Another BASIC Q., this time aboputMicroPuck2009

K

Kris Krieger

Guest
Hello, All,

Yeah, it's another dumb Q. from Kris ;)

I'm looking at this:

http://www.leddynamics.com/LuxDrive/content/Page_Micro_App.html#2009%20as%
20a%20Boost%20Driver

In the column for "minimum LED current", there is a dash. Does that
mean that, if I wanted, I could use the MicroPuck2009 to run 20mA, or
does it mean it only had onle "flat-rate" output?

I understand that resistors control Voltage into LEDs. But how do I get
something like this puck to not pump too many mA into fewer than the
suggested 15-parallel-20mA-LEDs, say, 6 or maybe 8?

Many Thanks in Advance!

- Kris K.
 
"Kris Krieger" <me@dowmuff.in> wrote in message
news:Xns9C3D8018C10D2meadowmuffin@216.168.3.70...
Hello, All,

Yeah, it's another dumb Q. from Kris ;)

I'm looking at this:

http://www.leddynamics.com/LuxDrive/content/Page_Micro_App.html#2009%20as%
20a%20Boost%20Driver

In the column for "minimum LED current", there is a dash. Does that
mean that, if I wanted, I could use the MicroPuck2009 to run 20mA, or
does it mean it only had onle "flat-rate" output?

I understand that resistors control Voltage into LEDs. But how do I get
something like this puck to not pump too many mA into fewer than the
suggested 15-parallel-20mA-LEDs, say, 6 or maybe 8?

Many Thanks in Advance!

- Kris K.
Click to expand...
Hi Kris

Firstly, an attempt to analyse what is inside this puck...

To get the boost (or buck/boost) configuration to work, there has to be a
coil inside this puck driven by a switch. When the switch is closed, the
coil charges up. When the switch goes open circuit, the energy inside the
coil has to flow somewhere, so the voltage across the coil ramps up until
something conducts. This is the basis of how all inductor based boost
converters work.

If the LED is present, this energy flows into the LED. If no LED is present,
you will probably get a large spark on the output and the circuit will work
no more. Hence the comment on the datasheet that an LED must always be
connected.

To control the current into the coil you need some form of current sense
resistor. Guessing at the architecture inside this device, I dont think
there is a current sense resistor inside it, so it is relying on the ON and
OFF times of the switch controlling the inductor to control the current to
the load.

Therefore, it looks like you are stuck with whatever current it gives you.
This is further backed up by the graph of LED current vs input voltage -
there is no 'tunability'.

You can always divert the excess current into another load in parallel with
the 20mA LED you want to drive, but you are better off looking at one of the
many LED drivers from the likes of TI, LT and Maxim (LT and Maxim have big
DIP packages and give away free samples if this makes your crusade any
easier...)

Hope this helps

--
Bill Naylor
www.electronworks.co.uk
Electronic Kits for Education and Fun
 
"Electronworks.co.uk" <newsgroups@electronworks.co.uk> wrote in
news:hvOdndytEpzPmtLXnZ2dnUVZ8t2dnZ2d@bt.com:

"Kris Krieger" <me@dowmuff.in> wrote in message
news:Xns9C3D8018C10D2meadowmuffin@216.168.3.70...
Hello, All,

Yeah, it's another dumb Q. from Kris ;)

I'm looking at this:

http://www.leddynamics.com/LuxDrive/content/Page_Micro_App.html#2009%20a
s% 20a%20Boost%20Driver

In the column for "minimum LED current", there is a dash. Does that
mean that, if I wanted, I could use the MicroPuck2009 to run 20mA, or
does it mean it only had onle "flat-rate" output?

I understand that resistors control Voltage into LEDs. But how do I
get something like this puck to not pump too many mA into fewer than
the suggested 15-parallel-20mA-LEDs, say, 6 or maybe 8?

Many Thanks in Advance!

- Kris K.



Hi Kris

Firstly, an attempt to analyse what is inside this puck...

To get the boost (or buck/boost) configuration to work, there has to be
a coil inside this puck driven by a switch. When the switch is closed,
the coil charges up. When the switch goes open circuit, the energy
inside the coil has to flow somewhere, so the voltage across the coil
ramps up until something conducts. This is the basis of how all inductor
based boost converters work.

If the LED is present, this energy flows into the LED. If no LED is
present, you will probably get a large spark on the output and the
circuit will work no more. Hence the comment on the datasheet that an
LED must always be connected.

To control the current into the coil you need some form of current sense
resistor. Guessing at the architecture inside this device, I dont think
there is a current sense resistor inside it, so it is relying on the ON
and OFF times of the switch controlling the inductor to control the
current to the load.

Therefore, it looks like you are stuck with whatever current it gives
you. This is further backed up by the graph of LED current vs input
voltage - there is no 'tunability'.

You can always divert the excess current into another load in parallel
with the 20mA LED you want to drive, but you are better off looking at
one of the many LED drivers from the likes of TI, LT and Maxim (LT and
Maxim have big DIP packages and give away free samples if this makes
your crusade any easier...)

Hope this helps
Click to expand...
Yes, that helps a great deal, thanks! :) I'm assuming, then, that the
MicroPuck is essentially an inductor-capacitor pair...? Based on your
suggestion of Maxim, I did find this:
"DC-DC Converter Tutorial" http://www.maxim-ic.com/appnotes.cfm/an_pk/2031/
so I downloaded the PDF and printed it out for further study.

Heh, "crusade" is prob the right term; I've been at this (tho' admittedly
sporadicalyl) for about a year - the time-expanse is due to the fact that,
when I started out with this idea (or damnfool notion, depending on one's POV
<L!>), the sum total of my Electronics knowledge (I kid you not) was "do not
trim the fat prong of a polarized plug"! =:-o ((When I took physics 101
30-some years ago, the prof did devote an hour to scribbling calculus on the
chalkboard and mumbling sotto-voce, but I don't count that as adding one iota
to my understanding)). I'm now to where I've figured out pretty much how to
connect solar cell, supercapacitor, diode, photo-controller, "Voltage Booster
Thingy", LEDs, and resistor(s), so considering the circumstances, I guess I
haven't done TOO badly.

At any rate, I had hoped that the Puck would be a good solution, but now that
I know that the Dash in the "minimum current" column of the various puck's
charts means "no minumum becuase the maximum is also the minimum", it will
save me a lot of time in that I won't be looking at them any further. So
Many Thanks for that!

Also, the Maxim link gave me a good search term, so I then found this:
http://www.reuk.co.uk/DC-Voltage-Multiplier-Circuit-Plans.htm

In essence, what i'm doing with the "electronics" (if I may be so bold as to
describe my rube-goldberg device as "electronics" <LOL!>) is an "emergency
light" I suppose, except that the housing will be decorative/artistic (I do
stained glass, including the use of clear textured glass in a away somewhat
analagous to drawing useing pen-and-ink, which I used to do until my hands
got too quivery). Oh, and it's battery-less (uses a supercapacitor) and
charges from the sun. And the solar cells can be plugged in. Aside from
those differences, it's exactly the same <LOL!>

What I want to add (which isn't shown because I have to figure out what the
thing I need is called <L!>) is one of those adaptor-type plugs so that the
solar-cell part can be plugged into the bottom of the Lamp - I do stained
glass and have designed a couple of lamps using clear textured (or maybe
opalized) glass to do a "candle alternative" type of table-top light for
small gatherings. I had hit a wall becasue I was trying to figure out how to
integrate teh solar panels into the top of th elight/lamp. I need to
configure them to provide teh same voltage as the supercapacitor (the one I'm
looking at, the Maxwell BCAP 350 Farad one that's about the size of a D-cell
battery) THen, this past Friday, I bought a small Mergency Fan that runs on
either D-cell batteries, or a small wall-plug adaptor. WHen I took it out of
th ebox, I had one of those ***oh DUUUUUUHHHH!!!*** moments, where I thought
"Now why can't this plug connect to a solar-panel rather than a wall socket
adapter??"

SO now I have to figure out what the plug-thingy is called and try to see
whether they can be purchased. That would *completely* free up the design of
the lamp itself, because I won;t be constrained by trying to unify the airy
look of clear textured glass, with nearly-black solar cells - the mini-panel
can (I hope) just be plugged into the bottom, then unplugged for use. I just
have to figure out how to do it so that plugging the cells in turns the light
off.


Anyway, thanks again for that info about the pucks - one thing always leads
to another, so that was very useful :)

- Kris K.
 
Kris Krieger wrote:
"Electronworks.co.uk" <newsgroups@electronworks.co.uk> wrote in
news:hvOdndytEpzPmtLXnZ2dnUVZ8t2dnZ2d@bt.com:



"Kris Krieger" <me@dowmuff.in> wrote in message
news:Xns9C3D8018C10D2meadowmuffin@216.168.3.70...

Hello, All,

Yeah, it's another dumb Q. from Kris ;)

I'm looking at this:

http://www.leddynamics.com/LuxDrive/content/Page_Micro_App.html#2009%20a
s% 20a%20Boost%20Driver

In the column for "minimum LED current", there is a dash. Does that
mean that, if I wanted, I could use the MicroPuck2009 to run 20mA, or
does it mean it only had onle "flat-rate" output?

I understand that resistors control Voltage into LEDs. But how do I
get something like this puck to not pump too many mA into fewer than
the suggested 15-parallel-20mA-LEDs, say, 6 or maybe 8?

Many Thanks in Advance!

- Kris K.



Hi Kris

Firstly, an attempt to analyse what is inside this puck...

To get the boost (or buck/boost) configuration to work, there has to be
a coil inside this puck driven by a switch. When the switch is closed,
the coil charges up. When the switch goes open circuit, the energy
inside the coil has to flow somewhere, so the voltage across the coil
ramps up until something conducts. This is the basis of how all inductor
based boost converters work.

If the LED is present, this energy flows into the LED. If no LED is
present, you will probably get a large spark on the output and the
circuit will work no more. Hence the comment on the datasheet that an
LED must always be connected.

To control the current into the coil you need some form of current sense
resistor. Guessing at the architecture inside this device, I dont think
there is a current sense resistor inside it, so it is relying on the ON
and OFF times of the switch controlling the inductor to control the
current to the load.

Therefore, it looks like you are stuck with whatever current it gives
you. This is further backed up by the graph of LED current vs input
voltage - there is no 'tunability'.

You can always divert the excess current into another load in parallel
with the 20mA LED you want to drive, but you are better off looking at
one of the many LED drivers from the likes of TI, LT and Maxim (LT and
Maxim have big DIP packages and give away free samples if this makes
your crusade any easier...)

Hope this helps



Yes, that helps a great deal, thanks! :) I'm assuming, then, that the
MicroPuck is essentially an inductor-capacitor pair...? Based on your
suggestion of Maxim, I did find this:
"DC-DC Converter Tutorial" http://www.maxim-ic.com/appnotes.cfm/an_pk/2031/
so I downloaded the PDF and printed it out for further study.

Heh, "crusade" is prob the right term; I've been at this (tho' admittedly
sporadicalyl) for about a year - the time-expanse is due to the fact that,
when I started out with this idea (or damnfool notion, depending on one's POV
L!>),
Click to expand...

Hi Kris,

It is not a damnfool notion, in my opinion.
However, it is a harsh set of requirements, unless you
have changed them since you posted way back when.

You have an energy budget. You intend to put energy in the bank
with solar cells. Their size will be limited in size by the size
of your decorative lantern. Their size is a major factor in
how much energy they will produce. How much light hits them will
also be a determining factor.

You intend to draw energy out of the bank to light your LEDs.
There is NO technology that can take more energy out of
the bank than is in the bank. (I get the sinking feeling you
still may think there is.)

There IS technology (the Micropuck you mention is one example) that
can boost (or buck) voltage, control current, pulse it, etc. - but
no matter what that technology does it DOES NOT increase the total
energy that can be withdrawn from the bank, once the charging has
stopped. Your charging is solar only - so you can withdraw only the
amount you can collect and store in the bank.

I get the impression from this post that you have not yet fully
appreciated the challenge of getting enough energy from solar to
achieve the effect you wanted. I hope I am wrong. As I recall,
you wanted to get more light than a typical solar powered "path
light" produces, and you wanted it available for much/most/all
of the nightime hours. Unless I misremember the requirements, or
they have changed, you're not going to get that.

I love the idea of artistic lanterns, and adding LED _accent_
lights might end up with a beautiful result. But as I recall,
you weren't after accent lights - you wanted illumination.

But let's put aside all that I remember about it. What is
important is the actual numbers. How much energy can you gather
and store in a typical day with the solar cells that will fit your
available space? How much energy will the project consume in
a typical night?

Ed



the sum total of my Electronics knowledge (I kid you not) was "do not
trim the fat prong of a polarized plug"! =:-o ((When I took physics 101
30-some years ago, the prof did devote an hour to scribbling calculus on the
chalkboard and mumbling sotto-voce, but I don't count that as adding one iota
to my understanding)). I'm now to where I've figured out pretty much how to
connect solar cell, supercapacitor, diode, photo-controller, "Voltage Booster
Thingy", LEDs, and resistor(s), so considering the circumstances, I guess I
haven't done TOO badly.

At any rate, I had hoped that the Puck would be a good solution, but now that
I know that the Dash in the "minimum current" column of the various puck's
charts means "no minumum becuase the maximum is also the minimum", it will
save me a lot of time in that I won't be looking at them any further. So
Many Thanks for that!

Also, the Maxim link gave me a good search term, so I then found this:
http://www.reuk.co.uk/DC-Voltage-Multiplier-Circuit-Plans.htm

In essence, what i'm doing with the "electronics" (if I may be so bold as to
describe my rube-goldberg device as "electronics" <LOL!>) is an "emergency
light" I suppose, except that the housing will be decorative/artistic (I do
stained glass, including the use of clear textured glass in a away somewhat
analagous to drawing useing pen-and-ink, which I used to do until my hands
got too quivery). Oh, and it's battery-less (uses a supercapacitor) and
charges from the sun. And the solar cells can be plugged in. Aside from
those differences, it's exactly the same <LOL!

What I want to add (which isn't shown because I have to figure out what the
thing I need is called <L!>) is one of those adaptor-type plugs so that the
solar-cell part can be plugged into the bottom of the Lamp - I do stained
glass and have designed a couple of lamps using clear textured (or maybe
opalized) glass to do a "candle alternative" type of table-top light for
small gatherings. I had hit a wall becasue I was trying to figure out how to
integrate teh solar panels into the top of th elight/lamp. I need to
configure them to provide teh same voltage as the supercapacitor (the one I'm
looking at, the Maxwell BCAP 350 Farad one that's about the size of a D-cell
battery) THen, this past Friday, I bought a small Mergency Fan that runs on
either D-cell batteries, or a small wall-plug adaptor. WHen I took it out of
th ebox, I had one of those ***oh DUUUUUUHHHH!!!*** moments, where I thought
"Now why can't this plug connect to a solar-panel rather than a wall socket
adapter??"

SO now I have to figure out what the plug-thingy is called and try to see
whether they can be purchased. That would *completely* free up the design of
the lamp itself, because I won;t be constrained by trying to unify the airy
look of clear textured glass, with nearly-black solar cells - the mini-panel
can (I hope) just be plugged into the bottom, then unplugged for use. I just
have to figure out how to do it so that plugging the cells in turns the light
off.


Anyway, thanks again for that info about the pucks - one thing always leads
to another, so that was very useful :)

- Kris K.
Click to expand...
 
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