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June 1, 2012
about a year ago
What’s that going on in the GIF video? It almost looks like you’re shining a flashlight at the camera, then shining the light on yourself? Is it an IR flashlight or regular?
If you did do this with a flashlight, it’s not at all representative of how you’d use the thing in real life. Can we get a real demo, please?
Maybe you in a hoody, blink eyes, make faces and talk.
Another cool demo is to rub your hands together until quite warm, then video one hand as it cools back to your normal skin temp.
News - Hardware Hump Day: Wheel-…
about 3 years ago
Kinda cool. Kinda overkill, but cool.
about 3 years ago
Yes, extra bits of resolution above accuracy are nice and useful - to a point.
But not when it's a waste.
And not when it clouds the fact that the accuracy could and should be better.
I spent a second on Amazon and found a $55 meter (granted no BT etc, so not a fair comparison, but bear with me).
Four digit, 4,000 count display, 0.5% accuracy. Extech EX330.
2^12 display. ~2^8 accuracy. That implies an "oversampling" (resolution over accuracy) of ~2^4 or actually 20.
The Mooshimeter captures 2^24, with 1%=~2^7 accuracy. Which gives an oversampling of ~2^17 or actually 168000.
This seems like wayyyyyy overkill.
I mean extra resolution is nice. But when it exceeds precision by that many orders of magnitude, who are you kidding?
When I took chemistry in high school, whoa so many years ago, the teacher informed us early on that if our reports carried more significant digits through each step than the instrument provided, our answer would be marked wrong. With this instrument, you've got to remember to round everything you write down (all those really nice 24 bit numbers) to 1%.
My points are:
1 - There's no excuse for a $100 instrument not to have better than 1% accuracy.
I mean come on 1% on frequency? Hello? What kind of crystal are you using? The internal RC?
Spend an extra $0.5 and get a precision reference so the instrument can self calibrate, and get yourself a crystal. $0.5=10X accuracy? (100X on frequency).
2 - Quit wasting your time collecting 24 bits of data if soooo many of them are ghosts. I mean do we really believe we're seeing 2^24 with unshielded probes? Put the ADC in 16 bit mode, collect the data at a higher rate (then you can do some of the stuff others have suggested, like: improve graphing, add triggering etc.), increase the accuracy...
I think this is really cool, and I may buy one. Especially if/when the price comes down a bit.
Two things I'd point out to the designers:
"Two channels" caught my eye - especially for a particular need of mine - closer examination reveals that, alas, it appears that only one can be voltage? One can be current, at a time, etc? Correct?
Diode check only to 1.0V? That seems low. I use my multimeter to check/show me the polarity of LEDs. I really would miss that. But then again, I guess this wouldn't be replacing my $12.95 "every day" meter, or my "good" $59.95 meter.
about 4 years ago
Running USB devices such as wifi or USB sticks from a something that is itself a USB device requires that device to be able to take on both the rolls of USB slave and host. This capability is called OTG (on the go). Some early examples were cameras that could hook to your PC and appear as a (slave) thumb drive to get your picture, but also act as a host and hook directly to a printer (without a PC) to print picture.
This capability is complex - both hardware and software.
Just from a hardware point of view - are you "getting" 5v in from the USB, or supplying it out to a device? Are you listening to the USB lines, or driving them?
Doing one or the other is hard enough. Being able to dynamically switch rolls is very complicated.
There are not that many micro controllers that support it. If you have a requirement, make sure you vendor gas a good code library and example code. Like I said - the code is very complex.
Not that important, but if you roll the design, I'm pretty sure the "bottom" of R8 should go to GND (not /DTR). And the signal coming out of the FET is still inverted DTR (/DTR) and it probably would be clearer if you labeled it as such (label the one to the left of th FET /DTR1 or something).
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