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February 2, 2007
News - Fluke, we love you but yo…
about 5 years ago
Wow... that's pretty messed up. I own and use MANY fluke meters (I have two sitting next to me right now), and have always held them in very high regard (I'd never consider buying a $15 Sparkfun DMM, no offense)... but this is pretty ridiculous. I really hope Fluke makes it right, but I'm not counting on it. Good to see people reaching out to them and hitting up their social media... the trademark stuff is certainly aimed at the big businesses, but we have the power of our voice. Even if it doesn't solve this immediate problem, maybe it'll influence future decisions.
And it looks like they've gone after a German company Yello Strom Gmbh about this similar issue (I have a strange feeling it has to do with the key word "Yello"): http://www.plainsite.org/dockets/index.html?id=2444199 . That link says that they're being represented by Adobe Systems, Inc... so maybe something good will come of it. But most likely they'll settle, and Fluke will still own the same flawed trademark, and Yello Strom will be happy to be done dealing with it. And then Fluke will move on to the next company, and the lawyers will get rich along the way.
News - OSHW DC Meetup and Survey
about 7 years ago
My roommate works in that building, so I sent him the link and he checked it out... said he had a good time. I sent him with an nRF24L01+ module to get signed... hope that wasn't too awkward. ;-) I've got a whole box of Sparkfun stuff on my desk, but I had a hard time finding anything big enough for a signature. :-P
I wish I could have made it but I was working, and I avoid DC like the plague... especially on a weekday.
about 7 years ago
I agree that the pullups are a little weird. The I2C pins are open drain output, and I'd expect the host to pull them up... though if you're using this in a standalone config (just using the alert pin), maybe the chip would freak out. And since they pull up the alert pin, I assume that's an open drain output as well.
The pullups won't cause damage on most systems though, since the ESD diodes (present on most chips) will shunt the higher voltage, and the pullup resistors will limit the current.
I think the VCC pin is dangerous though... if you didn't fully understand the documentation, most would expect to power the chip through the VCC pin, but in this case, you'd end up connecting your 3.3V rail directly to the battery pack. Or, in a worse scenario, connect it to your 5V system VCC and set your LiPo on fire.
It's nice that you don't need to connect regulated power to this (the datasheet recommended configurations show powering directly from the battery), but you just need to be extra careful and read the documentation. I'm just gonna leave the VCC header pin unpopulated to remind myself to not use it.
BTW, in regards to the comment on Figure 7, that's showing the 2S version (MAX17044), which needs a regulated voltage. They don't recommend a regulator for the 1S version (MAX17043)... though they don't explicitly recommend against one either.
about 7 years ago
That App note is very helpful. I agree that SYS OUT on this board isn't ideal, because the charger IC is expecting just a battery cell, not the whole system load plus battery. I'd imagine this is worse when the system load is larger.
Pg. 5 of that app note explains in detail, but also suggests if you want to connect it directly like this SYS OUT pin, to use a charger with no auto-termination, like the MCP73811/2. The MCP73812 would adapt to this board with very little change.
I believe adding a FET and Diode is a better, and still simple method though, because auto-termination should be better for the battery (it's not good to hold the battery at full charge like the MCP73811/2 would). This does add the requirement of verifying that you don't draw too much current from the USB port though (if the load draws 300mA and the charger is trying to charge at 500mA, you'll overload your USB port by using the FET).
I don't think that there's anything dangerous about this design though... just not ideal.
about 7 years ago
I've been printing directly on flex circuit for years (single layer 0.5oz copper on polyimide)... it works fine with every laser printer I've used. I print on a piece of paper to align, cut a piece of flex circuit, remove the oxidization on the copper with a green scrubby pad, then use masking tape to hold it in place over the printed section. Then I feed it through, untape it, and etch like usual.
I don't know how well this stuff would work though, since there's no backing. When you etch, the paper that you're stuck to will probably get weak and crumble. Then you've got a PCB held together only by the traces. :-P Also, if the thickness of the copper is 3 mil, that's about 2oz. copper... which won't be very friendly to etch (take a while, and difficult to get fine details).
News - Happy Free Day
about 9 years ago
Why are you trying to add stuff to your cart? You just needed to get a code to reserve the money, then buy stuff in the next 60 days with your code.
I got in, took my $30 freebee and ran... only took about 10 mins :) . When the servers were erroring before 9AM, I knew there was no point in even trying the quiz. It sucks that I slacked on ordering my first order... a couple weeks sooner would have got me another $10 :P .
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