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6706  Using Arduino / Project Guidance / Re: Doghouse automation design advice on: May 08, 2011, 09:57:41 am
I don't know a huge amount about FETs, they are very prone to being zapped though. Personally I'd be worried about running wires from them all over the place, but I may be being a bit paranoid.

Are they logic-level FETs? They are only getting 5v on the gate.

I'm not sure the diodes do anything, they certainly won't snub any motors/solenoids you drive although they might protect against -Ve spikes.

You could up the gate resistors (R1-21) buy 10x.

On the PCB.

What current are you expecting to drive with the FETs? The traces are pretty small. Especially the GND from all the FETs back to CONN3, that could be carrying the current of 10 motors.

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Rob



6707  Using Arduino / Project Guidance / Re: Doghouse automation design advice on: May 08, 2011, 07:33:35 am
The LDR won't work, it's just connected to VCC with no divider. You could connect it to GND and use the internal pull up resistor (dodgy) or add an external resistor and tap from the centre of the two.

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Rob
 
6708  Using Arduino / General Electronics / Re: Isolated N to N volts on: May 08, 2011, 07:24:49 am
I guess it pretty much has to be a transformer, it's just that I don't want to do it, I'd like a little black box filled with clever stuff by someone who knows about this type of electronics smiley

I may decide that the far side has to have it's own PSU/battery, that's certainly an option but I didn't want to force that as it might be a remote sensor(s).

I can also stipulate that one side will be for example 12v, and the source > 12v (or whatever headroom is required). In this case there are a 1000 options.
 
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Rob
6709  Using Arduino / Project Guidance / Re: Doghouse automation design advice on: May 08, 2011, 06:58:00 am
How about PDF, I don't seem to have anything to read PS.

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Rob
6710  Using Arduino / General Electronics / Isolated N to N volts on: May 08, 2011, 06:29:54 am
Can anyone tell me what you call a "DC/DC converter" that will take any DC voltage (well say 9-30v) on the input and produce the same voltage (a small loss is OK) on the output that is isolated from the input?

Please don't say a transformer smiley, I don't want to dick around changing from DC/AC/DC. 

I though a quick Google search would find something, and there are no end of DC/DC converters but they all have fixed OPs as far as I can see.

I'd like a PCB mount device, good for around 1-2A.

Maybe it can't be done because you have no reference across the isolation barrier, although a VCO could do that and I'm sure the Murata (or whoever) guys would be up to the job.

EDIT: Actually thinking about it 2A at 30V might be a bit of an ask. Still any ideas welcome.
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Rob

6711  Using Arduino / Programming Questions / Re: Multiple Timer SYNC problem on Mega board on: May 08, 2011, 06:14:09 am
From the data sheet

Quote
Modifying the counter (TCNTn) while the counter is running introduces a risk of missing a compare
match between TCNTn and one of the OCRnx Registers.

Maybe you should stop the counters, do the updates, then restart. Then there's this

Quote
Writing to the TCNTn Register blocks (removes) the compare match on the following timer clock
for all compare units.
I'm actually not sure what that means exactly  smiley-confuse, maybe do the TCNT write before the OCRn writes (although you said that they seem good after the first run)

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Rob



6712  Using Arduino / Networking, Protocols, and Devices / Re: Arduino as SPI slave on: May 08, 2011, 05:46:38 am
Yep you need to verify things are working at the source then follow the data until you find where it stops.

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Rob
6713  Using Arduino / Programming Questions / Re: Multiple Timer SYNC problem on Mega board on: May 08, 2011, 04:50:40 am
Not ignoring you selfonlypath, just trying to get my head around the problem smiley

Are you saying that if you call FrameFast when a serial char is available it works?

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Rob
6714  Using Arduino / Project Guidance / Re: What can improve at this code on: May 08, 2011, 04:30:11 am
Apart from the redundancy AWOL mentioned with this

        while(distance>=100){
            white=analogRead(SENZOR_ALB_FATA);
             Serial.println(white);
                if (white<1005){
                   go(-250,-250);
                    delay(1000);
              }
            distance=readDistance();
            go(-250,250);
        }
        while(distance<100){
                 white=analogRead(SENZOR_ALB_FATA);
                  Serial.println(white);
                     if (white<1005){
                       Serial.println("going back");
                       go(-250,-250);
                       delay(1000);
              }
                //  Serial.println(white);
                  // delay(500);
                  go(250,250);
                 distance=readDistance();
                 
             }
   
           }

You have two while loops that basically do the same thing  with the only real difference being one of the speed variables.

If you tell us what is supposed to happen someone may be able to provide more informed information.

For example, when the bot get within 100 of something it should reverse for 1 second  etc etc.

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Rob
6715  Using Arduino / Installation & Troubleshooting / Re: Mechanical specs on: May 07, 2011, 10:26:12 pm
True, but not everyone uses Eagle. Why can't some proper engineering drawings be made available?

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Rob
6716  Using Arduino / Networking, Protocols, and Devices / Re: Arduino as SPI slave on: May 07, 2011, 08:41:58 pm
Quote
I am seeing nothing

The print line

Serial.println (buf);

Will not print anything (or at least nothing viewable) if for example you have low binary values in the buf array.

Just to see I'd change it to

Code:
Serial.println (buf[0], HEX);

and then maybe a loop to dump the whole thing.

Code:
for (int i = 0; i < 100; i++)
    Serial.println (buf[i], HEX);

Although if the ISR is not firing of course there will be nothing useful to look at.

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Rob

6717  Using Arduino / General Electronics / Re: Power Switch on: May 07, 2011, 08:32:50 pm
Given that you need a switch anyway there's little point in having a transistor as well.

Was the C&K switch linked to above not suitable?

Have a look at

http://www.sparkfun.com/products/8769
http://www.sparkfun.com/products/597

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Rob
6718  Development / Other Software Development / Re: Bootloading from SD card on: May 07, 2011, 08:20:32 pm
With the SD I don't see why not, it's just getting the data from a different source. Don't know about the USB options though, that's effectively what's happening with the standard bootloader albeit not directly from a thumb drive. To get data directly from a drive you would have to be a USB master (or whatever it's called).

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Rob
6719  Using Arduino / Installation & Troubleshooting / Re: Mechanical specs on: May 07, 2011, 08:03:45 pm
There are several third-party drawings around including my own (www.robgray.com/temp/Arduino-PCB-dimensions.pdf) I haven't seen official ones though which make me wonder why that would be the case, surely that's part of normal documentation.

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Rob
6720  Using Arduino / Programming Questions / Re: Checking a character array against a string? on: May 07, 2011, 08:00:06 pm
I take it you are referring to this line

if(route == "10s")

You can't compare like this, look up "strcmp".


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Rob
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