Driver to drive?

[Mike]

In article <84aba9ac-cd81-437c-b3f4-2d0a558e97d9@googlegroups.com>,
<makolber@yahoo.com> wrote:

Unfortunately, it turned out that the APC SmartUPS 1000 (and some other
APC models as well) CANNOT be switched ON when the mains has failed!!

Some units require that you PRESS AND HOLD the on off button for a few seconds to start without AC power.

True: But a lot of APC brand units take the attitude that if there's no
utility power, there's no point *letting* you power the load.

All that will happen is it will lose power again when the
batteries expire. So no. You can't

This is a problem if you plan to use it as a short-term portable
power source.
--
--------------------------------------+------------------------------------
Mike Brown: mjb[-at-]signal11.org.uk | http://www.signal11.org.uk

 

[Phil Allison]

Jeff Liebermann wrote:

I beg to differ with your diagnosis. Unless the LED has magically
turned into a thermostat controlled flasher, it's not going to do
that.

** The OP is probably correct and I have seen the same symptoms with 3mm red LEDs. Over time, excess DC current damages the LED chips and they intermittently drop light output and blink on and off.

Caused havoc in a Mesa Boogie amplifier when most of the dropping resistors for the 20 odd LED/CdS cell opto-couplers were the wrong value, by a factor of 10, resulting in almost 100mA of drive current.


..... Phil

 

[Clifford Heath]

On 22/03/16 15:52, Phil Allison wrote:

Jeff Liebermann wrote:
I beg to differ with your diagnosis. Unless the LED has magically
turned into a thermostat controlled flasher, it's not going to do
that.
** The OP is probably correct and I have seen the same symptoms with 3mm red LEDs.
Over time, excess DC current damages the LED chips and they
intermittently drop light output and blink on and off.

I think I recall someone here surmising that the bonding had failed
due to thermal cycling - each time the bond heats, it disconnects
and starts to cool. Something like that could happen to the chip,
of course, but my money would be on the bond.

 

[Jeff Liebermann]

On Mon, 21 Mar 2016 21:52:04 -0700 (PDT), Phil Allison
<pallison49@gmail.com> wrote:

Jeff Liebermann wrote:


I beg to differ with your diagnosis. Unless the LED has magically
turned into a thermostat controlled flasher, it's not going to do
that.

** The OP is probably correct and I have seen the same symptoms with
3mm red LEDs. Over time, excess DC current damages the LED chips and
they intermittently drop light output and blink on and off.

That's quite possible. I've seen something like that only once, but
not at the claimed 0.5 second cycle time. With an old LED, it was
like about 5-10 seconds ON and 0.5 seconds OFF. It takes a while for
the heat from the LED to cause the wire bond to move, but less time
for the leads to conduct the heat away.

Caused havoc in a Mesa Boogie amplifier when most of the dropping
resistors for the 20 odd LED/CdS cell opto-couplers were the wrong
value, by a factor of 10, resulting in almost 100mA of drive current.


.... Phil

--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

 

On Monday, March 21, 2016 at 1:30:11 PM UTC-4, DaveC wrote:

The LED in my flashlight is blinking (2/sec). It's not the support
circuitry (constant current): the voltage across the LED is constant 4v. I
presume it's a failure mode of the LED. It happens immediately upon
power-on.

http://imgur.com/a/rIRDG

The form-factor is close to a 5x5mm (h x diam). Standard through-hole leads.

But it's a pretty high-intensity one. Don't know what makes it so, but I
classify anything with a yellow square visible in the center as
"high-intensity". Maybe not technically accurate, but there you are.

What I've found so far is either a standard 5mm LED but not very bright, or
SMD types requiring heat sinks.

It's a great little light, and I've not found anything as small,
long-lasting, with single AA that I like as much. And this is a learning
experience, so there's that.

Any pointers to a suitable replacement LED would be appreciated.

Thanks.

The blinking seems to come from intermittent LED die bond wires, whose
contact breaks as the LED die heats up. It's especially common in
over-driven LEDs.

Your LED looks like an 8mm unit with no lens, to my eyeball. Just about
any topless LED would substitute without affecting your optics. Matching
the height off the PCB would be the main consideration.

None of the through-hole packaged LEDs are made for the 300-odd mW your
flashlight is pounding through it. A sturdier choice would be one of the
1-to-3W SMD units, such as a Luxeon Rebel, etc. Put it on a copper pour
or foil for heat dissipation and you'll both live a lot longer and happier.

(You could stick copper foil tape on top of that existing PCB pretty easily.)

You could also consider one of the rectangular 0.5W SMD-types, such as the
5630 or 5050 formats on eBay.

http://www.ebay.com/itm/100PCS-SMD-5630-5730-Big-chip-0-5W-High-Power-White-Warm-white-LED-Light-/121915624110?hash=item1c62bccaae:g:a44AAOSwhkRWgf0o

Those are usually multi-chip though, producing inferior focusing. And don't
forget to heat-sink them. They still need it.

Personally, I'd prefer a single-chip power LED as my first-choice.

Cheers,
James Arthur

 

On Saturday, March 26, 2016 at 3:56:19 PM UTC-4, Andre Majorel wrote:

On 2016-03-22, Jeff Liebermann <jeffl@cruzio.com> wrote:

If it uses an MLCC capacitor, use a hot air gun to reflow, not
a soldering iron tip.

News to me. In what way are multi-layer ceramic caps and
soldering irons incompatible ?

Rapid, uneven heating can crack MLCC capacitors. YMMV.

Cheers,
James Arthur

 

On Sunday, March 27, 2016 at 1:20:13 PM UTC-4, John Larkin wrote:

On Sat, 26 Mar 2016 19:56:12 +0000 (UTC), Andre Majorel
cheney@halliburton.com> wrote:

On 2016-03-22, Jeff Liebermann <jeffl@cruzio.com> wrote:

If it uses an MLCC capacitor, use a hot air gun to reflow, not
a soldering iron tip.

News to me. In what way are multi-layer ceramic caps and
soldering irons incompatible ?

Not a bit.

I've seen a couple of the larger MLCCs crack. Now I tap both sides of
those with the iron beforehand, to even out the heat. Seems to work.

Cheers,
James Arthur

 

[whit3rd]

On Sunday, March 27, 2016 at 10:20:13 AM UTC-7, John Larkin wrote:

On Sat, 26 Mar 2016 19:56:12 +0000 (UTC), Andre Majorel
cheney@halliburton.com> wrote:

On 2016-03-22, Jeff Liebermann <jeffl@cruzio.com> wrote:

If it uses an MLCC capacitor, use a hot air gun to reflow, not
a soldering iron tip.

News to me. In what way are multi-layer ceramic caps and
soldering irons incompatible ?

Not a bit.

Oh, there's incompatibility, all right. At soldering temperatures, lots of
surface-mount devices are very delicate, a little mechanical stress and
they come apart. MLCC capacitors are made of ceramic (OK at temperature)
nickel-alloy endcaps (OK at temperature), and tin. When you get to
the softening temperature of tin, the endcaps can come off with
a little surface tension or jostle from an adjacent solder iron tip.

 

[krw]

On Sun, 27 Mar 2016 10:48:04 -0700 (PDT), dagmargoodboat@yahoo.com
wrote:

On Sunday, March 27, 2016 at 1:20:13 PM UTC-4, John Larkin wrote:
On Sat, 26 Mar 2016 19:56:12 +0000 (UTC), Andre Majorel
cheney@halliburton.com> wrote:

On 2016-03-22, Jeff Liebermann <jeffl@cruzio.com> wrote:

If it uses an MLCC capacitor, use a hot air gun to reflow, not
a soldering iron tip.

News to me. In what way are multi-layer ceramic caps and
soldering irons incompatible ?

Not a bit.

I've seen a couple of the larger MLCCs crack. Now I tap both sides of
those with the iron beforehand, to even out the heat. Seems to work.

Like ESD, it's the latent damage that's worrisome. I don't hesitate
to use an iron but I'm not too worried about what happens next year
(or if it even fails this year - just have to fix it).

 

On Sunday, March 27, 2016 at 11:45:30 PM UTC-4, Jon Elson wrote:

Andre Majorel wrote:

On 2016-03-22, Jeff Liebermann <jeffl@cruzio.com> wrote:

If it uses an MLCC capacitor, use a hot air gun to reflow, not
a soldering iron tip.

News to me. In what way are multi-layer ceramic caps and
soldering irons incompatible ?

Really, before I got my pick and place machine, I hand-soldered about 25,000
.1uF 0805 capacitors. NEVER ONCE had a bad one. I still hand-solder a fair
number of low production boards and prototypes, and have never seen a
problem with MLCCs.

Jon

I've never wrecked a 100nF 0805--those have a pretty small thermal mass.
The couple(?) I cracked were fatties, 1210(?) and as tall as wide IIRC.

It hasn't happened in a very long time though, despite me not always
bothering to be careful.

My current project uses a number of 1210 22uF 25V MLCCs but I didn't
solder them, Mr. Reflow did.

Cheers,
James Arthur

 

This old thread describes exactly our problem. The equipment was designed/built in the 2000s. Problem dealing with 1000uF 200V caps. Perhaps the OP was dealing with the same equipment.

On Saturday, October 11, 2003 at 2:41:06 PM UTC-7, Fritz Schlunder wrote:

"Yzordderex" <yzordderrex@verizon.net> wrote in message

What are we actually trying to do here? Just soft start a bus cap?
Boost 200v to 500v? I suspect it's just limit the charging current.

Yes, inrush current as well as overall current limit.

Maybe look at NTC thermister. NTC good for about 20 or 30 amps of DC
current. If you don't like that idea, just use a big diode bridge and
forget about the soft charge.

20A is way too big. Ideally, we don't want more than 2A.

So at the very lowest range 1000uF up to 200V we have an energy storage of
0.5CV^2. In this case:

0.5*0.001*200^2=20 Joules

At the higher range (but still assume 1000uF even though the OP said >1mF)
of 500V we have:

0.5*0.001*500^2=125 Joules

Now assuming we don't have some sort of switch mode constant current source
or other charging method using inductors, the total energy that must be
dissipated somewhere while charging the capacitor from 0V to 200-500V is 20J
or 125J respectively. That is way too much energy at way too high a
potential difference to avoid using inrush limiting.

If the DC bus voltage is stiff enough, the effect of charging the capacitor
instantly from it will be the same as discharging the capacitor by short
circuiting it while charged to 200V-500V.

Try short circuiting a 1000uF capacitor charged to 500V and you will
instantly understand why inrush limiting is required. To do this reasonably
safely wear sunglasses and use earplugs. The resulting bang is outright
deafening, and it will do severe contact damage (likely spewing small molton
balls of metal outwards). If you do this with a mechanical switch the
contacts will be eroded to the point of uselessness in probably the very
first closing cycle.

If the capacitor charging current must flow through diode(s), it doesn't
matter how large they are (well maybe a hockey puck size one might handle
it) they will be destroyed if they instantly dissipate 125J. How much
inrush limiting is really necessary depends upon how stiff the 200V-500V
supply is. If it is very stiff (plain mains sent through a bridge rectifier
for instance) you will need an inrush limiter that can handle the full 125J.
If the supply is something like the secondary of a transformer sent through
a bridge recitfier, then the leakage inductances and winding resistances
will dissipate/limit peak amplitude of that of that 125J and your inrush
limiter need not be anywhere near as big.


NTC thermistors are the easiest way to provide inrush limiting, although one
that can handle 125J or more is going to be awefully large and very uncommon
(maybe non-existant). As such the more practical method employed at these
levels might be to use a decent sized power resistor (maybe a 15W+ wirewound
at around 4.7R) in parallel with a relay. The relay is energized by some
form of delay circuit, preferrably one that monitors the voltage on both
sides of the 4.7R power resistor and turns on only when it approaches a
small enough value. The relay should be rapidly turned off when the device
is powered down.

If this is for a high power xenon stobe or similar application then you
really aught to use a switch mode constant current source for best
efficiency. That is more complicated. Perhaps an understatement.

How about a large resistor, says 10K, for a pre-power up switch, then power-up switch a few minutes later. It's a quick and dirty temporary solution until we have something better.

 

[Phil Hobbs]

On 03/28/2016 01:00 AM, dagmargoodboat@yahoo.com wrote:

On Sunday, March 27, 2016 at 11:45:30 PM UTC-4, Jon Elson wrote:
Andre Majorel wrote:

On 2016-03-22, Jeff Liebermann <jeffl@cruzio.com> wrote:

If it uses an MLCC capacitor, use a hot air gun to reflow, not
a soldering iron tip.

News to me. In what way are multi-layer ceramic caps and
soldering irons incompatible ?

Really, before I got my pick and place machine, I hand-soldered about 25,000
.1uF 0805 capacitors. NEVER ONCE had a bad one. I still hand-solder a fair
number of low production boards and prototypes, and have never seen a
problem with MLCCs.

Jon

I've never wrecked a 100nF 0805--those have a pretty small thermal mass.
The couple(?) I cracked were fatties, 1210(?) and as tall as wide IIRC.

It hasn't happened in a very long time though, despite me not always
bothering to be careful.

My current project uses a number of 1210 22uF 25V MLCCs but I didn't
solder them, Mr. Reflow did.

I have a set of the Metcal tweezers that work well for that. (You need
normal tweezers in your other hand if you want to reuse the
part--otherwise you have to shake it off and it gets lost.)

Cheers

Phil Hobbs


--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203
Briarcliff Manor NY 10510

hobbs at electrooptical dot net
http://electrooptical.net

 

[krw]

On Mon, 28 Mar 2016 09:44:54 -0400, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

On 03/28/2016 01:00 AM, dagmargoodboat@yahoo.com wrote:
On Sunday, March 27, 2016 at 11:45:30 PM UTC-4, Jon Elson wrote:
Andre Majorel wrote:

On 2016-03-22, Jeff Liebermann <jeffl@cruzio.com> wrote:

If it uses an MLCC capacitor, use a hot air gun to reflow, not
a soldering iron tip.

News to me. In what way are multi-layer ceramic caps and
soldering irons incompatible ?

Really, before I got my pick and place machine, I hand-soldered about 25,000
.1uF 0805 capacitors. NEVER ONCE had a bad one. I still hand-solder a fair
number of low production boards and prototypes, and have never seen a
problem with MLCCs.

Jon

I've never wrecked a 100nF 0805--those have a pretty small thermal mass.
The couple(?) I cracked were fatties, 1210(?) and as tall as wide IIRC.

It hasn't happened in a very long time though, despite me not always
bothering to be careful.

My current project uses a number of 1210 22uF 25V MLCCs but I didn't
solder them, Mr. Reflow did.


I have a set of the Metcal tweezers that work well for that. (You need
normal tweezers in your other hand if you want to reuse the
part--otherwise you have to shake it off and it gets lost.)

I don't like to reuse parts anyway but I've found that if I clean the
tip/tweezers with IPA (not the drinking kind), parts don't stick
nearly as badly. Burnt flux is sticky.

 

[Clifford Heath]

On 29/03/16 00:44, Phil Hobbs wrote:

I have a set of the Metcal tweezers that work well for that. (You need
normal tweezers in your other hand if you want to reuse the
part--otherwise you have to shake it off and it gets lost.)

Tap the tip with the part on the edge of a little tray or dish,
and the part (with stray solder blobs) drops in the dish.
Better than having stray blobs roaming your desk looking to
make trouble, even if you don't re-use the parts.

Clifford Heath.

 

[Phil Hobbs]

I have a set of the Metcal tweezers that work well for that.  (You need
normal tweezers in your other hand if you want to reuse the
part--otherwise you have to shake it off and it gets lost.)

I don't like to reuse parts anyway but I've
found that if I clean the
tip/tweezers with IPA (not the drinking kind), parts don't stick
nearly as badly.  Burnt flux is sticky.

For the normal cold tweezers, I agree. For the hot ones, I think it's mainly the surface tension of the molten solder that's the issue.

When debugging boards, it's often useful to be able to pull off some part to measure it or see what the circuit does without it. It's way quicker to put the original part back than find a new one and replace it. I agree that you don't want to do that when reworking a production board.

Cheers

Phil Hobbs

 

[George Herold]

On Friday, April 1, 2016 at 7:43:24 PM UTC-4, Michael Terrell wrote:

krw wrote:

On Fri, 01 Apr 2016 17:21:31 -0400, "Michael A. Terrell"
mike.terrell@earthlink.net> wrote:


krw wrote:

Michael A. Terrell wrote:

How were the new caps stored? If it is where they can adsorb
moisture, you can damage them with an iron that is too hot.

I haven't had any problems with cracking but I used to have problems
with end caps falling off. I haven't seen the issue for some time,
though perhaps it was a problem with the manufacturer. Our purchasing
group prefers Murata, so that's what I use (GRM series).


We pre baked some boards and other components before assembly and
reflow. That eliminated cracked multilayer SMD capacitors, tombstoning
of two lead components and losing end caps. That was in N Central
Florida which has plenty of humidity problems. The so called HVAC
'engineers' were clueless about how to control the humidity, so we had
to resort to baking. LSI SMD ICs were backed and heat sealed into
antistatic bags with moisture adsorbing packets.

Sure, baking humidity sensitive parts is common before pick-n-place.
It's a bit less common when hand (de)soldering, though. ;-)


We had a high failure rate on hand soldered FIR chips, before we
started baking them. The bottom of the packaging was the thinnest, and
it would bow out as it released steam during hand soldering. No one in
EE or ME believed me, until I finally got them to try it for themselves.

Grin, one of Mueller's theorems is;
If it happens it must be possible.

George H.

 

[krw]

On Fri, 1 Apr 2016 18:45:41 -0700 (PDT), George Herold
<gherold@teachspin.com> wrote:

On Friday, April 1, 2016 at 7:43:24 PM UTC-4, Michael Terrell wrote:
krw wrote:

On Fri, 01 Apr 2016 17:21:31 -0400, "Michael A. Terrell"
mike.terrell@earthlink.net> wrote:


krw wrote:

Michael A. Terrell wrote:

How were the new caps stored? If it is where they can adsorb
moisture, you can damage them with an iron that is too hot.

I haven't had any problems with cracking but I used to have problems
with end caps falling off. I haven't seen the issue for some time,
though perhaps it was a problem with the manufacturer. Our purchasing
group prefers Murata, so that's what I use (GRM series).


We pre baked some boards and other components before assembly and
reflow. That eliminated cracked multilayer SMD capacitors, tombstoning
of two lead components and losing end caps. That was in N Central
Florida which has plenty of humidity problems. The so called HVAC
'engineers' were clueless about how to control the humidity, so we had
to resort to baking. LSI SMD ICs were backed and heat sealed into
antistatic bags with moisture adsorbing packets.

Sure, baking humidity sensitive parts is common before pick-n-place.
It's a bit less common when hand (de)soldering, though. ;-)


We had a high failure rate on hand soldered FIR chips, before we
started baking them. The bottom of the packaging was the thinnest, and
it would bow out as it released steam during hand soldering. No one in
EE or ME believed me, until I finally got them to try it for themselves.

Grin, one of Mueller's theorems is;
If it happens it must be possible.

Sure. If a component can absorb water in its packaging, there's no
reason to assume that it won't after it's placed.

 

[Michael A. Terrell]

George Herold wrote:

Michael Terrell wrote:

krw wrote:

Michael A. Terrell wrote:

We had a high failure rate on hand soldered FIR chips, before we
started baking them. The bottom of the packaging was the thinnest,
and it would bow out as it released steam during hand soldering. No
one in EE or ME believed me, until I finally got them to try it for
themselves.

Grin, one of Mueller's theorems is;
If it happens it must be possible.

AKA: Murphy was an optimist. He was sure things would go wrong!

Are you still using small NTSC color monitors? I just bought a couple
of these to use with security cameras. They are supposed to be about
4.3" screens. They run on 12 VDC and cost under $18, each.

http://www.ebay.com/itm/141496485430

 

[China Mould Factory]

Somebody here need plastic injection molding factory in China? We custom make plastic and rubber parts as per 3D drawings or samples or prototypes. No MOQ required that helps you expand the marketing. We are small but responsible manufacturer. sales01(at)rpimoulding(d0t)com Vicky Respon Plastic Industrial Co., Ltd.

 

[Jon Elson]

DaveC wrote:

http://imgur.com/Trvs5mk

This is a beeper piezo in a Fluke 117 DMM which quite beeping. Scoped the
piezo’s pads and... nothing.

An inverter (from the CD4069) is connected across the piezo. Guess I don’t
understand anything about driving piezos.

Is this a standard practice?
Cheers.

There are two types of Piezo elements, 2-terminal and 3-terminal. The two-
terminal ones use an external frequency reference, and apply it to the two
terminals. On these, the device needs to send a signal reasonably close to
the resonant frequency of the disc to get a strong sound.

The 3-terminal ones are "self-oscillating", and have a small pickup
metallization that feeds back to the driver. This can be done with a couple
sections of a CD4069 and a couple RCs. The advantage is these will always
sound exactly at the resonant frequency of the disc, so you get the loudest
sound the device can make on that voltage.

Jon