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6316  Using Arduino / Motors, Mechanics, and Power / Re: Other ways of controlling water flow on: July 10, 2011, 07:15:45 am
Quote
does anyone know where to find Plaster of Paris in Australia
Maybe art supply shops.

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Rob
6317  Using Arduino / Programming Questions / Re: Digital pins D8-D15 briefly high at upload on: July 10, 2011, 07:13:58 am
During upload the processor is in a reset state and all IO pins should be Hi-Z and floating.

Do you have anything else connected to these pins?

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Rob
6318  Using Arduino / Motors, Mechanics, and Power / Re: Other ways of controlling water flow on: July 10, 2011, 03:04:47 am
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should I risk it?
I would say no. It's hard to see with that photo but I would expect only a single outlet and there would be no practical way to separate the valves.

Another thing to think about is the control voltage, anything made for a fridge will use mains I reckon which is more difficult to work with, and if you get it from the US that will be 110v.

Personally I would not buy anything from somewhere that didn't provide a full data sheet and in this case mechanical drawings. Maybe you can get these from GE.

Have a look at this

http://www.jameco.com/webapp/wcs/stores/servlet/ProductDisplay?langId=-1&productId=169835&catalogId=10001&freeText=169835&app.products.maxperpage=15&storeId=10001&search_type=jamecoall&ddkey=http:StoreCatalogDrillDownView

Small ports but they might have larger versions.

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Rob




6319  Using Arduino / Motors, Mechanics, and Power / Re: Other ways of controlling water flow on: July 10, 2011, 02:23:38 am
That Amazon valve looks to me like it's a mixer, ie hot and cold into a single output. If that's the case is that what you need? It's not normally the sort of thing used for garden control.

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Rob
6320  Using Arduino / Motors, Mechanics, and Power / Re: Other ways of controlling water flow on: July 10, 2011, 01:50:48 am
I haven't looked for ages but solenoid valves from places like Bunnings aren't that expensive are they?

BTW, it's VegEmite, (I had to go look at a jar to make sure smiley)
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Rob
 
6321  Using Arduino / Project Guidance / Re: wake up arduino through serial comm & interrupts on: July 09, 2011, 07:23:51 pm
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In this way, we can use INT0 for another purpose when arduino is awake.

The 14001 is not open drain though so how does the "other purpose" work when connected to a hard voltage?

Another option is a 74xx126 tristate buffer or a 4066 analogue switch.

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Rob
6322  Using Arduino / Programming Questions / Re: Fixing the randomSeed() function (when using analogRead) on: July 09, 2011, 11:11:51 am
There's no way you'll get very random from reading an ADC as you've found out, but there is low-value noise there. If you look at the LSB for each of those values you get this

0001 1110 0001 0101 1110 0001 0110 1000 0110 1001 0110 1001 1011 0100 1001 0110

Put that together and you have something resembling two 32-bit random numbers (maybe). How about doing that 100 times and seeing just how random it is.

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Rob
 
6323  Using Arduino / Project Guidance / Re: Open/close skylight + rain sensor failsafe on: July 08, 2011, 06:55:12 pm
I can't really picture how your system works but if you have to push this pole that will be difficult to replicate because a lot of force would be required I think.

One gadget that would  do it is a "linear actuator", look them up.

As for rain detection, there must be existing "sensors" that do this. Have a look for things used with weather stations, they often have tipping bucket things for measuring rain fall, you could use one to detect any rain (if it's sensitive enough to very small amounts).

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Rob
6324  Using Arduino / Networking, Protocols, and Devices / Re: Serial Communication between 2 mega on: July 08, 2011, 11:09:31 am
Baud rate should have nothing to do with it as such.

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I am always not getting the full 2000 * 17 bytes
How many are you getting?

What data are you sending and what are you receiving?

How fast is the Serial.print running? If it's < about 15x (the length of "I received: nn") the 4800 baud you may be overflowing the receive buffer.

You need to post both halves of the code.

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Rob
6325  Development / Other Hardware Development / Re: Oversized Mega Shield on: July 08, 2011, 10:57:23 am
That connector is almost exactly the same width as a Mega, from what I can see it will fit very nicely over the DC and USB jacks as the pins are set about 14mm back from the edge and they will sit nicely between the jacks and the headers.

So I think it's a very good match and you shouldn't need to go for a larger board.

Having said that I don't think there's any real reason not to.

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Rob
 
6326  Development / Other Hardware Development / Re: Learning eagle on: July 08, 2011, 10:47:00 am
Your getting there, a few comments

C1 and C2 should go to GND.

C3 and C4 are normally 1/10/22uf tant or electro types and therefore larger than you have shown.

There are no decoupling caps, put some as close as possible to the chip's GND and VCC pins.

Crystals normally have an X designator. Q is for transistors.

What is a 3n3333?

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Rob
6327  Using Arduino / Programming Questions / Re: no TX data after calling analogRead on: July 08, 2011, 08:17:26 am
Post your code, we need to see what you've done.

But you're not doing the analogRead on the same pin as the serial Tx are you?

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Rob
6328  Using Arduino / General Electronics / Re: Current Sensor on: July 08, 2011, 12:03:01 am
The measured voltage on the ACS712 is isolated from the other half of the chip, so it doesn't matter what level it is as long as its < than the isolation rating.

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Rob
6329  Using Arduino / General Electronics / Re: Current Sensor on: July 07, 2011, 06:42:58 pm
The ACS712 is a common choice. SOIC-8 package but you could solder some wires to the pins to use on a breadboard.

BTW that link to the ZMC10D-ND doesn't seem to work.
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Rob

EDIT: Same chip retrolefty pointed to, I forgot about the SF breakout board.
6330  Using Arduino / Programming Questions / Re: Need to understand Serial-RS485 master/slave addressing on: July 06, 2011, 11:26:42 am
Here are a couple of reworked versions of your function

Code:
void recieveMSG() {
    // 'clear" the frame in memory by dorking the last byte
    // so we can check the frame after it's been received
    charArray[3] = 0;
    while(Serial.available() == 0);          // wait for character
if (Serial.read() == 0x10) {             // if it's a sync char read the rest of the frame
for (int i = 0; i < 4; i++) {        // assumes 4 bytes in every frame
while (Serial.available() == 0); // wait for next character
charArray[i] = Serial.read();    // load char into array

// test here for valid frame, something like
if (charArray[3] != 0x2b || charArray[3] != 0x2c) {
// bad frame
}
}
}

void recieveMSG() {
    // 'clear" the frame in memory by dorking the last byte
    // so we can check the frame after it's been received
    charArray[3] = 0;
    while(Serial.available() == 0);            // wait for character
if (Serial.read() == 0x10) {           // if it's a sync char read the rest of the frame
while(Serial.available() < 4);    // assumes 4 bytes in every frame, wait for all 4
for (int i = 0; i < 4; i++) {     
charArray[i] = Serial.read();  // load chars into array

// test here for valid frame, something like
if (charArray[3] != 0x2b || charArray[3] != 0x2c) {
// bad frame
}
}
}

It's late here so I hope I got them right, if not my apologies in advance smiley

NOTES:
In a real system you should do more testing for frame validity, for example what happens if you only get 3 bytes?
If the first char received is not 0x10 the func exits, maybe loop inside the func or maybe handle this outside by rapid calling of the func so you don't block on receiving a frame.
Probably should return a value indicating good/bad frame.
Other stuff I can't think of right now.
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Rob
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