Transistors

Uncle Steve · May 10, 2013

Ok, this is a question that is not so battery-charger specific, but
is obviously related.

So here's a circuit fragment:

18V +----+--------__^------/\/\/-----------+
| 2n3055| 0R5 |
| | 5W /
| | \ 5R10W
| | /
|_______|> \
| |_ 2n2906 |
| | |
| | |
| | |
+------__^ 2n2222 |
| |
/ |
1M \ |
/ |
\ |
| |
| |
\ SW |
\ |
| |
5V +-----------+ |
|
GND +-----------+-------------------------+

So this circuit shows ~38mA going in to the base of the 2n3055, and
~13.9V across the 5 ohm resistor. It gets warm quickly.

If I change the 2n3055 for a TIP147 (PNP, beta 1k) and make the
obvious changes to the 2n2906 to make it work, there is ~80mA current
at the base of the TIP147, and ~14.1V across the 10W resistor.

WTF, over?

Needless to say I am happy that my $14.00 DVM has a transistor tester,
because with 10k feeding the 2n2222 the 2n2906 doesn't last very long
with a TIP147 in-circuit. Of course, in that configuration the base
of a 2n3055 still shows 38mA. These results suggest that the
base-emitter current of the 2n3055 cannot go any higher without a
larger power supply, but that is supposition that the 2n3055 somehow
limits the base current to some proportionate ratio to the collector-
emitter current available to it. Is that in any way a reasonable
explanation for what is occurring here?

Regards,

Uncle Steve

--
There should be a special word in the English language to identify
people who create problems and then turn around and offer up their own
tailor-made bogus non-solutions designed to completely avoid the root
causes of the situation under consideration. 'Traitor' might be a
good choice, but lacks the requisite specificity. One of the problems
with contemporary English is it lacks many such words that would
otherwise categorically identify certain kinds of person, place, or
thing -- making it difficult or impossible to think analytically about
such objects. These shortcomings of the English lexicon are
representative of Orwellian linguistics at work in the real world.

Phil Allison · May 10, 2013

"Uncle Steve"

Of course, in that configuration the base
of a 2n3055 still shows 38mA. These results suggest that the
base-emitter current of the 2n3055 cannot go any higher without a
larger power supply, but that is supposition that the 2n3055 somehow
limits the base current to some proportionate ratio to the collector-
emitter current available to it. Is that in any way a reasonable
explanation for what is occurring here?

** Yep.

The B-E current is related to the C-E current by a ratio called "beta" or
"Hfe". Beta is not however a fixed number, it varies over the range of
possible collector currents.

For a 2N3055 over the range of 0.1 amps to 3 amps, the number is fairly
constant at about 50 to 100 - depending on the particular device. The value
falls at lower and higher currents PLUS when the C-E voltage is very low.

See figure 3 " DC Current Gain, 2N3055 NPN "

http://www.onsemi.com/pub_link/Collateral/2N3055-D.PDF

All the graphs are worth study, as this is how most power transistors
behave.

.... Phil

Jim Thompson · May 10, 2013

On Thu, 09 May 2013 20:59:01 -0400, Uncle Steve <stevet810@gmail.com>
wrote:

Ok, this is a question that is not so battery-charger specific, but
is obviously related.

So here's a circuit fragment:

18V +----+--------__^------/\/\/-----------+
| 2n3055| 0R5 |
| | 5W /
| | \ 5R10W
| | /
|_______|> \
| |_ 2n2906 |
| | |
| | |
| | |
+------__^ 2n2222 |
| |
/ |
1M \ |
/ |
\ |
| |
| |
\ SW |
\ |
| |
5V +-----------+ |
|
GND +-----------+-------------------------+

So this circuit shows ~38mA going in to the base of the 2n3055, and
~13.9V across the 5 ohm resistor. It gets warm quickly.

If I change the 2n3055 for a TIP147 (PNP, beta 1k) and make the
obvious changes to the 2n2906 to make it work, there is ~80mA current
at the base of the TIP147, and ~14.1V across the 10W resistor.

WTF, over?

Needless to say I am happy that my $14.00 DVM has a transistor tester,
because with 10k feeding the 2n2222 the 2n2906 doesn't last very long
with a TIP147 in-circuit. Of course, in that configuration the base
of a 2n3055 still shows 38mA. These results suggest that the
base-emitter current of the 2n3055 cannot go any higher without a
larger power supply, but that is supposition that the 2n3055 somehow
limits the base current to some proportionate ratio to the collector-
emitter current available to it. Is that in any way a reasonable
explanation for what is occurring here?

Regards,

Uncle Steve

Tim Wescott · May 10, 2013

On Thu, 09 May 2013 20:59:01 -0400, Uncle Steve wrote:

Ok, this is a question that is not so battery-charger specific, but is
obviously related.

So here's a circuit fragment:

18V +----+--------__^------/\/\/-----------+
| 2n3055| 0R5 |
| | 5W /
| | \ 5R10W
| | /
|_______|> \
| |_ 2n2906 |
| | |
| | |
| | |
+------__^ 2n2222 |
| |
/ |
1M \ |
/ |
\ |
| |
| |
\ SW |
\ |
| |
5V +-----------+ |
|
GND +-----------+-------------------------+

So this circuit shows ~38mA going in to the base of the 2n3055, and
~13.9V across the 5 ohm resistor. It gets warm quickly.

If I change the 2n3055 for a TIP147 (PNP, beta 1k) and make the obvious
changes to the 2n2906 to make it work, there is ~80mA current at the
base of the TIP147, and ~14.1V across the 10W resistor.

WTF, over?

Needless to say I am happy that my $14.00 DVM has a transistor tester,
because with 10k feeding the 2n2222 the 2n2906 doesn't last very long
with a TIP147 in-circuit. Of course, in that configuration the base of
a 2n3055 still shows 38mA. These results suggest that the base-emitter
current of the 2n3055 cannot go any higher without a larger power
supply, but that is supposition that the 2n3055 somehow limits the base
current to some proportionate ratio to the collector- emitter current
available to it. Is that in any way a reasonable explanation for what
is occurring here?

OK. First, the drawing came through mangled. I hope I reconstituted it
correctly.

Second, the way you have it drawn, the 2N2222 isn't going to act like a
transistor. If you _really_ did it as drawn, the BE junction of the
2N2222 will act like a zener diode at around 6V, because that's just what
little transistors do when you challenge their BE junctions with too much
voltage.

Third, you've drawn the 2N2906 as an NPN, but my references says it's a
PNP.

Frankly, I don't see how this circuit can do _anything_, which leads me
to believe that either it is not drawn as built, or there's some more
zener breakdown or other oddball things happening.

Like JT said: you've got to put current _into_ the base of an NPN, and
pull current _out_ of the base of a PNP for them to act properly. You
don't seem to be making that happen.

--
Tim Wescott
Control system and signal processing consulting
www.wescottdesign.com

Jasen Betts · May 10, 2013

On 2013-05-10, Uncle Steve <stevet810@gmail.com> wrote:

Ok, this is a question that is not so battery-charger specific, but
is obviously related.

if you want to use a microcontroller you have to design
the low side switch part so that current flows out of
the 5V node, not into it.

so dont do this:

| |
| |
\ SW |
\ |
| |
5V +-----------+ |
|
GND +-----------+-------------------------+

do either this

|
|/
5V--[10K]--|
|>|
|
|
\ sw
\
|
------------+----------

or this:

sw |
/ |/
5V--/ --[10K]--|
|>|
|
|
------------+-------

--
ââ 100% natural

Jasen Betts · May 10, 2013

On 2013-05-10, Uncle Steve <stevet810@gmail.com> wrote:

Ok, this is a question that is not so battery-charger specific, but
is obviously related.

If you want to use a microcontroller you have to design
the low side switch part so that current flows out of
the 5V node, not into it.

so dont do this:

| |
| |
\ SW |
\ |
| |
5V +-----------+ |
|
GND +-----------+-------------------------+

do either this

|
|/
5V--[10K]--|
|>|
|
|
\ sw
\
|
------------+----------

or this:

sw |
/ |/
5V--/ --[10K]--|
|>|
|
|
------------+-------

if you wat to be sure put in a diode from the switch output to +5
, a microcontroller will have that internally.
it also has a diode from ground.

like this:

|
|
|/
5V--+--[10K]--|
| |>|
| |
`----|<-----+
|
.---->|-----+
| |
| \ sw
| \
| |
+-----------+----------

or this:
|
|
/ |/
5V-+-/ -+-[10K]--|
| | |>|
`-|<-+-|<-. |
| |
--------+-----+-------

the followig has no chance of working, because
once you put the protection diodes in it becomes
obvious that the current from the high side
switch components will just flow through the
top diode

|
.--|<---+ |
| | |
| \ SW |
| \ |
| | |
5V +---+-------+---|<---. |
| |
GND +--------------------+----------------+

infact the oscillations and other wierd behavior you
have seen may be due to your 5V supply being back fed.

--
ââ 100% natural

--- news://freenews.netfront.net/ - complaints: news@netfront.net ---

Uncle Steve · May 10, 2013

On Fri, May 10, 2013 at 11:29:31AM +1000, Phil Allison wrote:

"Uncle Steve"

Of course, in that configuration the base
of a 2n3055 still shows 38mA. These results suggest that the
base-emitter current of the 2n3055 cannot go any higher without a
larger power supply, but that is supposition that the 2n3055 somehow
limits the base current to some proportionate ratio to the collector-
emitter current available to it. Is that in any way a reasonable
explanation for what is occurring here?

** Yep.

The B-E current is related to the C-E current by a ratio called "beta" or
"Hfe". Beta is not however a fixed number, it varies over the range of
possible collector currents.

For a 2N3055 over the range of 0.1 amps to 3 amps, the number is fairly
constant at about 50 to 100 - depending on the particular device. The value
falls at lower and higher currents PLUS when the C-E voltage is very low.

See figure 3 " DC Current Gain, 2N3055 NPN "

http://www.onsemi.com/pub_link/Collateral/2N3055-D.PDF

All the graphs are worth study, as this is how most power transistors
behave.

I see the significance of these curves a little better now, and it's
probably somewhat unreasonable to compare a BJT with a Darlington.
The interesting thing is that the behaviour of the BJT seems to be
more 'reasonable' in this application since it protects the previous
stage.

The next step for me is to figure out how to predict these factors to
reduce the amount of fooling around I am still doing. Nevertheless,
there is nothing like making measurements to show what is in fact
going on with these devices.

Regards,

Uncle Steve

--
There should be a special word in the English language to identify
people who create problems and then turn around and offer up their own
tailor-made bogus non-solutions designed to completely avoid the root
causes of the situation under consideration. 'Traitor' might be a
good choice, but lacks the requisite specificity. One of the problems
with contemporary English is it lacks many such words that would
otherwise categorically identify certain kinds of person, place, or
thing -- making it difficult or impossible to think analytically about
such objects. These shortcomings of the English lexicon are
representative of Orwellian linguistics at work in the real world.

Uncle Steve · May 10, 2013

On Thu, May 09, 2013 at 07:11:43PM -0700, Jim Thompson wrote:

On Thu, 09 May 2013 20:59:01 -0400, Uncle Steve <stevet810@gmail.com
wrote:

Ok, this is a question that is not so battery-charger specific, but
is obviously related.

So here's a circuit fragment:

18V +----+--------__^------/\/\/--------+
| 2n3055| 0R5 |
| | 5W /
| | \ 5R10W
| | /
| | \
+------__v 2n2906 |
| |
| |
2n2222 +---| |
| |>----+ |
| | |
/ | |
1M \ | |
/ | |
\ | |
| | |
| | |
\ SW | |
\ | |
| | |
5V +-----+ | |
| |
GND +---------------+------------------+

So this circuit shows ~38mA going in to the base of the 2n3055, and
~13.9V across the 5 ohm resistor. It gets warm quickly.

If I change the 2n3055 for a TIP147 (PNP, beta 1k) and make the
obvious changes to the 2n2906 to make it work, there is ~80mA current
at the base of the TIP147, and ~14.1V across the 10W resistor.

WTF, over?

Needless to say I am happy that my $14.00 DVM has a transistor tester,
because with 10k feeding the 2n2222 the 2n2906 doesn't last very long
with a TIP147 in-circuit. Of course, in that configuration the base
of a 2n3055 still shows 38mA. These results suggest that the
base-emitter current of the 2n3055 cannot go any higher without a
larger power supply, but that is supposition that the 2n3055 somehow
limits the base current to some proportionate ratio to the collector-
emitter current available to it. Is that in any way a reasonable
explanation for what is occurring here?

Draw it up real purty, so you can tell PNP's from NPN's and can see
that current can only flow OUT of the NPN emitter and INTO a PNP
emitter... and DO THE MATH ;-)

Sorry, I was tired and really mangled the schematic. Fixed above.

Regards,

Uncle Steve

--
There should be a special word in the English language to identify
people who create problems and then turn around and offer up their own
tailor-made bogus non-solutions designed to completely avoid the root
causes of the situation under consideration. 'Traitor' might be a
good choice, but lacks the requisite specificity. One of the problems
with contemporary English is it lacks many such words that would
otherwise categorically identify certain kinds of person, place, or
thing -- making it difficult or impossible to think analytically about
such objects. These shortcomings of the English lexicon are
representative of Orwellian linguistics at work in the real world.

Phil Allison · May 10, 2013

"Uncle Steve"

Nevertheless,
there is nothing like making measurements to show what is in fact
going on with these devices.

** Give this man a Kewpie doll.

.... Phil

Uncle Steve · May 10, 2013

On Thu, May 09, 2013 at 10:57:58PM -0500, Tim Wescott wrote:

OK. First, the drawing came through mangled. I hope I reconstituted it
correctly.

No, this is actually it:

18V +----+--------__^------/\/\/--------+
| 2n3055| 0R5 |
| | 5W /
| | \ 5R10W
| | /
| | \
+------__v 2n2906 |
| |
| |
2n2222 +---| |
| |>----+ |
| | |
/ | |
1M \ | |
/ | |
\ | |
| | |
| | |
\ SW | |
\ | |
| | |
5V +-----+ | |
| |
GND +---------------+------------------+

Second, the way you have it drawn, the 2N2222 isn't going to act like a
transistor. If you _really_ did it as drawn, the BE junction of the
2N2222 will act like a zener diode at around 6V, because that's just what
little transistors do when you challenge their BE junctions with too much
voltage.

Third, you've drawn the 2N2906 as an NPN, but my references says it's a
PNP.

Frankly, I don't see how this circuit can do _anything_, which leads me
to believe that either it is not drawn as built, or there's some more
zener breakdown or other oddball things happening.

Like JT said: you've got to put current _into_ the base of an NPN, and
pull current _out_ of the base of a PNP for them to act properly. You
don't seem to be making that happen.

My brain isn't trained to recognize the symbols and circuits with any
fluency yet, so when I did the original drawing while tired, it didn't
register. Apologies for the confusion.

When I make silly errors like that when writing code it's also vastly
amusing.

Regards,

Uncle Steve

--
There should be a special word in the English language to identify
people who create problems and then turn around and offer up their own
tailor-made bogus non-solutions designed to completely avoid the root
causes of the situation under consideration. 'Traitor' might be a
good choice, but lacks the requisite specificity. One of the problems
with contemporary English is it lacks many such words that would
otherwise categorically identify certain kinds of person, place, or
thing -- making it difficult or impossible to think analytically about
such objects. These shortcomings of the English lexicon are
representative of Orwellian linguistics at work in the real world.

Uncle Steve · May 10, 2013

On Fri, May 10, 2013 at 11:13:48AM +0000, Jasen Betts wrote:

On 2013-05-10, Uncle Steve <stevet810@gmail.com> wrote:
Ok, this is a question that is not so battery-charger specific, but
is obviously related.

If you want to use a microcontroller you have to design
the low side switch part so that current flows out of
the 5V node, not into it.

so dont do this:

| |
| |
\ SW |
\ |
| |
5V +-----------+ |
|
GND +-----------+-------------------------+

When I actually hook this up to a microcontroller the 5V will be the
output from the pin designated for PWM, assuming I stick with that
strategy. As I said earlier, the switch is there to simulate a
microcontroller.

do either this

|
|/
5V--[10K]--|
|>|
|
|
\ sw
\
|
------------+----------

or this:

sw |
/ |/
5V--/ --[10K]--|
|>|
|
|
------------+-------

if you wat to be sure put in a diode from the switch output to +5
, a microcontroller will have that internally.
it also has a diode from ground.

like this:

|
|
|/
5V--+--[10K]--|
| |>|
| |
`----|<-----+
|
.---->|-----+
| |
| \ sw
| \
| |
+-----------+----------

Not sure what the purpose of the second diode is there. Doesn't look
like it can do much of anything.

or this:
|
|
/ |/
5V-+-/ -+-[10K]--|
| | |>|
`-|<-+-|<-. |
| |
--------+-----+-------

the followig has no chance of working, because
once you put the protection diodes in it becomes
obvious that the current from the high side
switch components will just flow through the
top diode

|
.--|<---+ |
| | |
| \ SW |
| \ |
| | |
5V +---+-------+---|<---. |
| |
GND +--------------------+----------------+

infact the oscillations and other wierd behavior you
have seen may be due to your 5V supply being back fed.

It's hard to say. When I was using a motor as a load there were wierd
things happening all over the place, but I was also making stupid
mistakes and damaging small signal transistors in non-obvious ways.

Regards,

Uncle Steve

--
There should be a special word in the English language to identify
people who create problems and then turn around and offer up their own
tailor-made bogus non-solutions designed to completely avoid the root
causes of the situation under consideration. 'Traitor' might be a
good choice, but lacks the requisite specificity. One of the problems
with contemporary English is it lacks many such words that would
otherwise categorically identify certain kinds of person, place, or
thing -- making it difficult or impossible to think analytically about
such objects. These shortcomings of the English lexicon are
representative of Orwellian linguistics at work in the real world.

Uncle Steve · May 10, 2013

On Fri, May 10, 2013 at 11:00:13PM +1000, Phil Allison wrote:

"Uncle Steve"

Nevertheless,
there is nothing like making measurements to show what is in fact
going on with these devices.

** Give this man a Kewpie doll.

I've always wanted a Kewpie doll.

It's interesting that all of the literature and web-pages I've read so
far have failed to impart an accurate sense of what these things do.
I don't know whether that is because the learning curve is so steep,
or whether the terminology is truly confusing to the uninitiated. I
think it might be easier to understand electronics if circuit diagrams
represented electron flow and electron charge potential more
obviously. After all it's the electrons moving around that gets
work done, correct?

Regards,

Uncle Steve

--
There should be a special word in the English language to identify
people who create problems and then turn around and offer up their own
tailor-made bogus non-solutions designed to completely avoid the root
causes of the situation under consideration. 'Traitor' might be a
good choice, but lacks the requisite specificity. One of the problems
with contemporary English is it lacks many such words that would
otherwise categorically identify certain kinds of person, place, or
thing -- making it difficult or impossible to think analytically about
such objects. These shortcomings of the English lexicon are
representative of Orwellian linguistics at work in the real world.

John Fields · May 10, 2013

On Thu, 09 May 2013 20:59:01 -0400, Uncle Steve <stevet810@gmail.com>
wrote:

Ok, this is a question that is not so battery-charger specific, but
is obviously related.

So here's a circuit fragment:

18V +----+--------__^------/\/\/-----------+
| 2n3055| 0R5 |
| | 5W /
| | \ 5R10W
| | /
|_______|> \
| |_ 2n2906 |
| | |
| | |
| | |
+------__^ 2n2222 |
| |
/ |
1M \ |
/ |
\ |
| |
| |
\ SW |
\ |
| |
5V +-----------+ |
|
GND +-----------+-------------------------+

So this circuit shows ~38mA going in to the base of the 2n3055, and
~13.9V across the 5 ohm resistor. It gets warm quickly.

If I change the 2n3055 for a TIP147 (PNP, beta 1k) and make the
obvious changes to the 2n2906 to make it work, there is ~80mA current
at the base of the TIP147, and ~14.1V across the 10W resistor.

WTF, over?

Needless to say I am happy that my $14.00 DVM has a transistor tester,
because with 10k feeding the 2n2222 the 2n2906 doesn't last very long
with a TIP147 in-circuit. Of course, in that configuration the base
of a 2n3055 still shows 38mA. These results suggest that the
base-emitter current of the 2n3055 cannot go any higher without a
larger power supply, but that is supposition that the 2n3055 somehow
limits the base current to some proportionate ratio to the collector-
emitter current available to it. Is that in any way a reasonable
explanation for what is occurring here?

Regards,

Uncle Steve

---
Version 4
SHEET 1 880 708
WIRE -16 0 -192 0
WIRE 96 0 -16 0
WIRE 176 0 96 0
WIRE 320 0 272 0
WIRE -16 64 -16 0
WIRE 96 112 96 0
WIRE 224 112 224 64
WIRE 224 112 192 112
WIRE -16 208 -16 144
WIRE 144 208 144 176
WIRE 144 208 -16 208
WIRE 144 240 144 208
WIRE 320 272 320 0
WIRE 144 352 144 320
WIRE -32 400 -80 400
WIRE 80 400 48 400
WIRE -192 480 -192 0
WIRE -80 480 -80 400
WIRE -192 624 -192 560
WIRE -80 624 -80 560
WIRE -80 624 -192 624
WIRE 144 624 144 448
WIRE 144 624 -80 624
WIRE 320 624 320 352
WIRE 320 624 144 624
WIRE -192 688 -192 624
FLAG -192 688 0
SYMBOL npn 176 64 R270
WINDOW 0 68 29 VRight 2
WINDOW 3 99 3 VRight 2
SYMATTR InstName Q1
SYMATTR Value 2N3055
SYMBOL npn 80 352 R0
SYMATTR InstName Q3
SYMATTR Value 2N2222
SYMBOL res 304 256 R0
SYMATTR InstName R1
SYMATTR Value 5.5
SYMBOL voltage -192 464 R0
WINDOW 123 0 0 Left 2
WINDOW 39 0 0 Left 2
SYMATTR InstName V1
SYMATTR Value 18
SYMBOL voltage -80 464 R0
WINDOW 3 24 96 Invisible 2
WINDOW 123 0 0 Left 2
WINDOW 39 0 0 Left 2
SYMATTR InstName V2
SYMATTR Value PULSE(0 5 0 100n 100n 1 2)
SYMBOL res 64 384 R90
WINDOW 0 0 56 VBottom 2
WINDOW 3 32 56 VTop 2
SYMATTR InstName R3
SYMATTR Value 2.7k
SYMBOL pnp 192 176 M270
WINDOW 0 61 61 VLeft 2
WINDOW 3 92 86 VLeft 2
SYMATTR InstName Q2
SYMATTR Value 2N2907
SYMBOL res -32 48 R0
SYMATTR InstName R2
SYMATTR Value 10k
SYMBOL res 128 224 R0
SYMATTR InstName R4
SYMATTR Value 1k
TEXT -176 656 Left 2 !.tran 5

--
JF

Jim Thompson · May 10, 2013

On Fri, 10 May 2013 08:58:49 -0400, Uncle Steve <stevet810@gmail.com>
wrote:

On Thu, May 09, 2013 at 07:11:43PM -0700, Jim Thompson wrote:
On Thu, 09 May 2013 20:59:01 -0400, Uncle Steve <stevet810@gmail.com
wrote:

Ok, this is a question that is not so battery-charger specific, but
is obviously related.

So here's a circuit fragment:

18V +----+--------__^------/\/\/--------+
| 2n3055| 0R5 |
| | 5W /
| | \ 5R10W
| | /
| | \
+------__v 2n2906 |
| |
| |
2n2222 +---| |
| |>----+ |
| | |
/ | |
1M \ | |
/ | |
\ | |
| | |
| | |
\ SW | |
\ | |
| | |
5V +-----+ | |
| |
GND +---------------+------------------+

So this circuit shows ~38mA going in to the base of the 2n3055, and
~13.9V across the 5 ohm resistor. It gets warm quickly.

If I change the 2n3055 for a TIP147 (PNP, beta 1k) and make the
obvious changes to the 2n2906 to make it work, there is ~80mA current
at the base of the TIP147, and ~14.1V across the 10W resistor.

WTF, over?

Needless to say I am happy that my $14.00 DVM has a transistor tester,
because with 10k feeding the 2n2222 the 2n2906 doesn't last very long
with a TIP147 in-circuit. Of course, in that configuration the base
of a 2n3055 still shows 38mA. These results suggest that the
base-emitter current of the 2n3055 cannot go any higher without a
larger power supply, but that is supposition that the 2n3055 somehow
limits the base current to some proportionate ratio to the collector-
emitter current available to it. Is that in any way a reasonable
explanation for what is occurring here?

Draw it up real purty, so you can tell PNP's from NPN's and can see
that current can only flow OUT of the NPN emitter and INTO a PNP
emitter... and DO THE MATH ;-)

Sorry, I was tired and really mangled the schematic. Fixed above.

Regards,

Uncle Steve

Jim Thompson · May 10, 2013

On Thu, 09 May 2013 20:59:01 -0400, Uncle Steve <stevet810@gmail.com>
wrote:

Ok, this is a question that is not so battery-charger specific, but
is obviously related.

[snip]
but that is supposition that the 2n3055 somehow
limits the base current to some proportionate ratio to the collector-
emitter current available to it. Is that in any way a reasonable
explanation for what is occurring here?

Nope, that is your main conceptual error.

Regards,

Uncle Steve

Uncle Steve · May 10, 2013

On Fri, May 10, 2013 at 07:38:44AM -0700, Jim Thompson wrote:

On Fri, 10 May 2013 08:58:49 -0400, Uncle Steve <stevet810@gmail.com
wrote:

On Thu, May 09, 2013 at 07:11:43PM -0700, Jim Thompson wrote:
On Thu, 09 May 2013 20:59:01 -0400, Uncle Steve <stevet810@gmail.com
wrote:

Ok, this is a question that is not so battery-charger specific, but
is obviously related.

So here's a circuit fragment:

18V +----+--------__^------/\/\/--------+
| 2n3055| 0R5 |
| | 5W /
| | \ 5R10W
| | /
| | \
+------v_| 2n2906 |
| |
| |
2n2222 +---| |
| |>----+ |
| | |
/ | |
1M \ | |
/ | |
\ | |
| | |
| | |
\ SW | |
\ | |
| | |
5V +-----+ | |
| |
GND +---------------+------------------+

PNP collector must be more negative than its emitter... swap emitter
and collector on the 2N2906.

I wish I could run that fancy ASCII schematic CAD tool, but I don't
use Windows.

But you're still in "fry" land :-(

WHAT is the OBJECT of your endeavor? Trickle charging a back-up
battery?

I wouldn't characterize 3A as a trickle, but in essence I hope to end
up with a battery charger that will charge the battery while it is
under a moderate 20W+ load. I have bit-banged serial out on the
microcontroller, so it will log status to the load device that way,
and inform it when mains power fails.

It is a learning exercise, but I hope to end up with something
vaguely resembling a UPS when all is said and done.

Regards,

Uncle Steve

--
There should be a special word in the English language to identify
people who create problems and then turn around and offer up their own
tailor-made bogus non-solutions designed to completely avoid the root
causes of the situation under consideration. 'Traitor' might be a
good choice, but lacks the requisite specificity. One of the problems
with contemporary English is it lacks many such words that would
otherwise categorically identify certain kinds of person, place, or
thing -- making it difficult or impossible to think analytically about
such objects. These shortcomings of the English lexicon are
representative of Orwellian linguistics at work in the real world.

Phil Hobbs · May 10, 2013

On 5/10/2013 10:22 AM, Uncle Steve wrote:

On Fri, May 10, 2013 at 11:00:13PM +1000, Phil Allison wrote:

"Uncle Steve"

Nevertheless,
there is nothing like making measurements to show what is in fact
going on with these devices.

** Give this man a Kewpie doll.

I've always wanted a Kewpie doll.

It's interesting that all of the literature and web-pages I've read so
far have failed to impart an accurate sense of what these things do.
I don't know whether that is because the learning curve is so steep,
or whether the terminology is truly confusing to the uninitiated. I
think it might be easier to understand electronics if circuit diagrams
represented electron flow and electron charge potential more
obviously. After all it's the electrons moving around that gets
work done, correct?

Except in PNPs.

Seriously, once current starts to be an intuitive concept for you,
you'll rarely need to think about electrons at all.

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 USA
+1 845 480 2058

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

John Fields · May 10, 2013

On Thu, 09 May 2013 20:59:01 -0400, Uncle Steve <stevet810@gmail.com>
wrote:

Needless to say I am happy that my $14.00 DVM has a transistor tester,
because with 10k feeding the 2n2222 the 2n2906 doesn't last very long
with a TIP147 in-circuit. Of course, in that configuration the base
of a 2n3055 still shows 38mA. These results suggest that the
base-emitter current of the 2n3055 cannot go any higher without a
larger power supply, but that is supposition that the 2n3055 somehow
limits the base current to some proportionate ratio to the collector-
emitter current available to it. Is that in any way a reasonable
explanation for what is occurring here?

---
No.

In reality it's the base-to-emitter current which controls the
collector-to-emitter current.

The ratio of Ice to Ibe is called 'beta' or 'Hfe' and describes the
current gain of the device.

From the curves you have, you can see that Hfe varies widely with
collector current and temperature, and also from device to device.

--
JF

Uncle Steve · May 10, 2013

On Fri, May 10, 2013 at 07:42:40AM -0700, Jim Thompson wrote:

On Thu, 09 May 2013 20:59:01 -0400, Uncle Steve <stevet810@gmail.com
wrote:

Ok, this is a question that is not so battery-charger specific, but
is obviously related.

[snip]
but that is supposition that the 2n3055 somehow
limits the base current to some proportionate ratio to the collector-
emitter current available to it. Is that in any way a reasonable
explanation for what is occurring here?

Nope, that is your main conceptual error.

Because the TIP147 is PNP and operates completely differently. Is the
issue here that the 3055 is 'fully on' with 5 uA driving the
2n2222?

Perhaps my frustration with arrangements other than the Sziklai Pair
is due to an irrational desire to decouple the 5v circuit from the 18V
section as much as possible. Other than in a darlington arrangement,
I am still having trouble making 2 2n2222 stages do what I want and
the frustration of things not working as I think they should is really
annoying.

But at pennies per transistor at least it's not expensive to fiddle.

Regards,

Uncle Steve

--
There should be a special word in the English language to identify
people who create problems and then turn around and offer up their own
tailor-made bogus non-solutions designed to completely avoid the root
causes of the situation under consideration. 'Traitor' might be a
good choice, but lacks the requisite specificity. One of the problems
with contemporary English is it lacks many such words that would
otherwise categorically identify certain kinds of person, place, or
thing -- making it difficult or impossible to think analytically about
such objects. These shortcomings of the English lexicon are
representative of Orwellian linguistics at work in the real world.

John Fields · May 10, 2013

On Fri, 10 May 2013 10:59:14 -0400, Uncle Steve <stevet810@gmail.com>
wrote:

On Fri, May 10, 2013 at 07:38:44AM -0700, Jim Thompson wrote:
On Fri, 10 May 2013 08:58:49 -0400, Uncle Steve <stevet810@gmail.com
wrote:

On Thu, May 09, 2013 at 07:11:43PM -0700, Jim Thompson wrote:
On Thu, 09 May 2013 20:59:01 -0400, Uncle Steve <stevet810@gmail.com
wrote:

Ok, this is a question that is not so battery-charger specific, but
is obviously related.

So here's a circuit fragment:

18V +----+--------__^------/\/\/--------+
| 2n3055| 0R5 |
| | 5W /
| | \ 5R10W
| | /
| | \
+------v_| 2n2906 |
| |
| |
2n2222 +---| |
| |>----+ |
| | |
/ | |
1M \ | |
/ | |
\ | |
| | |
| | |
\ SW | |
\ | |
| | |
5V +-----+ | |
| |
GND +---------------+------------------+

PNP collector must be more negative than its emitter... swap emitter
and collector on the 2N2906.

I wish I could run that fancy ASCII schematic CAD tool, but I don't
use Windows.

---
You might try changing your format.

Here's an example; it's the ASCIImatic for the LTspice circuit list I
posted for you earlier: (View using a fixed-pitch font.)

+18V-----------+-----+-C E---------+
| | B 2N3055 |
| | | |
[10k] E C |
| B 2N2907 |
| | |
+-------+ [5.5]
| |
[1K] |
| |
C |
IO>--[2.7K]--B 2N2222 |
E |
| |
GND>-----------+---------------------+

--
JF

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