Chip with simple program for Toy

[Tom Biasi]

On 5/7/2013 1:46 PM, Jim Thompson wrote:

On Tue, 07 May 2013 13:27:24 -0400, Tom Biasi <tombiasi@optonline.net
wrote:

On 5/7/2013 1:18 PM, Jim Thompson wrote:
On Tue, 07 May 2013 13:15:10 -0400, Tom Biasi <tombiasi@optonline.net
wrote:

On 5/7/2013 8:52 AM, Uncle Steve wrote:

As I understand it, volts are sort of like the size of the pipe;
amperes are like the pressure or the rate of flow, and power is the
throughput. Of course it isn't plumbing and there isn't any water.


Regards,

Uncle Steve

Even with water, pressure and rate of flow are not the same thing.
Power is the rate of doing work.


The length of the pipe divided by the diameter is proportionally
equivalent to resistance.

Volts equates to pressure

Current equates to flow rate

...Jim Thompson

I thought he might look it up himself Jim

Ooooops! Sorry! He is flailing quite a bit. I remember being there
;-)

...Jim Thompson

No need to apologize. At least you gave a helpful answer and didn't see

the need to "rip him a new one". After all, this is a basic group.

Regards,
Tom

 

[Jim Thompson]

On Tue, 07 May 2013 14:21:35 -0400, Tom Biasi <tombiasi@optonline.net>
wrote:

On 5/7/2013 1:46 PM, Jim Thompson wrote:
On Tue, 07 May 2013 13:27:24 -0400, Tom Biasi <tombiasi@optonline.net
wrote:

On 5/7/2013 1:18 PM, Jim Thompson wrote:
On Tue, 07 May 2013 13:15:10 -0400, Tom Biasi <tombiasi@optonline.net
wrote:

On 5/7/2013 8:52 AM, Uncle Steve wrote:

As I understand it, volts are sort of like the size of the pipe;
amperes are like the pressure or the rate of flow, and power is the
throughput. Of course it isn't plumbing and there isn't any water.


Regards,

Uncle Steve

Even with water, pressure and rate of flow are not the same thing.
Power is the rate of doing work.


The length of the pipe divided by the diameter is proportionally
equivalent to resistance.

Volts equates to pressure

Current equates to flow rate

...Jim Thompson

I thought he might look it up himself Jim

Ooooops! Sorry! He is flailing quite a bit. I remember being there
;-)

...Jim Thompson

No need to apologize. At least you gave a helpful answer and didn't see
the need to "rip him a new one". After all, this is a basic group.

Regards,
Tom

I only provide extra assholes to those already exhibiting such
behavior, like our special group of posters here who are
always-dead-wrong, but scream at the top of their lungs that they are
correct, and name-call anyone who dares to suggest a different
scenario.

I'm quite like you, I try to induce thinking. Doesn't always work :-(
And I do remember "being there". In my early teens I really flailed
around trying to make sense of how circuits work ;-)

...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.

 

[Tom Biasi]

On 5/7/2013 2:31 PM, Jim Thompson wrote:
In my early teens I really flailed

around trying to make sense of how circuits work ;-)

...Jim Thompson

I also. But the most memorable moments were the ones I figured out myself.

No internet then, just a building with some smelly old books.
Regards,
Tom

 

[Jim Thompson]

On Tue, 07 May 2013 14:39:51 -0400, Tom Biasi <tombiasi@optonline.net>
wrote:

On 5/7/2013 2:31 PM, Jim Thompson wrote:
In my early teens I really flailed
around trying to make sense of how circuits work ;-)

...Jim Thompson

I also. But the most memorable moments were the ones I figured out myself.
No internet then, just a building with some smelly old books.
Regards,
Tom

My great lurch forward was getting an old GE manual on Germanium
transistors.

My second great lurch forward was getting a technician job in MIT
Building 20. I could solder ;-) And I was simultaneously taking the
right circuit courses.

...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.

 

[George Herold]

On May 6, 6:04 pm, Uncle Steve <stevet...@gmail.com> wrote:

On Mon, May 06, 2013 at 03:40:00PM -0500, Tim Wescott wrote:
On Mon, 06 May 2013 16:15:36 -0400, Uncle Steve wrote:

On Mon, May 06, 2013 at 12:01:44PM -0400, Uncle Steve wrote:
Back again for some more abuse.

I'm building a 12V battery charger that will be controlled by a small
low-power microcontroller.  I've not yet hooked up the microcontroller,
but most of the code is written and I'm trying to finalize the charger
electronics before I hook it up.

The circuit is very simple.  An 18V 2A transformer, a bridge rectifier,
and filter capacitor feeds a main power rail.  A 5V regulator produces
a few mA for the microcontroller, which I won't show here.  The charger
is more or less as follows, though I will leave out the
resistor/divider taps which hook up to the ADC channels on the micro..

 +18VDC ---------------------------+
                        Q1 c   e   |    D1     R1
                       -----\_/--------->|----\/\/\--------+12(batt)
                            b|     |
                      +------+     |
                      |      |  +--+----------+
                      /  Q2 e\_/c             |
                     R4 \       |b              |
                      /       |            e  |c Q3
                      \       +--\/\/\------\_/
                      |           R2         |b
                      |                      |   R3     SW1
                LED1 \_/                     +--\/\/\-- \-- +5V
                     ---
                      |
                      |
 GND    --------------+------------------------------------ GND(batt)

Q1 - MJE3055
D1 - 1N4004
R1 - .5 5W

Q2 - BC557
R2 - 200K

Q3 - 2N2222
R3 - 1K
 R4 - 2k

The microcontroller will strobe R3 with PCM at about 488HZ with a duty
cycle dependant on the charge profile.  R1 is the sense resistor and
permits measuring instantaneous charge current.  I've got the battery
attached and can watch the voltage rise (and settle) as I manually
engage a switch attached as shown.  The battery voltage as it came from
Wallmart was about 12.7V.  Charge current with this circuit is 1.4A at
this point in its charge cycle.  The heat-sink gets rather warm, but it
isn't all that big and I'm going to target 3 or 4A as the peak charge
current so I'll probably substitute a TO-3 package with a much beefier
heat-sink when I put the project in an enclosure.

So far, so good.  The output of Q1 shows .6V ripple.  Attaching my
scope to the base of Q1 shows an idle (SW off) voltage of 16mV and a
120Hz signal with a 70mVpp with a duty cycle of 17%.  I'm not exactly
sure where this signal is coming from, although its frequency suggests
a causal relationship with the AC mains.  There does not appear to be
any ripple on the 5V rail, but my scope isn't good enough to really
zoom in on it.

The other side of the coin is that the Q2/Q3 network seems to be rather
sensitive.  When I pass my hand over the breadboard the distortion
described above doubles and I can get an amplitude of 1V on that
distortion by standing up suddenly while sitting in front of the idle
circuit.  It is difficult to say what is happening because I can double
the distortion by attaching the scope to a wall-wart USB charger, and I
know I haven't yet calibrated the scope all that well either.  (Scope
shows 4.5V from the 5V regulator.)  But the fact that I can affect the
circuit just by moving things in the general vicinity is, um, rather
shocking.

Besides installing the circuit in a metal case, are there any easy
solutions to fix that 16mV idle voltage?  Should I just change the
BC557 to a 2n2222 and work out how many of what kind of resistors I
need to supply the 3055 with the mA it needs to dump several amps into
the battery?  I like this version because it is easy to set up and has
a low part count, but I'd really like to get rid of the noise and the
sensitivity to movement.

As suggested, I moved this out of the existing thread.  It was an
mistake that I did not remove the references header.

At any rate, I set up a separate pair of 2n2222, 10K resistor, and BC557
similar to the input stage above as well as a LED.  Then I connected a
small spool of insulated wire to the base of the 2n2222 and then let it
out a couple of feet until the LED stayed onish without my hands being
near the device.

The result is a strong 6-7MHz signal for a bunch of cycles and then some
dead time.  It looks like there could be some FM in there, and on the
high part of the cycle there appears to be an additional small signal,
but I can't resolve any detail with my equipment.

If I hold the spool in my hand the amount of on time changes
considerably depending how much of my hand is in contact with the
plastic and insulation.  With palm open, there is one rise/fall cycle at
about 6.5MHz when my hand is about 6in from the wire.  As my hand gets
closer, a second peak appears and so on until there is a train of
several dozen cycles at or near the measured frequency.

Any idea what the hell that signal might be?

Regards,

Uncle Steve

I'm not making sense of your schematic.  If Q2 is a PNP it should have
its emitter to +18V and its collector to the base of Q1.  (Q1 should have
its collector _connected_!!).  Q3 is configured to deliver current to the
base of Q2, but it needs to pull current -- ?!?!?!?!

Could you be showing the emitters and collectors of Q2 and Q3 reversed?

I don't think so.  The arrangement is described as a Sziklai Pair, and
is described at the following URL:

I redrew your circuit and tried to make Q2/Q3 look like a Darlington
or Sziklai.. didn't work.

One issue I have with your 'pair' is that the idea of the pair is to
get more current gain. So a transistor with only a small maximum
current drives the bigger transistor. I your case you've got it
backwards. The BC557 has a max Ic of 100mA and the 2n2222 is 500mA.
It also seems like the BC557 wiil driven right near it's max
current... Maybe a beefier pnp is in order?

George H.

http://www.talkingelectronics.com/projects/TheTransistorAmplifier/The...

If it's doing anything at all (which presumably it is) then amongst your
various transistors you have tons of uncontrolled gain, so it's not
surprising that its oscillating or doing other weird stuff.

What's your goal?  A charge current that's proportional to the voltage at
the SW1 end of R3?

SW1 is a stand in for the TTL level output from a microcontroller pin
and will operate at 488Hz PWM as described above.

I'd have to think about how to take that collection of transistors and
make a stable circuit out of it, but if you're really building to that
schematic then I suspect that you need to make some changes!

The oscillation showing up at the base of Q1 may be the result of some
sort of capacitance issue with Q2/Q3.  I fiddled with a few small
ceramic capacitors in a naive fashion, but I did not accomplish
anything other than destroying a 2n2222.  I simply haven't
internalized enough information about how these things operate to
figure out what I should do to eliminate the distortion.

Note that if you're charging a lead-acid battery (gel or flood) the ideal
charge profile is to limit both voltage and current.  Voltage is limited
to some magic number (which I can never remember -- look it up), and
current is limited either by the charger's capabilities or the
battery's.  When the charge of the battery is low it accepts charge at
the constant current, but then as it charges you must drop the current to
hold the voltage constant.

I understand that.  The preliminary figures I have suggest that the
charge voltage should be 13.8V and the float voltage 13.5V.

The current strategy I'm working on will limit the average current
over time with PWM, measuring instantaneous current when Q1 is on to
drive a feedback loop to set PWM duty-cycle.  I'll be reading supply
voltage, and voltage at either side of the .5 Ohm sense resister at
various times throughout the PWM cycle.  The software will do ADC at
about 125KHz so there's lots of room to average things nicely.  I
assume there's no real problem with allowing current to spike at short
intervals if the battery naturally wants more amps than my PS will
supply on a continual basis.  I may be wrong, and it may be a simple
matter to install a load resistor with the sense resistor.  I'm still
in larval stage so this stuff is still a little mysterious.

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.- Hide quoted text -

- Show quoted text -

 

[Tim Wescott]

On Tue, 07 May 2013 10:18:15 -0700, Jim Thompson wrote:

On Tue, 07 May 2013 13:15:10 -0400, Tom Biasi <tombiasi@optonline.net
wrote:

On 5/7/2013 8:52 AM, Uncle Steve wrote:

As I understand it, volts are sort of like the size of the pipe;
amperes are like the pressure or the rate of flow, and power is the
throughput. Of course it isn't plumbing and there isn't any water.


Regards,

Uncle Steve

Even with water, pressure and rate of flow are not the same thing. Power
is the rate of doing work.


The length of the pipe divided by the diameter is proportionally
equivalent to resistance.

Volts equates to pressure

Current equates to flow rate

That depends on what system you're using to make a mechanical analog of
an electrical system.

And the head drop through a restriction is generally some constant times
the square of the flow -- quite unlike most electrically resistive
materials, which make for components whose voltage drop is some constant
times current^1.

(Apparently, for decades back at the dawn of electronics, people knew
that the current/voltage relationship through a resistor was

voltage drop = current^x,

but measurement technology was so crude that no one was sure -- even to a
factor of two -- what x was. The prime candidates were 1/2, 1, and 2.
Ohm didn't figure out that resistance happened -- he was the one that
showed that for nearly all materials, x = unity.)

--
My liberal friends think I'm a conservative kook.
My conservative friends think I'm a liberal kook.
Why am I not happy that they have found common ground?

Tim Wescott, Communications, Control, Circuits & Software
http://www.wescottdesign.com

 

[Jasen Betts]

On 2013-05-07, Uncle Steve <stevet810@gmail.com> wrote:

On Tue, May 07, 2013 at 06:43:00AM +0000, Jasen Betts wrote:
On 2013-05-07, Uncle Steve <stevet810@gmail.com> wrote:

I will consider that, but note that Q1 is NPN. What you propose
suggests I was counting on current-limiting to occur in the wrong
place.

You can do it like this using the transistors you have.

+18V ----+---+ _+----->|--[Rsense]-----> BAT+
| \ /|
| ----- '3055
| |
+ +
_\| /
------ BC557
|
change: [1K]
|
+
/
pwm in |/
--[2K2]--| PN2222
|\
_\|
+
|
0V ---+---

How do you arrive at 100 ohms?

it was just a guess, and your're right it's probably bit low for
a BC557 about 18ma in from base would would be better than about
180 so use 1K instead.

as you can see I'm not trying to get precise results transistors
vary but upto a factor of 3 in their gain ratio so ignoring the
small details often doesn't hurt the result.

I was using 200K because the value is
close to the threshold where it allows something like full power to
flow through the 3055.

yeah but i'm not desiging an analogue circuit my goal is to over
bias the transistors so they go into saturation, stay there and
stay cool.

With 100k or less I was seeing my (cheap)
meter show fluxuating nonsense voltages at the emitter of up to 1500V,
although my scope showed nothing much amiss at lower frequency
settings. I was thinking that the 3055 was somehow generating large
spikes with the rising edge of the pulse, but I did not test it
exhaustively.

I woudn't trust a cheap digital meter on a PWM signal, I'd add a
low-pass filter or envelope detector circuit depending on what I
wanted to measure.

--
⚂⚃ 100% natural

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[Jasen Betts]

On 2013-05-07, Uncle Steve <stevet810@gmail.com> wrote:

On Tue, May 07, 2013 at 08:52:59AM -0400, Uncle Steve wrote:
On Tue, May 07, 2013 at 06:43:00AM +0000, Jasen Betts wrote:
On 2013-05-07, Uncle Steve <stevet810@gmail.com> wrote:

I will consider that, but note that Q1 is NPN. What you propose
suggests I was counting on current-limiting to occur in the wrong
place.

You can do it like this using the transistors you have.

+18V ----+---+ _+----->|--[Rsense]-----> BAT+
| \ /|
| ----- '3055
| |
+ +
_\| /
------ BC557
|
[100] 0.25W
|
+
/
pwm in |/
---[1K]--| PN2222
|\
_\|
+
|
0V ---+---

How do you arrive at 100 ohms? I was using 200K because the value is
close to the threshold where it allows something like full power to
flow through the 3055. With 100k or less I was seeing my (cheap)
meter show fluxuating nonsense voltages at the emitter of up to 1500V,
although my scope showed nothing much amiss at lower frequency
settings. I was thinking that the 3055 was somehow generating large
spikes with the rising edge of the pulse, but I did not test it
exhaustively.

I quickly experimented with some lower value resisters and found that
the primary effect of using anything lower than 10K is damage to
either the 2n2222 or the BC557. The failure mode appears to be mainly
permanently shorting collector and emitter, but I observed partially
damaged transistors which would produce 1V at the base of Q1 in the
idle state. Since I've been doing a fair bit of fooling around in the
last 24 hours, it seems I've collected a half-dozen damaged
transistors, which probably contributed to some of the anomalous
readings I have had.

Using fresh parts and 100K between Q3 and Q2, everything is good. The
battery is only drawing 1.6A at this time so I can't easily test the
circuit at higher currents without draining the battery a whole lot.

100K seems high, a but BC557 does have quite a lot of gain and can
only handle 100mA, hoever the MJE3066 has much more gain then the
venerable 2N3055 so it hard to predict how strong that transistor need
to be.

A stronger transistor may be better suited there, eg BC327 or
MPSA56, or an even bigger one like BD78 or TIP42

If you want to increase the current just connect a load in parallel
with the battery, eg. a a car headlamp, or other dummy load.

The ripple at the base of Q1 is still there at 60mVpp which propagates
to the emitter, although I wouldn't see it without the diode. My
guess is that the Sziklai pair is too sensitive for this application,
but I don't really know why or what to do about it. The proximal
sensitivity to mass is another concern, and I don't know whether there
is an internal oscillation occuring that is amplified by a proximal
mass, or whether a proximal mass is triggering the amplification of
power-line hum. An extra .22uF filter capacitor on the 5V rail has no
effect.

Hmm, mysterious. You're not pluging the '3055 into a solderless
breadboard, or using long jumper wires to hook this up are you?

--
⚂⚃ 100% natural

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[Jasen Betts]

On 2013-05-07, Uncle Steve <stevet810@gmail.com> wrote:

On Tue, May 07, 2013 at 09:43:54AM -0700, George Herold wrote:
I don't think so.  The arrangement is described as a Sziklai Pair, and
is described at the following URL:

I redrew your circuit and tried to make Q2/Q3 look like a Darlington
or Sziklai.. didn't work.

One issue I have with your 'pair' is that the idea of the pair is to
get more current gain. So a transistor with only a small maximum
current drives the bigger transistor. I your case you've got it
backwards. The BC557 has a max Ic of 100mA and the 2n2222 is 500mA.
It also seems like the BC557 wiil driven right near it's max
current... Maybe a beefier pnp is in order?

Those are just the parts I have on hand, which were selected more or
less at random for the purpose of experimentation. I'm not really
concerned with the fact that the BC557 is 'smaller' than the 2n2222,
only that there is enough juice getting to the base of the MJE3055,
which appears to be true at this point. Before I hooked up the
battery, I used a 36VDC permanent magnet motor and stalled it by hand
to show almost 4A going through the sense resistor.

if you want to switch the 3055 by turning on a current to ground (where
the microconttoller is connected) you need to make the top NPN transistor
look like a PNP

The Sziklai pair arrangement does that almost perfectly

I suppose you're correct, as the diagrams of Darlington pairs don't

Perhaps I should move the 3055 to the other
side of the battery and try again.

That would work, but would also make monitoring the battery voltage
using the microcontroller much harder.

--
⚂⚃ 100% natural

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

 

[Uncle Steve]

On Wed, May 08, 2013 at 11:17:15AM +0000, Jasen Betts wrote:

On 2013-05-07, Uncle Steve <stevet810@gmail.com> wrote:
On Tue, May 07, 2013 at 06:43:00AM +0000, Jasen Betts wrote:
On 2013-05-07, Uncle Steve <stevet810@gmail.com> wrote:

I will consider that, but note that Q1 is NPN. What you propose
suggests I was counting on current-limiting to occur in the wrong
place.

You can do it like this using the transistors you have.

+18V ----+---+ _+----->|--[Rsense]-----> BAT+
| \ /|
| ----- '3055
| |
+ +
_\| /
------ BC557
|
change: [1K]
|
+
/
pwm in |/
--[2K2]--| PN2222
|\
_\|
+
|
0V ---+---

How do you arrive at 100 ohms?


it was just a guess, and your're right it's probably bit low for
a BC557 about 18ma in from base would would be better than about
180 so use 1K instead.

as you can see I'm not trying to get precise results transistors
vary but upto a factor of 3 in their gain ratio so ignoring the
small details often doesn't hurt the result.

After figuring out that it seems better in this case to have the
battery on the emitter side of the 3055 (probably doesn't really
matter, but this way seems easier) I rebuilt this configuration with
2.2k on the base of the 2n2222 (to reduce the drain on the uC pin,
perhaps for no good reason) and used 220 ohms on the base of the
BC557, which sets the current into the 3055 base at about 35mA and
10mA for the LED.

I was using 200K because the value is
close to the threshold where it allows something like full power to
flow through the 3055.

yeah but i'm not desiging an analogue circuit my goal is to over
bias the transistors so they go into saturation, stay there and
stay cool.

That's the bit I haven't yet figured out. When I understand how to do
that reliably, or at least to requirements, with arbitrary transistors
and without fooling around on a breadboard so much I'll be happier.

With 100k or less I was seeing my (cheap)
meter show fluxuating nonsense voltages at the emitter of up to 1500V,
although my scope showed nothing much amiss at lower frequency
settings. I was thinking that the 3055 was somehow generating large
spikes with the rising edge of the pulse, but I did not test it
exhaustively.

I wouldn't trust a cheap digital meter on a PWM signal, I'd add a
low-pass filter or envelope detector circuit depending on what I
wanted to measure.

There's no PWM yet, just a mechanical switch. The weird readings I got
on a couple of occasions were perhaps pathological cases where broken
transistors were doing something stupid.

I have a couple of wrinkles to figure out yet before I start
finalizing the software and begin testing the uC. I probably should
put a LM338 on the p/s to set the voltage to the bulk charge rate,
etc.


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.

 

[Jim Thompson]

On Wed, 08 May 2013 11:21:13 -0400, Uncle Steve <stevet810@gmail.com>
wrote:

On Wed, May 08, 2013 at 11:17:15AM +0000, Jasen Betts wrote:
On 2013-05-07, Uncle Steve <stevet810@gmail.com> wrote:
On Tue, May 07, 2013 at 06:43:00AM +0000, Jasen Betts wrote:
On 2013-05-07, Uncle Steve <stevet810@gmail.com> wrote:

I will consider that, but note that Q1 is NPN. What you propose
suggests I was counting on current-limiting to occur in the wrong
place.

You can do it like this using the transistors you have.

+18V ----+---+ _+----->|--[Rsense]-----> BAT+
| \ /|
| ----- '3055
| |
+ +
_\| /
------ BC557
|
change: [1K]
|
+
/
pwm in |/
--[2K2]--| PN2222
|\
_\|
+
|
0V ---+---

How do you arrive at 100 ohms?


it was just a guess, and your're right it's probably bit low for
a BC557 about 18ma in from base would would be better than about
180 so use 1K instead.

as you can see I'm not trying to get precise results transistors
vary but upto a factor of 3 in their gain ratio so ignoring the
small details often doesn't hurt the result.

After figuring out that it seems better in this case to have the
battery on the emitter side of the 3055 (probably doesn't really
matter, but this way seems easier) I rebuilt this configuration with
2.2k on the base of the 2n2222 (to reduce the drain on the uC pin,
perhaps for no good reason) and used 220 ohms on the base of the
BC557, which sets the current into the 3055 base at about 35mA and
10mA for the LED.

I was using 200K because the value is
close to the threshold where it allows something like full power to
flow through the 3055.

yeah but i'm not desiging an analogue circuit my goal is to over
bias the transistors so they go into saturation, stay there and
stay cool.

That's the bit I haven't yet figured out. When I understand how to do
that reliably, or at least to requirements, with arbitrary transistors
and without fooling around on a breadboard so much I'll be happier.

With 100k or less I was seeing my (cheap)
meter show fluxuating nonsense voltages at the emitter of up to 1500V,
although my scope showed nothing much amiss at lower frequency
settings. I was thinking that the 3055 was somehow generating large
spikes with the rising edge of the pulse, but I did not test it
exhaustively.

I wouldn't trust a cheap digital meter on a PWM signal, I'd add a
low-pass filter or envelope detector circuit depending on what I
wanted to measure.

There's no PWM yet, just a mechanical switch. The weird readings I got
on a couple of occasions were perhaps pathological cases where broken
transistors were doing something stupid.

I have a couple of wrinkles to figure out yet before I start
finalizing the software and begin testing the uC. I probably should
put a LM338 on the p/s to set the voltage to the bulk charge rate,
etc.


Regards,

Uncle Steve

You need a B-E resistor on the 3055. The lack of that probably
accounts for your observed instability.

I'm out this A.M., will post embellishments when I return.

...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.

 

[Uncle Steve]

On Wed, May 08, 2013 at 11:58:50AM +0000, Jasen Betts wrote:

On 2013-05-07, Uncle Steve <stevet810@gmail.com> wrote:
On Tue, May 07, 2013 at 08:52:59AM -0400, Uncle Steve wrote:
On Tue, May 07, 2013 at 06:43:00AM +0000, Jasen Betts wrote:
On 2013-05-07, Uncle Steve <stevet810@gmail.com> wrote:

I will consider that, but note that Q1 is NPN. What you propose
suggests I was counting on current-limiting to occur in the wrong
place.

You can do it like this using the transistors you have.

+18V ----+---+ _+----->|--[Rsense]-----> BAT+
| \ /|
| ----- '3055
| |
+ +
_\| /
------ BC557
|
[100] 0.25W
|
+
/
pwm in |/
---[1K]--| PN2222
|\
_\|
+
|
0V ---+---

How do you arrive at 100 ohms? I was using 200K because the value is
close to the threshold where it allows something like full power to
flow through the 3055. With 100k or less I was seeing my (cheap)
meter show fluxuating nonsense voltages at the emitter of up to 1500V,
although my scope showed nothing much amiss at lower frequency
settings. I was thinking that the 3055 was somehow generating large
spikes with the rising edge of the pulse, but I did not test it
exhaustively.

I quickly experimented with some lower value resisters and found that
the primary effect of using anything lower than 10K is damage to
either the 2n2222 or the BC557. The failure mode appears to be mainly
permanently shorting collector and emitter, but I observed partially
damaged transistors which would produce 1V at the base of Q1 in the
idle state. Since I've been doing a fair bit of fooling around in the
last 24 hours, it seems I've collected a half-dozen damaged
transistors, which probably contributed to some of the anomalous
readings I have had.

Using fresh parts and 100K between Q3 and Q2, everything is good. The
battery is only drawing 1.6A at this time so I can't easily test the
circuit at higher currents without draining the battery a whole lot.

100K seems high, a but BC557 does have quite a lot of gain and can
only handle 100mA, hoever the MJE3066 has much more gain then the
venerable 2N3055 so it hard to predict how strong that transistor need
to be.

A stronger transistor may be better suited there, eg BC327 or
MPSA56, or an even bigger one like BD78 or TIP42

I have enough gain at the moment, so this is a non-issue until I have
an excuse to make another run to the local electronics retailer.

If you want to increase the current just connect a load in parallel
with the battery, eg. a a car headlamp, or other dummy load.

Grin. I have just such a dummy load (25W or so) but it won't tolerate
13.5V (or more) so I'll have to be careful about how it gets hooked
up.

The ripple at the base of Q1 is still there at 60mVpp which propagates
to the emitter, although I wouldn't see it without the diode. My
guess is that the Sziklai pair is too sensitive for this application,
but I don't really know why or what to do about it. The proximal
sensitivity to mass is another concern, and I don't know whether there
is an internal oscillation occuring that is amplified by a proximal
mass, or whether a proximal mass is triggering the amplification of
power-line hum. An extra .22uF filter capacitor on the 5V rail has no
effect.

Hmm, mysterious. You're not pluging the '3055 into a solderless
breadboard, or using long jumper wires to hook this up are you?

It is a TO-220 package so fits in the breadboard, however I have been
wondering a little about the power rating of the breadboard rails...
The transformer is 55W so I suspect this might not be an entirely
academic issue.


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]

On Wed, May 08, 2013 at 12:11:13PM +0000, Jasen Betts wrote:

On 2013-05-07, Uncle Steve <stevet810@gmail.com> wrote:
On Tue, May 07, 2013 at 09:43:54AM -0700, George Herold wrote:
I don't think so. ?The arrangement is described as a Sziklai Pair, and
is described at the following URL:

I redrew your circuit and tried to make Q2/Q3 look like a Darlington
or Sziklai.. didn't work.

One issue I have with your 'pair' is that the idea of the pair is to
get more current gain. So a transistor with only a small maximum
current drives the bigger transistor. I your case you've got it
backwards. The BC557 has a max Ic of 100mA and the 2n2222 is 500mA.
It also seems like the BC557 wiil driven right near it's max
current... Maybe a beefier pnp is in order?

Those are just the parts I have on hand, which were selected more or
less at random for the purpose of experimentation. I'm not really
concerned with the fact that the BC557 is 'smaller' than the 2n2222,
only that there is enough juice getting to the base of the MJE3055,
which appears to be true at this point. Before I hooked up the
battery, I used a 36VDC permanent magnet motor and stalled it by hand
to show almost 4A going through the sense resistor.

if you want to switch the 3055 by turning on a current to ground (where
the microconttoller is connected) you need to make the top NPN transistor
look like a PNP

The Sziklai pair arrangement does that almost perfectly

I first tried that because I was having difficulty getting two 2n2222s
to produce enough gain. I believe I was not setting them up properly,
and is on my to-do list to understand how two NPN stages should work
in this kind of arrangement.

I suppose you're correct, as the diagrams of Darlington pairs don't

Perhaps I should move the 3055 to the other
side of the battery and try again.

That would work, but would also make monitoring the battery voltage
using the microcontroller much harder.

How so? I have a high-impedance resister-divider network hooked up to
the +ve battery terminal and ground, eventually going to a uC pin
configured for ADC. I'd just have to move it to span the battery
terminals instead of +batt and supply ground. The current arrangement
does have the advantage that all three r/d networks will have the same
scale.


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.

 

[Jasen Betts]

On 2013-05-08, Uncle Steve <stevet810@gmail.com> wrote:

On Wed, May 08, 2013 at 11:58:50AM +0000, Jasen Betts wrote:
On 2013-05-07, Uncle Steve <stevet810@gmail.com> wrote:
On Tue, May 07, 2013 at 08:52:59AM -0400, Uncle Steve wrote:
On Tue, May 07, 2013 at 06:43:00AM +0000, Jasen Betts wrote:
On 2013-05-07, Uncle Steve <stevet810@gmail.com> wrote:

I will consider that, but note that Q1 is NPN. What you propose
suggests I was counting on current-limiting to occur in the wrong
place.

You can do it like this using the transistors you have.

+18V ----+---+ _+----->|--[Rsense]-----> BAT+
| \ /|
| ----- '3055
| |
+ +
_\| /
------ BC557
|
[100] 0.25W
|
+
/
pwm in |/
---[1K]--| PN2222
|\
_\|
+
|
0V ---+---

How do you arrive at 100 ohms? I was using 200K because the value is
close to the threshold where it allows something like full power to
flow through the 3055. With 100k or less I was seeing my (cheap)
meter show fluxuating nonsense voltages at the emitter of up to 1500V,
although my scope showed nothing much amiss at lower frequency
settings. I was thinking that the 3055 was somehow generating large
spikes with the rising edge of the pulse, but I did not test it
exhaustively.

I quickly experimented with some lower value resisters and found that
the primary effect of using anything lower than 10K is damage to
either the 2n2222 or the BC557. The failure mode appears to be mainly
permanently shorting collector and emitter, but I observed partially
damaged transistors which would produce 1V at the base of Q1 in the
idle state. Since I've been doing a fair bit of fooling around in the
last 24 hours, it seems I've collected a half-dozen damaged
transistors, which probably contributed to some of the anomalous
readings I have had.

Using fresh parts and 100K between Q3 and Q2, everything is good. The
battery is only drawing 1.6A at this time so I can't easily test the
circuit at higher currents without draining the battery a whole lot.

100K seems high, a but BC557 does have quite a lot of gain and can
only handle 100mA, hoever the MJE3066 has much more gain then the
venerable 2N3055 so it hard to predict how strong that transistor need
to be.

A stronger transistor may be better suited there, eg BC327 or
MPSA56, or an even bigger one like BD78 or TIP42

I have enough gain at the moment, so this is a non-issue until I have
an excuse to make another run to the local electronics retailer.

If you want to increase the current just connect a load in parallel
with the battery, eg. a a car headlamp, or other dummy load.

Grin. I have just such a dummy load (25W or so) but it won't tolerate
13.5V (or more) so I'll have to be careful about how it gets hooked
up.

The ripple at the base of Q1 is still there at 60mVpp which propagates
to the emitter, although I wouldn't see it without the diode. My
guess is that the Sziklai pair is too sensitive for this application,
but I don't really know why or what to do about it. The proximal
sensitivity to mass is another concern, and I don't know whether there
is an internal oscillation occuring that is amplified by a proximal
mass, or whether a proximal mass is triggering the amplification of
power-line hum. An extra .22uF filter capacitor on the 5V rail has no
effect.

Hmm, mysterious. You're not pluging the '3055 into a solderless
breadboard, or using long jumper wires to hook this up are you?

It is a TO-220 package so fits in the breadboard, however I have been
wondering a little about the power rating of the breadboard rails...
The transformer is 55W so I suspect this might not be an entirely
academic issue.

I would't go over 200mA per contact on an unknown breadboard.
especially where an open circuit or unexpected resistance
could cause a problem.


--
⚂⚃ 100% natural

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

 

[Uncle Steve]

On Thu, May 09, 2013 at 07:06:21AM +0000, Jasen Betts wrote:

On 2013-05-08, Uncle Steve <stevet810@gmail.com> wrote:
On Wed, May 08, 2013 at 11:58:50AM +0000, Jasen Betts wrote:
Hmm, mysterious. You're not pluging the '3055 into a solderless
breadboard, or using long jumper wires to hook this up are you?

It is a TO-220 package so fits in the breadboard, however I have been
wondering a little about the power rating of the breadboard rails...
The transformer is 55W so I suspect this might not be an entirely
academic issue.


I would't go over 200mA per contact on an unknown breadboard.
especially where an open circuit or unexpected resistance
could cause a problem.

Too late! I have already determined that the conducters are capable
of handling 12V at 4A without melting anything. The battery is
another matter with a listed capacity of 180 Cold Cranking Amps, and I
am quite certain a short would cause major damage.


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.

 

[Jasen Betts]

On 2013-05-09, Uncle Steve <stevet810@gmail.com> wrote:

On Thu, May 09, 2013 at 07:06:21AM +0000, Jasen Betts wrote:
On 2013-05-08, Uncle Steve <stevet810@gmail.com> wrote:
On Wed, May 08, 2013 at 11:58:50AM +0000, Jasen Betts wrote:
Hmm, mysterious. You're not pluging the '3055 into a solderless
breadboard, or using long jumper wires to hook this up are you?

It is a TO-220 package so fits in the breadboard, however I have been
wondering a little about the power rating of the breadboard rails...
The transformer is 55W so I suspect this might not be an entirely
academic issue.


I would't go over 200mA per contact on an unknown breadboard.
especially where an open circuit or unexpected resistance
could cause a problem.

Too late! I have already determined that the conducters are capable
of handling 12V at 4A without melting anything.

not melted anything, but you've destroyed a few transistors in
mysterious circumstances.

If the Q1 (MJE3055) collector contact gets a bit loose all current will
go through Q2 (BC557) and destroy it.

Melt some solder, take the main current path off the breadourd.

The battery is
another matter with a listed capacity of 180 Cold Cranking Amps, and I
am quite certain a short would cause major damage.

100CCA, so it's just a little one (motorcycle?)

--
⚂⚃ 100% natural

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

 

[Uncle Steve]

On Fri, May 10, 2013 at 10:47:12AM +0000, Jasen Betts wrote:

On 2013-05-09, Uncle Steve <stevet810@gmail.com> wrote:
On Thu, May 09, 2013 at 07:06:21AM +0000, Jasen Betts wrote:
On 2013-05-08, Uncle Steve <stevet810@gmail.com> wrote:
On Wed, May 08, 2013 at 11:58:50AM +0000, Jasen Betts wrote:
Hmm, mysterious. You're not pluging the '3055 into a solderless
breadboard, or using long jumper wires to hook this up are you?

It is a TO-220 package so fits in the breadboard, however I have been
wondering a little about the power rating of the breadboard rails...
The transformer is 55W so I suspect this might not be an entirely
academic issue.


I would't go over 200mA per contact on an unknown breadboard.
especially where an open circuit or unexpected resistance
could cause a problem.

Too late! I have already determined that the conducters are capable
of handling 12V at 4A without melting anything.

not melted anything, but you've destroyed a few transistors in
mysterious circumstances.

Mainly due to bone-headedness.

If the Q1 (MJE3055) collector contact gets a bit loose all current will
go through Q2 (BC557) and destroy it.

Melt some solder, take the main current path off the breadourd.

Almost there.

The battery is
another matter with a listed capacity of 180 Cold Cranking Amps, and I
am quite certain a short would cause major damage.

100CCA, so it's just a little one (motorcycle?)

It's a "lawn and garden" battery. $20.00 on sale, so a good deal even
if it doesn't tolerate actual use all that well. As a backup power
solution it will be used only rarely.


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.

 

[Fred Abse]

On Mon, 27 May 2013 11:33:18 -0700, Rich Grise wrote:

Then again, your stomach contents are pH 2.0, so what is "strong"
exactly?

So, he should puke on the rust stains? ;-)

Welcome back, Rich.

Nice to know you're not dead ;-)

--
"For a successful technology, reality must take precedence
over public relations, for nature cannot be fooled."
(Richard Feynman)

 

On Saturday, September 11, 1999 3:00:00 AM UTC-4, Adam wrote:

Where a phone plugs into the wall (via RJ-11 cable) there are only two wires
connected. I tested them and found about 40 volts across them regardless of
the state of the phone. How is it that both power and audio can go through
these two cables? I am designing a circuit that monitors a phone line for
DTMF tones and then sends them to a microcontroller. I was planning to have
'in from line' and 'out to phone' jacks on it, so that it could be made to
passively monitor a phone or answering machine (or both with a splitter). I
was wondering if anyone knew about the inner workings of a phone and what
the best way to do this is? I noticed the from the base to the handset there
are four wires, are they sets of two going to the earphone/speaker? If so,
could I use the earphone wires? I would prefer to use the wires coming out
of the wall since then the whole package could be made more discreet, and
compatible with answering machines. The audio is sent somehow through those
wires, so could I just capacitively couple them to the A/D converter? (8870
DTMF decoder).

Thanks,
Adam

Has anyone heard of a phone switch called ATT/Philps Tel 5ESS-PBX Host? What kind of hook tone is that from there? it wound up like a siren and got to a medium pitch sound and went like a horn. that off hook tone was a medium pitch single tone. What kind of noise was that? what is the technical name for that ROH tone? Please let me know. Thank you.

 

On Wednesday, June 12, 2013 10:17:07 AM UTC-7, Jim Thompson wrote:

Anyone have views about which is best for drinking water...

multi-stage filters or R/O?



...Jim Thompson

--

| James E.Thompson | mens |

| Analog Innovations | et |

| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |

| San Tan Valley, AZ 85140 Skype: Contacts Only | |

| Voice480)460-2350 Fax: Available upon request | Brass Rat |

| E-mail Icon at http://www.analog-innovations.com | 1962 |



I love to cook with wine. Sometimes I even put it in the food.

Our last house had an R/O system when we bought it. I don't know if R/O is still like that but it had a storage tank with an elastic bladder that required an activated charcoal filter get out the plastic taste from the bladder. I changed it to cascaded charcoal filters, fine followed by very fine. If there is a flaw in the taste I can't detect it and my wife who is much more particular finds it acceptable.

Because there is no tank to restrict it, there's all the filtered water you want for cooking pasta or making soup.

G˛