gearhead wrote:
Hi all, I'd like to help out some friends on an antique motorcycle
forum that have a 6 volt regulator project.  One of them built a
regulator on perfboard and posted the schematic.  It has a couple of
things I'd tweak, but it works.
The main challenge:  his regulator design doesn't incorporate current
limiting.  Even the original relay-style mechanical regulators
incorporated current limiting, because the generators required it.
Somebody on the forum suggested the zxct1009, but it only comes in
surface mount which means we can't rejigger the existing perfboard
project to include the new chip.  It would mean having a custom-
printed circuit board, and soldering techniques perhaps a little too
demanding for somebody building his first circuit -- which probably
describes a lot of the guys on the forum.
pdf of the circuit:
http://www.hydra-glide.com/phpBB2/download.php?id=1173
I've tried to find a through-hole component that fits the bill, but
can't seem to come up with anything just right.  I saw the micrel
MIC5021, but it supposedly operates on 12 volts and up.
http://www.micrel.com/_PDF/mic5021.pdf
Now, perhaps they make that statement on the datasheet because the
chip actually also has a voltage doubler and the high side drive needs
that kind of voltage to turn on a mosfet, and it's possible the chip
itself will actually run on a much lower voltage.  But the datasheet
doesn't say anything to this effect.  Has anybody used the MIC5021 and
know if it might actually turn on at say 5 volts or perhaps know of
any other through hole chips for current sensing?

This is just a suggestion, but consider the circuit below.  If the
transistors are well matched Vchg should come pretty close to Vgen/10 +
47 * 0.02 * Ibatt -- and you can jigger your component values around to
change the numbers.  You'll _probably_ be able to make this work OK with
any two unmatched (but like part-number) PNP transistors, like 2N3904's,
but you'd do better to get a matched pair (DigiKey has some Zetex parts
that would do, if there are any through-hole ones).

Try this out with SPICE before you run with it: I just threw it down off
the top of my head, it's not exactly like anything I've done before nor
is it tested at all.

      Vgen        ___        Vbatt
       o-----o---|___|---o-----o
             |           |   -----
             |   0.02    |    Ibatt
            .-.         .-.
            | |100      | |100
            | |         | |
            '-'         '-'
             |           |
             |           |
              >|       |
               |---o---|
              /|   |   |\
             |     |     |
             |     |     |
     Vchg    |     '-----o
       o-----o           |
             |           |
            .-.         .-.
            | |4.7K     | |47K
            | |         | |
            '-'         '-'
             |           |
             |           |
            ===         ==>             GND         GND

"gearhead" <nos...@billburg.com> schreef in berichtnews:e66fa9e8-d621-4ba3-8c47-fc5752b3f045@m36g2000hse.googlegroups.com...





Hi all, I'd like to help out some friends on an antique motorcycle
forum that have a 6 volt regulator project.  One of them built a
regulator on perfboard and posted the schematic.  It has a couple of
things I'd tweak, but it works.
The main challenge:  his regulator design doesn't incorporate current
limiting.  Even the original relay-style mechanical regulators
incorporated current limiting, because the generators required it.
Somebody on the forum suggested the zxct1009, but it only comes in
surface mount which means we can't rejigger the existing perfboard
project to include the new chip.  It would mean having a custom-
printed circuit board, and soldering techniques perhaps a little too
demanding for somebody building his first circuit -- which probably
describes a lot of the guys on the forum.
pdf of the circuit:
http://www.hydra-glide.com/phpBB2/download.php?id=1173
I've tried to find a through-hole component that fits the bill, but
can't seem to come up with anything just right.  I saw the micrel
MIC5021, but it supposedly operates on 12 volts and up.
http://www.micrel.com/_PDF/mic5021.pdf
Now, perhaps they make that statement on the datasheet because the
chip actually also has a voltage doubler and the high side drive needs
that kind of voltage to turn on a mosfet, and it's possible the chip
itself will actually run on a much lower voltage.  But the datasheet
doesn't say anything to this effect.  Has anybody used the MIC5021 and
know if it might actually turn on at say 5 volts or perhaps know of
any other through hole chips for current sensing?

That Micrel chip is not a current sensor, it is a mosfet driver. Looking for
a highside current sensor, try the MAX4374. A ZXCT1008 or ZXCT1009 may be
even better. But I doubt you to need that special (and expensive) chips.

Can't be sure what current you want to limit, but usually the field current
is limited to limit the output voltage of the generator. Which in turn
prevents the battery from being overloaded. This is exactly what the circuit
of your schematic is supposed to do. Just use R1 to set the correct voltage.
For a 6V lead-accid battery this will be about 6,9V. So even for fully
loaded battery the voltage should never exceed that value. You may have to
take some voltage loss accross D6 into account which is about 0.2V for this
particular diode.

petrus bitbyter- Hide quoted text -

- Show quoted text -

"gearhead" <nos...@billburg.com> schreef in berichtnews:e66fa9e8-d621-4ba3-8c47-fc5752b3f045@m36g2000hse.googlegroups.com...





Hi all, I'd like to help out some friends on an antique motorcycle
forum that have a 6 volt regulator project.  One of them built a
regulator on perfboard and posted the schematic.  It has a couple of
things I'd tweak, but it works.
The main challenge:  his regulator design doesn't incorporate current
limiting.  Even the original relay-style mechanical regulators
incorporated current limiting, because the generators required it.
Somebody on the forum suggested the zxct1009, but it only comes in
surface mount which means we can't rejigger the existing perfboard
project to include the new chip.  It would mean having a custom-
printed circuit board, and soldering techniques perhaps a little too
demanding for somebody building his first circuit -- which probably
describes a lot of the guys on the forum.
pdf of the circuit:
http://www.hydra-glide.com/phpBB2/download.php?id=1173
I've tried to find a through-hole component that fits the bill, but
can't seem to come up with anything just right.  I saw the micrel
MIC5021, but it supposedly operates on 12 volts and up.
http://www.micrel.com/_PDF/mic5021.pdf
Now, perhaps they make that statement on the datasheet because the
chip actually also has a voltage doubler and the high side drive needs
that kind of voltage to turn on a mosfet, and it's possible the chip
itself will actually run on a much lower voltage.  But the datasheet
doesn't say anything to this effect.  Has anybody used the MIC5021 and
know if it might actually turn on at say 5 volts or perhaps know of
any other through hole chips for current sensing?

That Micrel chip is not a current sensor, it is a mosfet driver. Looking for
a highside current sensor, try the MAX4374. A ZXCT1008 or ZXCT1009 may be
even better. But I doubt you to need that special (and expensive) chips.

Can't be sure what current you want to limit, but usually the field current
is limited to limit the output voltage of the generator. Which in turn
prevents the battery from being overloaded. This is exactly what the circuit
of your schematic is supposed to do. Just use R1 to set the correct voltage.
For a 6V lead-accid battery this will be about 6,9V. So even for fully
loaded battery the voltage should never exceed that value. You may have to
take some voltage loss accross D6 into account which is about 0.2V for this
particular diode.

petrus bitbyter- Hide quoted text -

- Show quoted text -

On Apr 8, 10:03 am, Tim Wescott <t...@seemywebsite.com> wrote:



gearhead wrote:
Hi all, I'd like to help out some friends on an antique motorcycle
forum that have a 6 volt regulator project. One of them built a
regulator on perfboard and posted the schematic. It has a couple of
things I'd tweak, but it works.
The main challenge: his regulator design doesn't incorporate current
limiting. Even the original relay-style mechanical regulators
incorporated current limiting, because the generators required it.
Somebody on the forum suggested the zxct1009, but it only comes in
surface mount which means we can't rejigger the existing perfboard
project to include the new chip. It would mean having a custom-
printed circuit board, and soldering techniques perhaps a little too
demanding for somebody building his first circuit -- which probably
describes a lot of the guys on the forum.
pdf of the circuit:
http://www.hydra-glide.com/phpBB2/download.php?id=1173
I've tried to find a through-hole component that fits the bill, but
can't seem to come up with anything just right. I saw the micrel
MIC5021, but it supposedly operates on 12 volts and up.
http://www.micrel.com/_PDF/mic5021.pdf
Now, perhaps they make that statement on the datasheet because the
chip actually also has a voltage doubler and the high side drive needs
that kind of voltage to turn on a mosfet, and it's possible the chip
itself will actually run on a much lower voltage. But the datasheet
doesn't say anything to this effect. Has anybody used the MIC5021 and
know if it might actually turn on at say 5 volts or perhaps know of
any other through hole chips for current sensing?

This is just a suggestion, but consider the circuit below. If the
transistors are well matched Vchg should come pretty close to Vgen/10 +
47 * 0.02 * Ibatt -- and you can jigger your component values around to
change the numbers. You'll _probably_ be able to make this work OK with
any two unmatched (but like part-number) PNP transistors, like 2N3904's,
but you'd do better to get a matched pair (DigiKey has some Zetex parts
that would do, if there are any through-hole ones).

Try this out with SPICE before you run with it: I just threw it down off
the top of my head, it's not exactly like anything I've done before nor
is it tested at all.

Vgen ___ Vbatt
o-----o---|___|---o-----o
| | -----
| 0.02 | Ibatt
.-. .-.
| |100 | |100
| | | |
'-' '-'
| |
| |
| |
|---o---|
/| | |\
| | |
| | |
Vchg | '-----o
o-----o |
| |
.-. .-.
| |4.7K | |47K
| | | |
'-' '-'
| |
| |
=== ===
GND GND

I've done plenty of scheming about how to do it with discretes. But
like you said, I'd still want to use a chip in the end, to get matched
transistors. Pairs and arrays, I see ony surface mount, including
zetex.
If I have to go that way, might as well use the ZXCT1009F in SOT-23
with pins 1.9 mm apart according to the diagram. Almost a tenth of an
inch, could probably solder it right onto the pads of a perfboard, eh?

On 8 abr, 22:34, gearhead <nos...@billburg.com> wrote:





On Apr 8, 10:03 am, Tim Wescott <t...@seemywebsite.com> wrote:

gearhead wrote:
Hi all, I'd like to help out some friends on an antique motorcycle
forum that have a 6 volt regulator project.  One of them built a
regulator on perfboard and posted the schematic.  It has a couple of
things I'd tweak, but it works.
The main challenge:  his regulator design doesn't incorporate current
limiting.  Even the original relay-style mechanical regulators
incorporated current limiting, because the generators required it.
Somebody on the forum suggested the zxct1009, but it only comes in
surface mount which means we can't rejigger the existing perfboard
project to include the new chip.  It would mean having a custom-
printed circuit board, and soldering techniques perhaps a little too
demanding for somebody building his first circuit -- which probably
describes a lot of the guys on the forum.
pdf of the circuit:
http://www.hydra-glide.com/phpBB2/download.php?id=1173
I've tried to find a through-hole component that fits the bill, but
can't seem to come up with anything just right.  I saw the micrel
MIC5021, but it supposedly operates on 12 volts and up.
http://www.micrel.com/_PDF/mic5021.pdf
Now, perhaps they make that statement on the datasheet because the
chip actually also has a voltage doubler and the high side drive needs
that kind of voltage to turn on a mosfet, and it's possible the chip
itself will actually run on a much lower voltage.  But the datasheet
doesn't say anything to this effect.  Has anybody used the MIC5021 and
know if it might actually turn on at say 5 volts or perhaps know of
any other through hole chips for current sensing?

This is just a suggestion, but consider the circuit below.  If the
transistors are well matched Vchg should come pretty close to Vgen/10 +
47 * 0.02 * Ibatt -- and you can jigger your component values around to
change the numbers.  You'll _probably_ be able to make this work OK with
any two unmatched (but like part-number) PNP transistors, like 2N3904's,
but you'd do better to get a matched pair (DigiKey has some Zetex parts
that would do, if there are any through-hole ones).

Try this out with SPICE before you run with it: I just threw it down off
the top of my head, it's not exactly like anything I've done before nor
is it tested at all.

      Vgen        ___        Vbatt
       o-----o---|___|---o-----o
             |           |   -----
             |   0.02    |    Ibatt
            .-.         .-.
            | |100      | |100
            | |         | |
            '-'         '-'
             |           |
             |           |
              >|       |
               |---o---|
              /|   |   |\
             |     |     |
             |     |     |
     Vchg    |     '-----o
       o-----o           |
             |           |
            .-.         .-.
            | |4.7K     | |47K
            | |         | |
            '-'         '-'
             |           |
             |           |
            ===         ==> > >             GND         GND

I've done plenty of scheming about how to do it with discretes.  But
like you said, I'd still want to use a chip in the end, to get matched
transistors.  Pairs and arrays, I see ony surface mount, including
zetex.
If I have to go that way, might as well use the ZXCT1009F in SOT-23
with pins 1.9 mm apart according to the diagram.  Almost a tenth of an
inch, could probably solder it right onto the pads of a perfboard, eh?

Hello,

When you buy about 10 general purpose PNP transistors from one batch,
you will probably find several transistors that are within some mV
with same Ic.

When you design the 2 transistor current sensor at low
bias current, self heating can be neglected and it saves you from
soldering SMD devices like NXP's BCM857.  When matching is impossible,
you might add a trimmer potentiometer for nulling.

best regards,

Wim
PA3DJSwww.tetech.nl

Hi all, I'd like to help out some friends on an antique motorcycle
forum that have a 6 volt regulator project. One of them built a
regulator on perfboard and posted the schematic. It has a couple of
things I'd tweak, but it works.
The main challenge: his regulator design doesn't incorporate current
limiting. Even the original relay-style mechanical regulators
incorporated current limiting, because the generators required it.
Somebody on the forum suggested the zxct1009, but it only comes in
surface mount which means we can't rejigger the existing perfboard
project to include the new chip. It would mean having a custom-
printed circuit board, and soldering techniques perhaps a little too
demanding for somebody building his first circuit -- which probably
describes a lot of the guys on the forum.
pdf of the circuit:
http://www.hydra-glide.com/phpBB2/download.php?id=1173
I've tried to find a through-hole component that fits the bill, but
can't seem to come up with anything just right. I saw the micrel
MIC5021, but it supposedly operates on 12 volts and up.
http://www.micrel.com/_PDF/mic5021.pdf
Now, perhaps they make that statement on the datasheet because the
chip actually also has a voltage doubler and the high side drive needs
that kind of voltage to turn on a mosfet, and it's possible the chip
itself will actually run on a much lower voltage. But the datasheet
doesn't say anything to this effect. Has anybody used the MIC5021 and
know if it might actually turn on at say 5 volts or perhaps know of
any other through hole chips for current sensing?

| |
|---o---|

On Apr 8, 2:13 pm, Wimpie <wimabc...@tetech.nl> wrote:



On 8 abr, 22:34, gearhead <nos...@billburg.com> wrote:

On Apr 8, 10:03 am, Tim Wescott <t...@seemywebsite.com> wrote:

gearhead wrote:
Hi all, I'd like to help out some friends on an antique motorcycle
forum that have a 6 volt regulator project. One of them built a
regulator on perfboard and posted the schematic. It has a couple of
things I'd tweak, but it works.
The main challenge: his regulator design doesn't incorporate current
limiting. Even the original relay-style mechanical regulators
incorporated current limiting, because the generators required it.
Somebody on the forum suggested the zxct1009, but it only comes in
surface mount which means we can't rejigger the existing perfboard
project to include the new chip. It would mean having a custom-
printed circuit board, and soldering techniques perhaps a little too
demanding for somebody building his first circuit -- which probably
describes a lot of the guys on the forum.
pdf of the circuit:
http://www.hydra-glide.com/phpBB2/download.php?id=1173
I've tried to find a through-hole component that fits the bill, but
can't seem to come up with anything just right. I saw the micrel
MIC5021, but it supposedly operates on 12 volts and up.
http://www.micrel.com/_PDF/mic5021.pdf
Now, perhaps they make that statement on the datasheet because the
chip actually also has a voltage doubler and the high side drive needs
that kind of voltage to turn on a mosfet, and it's possible the chip
itself will actually run on a much lower voltage. But the datasheet
doesn't say anything to this effect. Has anybody used the MIC5021 and
know if it might actually turn on at say 5 volts or perhaps know of
any other through hole chips for current sensing?

This is just a suggestion, but consider the circuit below. If the
transistors are well matched Vchg should come pretty close to Vgen/10 +
47 * 0.02 * Ibatt -- and you can jigger your component values around to
change the numbers. You'll _probably_ be able to make this work OK with
any two unmatched (but like part-number) PNP transistors, like 2N3904's,
but you'd do better to get a matched pair (DigiKey has some Zetex parts
that would do, if there are any through-hole ones).

Try this out with SPICE before you run with it: I just threw it down off
the top of my head, it's not exactly like anything I've done before nor
is it tested at all.

Vgen ___ Vbatt
o-----o---|___|---o-----o
| | -----
| 0.02 | Ibatt
.-. .-.
| |100 | |100
| | | |
'-' '-'
| |
| |
| |
|---o---|
/| | |\
| | |
| | |
Vchg | '-----o
o-----o |
| |
.-. .-.
| |4.7K | |47K
| | | |
'-' '-'
| |
| |
=== ===
GND GND

I've done plenty of scheming about how to do it with discretes. But
like you said, I'd still want to use a chip in the end, to get matched
transistors. Pairs and arrays, I see ony surface mount, including
zetex.
If I have to go that way, might as well use the ZXCT1009F in SOT-23
with pins 1.9 mm apart according to the diagram. Almost a tenth of an
inch, could probably solder it right onto the pads of a perfboard, eh?

Hello,

When you buy about 10 general purpose PNP transistors from one batch,
you will probably find several transistors that are within some mV
with same Ic.

Doesn't gain determine the balance in a current mirror? If so, one
would have to match for gain. I did match for gain last time I
experimented with current mirrors. I'd like to hear from the experts
about the need for this.

When you design the 2 transistor current sensor at low
bias current, self heating can be neglected and it saves you from
soldering SMD devices like NXP's BCM857. When matching is impossible,
you might add a trimmer potentiometer for nulling.

best regards,

Wim
PA3DJSwww.tetech.nl

About temperature matching. I calculate that one tenth of a degree
centigrade difference between the transistors in a mirror would add
about one percent error to the current mirror. I wouldn't want
temperature vagaries causing any more error than that. I'm wondering
if you could count on discrete transistors on a board to stay within a
tenth of a degree to each other. More fodder for the experts.

Hi all, I'd like to help out some friends on an antique motorcycle
forum that have a 6 volt regulator project. One of them built a
regulator on perfboard and posted the schematic. It has a couple of
things I'd tweak, but it works.
The main challenge: his regulator design doesn't incorporate current
limiting. Even the original relay-style mechanical regulators
incorporated current limiting, because the generators required it.
Somebody on the forum suggested the zxct1009, but it only comes in
surface mount which means we can't rejigger the existing perfboard
project to include the new chip. It would mean having a custom-
printed circuit board, and soldering techniques perhaps a little too
demanding for somebody building his first circuit -- which probably
describes a lot of the guys on the forum.
pdf of the circuit:
http://www.hydra-glide.com/phpBB2/download.php?id=1173
I've tried to find a through-hole component that fits the bill, but
can't seem to come up with anything just right. I saw the micrel
MIC5021, but it supposedly operates on 12 volts and up.
http://www.micrel.com/_PDF/mic5021.pdf
Now, perhaps they make that statement on the datasheet because the
chip actually also has a voltage doubler and the high side drive needs
that kind of voltage to turn on a mosfet, and it's possible the chip
itself will actually run on a much lower voltage. But the datasheet
doesn't say anything to this effect. Has anybody used the MIC5021 and
know if it might actually turn on at say 5 volts or perhaps know of
any other through hole chips for current sensing?

"gearhead" <nos...@billburg.com> schreef in berichtnews:7226e6a4-ddd0-4da5-807a-5799069d795d@k13g2000hse.googlegroups.com...
On Apr 8, 1:30 pm, "petrus bitbyter"





pieterkraltlaatdit...@enditookhccnet.nl> wrote:
"gearhead" <nos...@billburg.com> schreef in
berichtnews:e66fa9e8-d621-4ba3-8c47-fc5752b3f045@m36g2000hse.googlegroups.com...

Hi all, I'd like to help out some friends on an antique motorcycle
forum that have a 6 volt regulator project. One of them built a
regulator on perfboard and posted the schematic. It has a couple of
things I'd tweak, but it works.
The main challenge: his regulator design doesn't incorporate current
limiting. Even the original relay-style mechanical regulators
incorporated current limiting, because the generators required it.
Somebody on the forum suggested the zxct1009, but it only comes in
surface mount which means we can't rejigger the existing perfboard
project to include the new chip. It would mean having a custom-
printed circuit board, and soldering techniques perhaps a little too
demanding for somebody building his first circuit -- which probably
describes a lot of the guys on the forum.
pdf of the circuit:
http://www.hydra-glide.com/phpBB2/download.php?id=1173
I've tried to find a through-hole component that fits the bill, but
can't seem to come up with anything just right. I saw the micrel
MIC5021, but it supposedly operates on 12 volts and up.
http://www.micrel.com/_PDF/mic5021.pdf
Now, perhaps they make that statement on the datasheet because the
chip actually also has a voltage doubler and the high side drive needs
that kind of voltage to turn on a mosfet, and it's possible the chip
itself will actually run on a much lower voltage. But the datasheet
doesn't say anything to this effect. Has anybody used the MIC5021 and
know if it might actually turn on at say 5 volts or perhaps know of
any other through hole chips for current sensing?

That Micrel chip is not a current sensor, it is a mosfet driver. Looking
for
a highside current sensor, try the MAX4374. A ZXCT1008 or ZXCT1009 may be
even better. But I doubt you to need that special (and expensive) chips.

Can't be sure what current you want to limit, but usually the field
current
is limited to limit the output voltage of the generator. Which in turn
prevents the battery from being overloaded. This is exactly what the
circuit
of your schematic is supposed to do. Just use R1 to set the correct
voltage.
For a 6V lead-accid battery this will be about 6,9V. So even for fully
loaded battery the voltage should never exceed that value. You may have to
take some voltage loss accross D6 into account which is about 0.2V for
this
particular diode.

petrus bitbyter- Hide quoted text -

- Show quoted text -

| Don't say the micrel chip is not a current sensor.  It does current
| sensing.
| And current limiting is for the generator, not the battery.

Hmm... Did you check the high-side current sensors I mentioned? As you know
the datasheet of the mic5021 can you explain how you get a signal from it
that is proportional to the measured current? I don't see it, but I like to
learn.

I am not aware of an automotive generator with a current limiter other then
the fields. Normaly the generator is big enough to provide the required
power for the vehicles appliances with a wide margin but yes, you can damage
it by overloading it. Most of the times however you will blow one or more
fuses when you try.

petrus bitbyter- Hide quoted text -

- Show quoted text -

On 8 abr, 23:32, gearhead <nos...@billburg.com> wrote:





On Apr 8, 2:13 pm, Wimpie <wimabc...@tetech.nl> wrote:

On 8 abr, 22:34, gearhead <nos...@billburg.com> wrote:

On Apr 8, 10:03 am, Tim Wescott <t...@seemywebsite.com> wrote:

gearhead wrote:
Hi all, I'd like to help out some friends on an antique motorcycle
forum that have a 6 volt regulator project.  One of them built a
regulator on perfboard and posted the schematic.  It has a couple of
things I'd tweak, but it works.
The main challenge:  his regulator design doesn't incorporate current
limiting.  Even the original relay-style mechanical regulators
incorporated current limiting, because the generators required it.
Somebody on the forum suggested the zxct1009, but it only comes in
surface mount which means we can't rejigger the existing perfboard
project to include the new chip.  It would mean having a custom-
printed circuit board, and soldering techniques perhaps a little too
demanding for somebody building his first circuit -- which probably
describes a lot of the guys on the forum.
pdf of the circuit:
http://www.hydra-glide.com/phpBB2/download.php?id=1173
I've tried to find a through-hole component that fits the bill, but
can't seem to come up with anything just right.  I saw the micrel
MIC5021, but it supposedly operates on 12 volts and up.
http://www.micrel.com/_PDF/mic5021.pdf
Now, perhaps they make that statement on the datasheet because the
chip actually also has a voltage doubler and the high side drive needs
that kind of voltage to turn on a mosfet, and it's possible the chip
itself will actually run on a much lower voltage.  But the datasheet
doesn't say anything to this effect.  Has anybody used the MIC5021 and
know if it might actually turn on at say 5 volts or perhaps know of
any other through hole chips for current sensing?

This is just a suggestion, but consider the circuit below.  If the
transistors are well matched Vchg should come pretty close to Vgen/10 +
47 * 0.02 * Ibatt -- and you can jigger your component values around to
change the numbers.  You'll _probably_ be able to make this work OK with
any two unmatched (but like part-number) PNP transistors, like 2N3904's,
but you'd do better to get a matched pair (DigiKey has some Zetex parts
that would do, if there are any through-hole ones).

Try this out with SPICE before you run with it: I just threw it down off
the top of my head, it's not exactly like anything I've done before nor
is it tested at all.

      Vgen        ___        Vbatt
       o-----o---|___|---o-----o
             |           |   -----
             |   0.02    |    Ibatt
            .-.         .-.
            | |100      | |100
            | |         | |
            '-'         '-'
             |           |
             |           |
              >|       |
               |---o---|
              /|   |   |\
             |     |     |
             |     |     |
     Vchg    |     '-----o
       o-----o           |
             |           |
            .-.         .-.
            | |4.7K     | |47K
            | |         | |
            '-'         '-'
             |           |
             |           |
            ===         ==> > > > >             GND         GND

I've done plenty of scheming about how to do it with discretes.  But
like you said, I'd still want to use a chip in the end, to get matched
transistors.  Pairs and arrays, I see ony surface mount, including
zetex.
If I have to go that way, might as well use the ZXCT1009F in SOT-23
with pins 1.9 mm apart according to the diagram.  Almost a tenth of an
inch, could probably solder it right onto the pads of a perfboard, eh?

Hello,

When you buy about 10 general purpose PNP transistors from one batch,
you will probably find several transistors that are within some mV
with same Ic.

Doesn't gain determine the balance in a current mirror?  If so, one
would have to match for gain.  I did match for gain last time I
experimented with current mirrors.  I'd like to hear from the experts
about the need for this.

When you design the 2 transistor current sensor at low
bias current, self heating can be neglected and it saves you from
soldering SMD devices like NXP's BCM857.  When matching is impossible,
you might add a trimmer potentiometer for nulling.

best regards,

Wim
PA3DJSwww.tetech.nl

About temperature matching.  I calculate that one tenth of a  degree
centigrade difference between the transistors in a mirror would add
about one percent error to the current mirror.  I wouldn't want
temperature vagaries causing any more error than that.  I'm wondering
if you could count on discrete transistors on a board to stay within a
tenth of a degree to each other.  More fodder for the experts.

Hello,

For such circuits matching on Vbe with constant collector current is
sufficient. I normally do it by connecting B to C, bias at required
current and measure the voltage across the diode.  Of course for high
volume applications I use a matched pair.

When 1% additional tolerance is unacceptable, you also should evaluate
all other components. I think of current sensing  resistor, other
resistors, voltage variatons, offsets in control loop etc. Regarding
temperature, put them close together, take some epoxy resin and some
piece of coper/alu, and temperature difference due to environment will
be negligible.

I can hardly imagine that your original application requires that high
accuracy.   Last year I designed several current limiting circuits for
hot swap applications and inrush current limiting and less then 5%
accuracy without adjustment and cheap components will be very
difficult.

Best regards,

Wim
PA3DJSwww.tetech.nl
please remove abc from the address.- Hide quoted text -

- Show quoted text -

Hi all, I'd like to help out some friends on an antique motorcycle
forum that have a 6 volt regulator project. One of them built a
regulator on perfboard and posted the schematic.

pdf of the circuit:
http://www.hydra-glide.com/phpBB2/download.php?id=1173

"gearhead" <nos...@billburg.com> schreef in
berichtnews:e66fa9e8-d621-4ba3-8c47-fc5752b3f045@m36g2000hse.googlegroups.com...





Hi all, I'd like to help out some friends on an antique motorcycle
forum that have a 6 volt regulator project. One of them built a
regulator on perfboard and posted the schematic. It has a couple of
things I'd tweak, but it works.
The main challenge: his regulator design doesn't incorporate current
limiting. Even the original relay-style mechanical regulators
incorporated current limiting, because the generators required it.
Somebody on the forum suggested the zxct1009, but it only comes in
surface mount which means we can't rejigger the existing perfboard
project to include the new chip. It would mean having a custom-
printed circuit board, and soldering techniques perhaps a little too
demanding for somebody building his first circuit -- which probably
describes a lot of the guys on the forum.
pdf of the circuit:
http://www.hydra-glide.com/phpBB2/download.php?id=1173
I've tried to find a through-hole component that fits the bill, but
can't seem to come up with anything just right. I saw the micrel
MIC5021, but it supposedly operates on 12 volts and up.
http://www.micrel.com/_PDF/mic5021.pdf
Now, perhaps they make that statement on the datasheet because the
chip actually also has a voltage doubler and the high side drive needs
that kind of voltage to turn on a mosfet, and it's possible the chip
itself will actually run on a much lower voltage. But the datasheet
doesn't say anything to this effect. Has anybody used the MIC5021 and
know if it might actually turn on at say 5 volts or perhaps know of
any other through hole chips for current sensing?

That Micrel chip is not a current sensor, it is a mosfet driver. Looking
for
a highside current sensor, try the MAX4374. A ZXCT1008 or ZXCT1009 may be
even better. But I doubt you to need that special (and expensive) chips.

Can't be sure what current you want to limit, but usually the field
current
is limited to limit the output voltage of the generator. Which in turn
prevents the battery from being overloaded. This is exactly what the
circuit
of your schematic is supposed to do. Just use R1 to set the correct
voltage.
For a 6V lead-accid battery this will be about 6,9V. So even for fully
loaded battery the voltage should never exceed that value. You may have to
take some voltage loss accross D6 into account which is about 0.2V for
this
particular diode.

petrus bitbyter- Hide quoted text -

- Show quoted text -

if it might actually turn on at say 5 volts or perhaps know of
any other through hole chips for current sensing?

Hi all, I'd like to help out some friends on an antique motorcycle
forum that have a 6 volt regulator project. One of them built a
regulator on perfboard and posted the schematic. It has a couple of
things I'd tweak, but it works.
The main challenge: his regulator design doesn't incorporate current
limiting. Even the original relay-style mechanical regulators
incorporated current limiting, because the generators required it.

I remember those old things and the electromecanical circuits that
controlled them, though I never got into their inner workings. So I do not
know about current control and how it was done.

English is not my native tongue.

Consider a ZDX1009. It is SMD but large enough to be mounted on perf board.
The datasheet shows the internal schematic which is very simple so you can
also build it using discretes. You have to use matched transistors as others
stated already.

petrus bitbyter

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