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1  Using Arduino / Networking, Protocols, and Devices / Re: Home automation idea, RS-485 over cat5 lines in home? on: May 15, 2012, 08:33:48 pm
Hmmm, yup I figured there would be an issue with the star configuration. I may end up going for a wireless solution, probably rf, mostly as they are quite inexpensive. Will have to think a bit more about it. Thanks for the link spirilis, it's a good read!

Thanks for the help guys.
2  Using Arduino / Networking, Protocols, and Devices / Home automation idea, RS-485 over cat5 lines in home? on: May 14, 2012, 07:33:47 pm
Recently I started thinking about ways I could automate/log sensors in my home at the lowest cost possible (aka, not ripping apart walls to install wiring, and not forking out heaps of cash for ethernet shields). I really like the idea of RS-485 in general, mostly due to the simplicity and cost of transceiver chips (under $2 a piece). The general idea would be to place a 'node' in each room, which would consist of an Arduino/microcontroller and a RS-285 transceiver chip. Each node would act as a slave device and would communicate with a centrally located master. Initially I considered connecting all of the devices wirelessly via radio, which I suppose would be fairly cheap, but I prefer hard wires connections. So it got me thinking, why not use an existing CAT5 plug found in most rooms? I believe there's typically a couple of unused twisted pairs.

So basically I'm wondering how feasible this idea would actually be. Some potential problems I'm looking at:
1) With RS-485, nodes should be placed in a line-like fashion, which isn't exactly possible with the existing ethernet configuration, as the lines propagate outward from a central switch/router. There could be some impedance/resistance issues.
2) Data could be effected when passing through switch/router (which I could bypass externally from router)

Anyone have some insight on this? I'm not 100% set on RS-485 and the CAT5 approach, other ideas are most welcome. Other thought would be to transmit signals over power (bit risky, not totally comfortable with this), transmission over phone lines (illegal I'm assuming), data via ethernet (ethernet chips are pricey), or focus on wireless via radio.

3  Forum 2005-2010 (read only) / Syntax & Programs / How to read large volume of serial data on: June 10, 2010, 08:57:22 pm
Hi all,

I'm using the Mega to read serial data sent from a compass unit. The issue is that the compass sends its status as a large block of data. Looking at the serial monitor, it's sending upwards of 200 bytes per few ms. The data is in this format:

Compass: 350
Pitch: 5
Roll: 6
Temperature: 15
Tilt: 15

I need to then extract only relevant information, such as the numerical integer that specifies the heading, pitch and roll. I'm sure I could buffer the data and then look at each character individually, but that seems rather computationally inefficient. Any idea how to approach this problem?

Also bear in mind that the Mega is going to be in real-time communication with a VB.NET GUI via another serial connection, so if possible I would like a method that does not interrupt this process.

Thanks in advance
4  Forum 2005-2010 (read only) / Syntax & Programs / Examples using FirmataVB and Ardunio? on: May 10, 2010, 10:43:59 am
Hello everyone,

Would anyone happen to have an example programs that uses FirmataVB and Visual Basic to communicate to the Ardunio they wouldn't mind sharing? I'm really new to VB and Ardunio and I typically learn by examples, anything at all would be greatly appreciated!

5  Forum 2005-2010 (read only) / Interfacing / Re: Gnoduino? on: December 31, 2010, 04:33:03 pm
Hey that's kinda neat. I'm a huge fan of Python and I could see myself possibly using this (that's if I ever migrate away from Windows).
6  Forum 2005-2010 (read only) / Interfacing / Re: Cross platform GUI suggestions on: July 20, 2010, 08:22:31 pm
Thanks for the suggestions everyone. Qt is a nice idea, I think I'll give that a try first. Mono and Blitzmax also look interesting, will have to read up on that a bit more. I've also heard good things about Processing, but isn't that based off Java? If so, perhaps It'd be better to learn Java instead?

Thanks again everyone!

7  Forum 2005-2010 (read only) / Interfacing / Cross platform GUI suggestions on: July 18, 2010, 02:05:39 am
Hey all,

Does anyone have recommendations on what would be the best programming choice for a GUI that is:

- cross platform
- creates a professional end product
- minimal required frameworks required to install on host PC
- great for hardware communication (to communicate via serial with Arduino)

I'm using VB.NET at the moment, and really appreciate the ease of coding, but looking to migrate to something a bit more flexible. Was looking into Java and Python. Java as it installed on nearly all computers natively and has great support/addons, but I've heard it's a bit of a blunder when it comes to hardware (is this true?). I've also been recommended Python, but I don't know much about this.

Any other ideas?

8  Forum 2005-2010 (read only) / Interfacing / Re: arduino mega + 4 stepper motors on: January 19, 2011, 10:12:21 pm
Here's a very good article on controlling a simple stepper setup, including some great diagrams and explanations (it has a 2nd page as well). Good luck!
9  Forum 2005-2010 (read only) / Interfacing / Re: arduino mega + 4 stepper motors on: January 19, 2011, 02:02:01 pm
I don't think PWM works for steppers. For a unipolar stepper you need to coordinate pulses to power the coils in a certain order. Sending the coordinated pulses faster will increase angular velocity. You can connect each stepper wire to a transistor to increase current handling capacity, and each transistor would be controlled by the microcontroller.
10  Forum 2005-2010 (read only) / Interfacing / Re: Quadcopter real time environment mapping on: December 27, 2010, 11:12:01 pm
OP, your post reminds me of what some folks did using the quadcopter + Microsoft Kinect. Might give you a bit of inspiration?
11  Forum 2005-2010 (read only) / Interfacing / Re: Need advice with MOSFET H-bridge on: December 14, 2010, 05:56:11 pm
Hmm yeah I can see this being a problem in power MOSFETs. I suppose in this case a solution would be to place an NPN transistor before the high side n-channel FETS and ties Vcc to the collector and the input to the FET to the emitter. Then when the NPN is turned on the FET would surely have enough voltage to turn on. Or am I overlooking something important? In any case, hopefully I don't have this problem with logic level n-FETS.
12  Forum 2005-2010 (read only) / Interfacing / Need advice with MOSFET H-bridge on: December 14, 2010, 01:32:37 pm
Hey all. I would like to construct a H-bridge to interface with my Arduino to control a DC motor (not spec'd at this point). I was originally thinking of using 4 n-channel logic level MOSFETs and control the switching directly from the Arduino. Then to ensure that the switches are triggered in the correct order and prevent shoot through, I will utilize some logic (NAND). One wire will control direction, the second wire will control the enable. I will also include flyback diodes for added protection.

Can anyone see any major issues with this design? From what I've seen, H-bridges are typically designed with 2 n-channel and 2 p-channel MOSFETs, which I can understand if one does not use any logic to control the gates, but are there any other advantages to this method over the 4 n-channel method? I'm trying to avoid p-channel logic MOSFETs as they are quite rare, costly and do not have as much power handling compared to their n-channel counterparts.

And yes, I suppose I could use some H-bridge package such as the L298, but I'd prefer this method as I will gain some experience with MOSFETs and I will get higher power handling capability (plus a neat looking circuit in the end). Thanks
13  Forum 2005-2010 (read only) / Interfacing / Re: Normally closed solid state relay (DC output) on: December 10, 2010, 03:57:44 am
Why not use a p-chanel MOSFET? Take a look at this link:

You can replace the MOSFET in the diagram with a much beefier one if desired.
14  Forum 2005-2010 (read only) / Interfacing / Questions on fundamentals of grounding on: November 30, 2010, 01:40:59 pm
Hey all. Just have a few basic grounding questions, would appreciate some clarification. Here's a hypothetical situations. Let's say I would like to use the Arduino connected to my laptop via USB to control a robot. The robot would utilize beefy DC motors which would be powered via an external power supply. The DC motors are switched by an Arduino using a BJT and MOSFET pair (circuit for illustration: Let's also assume the laptop and power supply are connected to the same mains receptacle.

Since the Arduino and external supply are using different grounds, what are the foreseeable issues? Or, are they actually on the same ground, since they are connected to the same mains? Would it be a wise choice to connect the ground of the Arduino to the ground of the power supply to common the two, or is that just a bad idea?

Now what if the Arduino was instead powered off a 9V cell instead of USB and the grounds were not common, any foreseeable issues? I'm curious whether the input of the BJT (where the digital out of the Arduino is fed into) would be 'seeing' a fluctuating voltage (since ground not the same) or if it would be a constant 5V.

15  Forum 2005-2010 (read only) / Interfacing / Re: Connecting USB controller to Ardunio? Possible? on: May 09, 2010, 03:39:11 pm
Thanks for the reply retrolefty. I'm not exactly sure if I'll be using servos, might end up using some hefty DC motors instead (maybe 20V or so, in case I'll need a motor controller, right?).

In theory, could I translate the USB data produced by the USB controller into a serial data, and have the Ardunio read the pulses? What if I fed the usb lead into an Ardunio shield such as this one: or possibly even this this?

On a side related question, if I connect a shield to the Arduino, does the shield occupy the I/O pins on the main board, or are they still available? Sorry, this is a really newbie question I know.

Thanks again, please keep the suggestions coming.
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