
.......... Phil
J
John Fields
Guest
On Mon, 30 Jan 2006 21:50:04 +0000, capnfishytakethisout@lineone.net
wrote:
If the boiler and all the rest of it is brand new, and you wired it
together and it doesn't work right, guess what... It's probably your
wiring that's at fault.
You've posted no schematics, nothing about what the problem is other
than that the relay is buzzing, and nothing about what you've done
to isolate the problem, and yet you seem to expect us to pinpoint
the solution for you because you say you can't afford to have a
professional come in and do it properly.
What's wrong with that picture?...
--
John Fields
Professional Circuit Designer
wrote:
---
If the boiler and all the rest of it is brand new, and you wired it
together and it doesn't work right, guess what... It's probably your
wiring that's at fault.
You've posted no schematics, nothing about what the problem is other
than that the relay is buzzing, and nothing about what you've done
to isolate the problem, and yet you seem to expect us to pinpoint
the solution for you because you say you can't afford to have a
professional come in and do it properly.
What's wrong with that picture?...
--
John Fields
Professional Circuit Designer
G
Geogle
Guest
Thanks to all help with ascii schematic, here are the figures again. In
the DMM, I assume
that HV probe is protected with respect to the Probe GND. But GND
itself is not protected
from the supply gnd. So adding the zener/filter cap must be good enogh
to protect the whole thing. Caution has to be taken to see that the
entire thing is treated as a live circuit.
In that way the battery thing may be more dangerous thing because
changing the battery
means, in case you forget to disconnect the probe you are in danger. (
Just a thought!).
First Picture:
.. DANGER HIGHVOLTAGE
..
.. .---------------. .---------------.
.. L | | 9V | | Probe HV
.. ------------ -------------- ----------
.. | | | |
.. | | | 7107 Mtr |
.. MAINS | 9 V | | |
.. | Supply | | |
.. | | | |
.. | | 0 | |Probe GND
.. ------------| -------------- ----------
.. N ----------------' '---------------'
(created by AACircuit v1.28.6 beta 04/19/05 www.tech-chat.de)
Second Picture:
.. DANGER HIGHVOLTAGE
..
.. .---------------. .---------------.
.. L | | 9V | | Probe HV
.. ------------ -------------- ----------
.. | | | |
.. | | | 7107 Mtr |
.. MAINS | 9 V | | |
.. | Supply | | |
.. | | | |
.. | | 0 | |Probe GND
.. ------------| ------|------- ------|---
.. N ----------------' | '---------------' |
.. | |
.. | Elec. Cap |
.. | \] |
.. |--------------|]------------|
.. | /]+ |
.. | |
.. | |
.. --------------->z------------|
Zener
(created by AACircuit v1.28.6 beta 04/19/05 www.tech-chat.de)
Third Picture:
.. Equivalent Circuit.
..
..
.. L
.. ---------------| |
.. | |
.. | Leakage Cap | Leakage Cap
.. --- ---
.. --- ---
.. | |
.. | |
.. | |
.. GND | | GND
.. | |
.. | |
.. |+ |
.. === z Zener
.. /-\ A
.. | |
.. | |
.. | |
.. N | |
.. ------------------ |.
On The assumption that HV Probe is already protected in DMM
Additional protection only for Probe GND
with respect to Supply GND
(created by AACircuit v1.28.6 beta 04/19/05 www.tech-chat.de)
the DMM, I assume
that HV probe is protected with respect to the Probe GND. But GND
itself is not protected
from the supply gnd. So adding the zener/filter cap must be good enogh
to protect the whole thing. Caution has to be taken to see that the
entire thing is treated as a live circuit.
In that way the battery thing may be more dangerous thing because
changing the battery
means, in case you forget to disconnect the probe you are in danger. (
Just a thought!).
First Picture:
.. DANGER HIGHVOLTAGE
..
.. .---------------. .---------------.
.. L | | 9V | | Probe HV
.. ------------ -------------- ----------
.. | | | |
.. | | | 7107 Mtr |
.. MAINS | 9 V | | |
.. | Supply | | |
.. | | | |
.. | | 0 | |Probe GND
.. ------------| -------------- ----------
.. N ----------------' '---------------'
(created by AACircuit v1.28.6 beta 04/19/05 www.tech-chat.de)
Second Picture:
.. DANGER HIGHVOLTAGE
..
.. .---------------. .---------------.
.. L | | 9V | | Probe HV
.. ------------ -------------- ----------
.. | | | |
.. | | | 7107 Mtr |
.. MAINS | 9 V | | |
.. | Supply | | |
.. | | | |
.. | | 0 | |Probe GND
.. ------------| ------|------- ------|---
.. N ----------------' | '---------------' |
.. | |
.. | Elec. Cap |
.. | \] |
.. |--------------|]------------|
.. | /]+ |
.. | |
.. | |
.. --------------->z------------|
Zener
(created by AACircuit v1.28.6 beta 04/19/05 www.tech-chat.de)
Third Picture:
.. Equivalent Circuit.
..
..
.. L
.. ---------------| |
.. | |
.. | Leakage Cap | Leakage Cap
.. --- ---
.. --- ---
.. | |
.. | |
.. | |
.. GND | | GND
.. | |
.. | |
.. |+ |
.. === z Zener
.. /-\ A
.. | |
.. | |
.. | |
.. N | |
.. ------------------ |.
On The assumption that HV Probe is already protected in DMM
Additional protection only for Probe GND
with respect to Supply GND
(created by AACircuit v1.28.6 beta 04/19/05 www.tech-chat.de)
G
Geogle
Guest
Phil,
I sincerely respect your cautions. However this thing is somethign I
want to keep as
a seperate entity where as the meter is never going to be used as a
normal DMM. So
it could be enclosed properly so that chances of accidental touch to HV
parts are
eliminated. Thanks again for being so much worried about the well
being.
Thanks again!
Rx: Lorazepam 1-1-1
I sincerely respect your cautions. However this thing is somethign I
want to keep as
a seperate entity where as the meter is never going to be used as a
normal DMM. So
it could be enclosed properly so that chances of accidental touch to HV
parts are
eliminated. Thanks again for being so much worried about the well
being.
Thanks again!
Rx: Lorazepam 1-1-1
P
Phil Allison
Guest
"Geogle"
** Ok - the penny has finally dropped.
** What you are planning is inherently fraught with danger !!
Very few *cheap* DMMs are SAFE AT ALL if used for measuring the AC
mains - particularly if the probes are left permanently attached.
Things to look for in a SAFE meter are:
1. The probes have a flange that stops fingers sliding down onto the metal
part.
2. The plugs on the end of the probes are fully shrouded.
3. The battery is NOT accessible unless a tool is used to open the meter -
ie there is not hatch or snap on cover.
4. The probes have to be removed from the meter to access the battery.
5. All current ranges are fused with a suitable HRC type fuse.
Folk ( especially electricians) have been electrocuted and maimed by badly
designed DMMs - while the probes were attached to the AC supply.
This happened when:
A. A probe plug detached from the meter and they tried to replace it and
received a fatal shock.
B. The battery fell out the back and the tried to replace it and received
fatal shock.
C. The meter was switched to the 10/ 20 amp current range and EXPLODED
violently in their face along with the leads.
......... Phil
** Ok - the penny has finally dropped.
** What you are planning is inherently fraught with danger !!
Very few *cheap* DMMs are SAFE AT ALL if used for measuring the AC
mains - particularly if the probes are left permanently attached.
Things to look for in a SAFE meter are:
1. The probes have a flange that stops fingers sliding down onto the metal
part.
2. The plugs on the end of the probes are fully shrouded.
3. The battery is NOT accessible unless a tool is used to open the meter -
ie there is not hatch or snap on cover.
4. The probes have to be removed from the meter to access the battery.
5. All current ranges are fused with a suitable HRC type fuse.
Folk ( especially electricians) have been electrocuted and maimed by badly
designed DMMs - while the probes were attached to the AC supply.
This happened when:
A. A probe plug detached from the meter and they tried to replace it and
received a fatal shock.
B. The battery fell out the back and the tried to replace it and received
fatal shock.
C. The meter was switched to the 10/ 20 amp current range and EXPLODED
violently in their face along with the leads.
......... Phil
S
SioL
Guest
"Boris Mohar" <borism_-void-_@sympatico.ca> wrote in message
http://www.sb-software.com/politicalinvaders/
Political Invaders is a game similar to space invaders, but rather than blasting aliens, you get to blast your favorite politicians,
commentators, and politically slanted news reporters with pies. All the while you'll have to dodge the bombs they throw at you.
Yep, there's Bush as well for us lefties.
--
Siol
------------------------------------------------
Rather than a heartless beep
Or a rude error message,
See these simple words: "File not found."
Also found this:
http://www.sb-software.com/politicalinvaders/
Political Invaders is a game similar to space invaders, but rather than blasting aliens, you get to blast your favorite politicians,
commentators, and politically slanted news reporters with pies. All the while you'll have to dodge the bombs they throw at you.
Yep, there's Bush as well for us lefties.
--
Siol
------------------------------------------------
Rather than a heartless beep
Or a rude error message,
See these simple words: "File not found."
C
Chris
Guest
Geogle wrote:
your meter.
1) Your 9V power supply is not _sufficiently_ isolated from the line
unless you've got a transformer with electrostatic shield.
2) There is no direct meter internal connection between the 9V battery
negative and the meter negative probe. You're just adding another
problem by connecting the two with a cap and zener.
3) Most cheapie meters can be damaged by applying line voltage to the
probes with the battery disconnected, or with the battery power off.
Since it takes anywhere between tenths of milliseconds and a few
milliseconds for the input filter cap of your 9V supply to get charged
up by the transformer, you're leaving yourself open to meter damage
there, too.
One of life's ancient principles is that you may not always get what
you pay for, but you always pay for what you get. Line-powered bench
DMMs cost more than battery-operated handheld DMMs for a reason, and
it's not just more accuracy.
If you open up a good benchtop DMM or look in the service manual,
you'll see that quite a bit of care has been taken to provide good
isolation between the line and the meter circuit power supply. You'll
also note that most bench DMMs specify a maximum voltage between the
probes and GND (usually between the negative probe and GND).
Many benchtop DMMs also have input circuitry that presents a high
limiting input impedance when they're unpowered.
Let's look at this from a cost standpoint, which is where I think
you're coming from. Using the Digi-Key catalog, I find that an
Energizer 9V Industrial Alkaline battery will cost $2.34 for 625mA-h at
9V. Six "D" Industrial Alkaline batteries in series will cost $8.28
for 20,500 mA-h at 9V.
According to this measure, you'll replace the 9V batteries 32 times for
each replacement of the 6 "D" batteries. Of course, the mA-h ratings
for both are based on a 25mA load, and the mA-H ratings are for
drawdown to 60% of nominal voltage. Both of these would favor the
larger D battery, and I'm sure the actual replacement ratio will be
somewhat lower than 32:1. The cost ratio, though, is only 3.5:1. 9V
batteries are a relatively expensive way to run something. You'll
easily save over 80% of the cost of running the meter by using 6 D
batteries in series. If you've got an old 7107-based meter that uses a
several mA, you'll be replacing batteries twice a year at worst. Most
of your job is done easily.
To do this relatively safely, start by snapping a 9V battery clip with
flying leads onto the 9V battery clip in the meter (note that red and
black will now be bass-ackwards). Drill a small hole in the meter
battery cover to allow the flying leads to be snaked through (you can
later fill this hole with epoxy if you want to return the meter to
regular service).
Purchase a thermoplastic (NOT metal!) project box bigger than the
meter, and also purchase two 3-cell D battery holders. Mount the
battery holders in the box, and drill a hole for the meter wires such
that the wires will fit through when the meter is affixed to the box.
I lined it up so the bottom of the meter was flush with the bottom of
the project box, so it could be stood up on end for visibility. I also
mounted a small stand on the bottom of the box to keep it from tipping
over (the D batteries tended to make it a little top-heavy).
Now either use epoxy glue or ty-raps to affix the meter permanently to
the project box. Install the 6 D batteries. Screw closed the cover on
the project box. Turn the meter on. You're done.
I've been where you are now. This works.
And this setup with the meter and plastic project box is just as safe
as the meter with the manufacturer-recommended 9V battery, if you know
what you're doing with electricity. You wouldn't try to replace the
enclosed battery on a meter while it's measuring line voltage either
way, no matter what some might say. Other than that, it just looks
kind of clunky.
Standard legal/moral/ethical disclaimers apply. Affix a visible
warning on the meter/plastic project box stating that hazardous
voltages may be present inside, if you so choose, or if you're dealing
with fresh grads who don't know which side of the soldering iron is
hot.
And if you really want to work hard to protect your cheapie meter, use
a series 220 ohm 3 watt wirewound in series with the red probe, and
place a line voltage rated MOV between the red and black probes.
|
| .------------.
| | .-----------. 220 ohm 5 watt
| | | | ___
| | | +o------o---|___|-------o
| | | | .-.
| | 6 D | | | | /-
| | | | | |/
| | | DMM | MOV| | DUT
| | Batteries | | | |
| | | | /| |
| | | | -/ | |
| | | | '-'
| | | -o------o---------------o
| | | |
| | '-----------'
| '------------'
(created by AACircuit v1.28.6 beta 04/19/05 www.tech-chat.de)
Good luck
Chris
Hi, Geogle. Thing2 and Thing3 won't do the job -- you'll still damage
your meter.
1) Your 9V power supply is not _sufficiently_ isolated from the line
unless you've got a transformer with electrostatic shield.
2) There is no direct meter internal connection between the 9V battery
negative and the meter negative probe. You're just adding another
problem by connecting the two with a cap and zener.
3) Most cheapie meters can be damaged by applying line voltage to the
probes with the battery disconnected, or with the battery power off.
Since it takes anywhere between tenths of milliseconds and a few
milliseconds for the input filter cap of your 9V supply to get charged
up by the transformer, you're leaving yourself open to meter damage
there, too.
One of life's ancient principles is that you may not always get what
you pay for, but you always pay for what you get. Line-powered bench
DMMs cost more than battery-operated handheld DMMs for a reason, and
it's not just more accuracy.
If you open up a good benchtop DMM or look in the service manual,
you'll see that quite a bit of care has been taken to provide good
isolation between the line and the meter circuit power supply. You'll
also note that most bench DMMs specify a maximum voltage between the
probes and GND (usually between the negative probe and GND).
Many benchtop DMMs also have input circuitry that presents a high
limiting input impedance when they're unpowered.
Let's look at this from a cost standpoint, which is where I think
you're coming from. Using the Digi-Key catalog, I find that an
Energizer 9V Industrial Alkaline battery will cost $2.34 for 625mA-h at
9V. Six "D" Industrial Alkaline batteries in series will cost $8.28
for 20,500 mA-h at 9V.
According to this measure, you'll replace the 9V batteries 32 times for
each replacement of the 6 "D" batteries. Of course, the mA-h ratings
for both are based on a 25mA load, and the mA-H ratings are for
drawdown to 60% of nominal voltage. Both of these would favor the
larger D battery, and I'm sure the actual replacement ratio will be
somewhat lower than 32:1. The cost ratio, though, is only 3.5:1. 9V
batteries are a relatively expensive way to run something. You'll
easily save over 80% of the cost of running the meter by using 6 D
batteries in series. If you've got an old 7107-based meter that uses a
several mA, you'll be replacing batteries twice a year at worst. Most
of your job is done easily.
To do this relatively safely, start by snapping a 9V battery clip with
flying leads onto the 9V battery clip in the meter (note that red and
black will now be bass-ackwards). Drill a small hole in the meter
battery cover to allow the flying leads to be snaked through (you can
later fill this hole with epoxy if you want to return the meter to
regular service).
Purchase a thermoplastic (NOT metal!) project box bigger than the
meter, and also purchase two 3-cell D battery holders. Mount the
battery holders in the box, and drill a hole for the meter wires such
that the wires will fit through when the meter is affixed to the box.
I lined it up so the bottom of the meter was flush with the bottom of
the project box, so it could be stood up on end for visibility. I also
mounted a small stand on the bottom of the box to keep it from tipping
over (the D batteries tended to make it a little top-heavy).
Now either use epoxy glue or ty-raps to affix the meter permanently to
the project box. Install the 6 D batteries. Screw closed the cover on
the project box. Turn the meter on. You're done.
I've been where you are now. This works.
And this setup with the meter and plastic project box is just as safe
as the meter with the manufacturer-recommended 9V battery, if you know
what you're doing with electricity. You wouldn't try to replace the
enclosed battery on a meter while it's measuring line voltage either
way, no matter what some might say. Other than that, it just looks
kind of clunky.
Standard legal/moral/ethical disclaimers apply. Affix a visible
warning on the meter/plastic project box stating that hazardous
voltages may be present inside, if you so choose, or if you're dealing
with fresh grads who don't know which side of the soldering iron is
hot.
And if you really want to work hard to protect your cheapie meter, use
a series 220 ohm 3 watt wirewound in series with the red probe, and
place a line voltage rated MOV between the red and black probes.
|
| .------------.
| | .-----------. 220 ohm 5 watt
| | | | ___
| | | +o------o---|___|-------o
| | | | .-.
| | 6 D | | | | /-
| | | | | |/
| | | DMM | MOV| | DUT
| | Batteries | | | |
| | | | /| |
| | | | -/ | |
| | | | '-'
| | | -o------o---------------o
| | | |
| | '-----------'
| '------------'
(created by AACircuit v1.28.6 beta 04/19/05 www.tech-chat.de)
Good luck
Chris
P
Phil Hobbs
Guest
John Larkin wrote:
Let's think about some topics
and exchange them.
BTW, all, please chime in with suggestions for things to include. No
more than 20% pet peeves, please. (Well, maybe 60%--this is s.e.d,
after all.)
male and probably poorly groomed.
Cheers,
Phil Hobbs
Terrific. You write and I'll direct.
Let's think about some topics and exchange them.
BTW, all, please chime in with suggestions for things to include. No
more than 20% pet peeves, please. (Well, maybe 60%--this is s.e.d,
after all.)
Nonononono. Might catch the never-get-overs. Besides, they're mostly
male and probably poorly groomed.
An excellent start.
Cheers,
Phil Hobbs
G
Geogle
Guest
Thanks much for the enlighening reply Chris.
It will be really helpful if you could give few more clarifications
about the reply.
Chris wrote:
resistance that may come in series here ?
connected to the ref. voltage, and is at a voltage between 0 and +ve
supply. How will the input circuit get damaged by the addition of a
zener that prevents the input swinging below and above the noraml
supply ? ( Remember the DMM is exclusively used for this purpose, and
the live and neutral are connected carefully to the appropriate inputs.
) Or for that matter what is the likely source for problem from
addition of the cap ? ( I guess the neutral, unless gets accidentally
connected to live, is not going to take the input above or below the
ref. voltage the input is having. Only the live is going to take the HV
proble swing to the line voltage - Am I not correct ? )
powered
before power filter caps reaching a suitable +ve voltage.
One likely solution is to add NiCad battery on the unregulated side
through a diode and provide 30mA or so charging current from the
unregulated input. That way the batteries are likely not going to be
low - unless power goes off for a long time.
Other lproblem is surge in supply (not the case at HV probe side). Both
are not handled by the suggestions I had.
exceed 0.5 amps, enough to damage the meter ?
It will be really helpful if you could give few more clarifications
about the reply.
Chris wrote:
What is the likely values of ( or the range ) of the leakage cap the
resistance that may come in series here ?
I checked the 7107 data sheet and one of the inputs are usually
connected to the ref. voltage, and is at a voltage between 0 and +ve
supply. How will the input circuit get damaged by the addition of a
zener that prevents the input swinging below and above the noraml
supply ? ( Remember the DMM is exclusively used for this purpose, and
the live and neutral are connected carefully to the appropriate inputs.
) Or for that matter what is the likely source for problem from
addition of the cap ? ( I guess the neutral, unless gets accidentally
connected to live, is not going to take the input above or below the
ref. voltage the input is having. Only the live is going to take the HV
proble swing to the line voltage - Am I not correct ? )
I quite agree with this. In fact one of the problem is inputs getting
powered
before power filter caps reaching a suitable +ve voltage.
One likely solution is to add NiCad battery on the unregulated side
through a diode and provide 30mA or so charging current from the
unregulated input. That way the batteries are likely not going to be
low - unless power goes off for a long time.
Other lproblem is surge in supply (not the case at HV probe side). Both
are not handled by the suggestions I had.
would a 220 ohm really give protection ? - won't the peak current
exceed 0.5 amps, enough to damage the meter ?
Thank again!!
R
Rich Grise, but drunk
Guest
On Sat, 04 Feb 2006 21:29:09 +0000, Roy L. Fuchs wrote:
troll-wannabe dogging me about my syntax?
You are the one that initiated the bitch-session, don't forget.
Oh, what fools these mortals be. ;-)
the other before one of us gives up in despair, because there's somebody
on planet Earth, that I'm stupider than?
Choose your weapon, boy. >:->
Are you proclaiming this simply as a diversion so that you don't have to
answer my question?
How many labia have you seen?
Reallly!
No shit!
Up till now, I'd had the opposite impression.
I also worship The Mother Of The Universe, and have founded the Neodruids,
which is based on the fact that we all exist within the cosmic womb of
creation.
But you're reacting like there's something _bad_ about making a
comparison between vulva parts and bifurcated connector receptacle parts.
Go figure!
--Oops! There's more:
Thanks,
Rich
--
-----BEGIN GEEK CODE BLOCK-----
Version: 3.1
GAT(E P) dpu s: a++ C++@ P+ L++>+ !E W+ N++ o? K? w-- !O !M !V PS+++
PE Y+ PGP- t 5+++)-; X- R- tv+ b+ DI++++>+ D-? G e+$ h+ r-- z+
------END GEEK CODE BLOCK------
(As if you've ever been in the same room with "everyday individuals")
Huh? _I_ "should be.. upset"? About what? That there's some usenet
troll-wannabe dogging me about my syntax?
You are the one that initiated the bitch-session, don't forget.
Oh, what fools these mortals be. ;-)
I don't know. Shall we have a stupid contest? See who can out-stupid
the other before one of us gives up in despair, because there's somebody
on planet Earth, that I'm stupider than?
Choose your weapon, boy. >:->
That's irrelevant.
Are you proclaiming this simply as a diversion so that you don't have to
answer my question?
How many labia have you seen?
Reallly!
No shit!
Up till now, I'd had the opposite impression.
I also worship The Mother Of The Universe, and have founded the Neodruids,
which is based on the fact that we all exist within the cosmic womb of
creation.
But you're reacting like there's something _bad_ about making a
comparison between vulva parts and bifurcated connector receptacle parts.
Go figure!
--Oops! There's more:
Does categorizing me as "retarded" somehow make your life more fulfilling?
Thanks,
Rich
--
-----BEGIN GEEK CODE BLOCK-----
Version: 3.1
GAT(E P) dpu s: a++ C++@ P+ L++>+ !E W+ N++ o? K? w-- !O !M !V PS+++
PE Y+ PGP- t 5+++)-; X- R- tv+ b+ DI++++>+ D-? G e+$ h+ r-- z+
------END GEEK CODE BLOCK------
C
Chris
Guest
Geogle wrote:
1) Interwinding capacitance for a standard transformer (between
primary and secondary) is usually in the range of 10 to 33pF. It's a
lot less for some transformers, which advertise low capacitance. For
60Hz, that's a very high impedance, but when you turn on the switch or
turn on power, the rate of rise of voltage is very high, so you can get
enough charge squirted into the secondary to damage a CMOS chip like
the 7107.
2) I'm just telling you what worked for me. The test stations I
constructed were in operation for several years. By the time we gave
up on trying to save money on 9V batteries, we had already smoked
enough meters to pay for a lot of batteries. Of course, meters are a
lot less expensive these days and alkaline 9V batteries are relatively
more expensive. But we would have been better off just starting with
our final solution, which was just going with 6 "D" alkaline batteries
in a plastic box mounted to the back of the meter.
3) If you decide to go with your line-powered 9V supply, you can use a
delay-on relay to ensure you've powered up first, like this:
| VCC
| +
| |
| .-.
| | |
| | |
| '-'
| |
| |
| o-----o-----.
| | | |
| +| | |
| --- - C|
| --- ^ C|
| | | C|
| | | |
| === === ===
| GND GND GND
|
(created by AACircuit v1.28.6 beta 04/19/05 www.tech-chat.de)
You can use a 5V DPDT relay, and choose your R and C values
appropriately to have the DPDT relay connect the voltage to the leads
only after meter power up. But I can tell you that reduced, but didn't
solve the problem when we were doing it. We still had meters blow up,
but they smoked when the relay closed rather than at power up.
Remarkable waste of time.
Just out of curiosity -- what are you doing here? Cheapie DMMs drift,
they only take readings once a second, and they are remarkably
unresponsive to anything even approximating a real-time event,
excepting I * R voltage drops in the line from heavy loads. Also, you
have to have somebody looking at them all the time.
Is it possible you have a DMM connected with RS-232 to a PC for
automated data collection? If so, you definitely need optoisolation
between the DMM RS-232 and the PC for any line voltage measurement.
That will definitely fry your meter. But that's another story.
Good luck
Chris
Hi, Geogle. Very briefly:
1) Interwinding capacitance for a standard transformer (between
primary and secondary) is usually in the range of 10 to 33pF. It's a
lot less for some transformers, which advertise low capacitance. For
60Hz, that's a very high impedance, but when you turn on the switch or
turn on power, the rate of rise of voltage is very high, so you can get
enough charge squirted into the secondary to damage a CMOS chip like
the 7107.
2) I'm just telling you what worked for me. The test stations I
constructed were in operation for several years. By the time we gave
up on trying to save money on 9V batteries, we had already smoked
enough meters to pay for a lot of batteries. Of course, meters are a
lot less expensive these days and alkaline 9V batteries are relatively
more expensive. But we would have been better off just starting with
our final solution, which was just going with 6 "D" alkaline batteries
in a plastic box mounted to the back of the meter.
3) If you decide to go with your line-powered 9V supply, you can use a
delay-on relay to ensure you've powered up first, like this:
| VCC
| +
| |
| .-.
| | |
| | |
| '-'
| |
| |
| o-----o-----.
| | | |
| +| | |
| --- - C|
| --- ^ C|
| | | C|
| | | |
| === === ===
| GND GND GND
|
(created by AACircuit v1.28.6 beta 04/19/05 www.tech-chat.de)
You can use a 5V DPDT relay, and choose your R and C values
appropriately to have the DPDT relay connect the voltage to the leads
only after meter power up. But I can tell you that reduced, but didn't
solve the problem when we were doing it. We still had meters blow up,
but they smoked when the relay closed rather than at power up.
Remarkable waste of time.
Just out of curiosity -- what are you doing here? Cheapie DMMs drift,
they only take readings once a second, and they are remarkably
unresponsive to anything even approximating a real-time event,
excepting I * R voltage drops in the line from heavy loads. Also, you
have to have somebody looking at them all the time.
Is it possible you have a DMM connected with RS-232 to a PC for
automated data collection? If so, you definitely need optoisolation
between the DMM RS-232 and the PC for any line voltage measurement.
That will definitely fry your meter. But that's another story.
Good luck
Chris
G
Geogle
Guest
Chris wrote:
That is really a cool idea!, though the power requirement of the
measuring device goes up with the inclusion of a relay. A solid state
relay of reasonable cost would be a nicer choice!.
thought
of asking for experts help - so the posting.
would prefer a microcontrller project for atomated collection of data.
Newer micros have even USB interface for things like flash attachments
for storage. Add an RTC and it will be really cool ( I haven't seen
one with built in RTC, but likely that they there.. )
Thanks much Chris!
That is really a cool idea!, though the power requirement of the
measuring device goes up with the inclusion of a relay. A solid state
relay of reasonable cost would be a nicer choice!.
It is just for home use, nothing serious. When the meter got damaged, I
thought
of asking for experts help - so the posting.
That would have been better. But concidering the power consumption, I
would prefer a microcontrller project for atomated collection of data.
Newer micros have even USB interface for things like flash attachments
for storage. Add an RTC and it will be really cool ( I haven't seen
one with built in RTC, but likely that they there.. )
J
John Fields
Guest
On Tue, 07 Feb 2006 22:06:24 +0000, capnfishytakethisout@lineone.net
wrote:
Good luck!
--
John Fields
Professional Circuit Designer
wrote:
---
Good luck!
--
John Fields
Professional Circuit Designer
E
ehsjr
Guest
Geogle wrote:
trickle* charger by a SPDT switch. In the off position, the NiCd
is connected to the charger (C/20 or lower) and in the on position
it's connected to the DMM. Add an auto-off circuit if you are
afraid of forgetting and leaving the thing on.
*= for the trickle charger you want to keep the charge rate
very low once the battery pack is charged. You can use a LM317
set for constant c and a 431 to pull current once the terminal
voltage is reached.
If you have to have 24x7 meter operation, here's what you can do
using a DPDT relay, charger and NiCds:
---------
Wallwart===|charger +|---------+ +------+----+
| | | | | |
| -|---+ o o | D
--------- | | | [C] M
| |>| <| |>| <| | M
+--------+ | | | | | |
| | | | | +----+
+---NiCd1----+ +---+ | |
| | | | |
+---NiCd2--- | ---+ | |
| | | |
| +-------------+ |
| |
+-----------------------------------+
The idea is that while one NiCd pack is charging, the other
is powering the meter. This will give you 24x7 use of the DMM.
A large C will power the DMM during the ~10 mS transition as
the relay switches. You can switch the relay based on the
voltage of the NiCd in use with a comparator & driver, powering
that circuit from the wallwart. Or you could do it based on
time.
Ed
I think we'd all love "a solid state relay of reasonable cost"
I think simplest would just be one NiCd pack, connected to a
trickle* charger by a SPDT switch. In the off position, the NiCd
is connected to the charger (C/20 or lower) and in the on position
it's connected to the DMM. Add an auto-off circuit if you are
afraid of forgetting and leaving the thing on.
*= for the trickle charger you want to keep the charge rate
very low once the battery pack is charged. You can use a LM317
set for constant c and a 431 to pull current once the terminal
voltage is reached.
If you have to have 24x7 meter operation, here's what you can do
using a DPDT relay, charger and NiCds:
---------
Wallwart===|charger +|---------+ +------+----+
| | | | | |
| -|---+ o o | D
--------- | | | [C] M
| |>| <| |>| <| | M
+--------+ | | | | | |
| | | | | +----+
+---NiCd1----+ +---+ | |
| | | | |
+---NiCd2--- | ---+ | |
| | | |
| +-------------+ |
| |
+-----------------------------------+
The idea is that while one NiCd pack is charging, the other
is powering the meter. This will give you 24x7 use of the DMM.
A large C will power the DMM during the ~10 mS transition as
the relay switches. You can switch the relay based on the
voltage of the NiCd in use with a comparator & driver, powering
that circuit from the wallwart. Or you could do it based on
time.
Ed
N
no
Guest
Be glad it somehow refused to charge. Never attempt to charge a NiMH
battery with a NiCd charger! People have burned down their houses this
way.
I can't see how it would. Thats the difference between a NiCd and an NiMH
charger. A NiCd charger may not detect when a NiMH battery is full and
continue rapid charging. The excess charge will turn into heat,
destroying the battery and possibly anything surrounding it.
C
Cliff
Guest
On Thu, 09 Feb 2006 13:25:57 -0500, Spehro Pefhany
<speffSNIP@interlogDOTyou.knowwhat> wrote:
Batteries
http://www.batterystation.com/cncmachine.htm
http://www.batterystation.com/
(Thanks to Bryce)
]
<speffSNIP@interlogDOTyou.knowwhat> wrote:
[
Batteries
http://www.batterystation.com/cncmachine.htm
http://www.batterystation.com/
(Thanks to Bryce)
]
Guest
Oops. Looks like he collected $7.2 BILLION...
http://www.arcticbeacon.com/9-May-2005.html
Nick
D
daestrom
Guest
<nicksanspam@ece.villanova.edu> wrote in message
news:dsnoo2$6re@acadia.ece.villanova.edu...
part of is making the payments. He claims the government should be
responsible.
Then he tries to show some unspecified mystery about WTC-7 which,
"...photographs of it show only insignificant fires."
The plaintiff probably doesn't even know what a 'significant fire' would be
if it occured in his living room.
daestrom
news:dsnoo2$6re@acadia.ece.villanova.edu...
Some *yahoo* shareholder is upset because the insurance company he owns a
part of is making the payments. He claims the government should be
responsible.
Then he tries to show some unspecified mystery about WTC-7 which,
"...photographs of it show only insignificant fires."
The plaintiff probably doesn't even know what a 'significant fire' would be
if it occured in his living room.
daestrom
R
rqlhgl@ieee.org
Guest
The capital K refers to the overall (device embedded in the circuit)
stability, k is the Rollet stability factor. Even if k <1 at some
frequencies one can make K>1 at all frquencies by lossy embedding and
or feedback. Having done this the overall circuit will be
unconditionally stable for all non-feedback terminations with
reflection coefficients no greater than1.
Dick
stability, k is the Rollet stability factor. Even if k <1 at some
frequencies one can make K>1 at all frquencies by lossy embedding and
or feedback. Having done this the overall circuit will be
unconditionally stable for all non-feedback terminations with
reflection coefficients no greater than1.
Dick
C
Chris
Guest
Jeff Dege wrote:
most things are kind of the same. Let's see...
Before anything else, I'm assuming you have a diode across your relay
coil already. If not, that definitely could cause your processor to
reset. Lenz' Law will rear its angry head, and put a voltage spile on
the switching side of the coil that will feed into your processor
output pin or power supply, if it doesn't kill the switching
transistor. Put a 1N400X diode directly across the coil as shown
_now_. That should have been first.
1) "Across the contacts" means directly next to, and in parallel with,
your switch contacts. It should look like this (view in fixed font or
M$ Notepad):
|
| VCCVCC .----- o --------o-----------------.
| + + | | | |
| | | | |6.8 ohms | |
| | | RY1 | .-. | .-.
| - C| o | | .-. | |
| ^ C| - - - - \ | | | | MOV | |
| | C| \ '-' | |(optional) '-' Load
| | | o \ | R-C | | | (Doorbell)
| '--o | |Snubber | | |
| | | | '-' C|
| | | --- | C|
| |/ | --- | C|
| -| | |2.2uF | |
| |> | | | |
| | '------o---------o-----------------'
| |
| ===
| GND
|
(created by AACircuit v1.28.6 beta 04/19/05 www.tech-chat.de)
2) It helps to turn down the lights, but all you really need to do is
keep it out of sunlight, and put a cardboard box cover over your stuff
so there's no shop light shining directly on it. You don't have to be
picky about this -- it's "rule of thumb" here. If you want technical
rigour, look toward s.e.d. ;-)
You assume you've got a 1 amp load with doorbells and chimes -- it
could be less, and could be a little more. Most bell transformers are
rated for about an amp. We're trying to be non-technical with this, so
I just made some assumptions.
By the way, since you've got a 16VAC system (you're reading 20VAC
unloaded), the choice for MOV isn't correct. Try the Littelfuse V47Z20
(Mouser P/N 576-V47ZA20, in stock, $0.42 ea. in single qty). For caps,
you might want to look first at what you have in your junkbox. This
all presupposes you can substitute the caps in the snubber for optimum.
But if not, you might want to look at
http://www.mouser.com/
and find a good cap. In order to complete things, if you don't happen
to have a well-stocked junkbox, here's your shopping list from Mouser:
1N4002 diode (625-1N4002)
6.2 ohm, 3 watt wirewound resistor (72-RWM410-8R2-5)
1.0uF 100V Metallized Poly Film cap ( 581-BN154E0105K)
30vRMS, 20mm MOV (576-V47ZA20)
Use these together, make an effort to get the relay physically farther
away from your PIC, and you should be OK.
Good luck
Chris
Hi, Jeff. You've got a 16VAC system rather than a 10VAC system, but
most things are kind of the same. Let's see...
Before anything else, I'm assuming you have a diode across your relay
coil already. If not, that definitely could cause your processor to
reset. Lenz' Law will rear its angry head, and put a voltage spile on
the switching side of the coil that will feed into your processor
output pin or power supply, if it doesn't kill the switching
transistor. Put a 1N400X diode directly across the coil as shown
_now_. That should have been first.
1) "Across the contacts" means directly next to, and in parallel with,
your switch contacts. It should look like this (view in fixed font or
M$ Notepad):
|
| VCCVCC .----- o --------o-----------------.
| + + | | | |
| | | | |6.8 ohms | |
| | | RY1 | .-. | .-.
| - C| o | | .-. | |
| ^ C| - - - - \ | | | | MOV | |
| | C| \ '-' | |(optional) '-' Load
| | | o \ | R-C | | | (Doorbell)
| '--o | |Snubber | | |
| | | | '-' C|
| | | --- | C|
| |/ | --- | C|
| -| | |2.2uF | |
| |> | | | |
| | '------o---------o-----------------'
| |
| ===
| GND
|
(created by AACircuit v1.28.6 beta 04/19/05 www.tech-chat.de)
2) It helps to turn down the lights, but all you really need to do is
keep it out of sunlight, and put a cardboard box cover over your stuff
so there's no shop light shining directly on it. You don't have to be
picky about this -- it's "rule of thumb" here. If you want technical
rigour, look toward s.e.d. ;-)
You assume you've got a 1 amp load with doorbells and chimes -- it
could be less, and could be a little more. Most bell transformers are
rated for about an amp. We're trying to be non-technical with this, so
I just made some assumptions.
By the way, since you've got a 16VAC system (you're reading 20VAC
unloaded), the choice for MOV isn't correct. Try the Littelfuse V47Z20
(Mouser P/N 576-V47ZA20, in stock, $0.42 ea. in single qty). For caps,
you might want to look first at what you have in your junkbox. This
all presupposes you can substitute the caps in the snubber for optimum.
But if not, you might want to look at
http://www.mouser.com/
and find a good cap. In order to complete things, if you don't happen
to have a well-stocked junkbox, here's your shopping list from Mouser:
1N4002 diode (625-1N4002)
6.2 ohm, 3 watt wirewound resistor (72-RWM410-8R2-5)
1.0uF 100V Metallized Poly Film cap ( 581-BN154E0105K)
30vRMS, 20mm MOV (576-V47ZA20)
Use these together, make an effort to get the relay physically farther
away from your PIC, and you should be OK.
Good luck
Chris