[BC] LED/Halogen Current Regulator

[Nick Palladino]

Hi everyone, here's a cheap and easy-to-build circuit that allows you to
drive any kind of LED:

http://www.unicrom.com/cir_regulador_corriente_LED-transistor.asp

The description is in spanish (my native tongue). So here's a brief
explanation on how it works:

No matter what the forward voltage drop or power supply voltage are, it
will regulate the current to a fixed value. I think the design is very well
known, but I tried it myself and it's got the advantage of keeping a
current constant regardless of the input voltage. It can also be used for
incandescent lamps as well, by setting the resistor to a value that forces
the appropriate current through the lamp.

How does it work?

The emmiter resistor mirrors the voltage drop in the diode, so the current
will always be 0.6 or 0.7V / R (emmiter). As a limitation voltage
regulation is 0.8/0.9 V above the voltage needed for the load, in other
words is a white leds needs 3.3V to operate, then we'd need 4.2V in order
to make the regulator work. If more voltage is available it will be
dissipated by the transistor.
I use it myself in a 3W white LED lamp I made and I works great. One thing
to take into account is that the transistor should be well heat sinked,
also you can put a rectifying diode in series between the transistor's
collector and the LED if there is too much power to dissipate.

Let me know your thoughts!

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[Brayl]

At 06:06 AM 2/20/2007 -0800, you wrote:
>
>Hi everyone, here's a cheap and easy-to-build circuit that allows you to
>drive any kind of LED:
>
>http://www.unicrom.com/cir_regulador_corriente_LED-transistor.asp
>
>The description is in spanish (my native tongue). So here's a brief
>explanation on how it works:
>
>No matter what the forward voltage drop or power supply voltage are, it
>will regulate the current to a fixed value. I think the design is very well
>known, but I tried it myself and it's got the advantage of keeping a
>current constant regardless of the input voltage. It can also be used for
>incandescent lamps as well, by setting the resistor to a value that forces
>the appropriate current through the lamp.
>

Yes the collector of a transistor looks like a current source. I remember
in electronics class putting diferent types of transistors on the curve
tracer and it would show a series of horizontal lines. This won't be a
precision current source though but would work for LEDs.

>
>
>How does it work?
>
>The emmiter resistor mirrors the voltage drop in the diode, so the current
>will always be 0.6 or 0.7V / R (emmiter). As a limitation voltage
>regulation is 0.8/0.9 V above the voltage needed for the load, in other
>words is a white leds needs 3.3V to operate, then we'd need 4.2V in order
>to make the regulator work. If more voltage is available it will be
>dissipated by the transistor.
>I use it myself in a 3W white LED lamp I made and I works great. One thing
>to take into account is that the transistor should be well heat sinked,
>also you can put a rectifying diode in series between the transistor's
>collector and the LED if there is too much power to dissipate.
>

It's not going to be the most efficient way to drive the LED. You might be
burning as much juice in the transistor and resistor as you are the LED.
How about a modern IC made just for this purpose like a MAX774. See app
note here.

http://www.maxim-ic.com/appnotes.cfm/appnote_number/3532

Certainly not as simple but it's what you really want. I'm sure there must
be ready built LED driver boards out there somewhere.

[Nick Palladino]

The diode drop (VD) usually 0.6/0.7V, tracks the VBE changes due to
temperature and thus suppresses temperature changes on Vbe.

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...... Original Message .......

[Nick Palladino]

The diode drop (VD) which is around 0.6/0.7V tracks the VBE changes

due to temperature and thus suppresses temperature changes on Vbe.

[Nick Palladino]

you can improve it by putting a diode accross the base-emmitter
junction to compensate for thermal changes. Anyway I did try it an you
can regulate with some precision, what factors would not make it
precise?

On 2/20/07, Brayl <n7...@sonic.net> wrote:
>

[Nick Palladino]

you can improve it by putting a diode accross the base-emmitter
junction to compensate for thermal changes. Anyway I did try it an you
can regulate with some precision, what factors would not make it
precise?

On 2/20/07, Brayl <n7...@sonic.net> wrote:
>

[Nick Palladino]

the diode compensates for thermal changes. Anyway I did try it does

regulate with some precision, what factors would not make it precise?

On 2/20/07, Brayl <n7...@sonic.net> wrote:
>

[bc-...@pardo.net]

>[Linear regulator for LED control]

For slightly higher cost you can buy a linear regulator "chip" that
allows you to use a smaller series resistor and thus achieve higher
efficiency. They are also temperature-compensated, so if the regulator
dumps a lot of power and gets hot it stays in regulation.

If a linear regulator runs "wide open" most of the time, efficiency can
be high. For example, if you match LED string voltage and battery pack
voltage, the regulator's series losses ban be small, especially if the
LED string voltage is high (so the resistor drop is a small percentage).
Most NiMH battery packs will initially put out a higher voltage, then
sag under load to a consistent level for most of their discharge. With
proper matching, the regulator might regulate only during the first part
of the discharge, then have only series losses for the rest of the
discharge. Efficiency can exceed 90%.

Switch-mode buck and boost regulators also typically provide best
efficiency when input and output voltages are nearly the same. A
switch-mode boost regulator will maintain uniform light levels as the
battery nears the end of discharge, and as result will run out of light
suddenly. A buck regulator will tend to go from regulation to simple
conduction and thus behave more like a linear regulator in terms of
'fade out'.

A switch-mode regulator will be more electrically noisy.

A linear regulator may need a suitable capacitor to avoid oscillation.

For setups I have studied, linear regulators can be assembled easily for
around US$2, whereas switch-mode regulators are more complex than I
typically want to build, and cost around US$20 to buy assembled.
However, switch-mode regulators are (for the systems I have looked at)
more flexible in that they have better efficiency when the battery and
LED string voltage diverge. A switching regulator may provide better
efficiency for variable brightness, since it can be matched for
full-load voltage but not lose efficiency when driving the LED string at
reduced voltage for reduced light output.

Keep in mind that the LED string voltage will also vary with
temperature.

The efficiency of linear regulators is fairly straightforwrd, but it is
hard to make broad statements about switch-mode regulators, whose
efficiency varies with the design, the LC components used, and so on.
Here's two tables for comparison:

http://taskled.com/tech.html
http://taskled.com/techfatman.html

Note the first never gets better than high 80s, while the 2nd rarely
does that poorly.

If efficiency truly concerns you, note also that some LEDs can give much
greater lm/W when under-driven. There was a table posted at
candlepowerforums for a sample Luxeon which gave about 30% higher lm/W
when under-driven to 1/2, and almost 100% higher lm/W when under-driven
to 1/10. I don't know how typical this is across brands, models, bins,
etc., but that's a big difference. My guess is part of the difference
is thermal, and good cooling (heat sinking) is needed to achieve these
levels.

[kur...@mtco.com]

>
> Hi everyone, here's a cheap and easy-to-build circuit that allows you to
> drive any kind of LED:
>
> http://www.unicrom.com/cir_regulador_corriente_LED-transistor.asp
>

yep, that's a classic circuit! I've used it for a number of
applications. There's a slight variation of this circuit that uses the
voltage across the sense resistor to turn on a second npn transistor.
This second npn then "steals" the base current of the first npn; i.e the
collector of the second npn is connected to the base of the first, and the
emitter is connected to ground. It's a bit more precise in the sense
that it has a sharper limiting characteristic.

The only downside of either of these circuits is that you use up 1.4v
(roughly) just to make the current limit circuit work. That means that
you need an extra NiMH or Nicad cell.

My preference is to go with a slightly more elaborate linear current
regulator. I don't have access to the schematic right now, but it's
fairly basic. It consists of an op-amp, a voltage reference, an output
drive transistor, and a sense resistor. Maybe a couple of extra resistors
too... The advantage is that I can use it with 4 NiMH cells to run a
3W Luxeon. The circuit only requires 0.2v or 0.3v headroom; i.e. if the
Luxeon is using 3.7v, then the battery voltage can be as low as 4.0v.
If anyone is interested, I can dig up the schematic later.

regards,
Steve Kurt

[Nick Palladino]

Right, Im actually using a 6V SLA battery, that allows me to have some extra Volts. Besides the transistor runs really cool because it dissipates less than 1W, and the LED is well dissipated. Efficiency could be a problem because I'm using 6V (nominal) x 0.4A = 2.4W and the LED uses 3.3 V x 0.4 A 1.32W So the device is slightly above 50% in effiency. Maybe another led can be added in series, maybe a 2V Led than draws 400 mA or some egular leds in paralell. Other than that I noticed that the circuit is pretty stable when it comes to regulation.

Nick.

[Nick Palladino]

Right Kurt, this is the circuit you probably mean:

http://unicrom.com/cir_regulador_corriente_LED.asp

I also  put it on the same site, but I feel the one using just a transistor is good enough for this purpose. I'm using it with a power LED and I also did tests to see if the current was what it was supposed to be and it ran for about 6 hours at 400 mA.

I see no point in making anything more sophisticated than this, for a bike project. I also know the two transistors design you mean, it's used basically as a current limiter.

I think this is good enough to control an LED, and so far it proved to be reliable. Of course there are dedicated ICs but if you want to go simple and cheap and at the same time reliable, this is the way to go.

Thanks

Nick.

[John Phillips]

I'm also currently experimenting with simple constant-current
regulators, with a view to changing the light source of an existing
four-cell incandescent light over to a single 1-W power LED. The
objective is simplicity and low cost using readily available components.

My first thought was a linear regulator. I found some good information
on two common constant-current source configurations here:

http://www.jefspalace.be/analog/input%20stage/constant%20current%20source.php

Trying both circuits, the two-transistor circuit indeed has much better
regulation than the diode circuit, as the text says, due to the extra
gain stage and the potential to remove the sensing base-emitter junction
from the heat-generating main transistor. The cost of a small-signal
transistor to replace the two diodes is insignificant considering the
improved performance and I think well worth it.

I used the following components for a PNP (positive-rail) version that
is designed to work from 4.2 V to 6 V providing 320 mA LED current:

R3 = 2.2 Ohms
R4 = 560 Ohms
Q2 = BD140
Q3 = BC558

For an NPN (negative-rail) version, as drawn, Q2 = BD139 and Q3 = BC548.
I used these transistors simply because they were plentiful and cheap
at my local electronics store. Hundreds of other types will work. Just
watch the dissipation in Q2. For a 6-V input, 320 mA LED current and at
an ambient temperature of 25 degrees Celsius the BD140's TO-126 package
was just at what I considered to be the limit of being able to run
without a heat-sink.

The power LED was placed in the collector circuit of Q2.

The circuit drops out of regulation below about 4.2 V, the current
rolling off fairly linearly down to the LED's forward voltage. It is
temperature dependent, the Vbe of Q3 changing by approximately -2
mV/Kelvin, which means a current change of about -0.3%/K at normal
ambient temperatures. This is the same as the two-diode circuit.

For a 6-V input the efficiency is only about 57%. Using four Ni-MH
cells, as planned, the efficiency is about 68-70%: still not great, but
the circuit is simple.

Q3's Vbe voltage drop across R3 largely dictates the drop-out voltage:
Vbe(Q3) + Vf(LED) + Vsat(Q2). Replacing Q2's base-drive components (R4
and Q3) with an LM334 IC and resistor as in the following circuit would
lower the voltage drop across the current-sensing resistor to around 67
mV and lessen current wastage in the base drive (only the required base
current for Q2 is supplied via the LM334 rather than supplying the most
it would ever need at minimum input voltage via R4 and bypassing, to
waste, what is not required via Q3):

http://www.worldtorch.com/LDO-fixed-current.php

This would enable one to drop the number of cells to three. With Ni-MH
cells the efficiency would be about 88-90%.

Going back to an all-discrete-transistor circuit, I figured out that
replacing R4 with a transistor and rearranging the placement of Q3 (also
changing to its complement) and moving the current-sensing resistor into
the collector circuit of Q2, between the power LED and the power rail,
leads to a three-transistor configuration that is more frugal with
current in Q2's base-drive section than the two-transistor
configuration. Although it still suffers from the 0.7-V drop across the
current sensing resistor, it occurred to me that this configuration
leads to an interesting possibility that I am about to try. For a
start, closed-loop gain is substantially increased. If a little
hysteresis was introduced (Schmitt-trigger action) the regulator would
then become unstable in the linear mode, opting to operate in
switch-mode: Q2 fully off or saturated. Add an inductor and a Schottky
diode to smooth out the current ripple and one should have a simple
hysteretic buck switch-mode current regulator with about 0.85 V
drop-out.

Then I found the following:

http://sound.westhost.com/appnotes/an003.htm

This is basically the circuit I had in mind, though without hysteresis.
Instead I think it appears to rely on phase shift at the C2-L1-D2 to
trigger oscillation. The author says it will transit from switch-mode
to linear mode as the input voltage falls below about 5 V, dropping out
of regulation at about 4.2 V.

My plan is to try configuring the emitters of Q1 and Q2 as a long-tail
pair via a resistor to the negative rail to make them into a Schmitt
trigger. The amount of hysteresis, set by the resistor, should
determine the current ripple. I think C2 could then be replaced by a
ceramic capacitor with much less capacitance or perhaps even eliminated.
I expect the circuit should then operate in switch-mode right down to
drop-out voltage more efficiently than in linear mode.

Admittedly not as efficent or flexible as something like a MAX774, but
FAR cheaper where I live.

Cheers,
John.

Nicolas Palladino wrote:
>
> Hi everyone, here's a cheap and easy-to-build circuit that allows you to
>
> drive any kind of LED:
>
> http://www.unicrom.com/cir_regulador_corriente_LED-transistor.asp
>

> The description is in spanish (my native tongue). So here's a brief
> explanation on how it works:
>
> No matter what the forward voltage drop or power supply voltage are, it
> will regulate the current to a fixed value. I think the design is very
> well
> known, but I tried it myself and it's got the advantage of keeping a
> current constant regardless of the input voltage. It can also be used
> for
> incandescent lamps as well, by setting the resistor to a value that
> forces
> the appropriate current through the lamp.
>
>
>

> How does it work?
>
> The emmiter resistor mirrors the voltage drop in the diode, so the
> current
> will always be 0.6 or 0.7V / R (emmiter). As a limitation voltage
> regulation is 0.8/0.9 V above the voltage needed for the load, in other
> words is a white leds needs 3.3V to operate, then we'd need 4.2V in
> order
> to make the regulator work. If more voltage is available it will be
> dissipated by the transistor.
> I use it myself in a 3W white LED lamp I made and I works great. One
> thing
> to take into account is that the transistor should be well heat sinked,
> also you can put a rectifying diode in series between the transistor's
> collector and the LED if there is too much power to dissipate.
>

> Let me know your thoughts!
>
>

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[John Phillips]

One more thought: To lower the voltage drop across the current-sensing
resistor in the simple transistor circuits one could use a small-signal
germanium transistor, though they are rarer now and getting more
expensive. Vbe would be about 0.3 V. Temperature co-efficient would be
about the same as for silicon.

Cheers,
John.

> switch-mode: Q2 fully off or saturated. Add a Schottky diode and an
> inductor

> to smooth out the current ripple and one should have a simple
> hysteretic buck switch-mode current regulator with about 0.85 V
> drop-out.
>
> Then I found the following:
>
> http://sound.westhost.com/appnotes/an003.htm
>
> This is basically the circuit I had in mind, though without hysteresis.
>

> Instead I think it appears to rely on phase shift at the C2-L1-D2 node

[John Phillips]

Another advantage of the variation of the circuit that uses a separate
transistor to sense voltage developed across the current-sensing
resistor: Its voltage overhead is one Vbe + Vsat which, for most
average silicon transistors, is about 0.7 V + 0.15 V = 0.85 V, i.e. 0.55
V lower drop-out voltage than the two-diode version.

http://www.jefspalace.be/analog/input%20stage/constant%20current%20source.php

Cheers,
John.

kur...@mtco.com wrote:
>
> >
> > Hi everyone, here's a cheap and easy-to-build circuit that allows you to
> > drive any kind of LED:
> >
> > http://www.unicrom.com/cir_regulador_corriente_LED-transistor.asp
> >
>

> yep, that's a classic circuit! I've used it for a number of
> applications. There's a slight variation of this circuit that uses the
> voltage across the sense resistor to turn on a second npn transistor.
> This second npn then "steals" the base current of the first npn; i.e
> the
> collector of the second npn is connected to the base of the first, and
> the
> emitter is connected to ground. It's a bit more precise in the sense
> that it has a sharper limiting characteristic.
>
> The only downside of either of these circuits is that you use up 1.4v
> (roughly) just to make the current limit circuit work. That means that
> you need an extra NiMH or Nicad cell.
>
> My preference is to go with a slightly more elaborate linear current
> regulator. I don't have access to the schematic right now, but it's
> fairly basic. It consists of an op-amp, a voltage reference, an output
> drive transistor, and a sense resistor. Maybe a couple of extra
> resistors
> too... The advantage is that I can use it with 4 NiMH cells to run a
> 3W Luxeon. The circuit only requires 0.2v or 0.3v headroom; i.e. if
> the
> Luxeon is using 3.7v, then the battery voltage can be as low as 4.0v.
> If anyone is interested, I can dig up the schematic later.
>
> regards,
> Steve Kurt
>
>

[Steve Kurt]

Nicolas Palladino wrote:
> Right Kurt, this is the circuit you probably mean:
>
> http://unicrom.com/cir_regulador_corriente_LED.asp

this is essentially the op-amp circuit I was thinking of, except that a
voltage reference, or at least a zener diode, is used in place of the
two diodes in series. While the use of the plain diodes is better than
nothing, it's generally quite affordable to substitute a zener diode
instead. $0.30 or so at Digikey. Even a decent voltage reference,
like a LM4040 (I think..) is fairly low cost. ummm... about $1 at
Digikey in low quantities.

>
> I also put it on the same site, but I feel the one using just a
> transistor is good enough for this purpose. I'm using it with a power
> LED and I also did tests to see if the current was what it was supposed
> to be and it ran for about 6 hours at 400 mA.
>
> I see no point in making anything more sophisticated than this, for a
> bike project. I also know the two transistors design you mean, it's used
> basically as a current limiter.
>
> I think this is good enough to control an LED, and so far it proved to
> be reliable. Of course there are dedicated ICs but if you want to go
> simple and cheap and at the same time reliable, this is the way to go.

as always, the design usually has some price or cost that restricts the
design. This is usually a bigger concern for a design that is produced
in large quantities. For low volume designs, the cost of the design
and testing may far exceed the cost of the materials used in the design,
so it may be more practical to use more precise or reliable components.
For a hobbyist, sometimes it is just fun to see how simple and basic
you can make the design, and other times you want to make it fairly
precise so you never have to fiddle with it again. For these reasons,
it's good be aware of many circuits that do the same basic job.

cheers,

[John Phillips]

Doh! I correct myself.

Both versions of the circuit have a regulating voltage overhead of
approximately 0.7 V + 0.15 V = 0.85 V, i.e. when using them as LED
constant-current sources, if the supply is less than 0.85 V above the
LED forward voltage, they will drop out of regulation.

John.

[Nick Palladino]

DOES ANYONE KNOW WHY DO I ALWAYS GET THIS MESSAGE WHENEVER I EMAIL TOPICA???

"snd_pcm_hw_param...@ghostdivers.com" < snd_pcm_hw_param...@ghostdivers.com>		hide details	12:39 am (11 hours ago)
	to			nicolas....@gmail.com
	date			Feb 21, 2007 12:39 AM
	subject			Re: [BC] LED/Halogen Current Regulator

invalid email

[Nick Palladino]

What about creating a reference with a regular diode plus a schottky diode? The reference in the current sensing resistor would be less than 0.3V

> mV/Kelvin, which means a current change of about - 0.3%/K at normal

[Nick Palladino]

The reason I used diodes instead of a Zener is because I want to keep emmiter's resistor voltage as low as possible, because even though I'm using 6V I could as well be using 4 Volts. If the circuit is only going to be used with 6V then a 2.5V / 3V Zener Diode is a great choice, then I agree with you. But in the case you want to leave it open to other voltage sources then two diodes is the way to go.

Thanks

Nick.

[jim g]

${top_text_ad}
Brayl <n7...@sonic.net> wrote:

>>
...I'm sure there must be ready built LED driver boards out there somewhere.
<<

Check out the TaskLED bFlex driver, recently improved with a bicycle-specific UI. I don't think I've heard anyone here mention this yet. I'm working on a dual Cree light and using this as the driver.

http://taskled.com/bflex.html

-Jim G

--
from jim g via yojimg dot net

${bottom_text_ad}

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[John Phillips]

Nicolas,

That technique is certainly a possibility with the two-diode-reference
version of the circuit. The V/I characteristics of a Schottky diode may
be less sharp than a regular PN-junction silicon diode.

You might like try it. :-)

John.

> > > mV/Kelvin, which means a current change of about -0.3%/K at normal

> > --
> > To subscribe to this list send a BLANK email to
> > bikecurren...@topica.com
> > To unsubscribe from this list send a BLANK email to
> > bikecurrent...@topica.com
> >
> >
>

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[Francis Cooke]

Nick wrote:
NP> Re: [BC] LED/Halogen Current Regulator invalid email

You're not alone. I get similar messages. As I understand it the
list is mirrored somewhere and we (and some others) are only
communicating via the mirrored version, and getting rejection messages
from those nice people at Topica.

Francis

[Nick Palladino]

I hope we can come up with something. It's really annoying!

[John Clary]

On 2/22/07, Nick Palladino <nicolas....@gmail.com> wrote:
> I hope we can come up with something. It's really annoying!
>
> On 2/22/07, Francis Cooke <fra...@aukadia.net> wrote:
> >
> > Nick wrote:
> > NP> Re: [BC] LED/Halogen Current Regulator invalid email
> >
> >
> > You're not alone. I get similar messages. As I understand it the
> > list is mirrored somewhere and we (and some others) are only
> > communicating via the mirrored version, and getting rejection messages
> > from those nice people at Topica.
> >
> >

Those "invalid email" messages are coming from a spam address
harvester that has been shut down.

--
Opus

My gas is up to $.99 a burrito, $5.99 for premium, and I'm only
getting 20 miles to the regular burrito.

[Ian Boehm]

> You're not alone. I get similar messages. As I understand
> it the list is mirrored somewhere and we (and some others)
> are only communicating via the mirrored version, and getting
> rejection messages from those nice people at Topica.

Which neatly brings me to the topic of what progress has been made with
the proposal to move this list to another host?

Cheers
__o
_`\<,
...(*)/(*)
Ian
-------------------------------------------------------------
Ian Boehm e-mail: I.B...@bom.gov.au

[Joe Gross]

On Fri, Feb 23, 2007 at 10:14:39AM +1100, Ian Boehm wrote:
>
> > You're not alone. I get similar messages. As I understand
> > it the list is mirrored somewhere and we (and some others)
> > are only communicating via the mirrored version, and getting
> > rejection messages from those nice people at Topica.
>
> Which neatly brings me to the topic of what progress has been made with
> the proposal to move this list to another host?

I've got a new list on Google Groups at
http://groups.google.com/group/bikecurrent that's mirroring the Topica
content.

If Whitney (list owner) is still interested in doing a move I'm happy
to help.

Joe

[Nick Palladino]

I think moving to google groups would be a great idea. It looks much better
but I'm not sure if people are required to have a gmail acct in order to
post.

Nick

___
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...... Original Message .......
On Thu, 22 Feb 2007 14:58:51 -0600 "John Clary" <opust...@gmail.com>
wrote:

>On 2/22/07, Nick Palladino <nicolas....@gmail.com> wrote:

>> I hope we can come up with something. It's really annoying!
>>
>> On 2/22/07, Francis Cooke <fra...@aukadia.net> wrote:
>> >
>> > Nick wrote:
>> > NP> Re: [BC] LED/Halogen Current Regulator invalid email
>> >
>> >
>> > You're not alone. I get similar messages. As I understand it the
>> > list is mirrored somewhere and we (and some others) are only
>> > communicating via the mirrored version, and getting rejection messages
>> > from those nice people at Topica.
>> >
>> >

[Francis Cooke]

NP> I think moving to google groups would be a great idea. It looks much better
NP> but I'm not sure if people are required to have a gmail acct in order to
NP> post.

No, they aren't. My only reservation would be that googlegroups
passes attachments and I can't see any way of turning that off - maybe
I'm missing something. (Yahoogroups also pass attachments but with
them its a option that can be turned off).

Francis

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[Bob Sutterfield]

On 2/26/07, Francis Cooke <fra...@aukadia.net> wrote:
> NP> I think moving to google groups would be a great idea. It looks much better
> NP> but I'm not sure if people are required to have a gmail acct in order to
> NP> post.
>
> No, they aren't. My only reservation would be that googlegroups
> passes attachments and I can't see any way of turning that off - maybe
> I'm missing something. (Yahoogroups also pass attachments but with
> them its a option that can be turned off).

I too see no such switch in the ggroups Group Settings or Management
Tasks pages. Perhaps ggroups relies on gmail's spam and malware
filters to scrub incoming messages. I'll ask the developers about it
because I think it's an important feature anyway.

I use gmail for both home and work. Those two accounts' spamboxes
have accumulated a combined 7692 messages over the past 30 days, and I
have seen fewer than a dozen spams that have leaked through, and none
with attached malware.

[Francis Cooke]

>> My only reservation would be that googlegroups

>> passes attachments and I can't see any way of turning that off ...

BS> I too see no such switch in the ggroups Group Settings or Management
BS> Tasks pages. Perhaps ggroups relies on gmail's spam and malware
BS> filters to scrub incoming messages.

I think it does - but my concern was as much about wasted bandwidth as
about malware. If people are going to start distributing multi-Mb
files that turn out to be a circuit diagram for a regulator I would be
unimpressed ;-)

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Best regards,
Francis mailto:fra...@aukadia.net

[Per Elmsäter]

On 2/26/07, Francis Cooke <fra...@aukadia.net> wrote:

>> My only reservation would be that googlegroups
>> passes attachments and I can't see any way of turning that off ...

BS> I too see no such switch in the ggroups Group Settings or Management
BS> Tasks pages.  Perhaps ggroups relies on gmail's spam and malware
BS> filters to scrub incoming messages.

I think it does - but my concern was as much about wasted bandwidth as
about malware.   If people are going to start distributing multi-Mb
files that turn out to be a circuit diagram for a regulator I would be
unimpressed ;-)

Googlegroups web interface does such a good job that it's not even necessary to use anything else. Hence you open the attachments that interest you. Gmail kind of works pretty much the same way

 

--
Regards
Per Elmsäter