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1  Using Arduino / Project Guidance / Re: Indoor positioning... agian on: September 18, 2013, 01:47:17 pm
Are the people allowed to be forced to carry a device to identify them?

The reason I ask is while it may be unreliable to count the entrance and exits, maybe if you do something like an RF scanner at the doorways with unique rfid tags on each person.  That way when a person passes through the gate, then you know, theoretically, where they are.  Though you have to make the assumption the room/rooms were empty.
Note, my knowledge of RFID is mostly academic and possibly been corrupted by science fiction, so I am not 100% confident in this solution and have no clue where to begin.
Yes, you can force people to wear a tag. 

Your solution is doable but passive RFID has a bit too short of a range for it to work like this - or it would require for a person to actually "scan" the tag.

Otherwise, I think the feasible options have already been covered in this thread and the other threads you have created previously for the same question.
The reason why I made this topic again is because there were a few advances in RF communication during that time. Both Bluetooth LE and NFC have become available for a reasonable price. And both of them could be used for this purpose (Bluetooth LE probably more than NFC). I am just interested if anyone actually did any experiments with these technologies for this purpose.
2  Using Arduino / Project Guidance / Re: Indoor positioning... agian on: September 18, 2013, 07:19:50 am
Is it one room in isolation, or (seems more likely) detecting this for multiple adjacent rooms? Any RF based solution is likely to be problematic if you're trying to cover multiple rooms, since signals won't go through walls when you want them to but definitely will when you don't.
It's for multiple adjacent rooms. Well for the moment I just want one room. I need to know when a person enters/leaves this room. So I don't need range to cover the whole house, but I need to limit it to one room only. Or at least accurately distinguish between a person that's in the room and a person that isn't.
3  Using Arduino / Project Guidance / Re: Indoor positioning... agian on: September 17, 2013, 07:55:32 pm
If it's just for home automation, do you really need to know anything other than whether the room is empty?
You don't really. But even figuring that out is hard. PIR sensors are useless from my experience because they assume that somebody is moving and you can't have an immediate feedback when somebody leaves the room. You also have a lot of blind spots with just one sensor in one room. I've tried counting the number of people that enter and leave the room but even that is unreliable.

And I would love to actually identify who is in the room.

The below seems to indicate that signal strength may not a reliable indicator of distance. If signal strength were a good indicator of distance, you would see it being a lot.
I don't really get how this is connected to my problem. This is collecting signal data from wifi devices (or only access points - I am not sure) around the city. And that really doesn't have much to do with localization of one or multiple sources of RF transmission.
4  Using Arduino / Project Guidance / Indoor positioning... agian on: September 17, 2013, 02:23:09 pm
I'm here again with the same question as always. Is there a way to correctly get the number of people (and identification of them) in a room? I don't need a 10cm accuracy but it needs to detect when somebody enters a room or exits.

Technology of course did advance a bit in the last few years and I've read a lot about Bluetooth LE. Here is actually a design for a small bluetooth LE beacon:
The real question is ... can this (combined with a Bluetooth reciever) actually be used to detect when someone is in the room or not?

And the other option that I've found is Active RFID. A dual reciever module like this:

I know that RSSI can't really be used for indoor positioning-distance calculation if you have a single reciever. But could this module work? You get an RSSI value from each reciever and in theory you should be able to get the distance. Of course I have no idea if this could work in a real world. These things have a range of 8m so in theory you wouldn't even need RSSI because a person would probably drop out of range when leaving the room (maybe it's worth mentioning that I live in an older house with brick walls and I would be using this to control my home automation system).
5  Community / Exhibition / Gallery / Re: XBMC TableTop controller on: September 01, 2013, 07:59:14 am
Here you go:

A little later than promised. I included the Arduino and Java source code, the PCB design and the case design. It's a bit thrown together so there may be some bugs. I am here if you have any questions.
6  Community / Exhibition / Gallery / Re: XBMC TableTop controller on: August 30, 2013, 06:47:46 am
There are really only two main components to this. An arduino PCB and a 24x2 character LCD (this one to be exact: ). I would add a picture of the board but I don't have any - I slightly miscalculated the bottom plate so the only way too keep it on was to glue it in place. But I can give you the PCB design:

This is the smallest that I could go with at home PCB design. Anything else would probably be impossible to make with a toner transfer method. You'll see that the serial port is connected to two pins. That's because I am using an external serial converter. I am using a Nokia DKU-5 cable (they are using a prolific PL2303 controller and they are dirty cheap on ebay, but you can use an external FTDI board or anything that you want). As for wireless - I guess it's possible but it will need some work. I went with wired because I don't want to change/recharge the batteries all the time.

I'll upload the code as soon as I finish adding a GUI for the XBMC connection settings (should be later today).
7  Community / Exhibition / Gallery / XBMC TableTop controller on: August 29, 2013, 12:19:58 pm
Here is one of my latest crazy projects. I am using XBMC as a media center software on my HTPC and I don't like pushing pause to see "where in the show I am". I also don't like the remote as much. So I designed this little thing as a quick project. It's a basic XBMC controller. It has enough buttons to control most often used XBMC features and I also modifying the software so it can interface with my home automation system. It has an LCD that basically shows what is currently playing and it's progress (with a nifty progress bar included).

This was a quick design and everything (circuit, software and the case) was done in three days. So forgive me if the case isn't the best looking one - I think it looks like some sort of weird industrial thing. Part of the case also unstuck from the 3D printer while it was printing so it's a bit bent around the edges.

And when the XBMC is turned on and nothing is playing:

If anyone is interested I can of course post the schematic and the software (it's written in Java so it should work on Linux/Mac/Windows).
8  Community / Exhibition / Gallery / RHome - Android/Arduino home automation system on: August 02, 2013, 03:29:27 pm
A lot of members on this forum probably know that I have a big interest in home automation and I've posted one project before. But I think I have finally made something really worth sharing.

My new system is based on Android (it uses an Android tablet as a main control device) and Arduino (used as a hardware controller). Here is a small presentational video:

And check out more at this projects website:

This projects is open source, so I welcome everyone with too much time on their hands to try it  smiley-cool
Comments, suggestions, ... ?
9  Using Arduino / General Electronics / Re: Powering an arduino and an android tablet on: September 09, 2012, 03:11:07 pm
That schematic was just a quick sketch - so there could be some errors there. And missing capacitors too.

But does it really matter which diode I use? After all, I will be using V-regs to lower the voltage even further. So it shouldn't matter if there is a drop at the diode. At least that is what I think...

I'll try this as soon as possible and we will see if it works
10  Using Arduino / General Electronics / Re: Powering an arduino and an android tablet on: September 09, 2012, 11:10:01 am
Well I am not using the arduino board itself so the onboard regulator isn't really my concern. But either way, I can't use USB power alone because I need higher current to run a few servos.

I have a few LM317 regulators around - would that work? A quick schematic of what I was thinking about:

J1 is a 3.7V output for the tablet
J2 is 5V output for the arduino
If I wired things like this, would the power be only drawn from the DC power source? Or would it draw power from the li-po too?
11  Using Arduino / General Electronics / Re: Powering an arduino and an android tablet on: September 09, 2012, 06:37:01 am
Perhaps relevant for your initial problem: Can you charge the tablet form a power jack? If so you can try to use a combined notebook power supply with additional USB power out. E.g. So you can drive the tablet by power jack and the Arduino via USB - if 5 V/1 A via USB fits your need.
Sadly I can't! It only charges through the USB connector.

If you ran both thru diodes, the source with the higher voltage would reverse bias the lower voltage source's diode and keep that source turned off.
So if I understand this correctly - if I have a 7.4V battery and a 9V power adapter, it would use the 9V power supply by default? But what would happen if I used a combination of a voltage regulator (L7805) and a few diodes to bring the voltage of the power source down. Because I need 5V for the arduino, and I also need 4V for the tablet.
12  Using Arduino / General Electronics / Re: Powering an arduino and an android tablet on: September 07, 2012, 08:08:40 am
Hmmm I just got a new idea. I have a few spare 2 cell lipos for one of my RC planes. I could lower the voltage from that by using a few diodes. Now if I connected a battery and a power supply at the same time which one would power the thing? Would it just draw power from both, or would it only use one of the power sources?
13  Using Arduino / General Electronics / Powering an arduino and an android tablet on: September 04, 2012, 06:24:04 am
I have a small problem with one of my projects. I am using a cheap adroid tablet and arduino for a home automation project. Now there is a problem with how to power this thing. Arduino will be powered with an external wall power supply (and a voltage regulator of course) because I need a higher current than a standard usb can provide. But that isn't really the problem. The problem is in powering the Android tablet. When acting as an USB host, the tablet won't charge from the USB port which really complicates things. So I looked inside and the battery is a standard 1 cell lithium battery connected with 2 wires. So for the test, I desoldered the battery and connected a regulated 5V power source (with three diodes wired in series so the voltage was about 3.9V) - and the thing worked perfectly. Android just showed the battery as full and that was it. Now for the problem - I would like to use the battery as an UPS. I know that I can't just wire the battery and the wall adapter together and hope that it won't blow up. But is there a simple way to isolate the battery from the power supply?
14  Using Arduino / Sensors / Re: Room presence detection with RFID on: February 19, 2012, 01:49:44 pm
I linked to a specific reader in the second link in my post. It says that it can work with 80 tags at once which is more than enough.
15  Using Arduino / Sensors / Room presence detection with RFID on: February 19, 2012, 09:27:51 am
I have been trying to crack the room presence detection (for home automation) problem for more than a year now. And for now the only reasonable (cheap) solution seemed the IR sensor approach - use it to count how many people are in the room. And this usualy works pretty well but it has problems when people are too close together or just stand in front of a sensor.

RFID for the most part was unusable because of the short range (few cm) and a quite expensive hardware. But after some browsing I found the solution - active RFID. And it is cheap too. I found a seller on ebay that sells RFID receivers and transmitter tags for a realy realy low price: . The detection range is about 8m and apparently it works realy well (I found talks about it on some forum). The only problem is that the tags are not that cheap (but not expensive either) and that you have to wear them.

If I wanted to interface a reader like this one:
to the arduino (without computer), what would be a better choice - USB one or an RS232? Or would I need level translators on both of them? In this case it is proabably better to go with USB and use the computer for processing.
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