ZLT-CCR2 PCBs

[MrAl]

Hi there operator_smooth,

Oh ok, 260mT means 2600 gauss, so that sounds good.

I'd be very interested to find out what kind of results you
get from the new parts too. I'd even maybe like to start
a small database where we can store results from
experiments like these for future reference. A lot of
people like this circuit and it would be nice if they (we)
could just go look up the configuration and find parts
that work well without doing too much work. On the other
hand, experimentation is part of the fun /ubbthreads/images/graemlins/smile.gif

Myself as well as others have run circuits without any
input cap at all. You're correct in that the input cap
smooths the pulses through the batteries and that could
make them last longer. Reducing the input pulse by half
would probably be a reasonable goal, so if you'd like
to try that too i can suggest a capacitor value that
will achieve that...i need to know your battery type and
how many in series, and your output current.

Reducing the peaks though the battery makes it easier on
the battery, but i think if your using NiCd's you might
not notice too much difference in run time as this type
handles pulses pretty well.

BTW, on the core calculations,
for a core
OD=10.6mm
ID=5.2mm
HT=4.4mm
with an AL of 740 and 6 turns of wire the sat current
comes in around 0.88 amps. This is fairly close to
your estimate of 1 amp i guess.


Take care,
Al

 

[operator_smooth]

MrAl, I want to use this circuit with two alkaline cells, i.e. 3V max of input. I know that those have significant internal resistance.

Can you suggest resitor values that work with this input voltage? I have some 15mR resitors and 5.1R ones too, also some 1.13kR and 1.20kR - can any of these be used in the ZLT++?

 

[Leeoniya]

designing for 1xCR123A, do post inductor and cap part numbers that work well. also, MrAl if you could post the part # of your inductor i woul dbe interested in getting a few off digikey to play with. and what gauge wire was used for 6 turns?

thanks,
Leon

 

[operator_smooth]

I have now built the CCR-2 circuit but I can't make it work very well. Maybe I need an R5 with greater resistance.

As for the inductors, I got very good results with the MEGGITT 3631B220ML inductor, but also with an axial inductor from BI Technologies, which you can find here: http://www.elfa.se/elfa-bin/setpage.pl?http://www.elfa.se/elfa-bin/dyndok.pl?vat=0&dok=2015770.htm (I have the 22uH one). I got something like 0.85 efficiency using the same rough measurements as described earlier.
The hand wound inductors did not perform too well.

I also tried putting an extra 47uF cap on the output, but without much difference.

 

[operator_smooth]

MrAl, I have an idea, but I'm not sure that it will work. It is to insert a zener diode with the drop of Vb (the low input voltage) in series with the R5 resistor to make the voltage across the bias network drop to zero at Vin = Vb. This way, the peak current through the inductor at Vb would only be determined by the value of Rsense. This would make the calibration procedure easier because (provided that R3 is set to 5R) the only resistor that needs to be adjusted is R5, and for this a variable (trimmer) resistor could be used. But again, I don't know if this would work at all.

 

[MrAl]

Hello again,

Leeoniya:
The inductor i used was a core from All Electronics and 6 turns of #24 wire.
They arent hard to make really. If you want to purchase one from Digikey
you can look for something maybe 50uH or better and a sat current of 2 amps
or better. Operator_smooth seems to have some good results with his
purchased inductors too.


operator_smooth:
If you add 100uf to the input the peak current though the battery will
be much less. That should increase the run time.
The 15m ohm resistor needs to be adjusted for your circuit. We've always
used a short length of thin wire (#32) starting with about 4 inches, then
making it shorter to increase output current to the desired level.
5.1 ohms should work fine for the 5 ohm value.
The R5 resistor really needs to be adjusted also, but your idea of the
zener sounds interesting too. All i can say without doing any calculations
is that you'd have to try it. You'll probably have to use a zener that is
below the Vb low point because zener voltages arent spec'd that closely,
but with a series resistor you should get some results. As the input voltage
rises, the inductor peak current is reduced which is what we want.
I'd start with about 1k and work it down, checking output current at
low batt, medium batt, and high batt voltage.


Take care,
Al

 

[operator_smooth]

Back with some results.

I do not have a zener diode with the voltage I need, but I connected two 1N4001 in series and an used adjustable 1kR resistor and got a very good result. The total voltage across the two diodes was around 1.3V. I measured 0.32A @ 2.88V, 0.33A @ 2.33V and 0.25A @ 1.3V.

 

[MrAl]

Hey there operator_smooth,

Wow, that does sound pretty good. I like the idea of the
two diodes too, although i'd like to see some data
over a temperature range of say 20 deg C to maybe 40 deg C.
The diodes drop (and zener also) will be a bit temperature
sensitive, but it should still work to some degree.
Nice idea.
BTW, the calculator i was talking about is now available
as a free download. I've posted it in the other thread.
You can do calculations with inductors and cores and
stuff like that, just by entering the parameters.
For example, suppose you wish to calculate the
magnetic path of a core who's dimensions are
given by it's OD and ID, one of the formulas included in
the file "EE_Formulas.dat" (which loads via menu open)
is called:
"Core_ml{Toroid}(OD,ID)"
You just copy that text (after loading and clicking "Show")
and replace OD with the actual size and ID with the actual
ID....so for that core with 10.6mm OD and 5.2mm ID you would
do this:
Core_ml{Toroid}(10.6/10,5.2/10)
Then highlight it and click "In Place Eval"
and the result will be placed after it with an equals sign.
Note the values of OD and ID have to be divided by
10 because the formula takes dimensions of cm, but if you
wanted to you could first convert the OD and ID using the
conversion formulas also in that file.

Let me know if you check it out.

Take care,
Al

Core_ml{Toroid}(OD,ID)

 

[operator_smooth]

MrAl, would you please post the link to that thread, I would really like to check out your code.

I have been working on a peak current calculator for the ZLT circuit, which takes the following parameters: Vin, Vled, Iout and L and makes some assumptions about the off time (Toff = 1.7us) and the schottky forward voltage (Vschottky = 400mV).

Do any of the following equations look correct?
Inductor "charging" time: Ton = Ipeak * L / Vin
Inductor energy: E = Ipeak * Ipeak * L / 2
Power transfered to output: Pout = E / (Ton+Toff) * n, where n is estimated efficiency, e.g. 0.85.

If it is assumed that Pout = Iout * (Vschottkey + Vled)
then it should be easy to solve the equations (iteratively or explicitly) to find Ipeak for the given values of L, Iout, Vin and Vled?

To calculate Rsense some assumptions must be made about the sense voltage Vsense. Looking at the charts in the zxsc300 specs I think that a good linear approximation would be: Vsense = 15mV + 0.02mV/V * Vin

 

[MrAl]

Hi there operator_smooth,

Here's the link to the thread:
http://www.candlepowerforums.com/ubbthreads/showflat.php?Cat=&Number=888528&page=1&view=collapsed&sb=5&o=365&fpart=1

Here's the link to the download:
http://www.rapideuphoria.com/mafc-102.zip

Hey you've got some pretty good ideas there.
I like the idea about calculating the Vsense too, but
it may be that we would have to calculate two values:
an upper limit and a lower limit.
In any case, it would be simple to write out an equation
for the calculator something like this (for Vsense):

ZLT_Vsense(Vin)=0.015+0.00002*Vin

and for inductor energy:

ZLT_InductorEnergy(Ipeak,L)=Ipeak^2*L/2

These two (as well as any more you care to add) can
be saved to a file called for example 'ZLT_Formulas.dat'
for later use by clicking on the menu File/SaveAs. The
entire set of formulas can then be reloaded by clicking
on the menu File/Open.

Sound simple enough?

When the person who wishes to calculate a value goes to
use the calc, they would first open the formulas file
by clicking on the File/Open menu, then click "Show"
then select the formula they wish to use. Let's say
they select
ZLT_Vsense(Vin)=0.015+0.00002*Vin
They would then copy and paste
ZLT_Vsense(Vin)
then replace 'Vin' with their input voltage like:
ZLT_Vsense(3)
then highlight that line and click "In Place Eval".
The answer then appears to the right of the
"ZLT_Vsense(Vin)"
with an equals sign.
It's easier to do then to explain


Take care,
Al

 

[operator_smooth]

Hi again,

very interesting concept with loadable/savable formulae and in-place evaluation. Which programming language did you write it in? The syntax in the files looked a bit like Pascal or VB. The contents of the files mentioned "Euphoria", is it a code name for a project or some kind of scripting language? Usually I write programs in C and only to perform one specific function, e.g. one kind of calculation.

I have now built the converter and modded a flashlight (Sonca 2-AA). I have taken some pictures (it really works great with magnifying glass, MrAl!), which I want to share with all who might be interested.


First, the experiment rig:

I found that I had some inductors form earlier projects that had some interesting cores, so I stripped one and wound my own coil. It worked pretty well and was smaller than the inductors I bought.

Here is a lineup of the inductors and the stripped core:

The converter:

Top:

Bottom:

Side:

Now the flashlight:

Plenty of space inside, that's a good thing:

The reflector had to be sawn off at the base:

Now the hard part: to make the LED, converter and some sort of heatsink fit there... it took me a while and it is not pretty but it works:

And the completed mod:

The light: compare to an unmodified flashlight with fresh cells (luxeon to the right):

The beam is more diffused and kind of soft compared to the incandescent light, but it is still well-defined and much brighter.

ADDED LATER:
I put the two flashlights in the freezer for an hour or so. When I took them out the LED flashlight would not light up - instead it flashed briefly when the switch was depressed. After a minute or two it lit up when turned on, but not too brightly. When it warmed up a bit it lit up normally. I don't know if this is because the electronic parts can't handle sub-zero temperatures or if it is a mechanical issue (things contracting and stretching when cooled/heated), but I would really like to know if others have experienced similar problems with the ZLT-* circuits. One thing is certain - I won't be keeping this one in my car.

UPDATE:
I froze the LED assembly and the cells. It looks like the LED assembly works properly at the freezer temperature when tested with "warm" cells. The cells however perform poorly at that temperature and could be the source of the problem. The circuit compensates for the lower input voltage by increasing the peak current and this could make the voltage fall below the minimum operating voltage of the circuit. It is also likely that humidity from the air trapped inside the flashight forms small ice crystals on the battery poles, switch surfaces etc. and adds more resistance which in turn lowers the input voltage even further. I still have to find a way to test this theory though.

 

[MrAl]

Hi again operator_smooth,

WOW, really nice close up pics! That's nice because we
can see more of the details of the circuit after it's built.
It's one thing to talk about the circuits, another thing
altogether to actually see the circuit built up. I think
it adds another dimension.

So you seem to have had a problem after cooling the light
down for a few minutes...maybe we could look into that.
I know there are some aspects of the Zetex circuits that
are temperature sensitive, but they should be so bad
that cooling them for a few minutes means they dont
work.

How cold was the freezer, and how long left in there?

Are you using the version with the diode in series with
the resistor for biasing, or just a resistor, or no
biasing yet?

Also, do you have any freeze spray? Perhaps you could
isolate the part that bothers the circuit once cooled.

I'd like to know this myself and see if we can correct
it.

Oh so you found the calculator interesting? It's the start
of a calculator to do engineering calculations and hopefully
will eventually be useable in the EE course (and more).
I found that i use the same formulas many times so storing
them in a simple file seemed to be a good idea. Being
able to load them back into the calc means i can take up
where i left off the night before or just to have the
formulas available again next time i need them.

It was written with a language called "Euphoria" as you
noticed /ubbthreads/images/graemlins/smile.gif If you understand the C language then you'd
have no problem with Euphoria because it's sorta like
a subset of C only with 'sequences'.

There's a free public domain interpreter available at
http://www.rapideuphoria.com/

and a message board where people talk about projects at
http://www.listfilter.com/EUforum/

You can create windows and buttons and stuff like that
pretty easy with user libraries (like mine ) or do
console apps. Most of the libraries use the
Windows API dll's (quite easy to do too) which provide
all kinds of controls and windows and other graphics.
That calculator was written using Euphoria and the
windows api called by my library i named the
"WinClass Library".
If you are interested in knowing more about this language
let me know. We can even start a new thread. At one
time i was thinking of trying to get people to start programming
so they could program their own stuff in the EE course,
but im not sure if that would be fast enough so i made
the calculator instead.

Take care,
Al

 

[operator_smooth]

MrAl, looks like I just missed your post while updating my own. Thanks for the Euphoria links.

I don't really know the temperature, but it is cold enough to make a 40% vodka freeze solid. The LED assembly has been put there for ½ an hour pr so, which should be enough to cool it down to freezer temperature. I am using the version with the diode - I found an 18V zener that had a voltage drop of 0.8V or so when forward-biased and it worked well in this setup.

By the way, the circuit board was in fact carved with a knife and not etched. I am still on a lookout for PCB designs, but now I have one that is usable, though not very pretty. I will try to make a drawing and post it here.

 

[Leeoniya]

like i said, i'll route the board if anyone can give me part numbers so i can pull off the footprint layouts component dimensions. while the circuit is under development and with such a huge variety of inductor and capacitor sizes, combined with the additional resistor network, the combinations of different versions and different revisions will be mind boggling. i'd be autorouting for days straight just to keep up with the changes. i'll autoroute something once some final components are known and whether or not to use a 2-sided or 1-sided design as well as the board diameter an/or length/width.

the way i actually like to route, i route pads even for inductors. This approach helps keep the assembly clean and uniform, with no stray solder smeared all over the board. it makes QC much easier because u will never have any ghost solder bridges by accident. this does make the board less generic so to speak, cause you can only use components that have the same package footprints. but the headache eliminated during assembly is worth it. but for inductors, especially that are hand wound, you can always just solder the ends of the coil to the pads.

regards,
Leon

 

[operator_smooth]

Leeoniya, you are absolutely right. As for the inductor I think it could be the best option just to leave some pads to connect it to. Also, I think that the the design should be single-sided because it gives some freedom regarding the bottom side of the board and is much easier to produce at home.

I don't have all the part numbers, but maybe this can help:

The chip itself off course (ZXSC300)
Input + Output caps: 10 uF multilayer ceramic, X7R, case style 1206
Schottky: ZHCS2000 (Zetex) SOT-23
Transistor: FMMT617 (Zetex) SOT-23
Resistors: case style 805

I don't have any part number for the diode yet...

UPDATE:
The zener diode I used is most probably this one:
BZX83V018 0,5W 18V, case style DO35

 

[operator_smooth]

OK, here is what the board I used looked like (the diode is not shown, it kind of goes from the upper right corner to Vsense pin on the IC):

Now, I've tried to figure out if it can be done better and made this drawing (D2 is the zener diode):

But I haven't tried it yet.

Any ideas for improvement will be appreciated.

ADDED LATER:
By the way, don't rely on these drawings - they were initially made with MSPaint and the proportions of the components could be completely wrong.

 

[MrAl]

Hi there guys,

operator:
Which inductor did you purchase where you got reasonable
results with the Zetex circuit? From Digikey?
I like the idea of those circuit boards you're building...
very little copper has to be removed from the board, and
they are all straight cuts.

Take care,
Al

 

[operator_smooth]

Hi MrAl.

The one of the inductors was bought from Farnell (http://www.farnell.com) and the other one from ELFA (http://www.elfa.se)

What I think is the main factor with those inductors is that they can handle the required current and have low resistance. I think that most inductors with similar specs will work well in the ZLT* circuits.

Thank you for your comment in the PCB design - I intend to try it today. Actually, it should be fairly easy to modify this design to fit almost any inductor with a reasonable size e.g. like this:

BTW: does anybody here know which diode can be used to get a 1.5V or so voltage drop? I was thinking of using a red low power LED for this purpose, those have Vf of 1.8V or so but this may still work well (and look cool too). It would be more ideal to have a 1.2-1.5V zero point, but I am not sure that diodes with that kind of Vf exist

 

[operator_smooth]

I have now built the circuit with the new layout - and with the LED. It seems to work well.

I stripped the PVC insulation from the inductor that I bought from ELFA and bent the leads to make it an "SMD" part. With this and the other components the completed circuit (in action) looks like this:

I know that it could probably be made smaller, but it is a PoC construction and I wanted some room for error. Here is the size compared to the LS:

 

[MrAl]

Hello again,

Leon:
If you can post some pics of your board that would be nice
so we can see the final board.

operator:
Oh yes, that's pretty small. Looks like it will fit right
under the LS just about right.
BTW those pics are comming out very clear...thanks for
posting them. Cant beat a good pic like that so you can
see exactly what it looks like /ubbthreads/images/graemlins/smile.gif

Take care,
Al