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16  Using Arduino / Project Guidance / Re: Token detection. on: April 17, 2014, 04:12:10 am
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I don't think there is a cheap solution to this. I think you are unrealistic to think so.
 If you want a solution that produces useful data you can get a laser displacement sensor , mount it on an X/Y frame that moves
the sensor back and forth with one stepper motor and moves the slide across the other axis with another stepper motor. I guarantee if you collect the displacement data and map the readings to your x/y coordinates the tokens will show up as readings of the same height that occupy the same area per token. I really couldn't tell you if an arduino has enough memory to process the data but you could certainly store to an SD CARD and process it on a PC.  Do you have any other ideas that produce reliable data ?

Either you or me have completely misinterpreted the rare information the OP provided yet. If he just have a bunch of objects that he wants to put on some kind of detector surface and he just has to know which one is there, your solution would be completely over-engineered and the RFID solution was realistic and feasible. Your solution makes sense if he cannot change the objects but has to identify them by their shape and size. But in that case I would forget the Arduino, take a standard PC (could be one of the cheap ARMs) and connect a camera to it. OpenCV will help identify the tokens.
But that's a huge amount of guess-work, the OP has to deliver more information about his project.
17  Using Arduino / Project Guidance / Re: Possible problem using DS1307 RTC while using emonTx Arduino Shield on: April 17, 2014, 04:03:43 am
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So because they are directly connected, I can't use the RTC and the emonTx at the same time?

You can use both but you have to modify the emonTx shield, at least if your pin description is correct (you haven't provided a link to that product yet).
As I wrote in my first post you have to remap one pin on the shield and you can use both at the same time. You may also have to modify the library (if there is one) to use the modified pin out.

You have other options:
- use another Arduino type. Leonardo or Mega2560 would be candidates because they don't have the I2C pins shared with analog inputs.
- Connect the DS1307 to other pins and use a software emulation to do the I2C protocol.
18  Using Arduino / Networking, Protocols, and Devices / Re: problem to use the SimpleModbusMaster library on: April 17, 2014, 03:57:38 am
The AVR side of the Yun is an ATmega32U4, the same processor as the Leonardo has. On these Arduino types the "Serial" object is not a HardwareSerial class instance but connected to the USB serial emulation. Use the "Serial1" object there to access pins 0 and 1.
19  Using Arduino / Networking, Protocols, and Devices / Re: mfrc522 RFID module level conversion voltage question (MRF-522) on: April 17, 2014, 03:54:15 am
Your chip seems to be more tolerant than the datasheet specifies. There the maximum tolerable voltage on the interface pins is defined as Vcc + 0.5V which is slightly below 4V in your case. To be on the save side you should use level converters for MOSI, SCKL and SS.

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(there are a scattering of resistors on the module but they don't appear to be in series with those digital lines)

That don't help much in most situations as it only limits the current but you still have a higher voltage on the pins.

20  Using Arduino / Networking, Protocols, and Devices / Re: FTP Server with Arduino Uno + Wiznet on: April 17, 2014, 03:42:18 am
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Just wanted to know if anyone found a way to download files from a server to the arduino SD card using HTTP yet. Please let me know, working on a project that requires this feature, i only need to transfer one specific text file after it is updated. Any ideas on how i could achieve this?

The WebClient example is exactly doing that just not saving it to the SD card. Combine that with ReadWrite example from the SD library and you have your solution.

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I tried using the PUT method with the TinyWebserver here https://github.com/ovidiucp/TinyWebServer
no luck..... it does not respond to the request

If you want to get a file and store it on the Arduino's SD card, you don't need a web server but a client (the server is serving it and not consuming).
21  International / Deutsch / Re: Wie ein LCD ansteuern ; LMC 1602 I2C ; Tutorial ; Sketch on: April 16, 2014, 04:55:28 pm
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Ich bin mir da nicht sicher, korrigiert mich da bitte falls ich falsch liege,
aber ich denke, dass dieses LCD Display einfach ein ganz normales LCD ist, wo einfach bloß ein I2C Portexpander
(oder sowas in der Art) dran ist.

Das ist genau so. Da aber die Verdrahtung vom I2C Portexpander zum Display von Modul zu Modul etwas unterschiedlich gehandhabt wird, hat der Bibliotheksprogrammierer einfach diese Art der Festlegung gewählt. Man muss dann für das eigene Modul herausfinden (gut wenn der Verkäufer auch ein Datenblatt bereithält), welcher Ausgang des I2C Portexpanders auf welchen Display-Pin geht.
22  International / Deutsch / Re: WIFI+UDP+NTP keine Verbindung on: April 16, 2014, 04:47:34 pm
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zu1. Nein sehe ich nichts.

Dann bezweifle ich, dass die Verbindung über die Fritzbox geht. Wenn das Tool funktioniert und einen Zeitwert liefert, aber auf der Fritzbox keine Pakete durchgehen, dann hast Du womöglich eine falsche Vorstellung, wie Dein Netzwerk aufgebaut ist.

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zu 2. ich bekomme auch kein TCP hin. Nix ist erreichbar. Nur in meinem Netztwerk ist das shield sichtbar. Auch wenn ich das Shield als Webserver laufen lasse, ist die IP des Shields  aus meinem netzwerk nicht erreichbar.

Was heisst sichtbar? Kannst Du den Arduino anpingen? Ich fürchte, wenn sowohl TCP als auch UDP nicht gehen, liegt das Problem komplett anderswo und so aus der Ferne würde ich auch auf die Fritzbox tippen, allerdings sind das im Normalfall sehr zuverlässige und einfach zu konfigurierende Geräte. Wenn Du das Teil also nicht komplett verkonfiguriert hast, sollte das schon hinzukriegen sein.
Versuche ein Notebook mit WiFi aufzutreiben, damit Du dort direkt den WLAN-Verkehr sniffen kannst und sehen kannst, was die Fritzbox auf die Anfragen des Arduinos zurückgibt.
23  Using Arduino / Project Guidance / Re: Possible problem using DS1307 RTC while using emonTx Arduino Shield on: April 16, 2014, 04:39:21 pm
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So just to confirm, can´t I use those inputs instead of A4 and A5? After some research I've read that SCL and SDA are/were used for I2C, and that was previously done using the A4 and A5 pins.

The SDA/SCL pins are directly connected to A4/A5 on the Arduino Ethernet board. The additional pins are there to extend the compatibility with the different Arduino board types. So you can use the SDA/SCL pins with a shield and on the UNO (and Ethernet and some other types) they are connected to A4/A5, on the Mega2560 they are connected to D20/D21 and on the Due/Leonardo they are separate pins that are not used otherwise.

BTW: SCL is solely an output on the Arduino (in your usage), while SDA is an input as well as an output, that depends on the current state of the I2C communication.
24  Using Arduino / Sensors / Re: wiring up a sharp GP2Y0A02 distance sensor on: April 16, 2014, 04:33:24 pm
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You mention calibrating... how would i do that?

That's easy: put a big obstacle in front of the sensor, read the value it puts out and measure the distance manually. Do this for several distances and use that as the reference table.

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as far as point b is concerned, perhaps the arduino analog input is also converting the numbers it receives some how?

The Arduino is not receiving the numbers, it's measuring them. The value you get is telling you that that many times a 1023th of the reference voltage (if you've not chosen something different explicitly, that's the voltage you're powering the Arduino with) is currently present on the analog input pin. The problem here is that if you're powering the Arduino by USB this voltage may vary over time so you don't get really usable values (although you might get a trend in any case).

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I'm trying to compare this number with the chart on page 3 under the "Electro-Optical Characteristics section".

I don't have a chart there, just a table.

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How am i supposed to understand the line that has the parameter "Output Voltage"?  does it mean that if I measure 0.4 volts on the wires, then value i get should be divided by 150?

No, it means, if you get a value of 82 (which equals 0.4V if you power with a stable 5V) the obstacle is about 150cm away. But as you also can see there, that value can be in the range between 51 (=0.25V) and 112 (=0.55V). That's why I told you that you might have to calibrate by looking what your sensor is giving you at that distance. If you look at page 4 you can see the curve that describes the relationship between the measured voltage and the distance the obstacle has from the sensor. The calculation is not done by a simple division. If you want a realistic value you have to do at least a square approximation.

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It'd be nice to get the algorithm correct for learning purposes and for being able to control my robot with accuracy...

I don't know if that's the right sensor if you want accuracy for your robot.
25  Using Arduino / Sensors / Re: wiring up a sharp GP2Y0A02 distance sensor on: April 16, 2014, 10:43:20 am
According to the datasheet anything closer than 20cm is not detected correctly but recognized identically as a far away target.

The read value is not in cm it's just a voltage level. The highest value is at about 510 when the obstacle has a distance of about 20cm. At 50cm it's around 350 and from about 130cm the value stays more or less at approximately 100. (See Fig.2 on page 5 of the datasheet). That curve is not linear, so it's not an easy calculation to get a distance in cm out of that sensor and it probably has to be calibrated first. Do you need absolute values from the sensor? Isn't it enough to know when it approaches an obstacle?
26  Using Arduino / Sensors / Re: IR Pulse Sensor Help on: April 16, 2014, 10:26:22 am
I don't know how exactly this sensor works as the don't provide schematics for it (and we see again, that you should never buy anything from a supplier that doesn't provide datasheets or equivalent documentation for their products).

I guess that the LED emits some light that goes through your finger and the sensor detects how much of it went through. That value probably changes in the rhythm of the heart beat. Have you tried covering the sensor and your finger in it so that no sun or synthetic light is reaching it? I would expect the sunlight not to have a high impact but synthetic light has. Usually these kinds of sensors are in a kind of part-finger-glove to keep away external light sources.
27  International / Deutsch / Re: Hilfe bei IR-Codes senden… on: April 16, 2014, 10:18:35 am
Du müsstest die Bibliothek anpassen und aus dem "unsigned long data" im Methoden-Kopf ein "uint64_t" machen. Der Rest des Codes könnte dann schon funktionieren.
28  Using Arduino / Networking, Protocols, and Devices / Re: Wire not working on Due? on: April 16, 2014, 10:10:11 am
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The Due apparently has internal pull-ups on SDA(20), SCL(21) as I can measure 3.3V on the pins. Yet when Wire.begin() is called out it (communication to my RTC module) does not work.

The Due has such pull-ups (1k5 according to the schematics) on pin 20 and 21 and it doesn't have on SDA1 and SCL1.
A 10k pullup is probably too weak if the bus is more than a few centimeters long, don't forget it goes to 3V3 and not 5V.

What do you mean by Wire.begin() is working or not working? Wire.begin() does not communicate with your RTC module, it just configures the hardware that the TWI module will be used.

I ask again for a wiring diagram.
29  International / Deutsch / Re: Hilfe bei IR-Codes senden… on: April 16, 2014, 07:54:12 am
Habe ich das richtig erraten? Du hast 2 Arduinos, einen benutzt Du zum Senden, den anderen zum Empfangen. Du schaust zuerst, was der empfangende als Resultat der Ansteuerung mit der Fernbedienung ausgibt und programmierst den anderen Arduino dann so, dass er diesen Code versenden soll. Mit dem empfangenden Arduino wird das gesendete Signal wieder dekodiert und da bekommst Du ein anderes Resultat als erwartet. Stimmt das soweit?
30  Using Arduino / Sensors / Re: IR Pulse Sensor Help on: April 16, 2014, 06:30:05 am
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This might be because I am placing my finger in the wrong place? or could be a problem with my code/ circuit.

Your finger should be placed between the LED and the sensor plate below it. If you did that correctly and the sensor works, the LED on pin 13 should blink at each heartbeat.

In the serial monitor you should get positive and negative values alternating in about the same rate as your heart beats.
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