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Old 08-02-2014, 08:08   #76
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Re: The FrankenBebi Project

Corrected... Thank you
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Old 10-02-2014, 11:53   #77
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Re: The FrankenBebi Project

We have posted an in-depth description of the latest FrankenBebi circuit design, including theory of operation, component selection, and some test results. It can be viewed online or downloaded as a PDF File (150KB)
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Old 09-06-2014, 10:35   #78
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Re: The FrankenBebi Project

It's been a while, any new news?
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Old 16-06-2014, 11:38   #79
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Re: The FrankenBebi Project

I sent them an email a week or so ago and have had no response
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Old 28-01-2015, 23:00   #80
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Re: The FrankenBebi Project

What happened? I thought we were going to order some of these? Anyone else making these?
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Old 30-01-2015, 16:52   #81
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Re: The FrankenBebi Project

I have no idea what happened to David and the original FrankenBebi site, and I've sure tried to find out. Since the domain name expired and there still seems to be some interest in the project, I grabbed frankenbebi.org and have begun to upload what data / information I have. Right now the schematic and circuit description are posted. In a few weeks I should be able to upload the circuit board layout, test procedure, parts list, and perhaps more.
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Old 30-01-2015, 17:10   #82
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Re: The FrankenBebi Project

Capt-Coulion is off sailing on his boat and doesn't seem to have any further interest in the project. I hope you can resurrect it Paul.
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Old 30-01-2015, 18:12   #83
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Re: The FrankenBebi Project

Paul-
On reading the circuit description, a couple of possible complications strike me. Perhaps they are not an issue in a commercial volume setting, and noting that DigiKey has dropped the LEDs, perhaps these are being obsoleted even as we speak.

But the LEDs are said to be power-matched by Cree (the maker) which implies they are bought in sorted batches. There are about 75 sorted batches ("bins") of these sold, with different brightness (2:1 range) and power consumption and color variance.

And if the power consumption is NOT matched, the "five strings of three" will not function properly, one string of the LEDs will hog the power and the brightness. That's a design weakness, using multiple strings instead of driving them all, or driving them all in one string.

And unless a user buys a large number at once, trying to buy "all the same bin group" can be very futile for the single build.

So...perhaps Cap was put off by the potential complexities that arise if the project can't be done at a large enough scale? Which means an investment up front?
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Old 30-01-2015, 20:04   #84
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Re: The FrankenBebi Project

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Paul-
On reading the circuit description, a couple of possible complications strike me. Perhaps they are not an issue in a commercial volume setting, and noting that DigiKey has dropped the LEDs, perhaps these are being obsoleted even as we speak.

But the LEDs are said to be power-matched by Cree (the maker) which implies they are bought in sorted batches. There are about 75 sorted batches ("bins") of these sold, with different brightness (2:1 range) and power consumption and color variance.

And if the power consumption is NOT matched, the "five strings of three" will not function properly, one string of the LEDs will hog the power and the brightness. That's a design weakness, using multiple strings instead of driving them all, or driving them all in one string.

And unless a user buys a large number at once, trying to buy "all the same bin group" can be very futile for the single build.

So...perhaps Cap was put off by the potential complexities that arise if the project can't be done at a large enough scale? Which means an investment up front?
For home builds, from a brief play around on some breadboard it seems easy to match each string so they all draw very similar amps by measuring the voltage drop across each one. I got them from Mouser a while ago.
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Old 30-01-2015, 22:15   #85
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Re: The FrankenBebi Project

Hellosailor, you may be right about the difficulty in getting the binned LEDs, although I doubt that is what made Cap go silent. Cap didn't seem to be concerned about getting binned parts, but I haven't tried myself.

I bought unbinned LEDs from Mouser and the Vf / current matching was quite good within my batch. There is a significant series resistance in the LED diode that does a good job helping keep the current matched. Still absolute worst-case Vf spread will create problems.

Without the binned LEDs, we could probably reconfigure the LED strings (say 2x8 instead of the 3x5 we have now), and add series resistors to each of the strings. This would add eight resistors to the design, and increase the current from 100mA to 160mA. This would still be easier than including three current-regulators. There isn't enough voltage available to add series resistors to the three-LED strings (the light would dim significantly at low battery voltages.)

But if the binned LEDs are still available then this is the simplest solution, and is pretty robust. I've run the numbers for worst-case values within a bin, and I'm comfortable with the matching.
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Old 30-01-2015, 23:24   #86
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Re: The FrankenBebi Project

Great news Paul that you are beathing life back into the project. I look forward to the results.
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Old 30-01-2015, 23:39   #87
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Re: The FrankenBebi Project

Tried to go to the web page New News at The FrankenBebi Project and FrankenBebi | A New Home for the FrankenBebi Project but "not found"
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Old 31-01-2015, 00:35   #88
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Re: The FrankenBebi Project

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That second one should work. I just configured the URL / DNS server info this afternoon, so it might take a while for the new address to propagate through the internet. Try again Saturday and let me know if there are still problems.

Here it is again: www.frankenbebi.org
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Old 31-01-2015, 05:35   #89
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Re: The FrankenBebi Project

FrankenBebi | A New Home for the FrankenBebi Project worked for me.

Thanks Paul!
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Old 31-01-2015, 10:42   #90
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Re: The FrankenBebi Project

Thanks, Paul.
I know that Cree (and every other reputable LED maker) will always have binned parts available. The problem only comes in for the smaller buyer on the secondary market, i.e. especially on the consumer "50 for $10" market.
I've been aware of, and careful of, the runaway "almost" matched parts market since building an 8-transistor kilowatt (150W@) array in a bootstrap power regulator some years ago. They were all matched, sure, but the wiring wasn't all the same length and that little "extra two inches" meant that #1 would go into thermal runaway and cook itself. After that happened twice, I learned better about matching wire lengths. And, reading the fine print. The next 20 years went flawlessly, as planned.(G)
So when the LED makers say "don't so this" I faithfully wimp out and follow their commands, especially when the LEDs are going to be installed Way Up There.


With 3-4V LEDs and a nominal 12V supply, the options are kinda limited though.


Other concepts (like using two banks of LEDs and pulsing each one too fast for the eye to see that they are alternating) brings up that fine bugaboo of RFI, and that's another stopper to me. Don't even want to go there!
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