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9691  Using Arduino / General Electronics / Re: sorted... Why have Darlingtons? on: January 17, 2013, 10:15:29 pm
These #s don't look good tho:
Vce Saturation (Max) @ Ib, Ic: 4V @ 20mA, 5A

IC = 3A, IB = 12mA, Vcesat = 2V

P=IV = 6W, heatsink recommended I think!
9692  Using Arduino / Project Guidance / Re: Making a custom keyboard with arduino? on: January 17, 2013, 10:09:57 pm
Using 17 pins, you can use keypad.h library to read a 72 key keypad.
Electrically arranged as 8x9, physically any way you want.
Probably easier to manage fn as seperate key not part of the keypad.
Multi-press, that would be managed in your sketch.
So 17 for matrix, fn key, and 2 pins for serial interface.
9693  Using Arduino / Project Guidance / Re: need an estimate of time required to scan 11x8 matrix on: January 17, 2013, 10:00:58 pm
Because that's the stated requirement smiley-wink
9694  Using Arduino / Microcontrollers / Re: Help in programming the Atmega1284 with maniacbug-mighty-1284p. on: January 17, 2013, 09:53:03 pm
Ok, I am sticking with user error/poor wiring.
I just bootloaded & downloaded a simple sketch, both succeeded on first pass.
Datecode on chip: 1050

The Rx/Tx wires do not overlap the crystal pins.
9695  Using Arduino / LEDs and Multiplexing / Re: 5x5x5 LED cube help on: January 17, 2013, 09:24:31 pm
Yes.
An Uno has 6 - 3, 5, 6, 9, 10, 11
9696  Using Arduino / LEDs and Multiplexing / Re: 5x5x5 LED cube help on: January 17, 2013, 09:20:49 pm
Correct - no external supply needed. Use superbright LEDs tho.
9697  Using Arduino / LEDs and Multiplexing / Re: 5x5x5 LED cube help on: January 17, 2013, 08:52:00 pm
You are misunderstanding - only 5 LEDs at a time will be on. That's why the discussion of cycling thru the 5 groups, and the 5 layers.
5 x 20mA = 100mA max.
9698  Using Arduino / Installation & Troubleshooting / Re: Arduino Mega2560 and Ethernet Shield regulator generate too much heat on: January 17, 2013, 08:50:12 pm
12V were needed elsewhere tho.
9699  Using Arduino / Audio / Re: Piano sounds frequencies and tone function questions on: January 17, 2013, 08:47:17 pm
"there is an inexpensive substitute for the ssm2164: V2164 (coolaudio)
http://www.mammothelectronics.com/Coolaudio-V2164D-Quad-Voltage-Controlled-Amplifier-p/400-1034.htm"

Is there a datasheet available? Pinout? I'm not seeing one on the page.

Ah - here we go
http://www.coolaudio.com/products.html
9700  Using Arduino / LEDs and Multiplexing / Re: 5x5x5 LED cube help on: January 17, 2013, 08:29:45 pm
You can drive the anode with 5 arduino pins.  PNP transistors are not needed.
9701  Using Arduino / Microcontrollers / Re: Help in programming the Atmega1284 with maniacbug-mighty-1284p. on: January 17, 2013, 04:47:40 pm
There is no ground plane on this protoboard. FTDI Basic plugs onto the 6-pin header to the left of the crystal, MKii plugs onto 6-pin header above the board. All signals are 30 guage wirewrap to wirewrap socket pins.  I do not see any serial download issues.
9702  Using Arduino / Installation & Troubleshooting / Re: Arduino Mega2560 and Ethernet Shield regulator generate too much heat on: January 17, 2013, 04:25:20 pm
Put a heat sink on the regulator.

Or regulate the 12V source down to 7.5V before bringing it into the board.
9703  Using Arduino / General Electronics / Re: output voltage digital I/O on: January 17, 2013, 04:23:31 pm
Do you have
Code:
pinMode (pinX, OUTPUT);
in void setup? Missing that is often the culprit.
9704  Using Arduino / Project Guidance / Re: controling in between 100 and 255 outputs on: January 17, 2013, 02:55:21 pm
"how many devices can be connected using ISP and a arduino as a Master ? "
Depends how you wire them up, doesn't it?

Use a part that buffers the signals as it passes them along, like WS2801, the number is probably reaaaaally high, limited by your abillity to distribute power.  That's basically what LED strips are - how long are those strings?

Use parts that are all driven in parallel, with SCK-MISO-MOSI going to all pins and unique chip select or latch pins, you are only limited by the number of slave select pins available.
For an Uno, that would be 17.

For some combination of the two, there are too many possibilities to count. As I described above, I demonstrated 20 shift registers controlled with just 3 pins, and made 5 sets doing of boards do that.

The schematic I showed had 64 parts being controlled - the key would be in proper distribution of the control signals and power.  Termination of the signals might be needed, altho with SPI at 1/4 of system clock, that's 4 clock cycles (250nSO) for signals to settle, making for a pretty tolerant system.
9705  Using Arduino / LEDs and Multiplexing / Re: 5x5x5 LED cube help on: January 17, 2013, 02:40:38 pm
"wouldnt turning on group 1 section 1 turn on that whole section? not individual LEDs?"
Only if the anodes were driven high for all LEDs. Otherwise, just the LEDs with High anodes turn on.

The idea is you enable 1 group of 5 LEDs at a time, a 5x5x5 cube would have 25 groups to cycle thru. 4% duty cycle.
Driving each group for 1667microseconds would yield a 24 Hz refresh rate - leaving over 25,000 cyckes in between writes to do other stuff.
I would imagine a loop within a loop to cycle thru the groups & layers, reading from a 25-byte array (upper 3 bits ignored) to send out a new byte every 1667uS. 2nd array of 5 keeps track of group enable pins, 3rd array of 5 keeps track of layer enable pins.
There are 5 anode drive pins, 5 group select pins, 5 layer select pinsl, so the whole cube is multiplexe with just 15 pins, directly controllable by a single '328P chip with no extra shift registers. Just 15 resistors and 20 transistors.
I didn't make one myself, just helped the original requestor with a design that could be done.
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