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1  Using Arduino / Microcontrollers / Re: Simply no market for it. on: April 20, 2014, 09:35:09 pm
The Arduino - as a whole - represents a "hobbyist" and "low end" commercial market.

However successful it undoubtedly is, it pales into insignificance beside the "real" markets. ...

I fully agree with you.  But that the Arduino could use a "best of both worlds" component surely doesn't imply at all that it is the only application that could use such a component.
2  Using Arduino / Microcontrollers / Re: The one thing I don't understand about the Yun and Tre is... on: April 20, 2014, 02:20:30 am
is there a question ?

I refer you to the first and final sentences, the sentences that end in a question mark.
3  Using Arduino / Microcontrollers / The one thing I don't understand about the Yun and Tre is... on: April 20, 2014, 01:30:06 am
Why can't some semiconductor company that specializes in microcontrollers step up and make one IC that does the work of both an 8-bit microcontroller and the microprocessor that these boards contain?  Because it seems like a hack to have two parts and it certainly makes software development harder to write two pieces of code every time for one project specification.  It seems to me that the Atmel part (the lowly 8-bit microcontroller) is there for the GPIOs, the interrupts pins, the ADC, the PWM pins, the timers, the I2C, SPI, USB, and serial ports, and the microprocessor is there for the large external memory and raw horsepower.  Why can't that microprocessor get the lowly bits and pieces of the 8-bit part tacked on, and maybe a few DAC pins for good measure as well?
4  Using Arduino / General Electronics / Re: custom pcb on: April 19, 2014, 08:51:53 pm
i just need the board to designed, not to have it fully manufactured(ex. transistors) .

You mean you want the board manufactured, but not populated with components, right?  Nobody is going to design your board for you unless you hire an engineering consultant and pay them thousands of dollars.

Do you have a design yet?  Maybe you should tell us the size and what your budget is.  I have used OSHPark and Bay Area Circuits which you can order from directly out of DIPTrace.  Both are about the same price which is higher than the Chinese places.  OSHPark is $5 per square inch and you get three copies.  For example, if your board is 4"x2", that is 8 square inches and you pay $40, postage included, and get three boards.  If you need two, getting three isn't a bad way to go just in case.  

These guys are hyper-cheap and not as good of quality as the two listed above, but they are so cheap you can afford to gamble:

http://imall.iteadstudio.com/open-pcb/pcb-prototyping.html

Turn around time is a lot slower than the two US companies I mentioned.  If you are in the US, at least.
5  Using Arduino / General Electronics / Designing current sources for driving LEDs. on: April 17, 2014, 01:08:13 am
For high power LEDs, it is very inefficient to use resistors to limit current.  The resistor can end up dissipating more energy as heat than the LED does.  So for a lot of the power LEDs out there, there are power supplies which are AC-to-DC power supplies whcih also limit current.  My question is how does one go about designing a DC-to-DC (no voltage change) current source like this rather than buying off the shelf?  For example, a white power LED might have a forward current of 30V and take up to 1.5A.  Let's say you already have a power supply that can provide 30V and 5A.  How do you design a circuit so that it limits current to 1.5A?  At that point I would assume you could control brightness with a logic level MOSFET and the PWM capability of the Arduino.  Does anyone have a good reference concerning designing such a current limiting circuit?  Thank you.
6  Using Arduino / General Electronics / Re: Shift registers - only good for LEDs? on: April 15, 2014, 10:46:50 pm
I have used a shift register to control a character LCD with only three Arduino pins:
http://42bots.com/tutorials/arduino-controlled-lcd-using-a-shift-register-and-the-spi-library/

So, definitely good for more than LEDs...

Specialized ones have additional applications, though I think the thread is mostly talking about the general purpose and cheapo shift registers.  For example, most VFD drivers are simply high voltage shift registers.  Here are two I have used with no problems:

MAX6921 (20 output, 76 volts)
PT6306 (64 outputs, 70 volts)

The second one is both a lot cheaper than the Maxim part and also has three times the outputs.  It works great for displays with a large number of grids and segments.

Don't lick the project board when running it at 70 volts.  smiley-mr-green
7  Community / Bar Sport / Re: Has Atmel significantly raised 8-bit MCU prices recently or is this Digikey? on: April 14, 2014, 04:33:28 pm
Good catch on the prices.  Maybe Digikey is trying to take advantage that they are the only ones who have much stock right now.  Hopefully it will all normalize.  Possibly, Atmel got behind on production.
8  Using Arduino / LEDs and Multiplexing / Re: Maxim 7219 - Real and Fake compared on: April 14, 2014, 02:10:52 am
Yep, mine are the fakers for sure.  Except for the ones I got directly from Maxim, those are just like the "real" photos.  Though, and I must stress this, the "fakes" do work for me.

I also have some SOP "MAX7219s".  Any information in determining if these are real or not?  Typical auction:

http://www.ebay.com/itm/50PCS-MAXIM-MAX7219CWG-MAX7219-SOP-24-LED-Display-Driver-IC-8DIG-24SOIC-/310723512133

Almost certainly fake, I would think.

Thanks for the photos, that was great.

9  Community / Bar Sport / Re: Has Atmel significantly raised 8-bit MCU prices recently or is this Digikey? on: April 13, 2014, 11:45:36 pm
This has forced me to go count what I have left to make sure Atmel doesn't leave me high and dry.

14 ATMega328P-PUs out of the initial buys of 60 (10 came from Jameco with bootloaders which I don't use).
11 ATMega328-PUs out of the buy of 25.
16 ATMega32P-AU out of the buy of 25.

Lots of ATTinys still - 25 ATTINY88-PU, 48 ATTiny85-20PU, 22 ATTiny85-20SHR.  All a lot cheaper when I ordered them.

Various other chips - Mega, XMega, UC3 via sampling.

I should be set for a bit.  Waiting for the price to come back down...
10  Using Arduino / LEDs and Multiplexing / Re: Cost of the Atmega328p-pu going up? on: April 13, 2014, 10:43:18 pm
I posted a message concerning this relatively recently.  I agree with you.  I have a few points of data of my buys over the past couple of years and prices now are quite a bit higher.

http://forum.arduino.cc/index.php?topic=228782.0
11  Using Arduino / LEDs and Multiplexing / Re: Maxim 7219 Eagle PCB & iTead files for Adafruit 0.56" 7 segment clock display's on: April 13, 2014, 06:51:03 pm
Sorry joeN, I was forgetting non-members can't see pictures on picaxe forum. But edr1924 is correct, by my understanding, those are real maxim chips. The pin 1 dimple is the simplest tell-tale.

Hey, no problem at all.  I will wait patiently until they finally OK me.  I'd like to see the images.  Though, I do have the cheap 50 cent Chinese sourced chips (almost 200) and ten ones I know are real as they came directly from Maxim (thank you, Maxim, for your generosity).  I think I will simply pull them out and look at them under the microscope.
12  Using Arduino / LEDs and Multiplexing / Re: Maxim 7219 Eagle PCB & iTead files for Adafruit 0.56" 7 segment clock display's on: April 13, 2014, 01:58:34 pm
Well, the people who run the PIXAxe forum are a bunch of (redacted) and you can't even view the attachments without registering and there is no automatic registration, every registration must be OKed.

I bet I have fake chips, then.  Other than the 10 or so I got directly from Maxim as samples.  Funny thing, they work fine and I have used as many as 20 of them in a single project.  I don't get noise out of them.  In fact, I wonder how you could get noise out of them other than as EMF which manifests itself somewhere else, like on your computer or radio as sound.  These chips do so little I wonder how Maxim can price them like they do.  On the other hand, I wonder how the Chinese company cloning them can afford to sell them for 50 cents.  There can't be that much demand for fakes, right, other than the hobbyist market which we know is tiny.

For PWM chips I mean chips like the TI TLC5940 and Worldsemi WS2803.  These chips you give each channel a value for its output (10 bit for TLC5940 and 8 bit for WS2803) and it sends that duty cycle to the LED.  So it works to dim the LED and allows you to mix different levels of red, green, and blue for RGB displays to get "full color".  But you have to do the multiplexing yourself.  That is what the MAX7219 will do for you that simplifies your code quite a bit.
13  Using Arduino / General Electronics / Re: Pull-up Resistor on: April 13, 2014, 04:37:16 am
Off subject, but I can't help but notice that two of the posters in this thread have personal icons sourced from different but equally brilliant Kubrick films.

OTOH, I have an icon sourced from a really piss poor comedy written and directed by talentless hacks.

smiley-sad
14  Using Arduino / LEDs and Multiplexing / Re: free Maxim 7219 PCB for Adafruit 0.56" 7 segment clock display's on: April 13, 2014, 04:24:22 am
Can't you just zip them up and attach them here?

I like those chips too, though chips with PWM functionality are really a lot more capable.  7219's are available on eBay at 'fell off the truck' prices of well less than $1 USD each delivered.

www.ebay.com/itm/25PCS-IC-MAX7219CNG-MAX7219-DIP-24-DRIVER-LED-DISPLAY-8DGT-NEW-GOOD-QUALITY-/290746404262

15  Using Arduino / General Electronics / Re: Shift registers - only good for LEDs? on: April 13, 2014, 12:48:15 am
Serial-to-parallel shift registers like the 74HC164 or 74HC595 are good for driving a lot of outputs with a few microcontroller pins.  Any time you have that situation, consider a 74HC164 or 74HC595 shift register.  LEDs are obvious, but if you really wanted to write, for example, a parallel memory's address pins or the digital input of a parallel DAC, you could use a 74HC164 or 74HC595 shift register to be able to send signals to them without eating all your pins.

Parallel-to-serial shift registers like the 74HC165 are good for reading a lot of inputs with a few microcontroller pins.  Any time you have that situation, consider a 74HC165 shift register.  A large set of switches are obvious, but if you really wanted to read, for example, a parallel memory's data pins or the output of a parallel ADC, you could use a 74HC165 shift register to be able to retrieve signals from them without eating all your pins.

In both cases, you trade pins for speed.  With the Arduino and its very slow default port access speeds, you might lower the number of times you can touch an external device to a few thousands of times per second if you are using a shift register to control a large number of inputs or outputs.  Still, this is usually fast enough for most applications.

This document says the 74HC164 can source 25mA per pin or sink 20mA per pin and dissipate 750mW per package.  I would say it is perfectly fine to drive normal LEDs on such an IC.  Limit current to 20mA with resistors.

http://easyelectronics.ru/datasheet/74HC164.pdf
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