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22171  Using Arduino / Installation & Troubleshooting / Re: Sketch won't load after power off/up, need to reset on: May 10, 2011, 04:39:02 pm
Has the LCD got a backlight you are trying to power, if so have you got a current limiting resistor in series with it?
22172  Using Arduino / Project Guidance / Re: Arduino Voltage regulator? on: May 10, 2011, 04:36:24 pm
The resistance is always going to be the same so why not measure it first and incorporate the value into the program. Then all you have is a programmable voltage output. You will need some external hardware to control this as the arduino can only output up to 5 volts directly, as can virtually all other micro controllers.
22173  Using Arduino / Project Guidance / Re: BNC TTL Triggers and USB Output on: May 10, 2011, 04:32:24 pm
Without knowing what these signals are it is impossible to give you any sort of solution or evaluation.
22174  Using Arduino / Project Guidance / Re: I2C light control on: May 10, 2011, 04:30:26 pm
You don't need the diode D2 in the return path.
You need more capacitors each side of the of the regulator.
You can't control AC lights with PWM:-
1) Because the PWM frequency is not syncronised with the AC
2) Because your incandecessent lamps will not respond to such fast switching

Note that if you rectify 12V AC you will get 12 * 1.414 = 16.968V DC, that might be too much for the regulators to cope with heat wise.
22175  Using Arduino / LEDs and Multiplexing / Re: 595 & 4021 multiplexing on: May 10, 2011, 11:24:58 am
If you are not conformable with bit wise operations try the bitSet() and bitClear() functions they might be easer to get your head round.
22176  Using Arduino / LEDs and Multiplexing / Re: How many LED's can you run off an Arduino Uno on: May 10, 2011, 11:21:50 am
In the end you will have one power source to the Arduino(brain) at between 3-5V and one to the LEDs
No what you end up doing is powering it all off an external supply.
You are mixing up power drawn from the arduino chip, power drawn from the arduino regulator and power drawn from an external supply.
Remember power is volts times current so you can have a supply capable of providing power but it doesn't have to, it will only supply the power the circuit needs.
22177  Using Arduino / General Electronics / Re: Wiring a Z80 to Arduino... on: May 10, 2011, 11:17:02 am
Luxury we used to dream about eight 1 x n bit RAM chips.
22178  Using Arduino / Installation & Troubleshooting / Re: Sketch won't load after power off/up, need to reset on: May 10, 2011, 11:10:27 am
So load up the blink sketch into the arduino.
Does that work from power up?
Add the photoduino shield nothing more, and nothing attached to the shield.
Does it now require a reset before the blink will start?
If so there is something wrong with the shield's construction. There is nothing in the schematic that would affect the reset.
The other possibility is that your computer is not initialising the COM port correctly on plug in, but if you get the same effect from just powering it up with a 500mA supply then it points to the shield.
22179  Using Arduino / General Electronics / Re: Wiring a Z80 to Arduino... on: May 10, 2011, 10:10:19 am
Also the Signetics 2650 was fully static and pre dates the Z80 by a couple of years.
It was used in the first Phillips games consoles and was the first Micro computer I built in 1975. I used it in a couple of embedded systems as well, including the first micro processor controlled ham radio repeater in the U.K. in 1976.

My first computer - home built and designed
22180  Using Arduino / Project Guidance / Re: Hardware Interfacing on: May 10, 2011, 08:01:38 am
I don't think I2C would be a possibility because this project is for a senior design class and we aren't allowed to use pre-made boards.

Why can you not make an I2C board yourself? It is just like any other board, there is no need for it to be pre-made.
22181  Using Arduino / General Electronics / Re: 100 RGB-LEDs controlled with arduino and MAX/MSP on: May 10, 2011, 07:53:55 am
In which case simply attach a transistor to a PWM output and drive all the LEDs of one colour in parallel. Each LED needs it's own current limiting resistor.

See the schematics here:-

Do this three times one for each colour. Make sure the transistor can handle the current from all the LEDs.
Note not all pins are capable of PWM output, see the data sheet for your arduino.
22182  Using Arduino / LEDs and Multiplexing / Re: large matrix using tlc5940 and 74hc595/uln2003A on: May 10, 2011, 07:48:21 am
but will the current drop across all the components
You get a voltage drop across components, and you get current flowing through components but current drop is not a real term.
What do you mean?
22183  Using Arduino / LEDs and Multiplexing / Re: RGB matrix questions on: May 10, 2011, 07:45:08 am
the message:-
"avrdude stk500_getsync(): not in sync: resp=0x00"
means it has not communicated at all with the processor. This can be due to lack of boot loader, not resetting at the right time or no communications either no connection or wrong speed.
22184  Using Arduino / LEDs and Multiplexing / Re: TLC5940 and 12V Power on: May 10, 2011, 07:40:13 am
For a start decoupling is needed, between +5 and ground and between 12V and ground.

The TLC5940 can operate with a 12V supply to the chip. In fact it will operate up to 17V.

I don't think I will need any resistors at all for the TLC5940.
Yes you need a current setting resistor.

Should I ground the 12V supply to the arduino?
If you don't nothing will work.

I have read that I need to get rid of the IREF 2.2 resistor and that makes sense to me because the higher voltage I am trying to use. 
Makes absolutely no sense to me.

The LEDs have their own resistors already built into the strips.
That suggests they might not be suitable for driving with the TLC5940 - how much current do they take?
22185  Using Arduino / General Electronics / Re: Voltage regulator question on: May 10, 2011, 05:25:20 am
but I tried out my idea an its working really well
So what did you do to fix it?

there is not a decoupling capacitor in sight.
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