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16  Using Arduino / Project Guidance / Re: Batch Controller with Multiple load cells on: July 03, 2014, 04:50:59 am

Not sure what your plan is for reading this PWM value, but in answer to your question about an LED at 10V I presumed a red LED with 1.9V forward voltage using 20mA and fed it into to arrive at a 1/4W 470 Ohm resistor driving the LED at 17.2mA if fed with 10V.  The size of the current limiting resistor will vary depending on the forward voltage of the LED, supply voltage and desired current.

Cheers ! Geoff
17  Using Arduino / Project Guidance / Re: Help needed generating 30 KHz PWM signal on: July 02, 2014, 10:02:06 am

There's this tutorial on Arduino PWM that might be handy reading.  Also, are you sure your receiver isn't 38kHz - only that's the frequency used by common iR remote controls?

18  Using Arduino / Project Guidance / Re: Checksuming a string and a text file on: July 02, 2014, 09:56:30 am

There are a few CRC examples on the forum and by google-fu.  This one seems promising and compact.

19  Using Arduino / Project Guidance / Re: help on: July 02, 2014, 09:49:40 am

How exactly will it play the records - do you have a turntable that can be controlled somehow?

20  Using Arduino / Project Guidance / Re: Custom control interface for an old (late 90's DMX/Smpte lighting controller) on: July 02, 2014, 09:46:26 am
Hi Duncan

Looks like you're on the right track - or one of them as there's always many ways to go about most things.  The choice of a mega will certainly give you enough IO pins to do the job, if you're going to direct connect them all without using any multiplexing.  Your idea with the relays looks to be perfectly sound too from what it says on p15 of that manual.

To somewhat simplify your code can I suggest you look into arrays such that you could define an array for the switchPins, and one for the corresponding LEDs and one for the strings to output to the display.  This would allow you to reuse your code by looping through from 0-15 to check the switches, if that particular one is pressed then using the same index to the LED array will light up the correct LED and you've then got an easy way of writing the Cue text to the LCD.  Hope this makes sense.

To illustrate
// something like this
const int CueSwitch[16] = {
const int LEDpin[16] = {
char *CueMessage[16] = {
  "Audience Lights",
  "Other lights",
  "Xmas lights",
  "Lights16" };

void setup() {
  for(int i = 0; i<16; i++) {
    pinMode(CueSwitch[i], INPUT_PULLUP);
    // test each LED in sequence on startup
    digitalWrite(LEDpin[i], HIGH);
    digitalWrite(LEDpin[i], LOW);

void loop(){
  for(int i=0;i<16;i++} {
    // do your stuff
  }  // end of for loop
} // end of loop()
In the "do your stuff" loop that would be reading the state of CueSwitch[ i ] and if it's pressed lighting up LEDpin[ i ] and outputting CueMessage[ i ] to the display then doing the relay actions.  If it's not pressed turn off LEDpin[ i ].  Make sure you look up debouncing switches if you're not familiar with that.

Using the arrays like this allows some flexibility to swap IO pins about if needs be - see the LEDpin array that I jumbled on purpose as an example.

Hope this helps.  All the best with your project!
21  Using Arduino / Project Guidance / Re: DMX shield on top of arduino uno on: July 02, 2014, 08:56:40 am

From your photo it's difficult to see, but it appears your character LCD is just showing a row of blocks on the bottom row of characters.  This is what it shows when it's not receiving or recognising the initialisation commands from the Arduino.  Without seeing your wiring schematic my first guess is that the shield is using some of the Arduino IO pins that the display needs also.  This conflict means that the LCD display is receiving signals it is not able to process.

If it's a regular character LCD with a 16-wire interface it uses a lot of the IO pins on an Arduino so that's not surprising.  To fix, look up the IO that the shield requires and choose different ones for the LCD.

22  Using Arduino / Project Guidance / Re: New project, new experience. on: July 02, 2014, 08:50:53 am

That doesn't sound vague at all.  And yes, if you prototype it with Arduino you will be able to produce your own boards based on the same hardware..  Typically that's cheaper than trapping an Arduino and a stack of shields in every project, though that can sometimes be more convenient for a 1-off.

All the best with your project,
23  Using Arduino / Project Guidance / Re: RS232 telematic project with xbee & gps on: July 02, 2014, 08:47:59 am
Hi, and welcome

At this early stage I don't think it matters terribly what you select.  If you can physically use an Arduino Uno they have the widest variety of shield choices.  In your first project you'd probably use shields as that will keep the hardware complexity to a minimum and there are typically well written software libraries that will assist you to keep your code simple too.

Just break the project down into bite-sized chunks, and start chipping away at it.  The libraries and shields will come with examples of how to use them, and often online tutorials to show you how too.

All the best!
24  Using Arduino / Project Guidance / Re: How to Interfacer RFID reader that outputs in HEX on: July 02, 2014, 08:41:15 am

HEX is just the way the serial terminal is displaying the output as a human-readable value.  It could have shown you a stream of 1's and 0's but that would have even been harder to read for us.  To the Arduino this is all the same but it's up to us to define whether the information is treated as numbers, characters, bytes, hex or bitmaps etc.

Do you know what values you were expecting to see with the tags you have?
25  Using Arduino / Project Guidance / Re: Arduino Micro with a TFT LCD display, LED's and a button on: July 02, 2014, 08:35:05 am

Since you've started out with some pretty large plans, might I suggest breaking your project into smaller pieces, working out how each of those works, then merge them all into your final project.

For example you might use this instructible which shows how to display an image on the TFT with some introductory Arduino tutorials which will show you about switches and LEDs.

The pro micro isn't a limitation, though you will need to translate pin locations to suit your board as most tutorials use the Uno as their teaching platform.

All the best with your project,
26  Using Arduino / Project Guidance / Re: GSM Modem connectivity Problem (Changing default Library Pins) on: July 02, 2014, 08:26:20 am

You've not mentioned which Sim900 shield you are using, but I expect you'll need to make a modification to a jumper on the board to also move the electrical connection used on the shield to the pins you're setting in software.

On the software side you're telling the Arduino where to send and receive data, but unless the electrical pulses are routed to those pins on the shield physically as well there's going to be nothing for the Arduino to talk to.

On some of these Sim900 shields there is a jumper block to allow you to choose between different sets of pins.  If there's not you may need to cut the traces and run your own wire to the pin headers on the shield you wish to use.

Cheers ! Geoff
27  Using Arduino / Microcontrollers / Re: I want to make a camera... using cellphone camera on: July 02, 2014, 02:17:27 am
I don't quite understand your motivation for this question.  If you don't have the smartphone camera yet (based on how you've not selected one) and all you want to do is run a battery powered camera for 5 hours - if money's no barrier to paying someone to build one for you (so it's not about learning, or the experience, or the fun, and the proud afterglow of making it yourself) why not just skip that step and buy a commercially available product?

28  Using Arduino / Microcontrollers / Re: Mega 2560 not recognized on: June 30, 2014, 11:22:10 pm
Have you had any success using the ICSP header on the board to program it?

29  Using Arduino / Project Guidance / Re: Problem programming ATtiny85 on: June 29, 2014, 11:21:06 pm
I'm guessing some arcane change under the hood between Arduino versions...As our colleague raschemmel pointed out, it's a pity not to get an understanding of why something doesn't work, but good nevertheless to get a result.
I think you're correct with that.  I suspect the error is actually something the IDE was not written to anticipate, so it's steering us in the wrong direction.  As one of my old lecturers used to tell us "All's well that ends".

Glad to read you got it going,
30  Using Arduino / Project Guidance / Re: Batch Controller with Multiple load cells on: June 28, 2014, 08:20:01 am

You are certainly playing with bigger components than most : )
Is the 2560 the best option (I do need 5v in and out, so the 3.3v Arduinos are out)?
It's got a heap of IO options and the operating voltage you want, so it's as good or better than any other choice.  You can always add functionality to any Arduino with other ICs or even a 2nd Arduino.  If you've not bought it yet, you can always hold off buying until you have all your IO that you need to do worked out, then map it to the board you're choosing.  Looks like you're most of the way downt that path.
What is the best way to connect RS-232 to the Arduino?
There are a lot of modules and boards based around the Maxim MAX232 chip that can do this for you.
What would be a good way to store batch data for each batch?  Is there an easy way to upload it to a computer or the internet? (I just noticed Temboo while creating an account)
The simplest way to connect to a PC will be to use the onboard USB on the Arduino and have a program written on the PC side (often you'll find examples showing how this can be done with the Processing language that Arduino is based on).  Other connectivity to your PC could by by bluetooth or some other radio, or you could upload directly the interwebs using a WiFi or ethernet shield to get on your local network.  There are lots of options for this.
Is there an easy way to bring the 0-10v down to 0-5v and maybe have some safety to prevent the Arduino from being damaged?
Google search Voltage divider, or potential divider (link to Wikipedia article) for how to do this with just 2 resistors.  There are also lots of online resistor calculators (links to one) to make the design process easier too.
Why does the HX711 output to the analog pins? (Do they have enough resolution for that?)
Reading the data sheet, it doesn't.  It communicates digitally with an IO line and a clock line.  I haven't used one of these but my presumption is the analog pins are being used as digital pins (all analog pins can be used that way) in the example sketch.  On a Uno, you have 20 digital IO pins being D0 to D13 plus A0 through A5 can also be addressed as D14 thru D19.

I do not have an answer for your final questions.  Hope someone else can fill in those gaps for you shortly.

Cheers ! Geoff
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