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241  Using Arduino / General Electronics / Re: How do I calculate the values for an LC or PI filter? on: June 26, 2014, 04:49:49 pm
Plus one, Resinator.
242  Using Arduino / General Electronics / Re: resistor ladder question on: June 26, 2014, 09:25:18 am
The chip looks like a much better solution. Or some other DAC chip.
243  Using Arduino / General Electronics / Re: Stepper motor issues with L297/8 on: June 26, 2014, 08:07:56 am
Photo of the layout?

Heatsink?

Power supply ratings?
244  Using Arduino / General Electronics / Re: resistor ladder question on: June 25, 2014, 07:16:55 pm
Quote
With a bag of 1% or 2% resistors and a meter, I'm pretty sure that some will be closer to dead nuts than others so those would be the ones for the high order bits.

Hm. You may have a point, there. 1% off on bit D7 is going to be 1/2 of 1% of full scale output, whereas the entire bit D0 is only 1/255 of full scale.
245  Using Arduino / General Electronics / Re: Stepper motor issues with L297/8 on: June 25, 2014, 01:28:00 pm
Actually, the L297/L298 combo -is- a chopper stepper driver. The L298 is rated for 2A, but you _MUST_ use a heat sink to get anywhere close to that.

With 5V in, the L298 drops out a few volts. So the 2.5 ohm coil resistance plus the 1 ohm sense resistor is probably limiting current below 1A without chopper action. Without a heat sink, the L298 may remain cool. But boost the voltage, current goes up, L298 overheats.
246  Using Arduino / General Electronics / Re: resistor ladder question on: June 25, 2014, 01:14:34 pm
What do you mean, matching resistors? You only need a bunch of resistors, and another bunch of double the value. If the standard values don't yield quite what you need, just use two in series to get the doubled value.



2% resistors should be good enough. Use resistors of high enough value that the impedance of each pin is inconsequential. 10k/20k should be fine. Or 12k/24k. Those are standard values in 2% resistors.

Or you could add something like a 4050 CMOS HEX buffer, if you are worried about different pins of the Arduino having different impedances.
247  Products / The Arduino Starter Kit / Re: PDF of book that comes with the Arduino starter kit on: June 25, 2014, 09:09:31 am
One of my pet peeves is textbooks with errors in them. I'm less concerned by typos than I am by statements that are just wrong.

And there are far too many out there like that. Sad to hear that the project book for the official Arduino Starter Kit is yet another.
248  Using Arduino / Project Guidance / Re: Capacitive feedback on: June 25, 2014, 09:06:45 am
I found that 300uA was just perceptible on the thin flesh between my fingers. My fingertips were less sensitive, presumably because the thicker skin spreads out the current before it gets to where the nerves are. The skin on my arms is also less sensitive, presumably because there are fewer nerves.

1mA caused a definite sensation, not exactly painful, but not pleasant. 10mA is very uncomfortable. I never went beyond that, and kept the touch points about an inch apart.
249  Using Arduino / Project Guidance / Re: FFT of given Analog Signal ! on: June 25, 2014, 09:02:21 am
http://www.imaps.org/chapters/centraltexas/Symposium_Presentations/Introduction%20to%20DSP%20with%20the%20ARM%20Cortex-M4%20Microcontroller%20-%20Feb%202012.pdf
250  Using Arduino / Project Guidance / Re: FFT of given Analog Signal ! on: June 25, 2014, 08:56:58 am
Something ARM Cortex based, maybe? Teensy 3.1 has an ARM Cortex M4. It has FFT DSP functions.

https://gist.github.com/TJC/5633491

That exhausts my knowledge of the subject.
251  Products / The Arduino Starter Kit / Re: Project 15 Hacking BUTTON on: June 24, 2014, 10:56:35 pm
OK, I think I get it. The aim of the project is to show that an optoisolator can turn a button on and off.

Which Optoisolator are you using? Both the input and output sides are polarity sensitive, unless the output is a triac, in which case it probably won't work with that low a voltage.

I presume this is an optoisolator included in the kit. Check your wiring again for proper polarity.
252  Using Arduino / Project Guidance / Re: Lacking Knowledge on: June 24, 2014, 05:33:41 pm
Busy week. I will get back to it.
253  Using Arduino / General Electronics / Re: Need help learning to calculate a base resistor for a transistor on: June 24, 2014, 12:28:10 pm
Plus one, Krupski.
254  Community / Local Groups / Olympia and Lacey, WA - Shapeoko 2 build and general meeting Thurs June 26 on: June 24, 2014, 11:06:03 am
Come check out the new OlyMEGA Shapeoko2 CNC 3d Carving tool. Well, really it will be the first unveiling of the box of goodies that showed up yesterday morning. We are going to keep the box sealed until Thursday at 7:30PM. It is from the right place and does weigh a bit, so I am pretty sure it has everything in it. 

We will be building the CNC tool over a couple of meetings coming up in the next month. Keep your eyes out for those meetups to be announced.

Hope to see you all there.

General meeting open to the public: show and tell of projects completed or in process. Make connections with other people who like to make things. Collaborate, discuss and start making something!

http://www.meetup.com/OlyMEGA/events/184847572/

255  Community / Local Groups / Re: Seattle, Washington Arduino Meetup on: June 24, 2014, 11:02:26 am
Too bad they aren't posting any meetups. Only three in 2012, nothing since then.
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