FreeTrack Forum

Welcome, you're not connected. ( Log in - Register )

FreeTrack Forum > FreeTrack : English Forum > Support : Tracking System > Led's and webcam to be used

RSS >  Led's and webcam to be used
booze23 #1 31/05/2008 - 17h41

Class : Apprenti
Posts : 6
Registered on : 05/05/2008

Off line

Hi,

I recently bought some SFH 485 Infrared leds...the only issue with them is that they have a view angle of 20 deg per side (not 40 deg per side). Would this be a problem?

Also, I want to buy either a logitech quickcam messenger or a logitech quickcam express. Anyone know if these have caused any particular problems. I already read the characteristics of these cameras on the website, but I want to know if I should be aware of anything else. Thanks.

Booze23
tristan68 #2 01/06/2008 - 00h01

Electronicien en chef
Class : Electronicien en chef
Posts : 651
Registered on : 10/07/2007

Off line

Hello Booze23


Yes , the SFH485 has only a view angle of  20 degrees per side.

This value is a bit narrow for freetrack use.

You'll have to test it.

If you loose tracking when turning your head, then file your leds case flat near the chip using sandpaper.
This will widen the viewing angle of your leds.


cya
Edited by tristan68 on 01/06/2008 at 00h01.
didja #3 01/06/2008 - 01h33

Webmaster (admin)
Class : Webmaster (admin)
Posts : 1043
Registered on : 09/07/2007

Off line Www

Hi Booze !

According to the webcam compatibility list, both Messenger and Express cam would be okay. However, lot of people use the Microsoft VX-1000. Maybe you should think of this one as well... ?

Rémy
Posted Image
Farthen #4 01/06/2008 - 02h24

Class : Apprenti
Posts : 2
Registered on : 01/06/2008

Off line

I also bought those LEDs, my experience is that it doesn't work very well....
If I move the head (rotate/look to the left/right) it will show up as if I was moving my head from the left to the right without rotating. Also the "Rotation" gets stuck and "NAN" appears.... maybe I gotta check the FAQ Answer to this, but I think it's because of the LEDs.

Thank you,
Farthen
didja #5 01/06/2008 - 02h41

Webmaster (admin)
Class : Webmaster (admin)
Posts : 1043
Registered on : 09/07/2007

Off line Www

Hi Farthen ! :)

Yeah, that may be the LEDs... :wacko: Have you try to sand them ?

For the NAN error, you're right, you should have a peak to the FAQ ;) ...

Rémy :)
Posted Image
Farthen #6 01/06/2008 - 07h16

Class : Apprenti
Posts : 2
Registered on : 01/06/2008

Off line

No, I didn't try it yet, wanted to ask first if this was really the LEDs.
Now the first thing what I do is to sand them..... I will post the results later.


EDIT: I sanded them now and it works very good... well... there is a little delay, but I will try to tweak to settings.
I now run at ~25 FPS and Jitter at only 1 or 2...

Webcam used: Logitech QuickCam Express, but a very old one.
IR filter removed and floppy disk magnetic thing on top.



Thank you for every help you gave me ;-)


Farthen
Edited by Farthen on 01/06/2008 at 11h19.
didja #7 01/06/2008 - 13h58

Webmaster (admin)
Class : Webmaster (admin)
Posts : 1043
Registered on : 09/07/2007

Off line Www

Great ! :)

Enjoy it ! ;)

Rémy
Posted Image
booze23 #8 01/06/2008 - 14h37

Class : Apprenti
Posts : 6
Registered on : 05/05/2008

Off line

Hi everyone,

Thanks alot for the good feedback. I actually looked up another forum and decided to buy the Microsoft VX 1000 cam. Plus I bought a usb wire, which I am going to hack. My plan is to use the computer as power supply to the led's, because I don't want to use batteries.

I read in wikipedia that the usb voltage input is 5 V, and the current input is 100 mA. I want to put three sfh 485 leds in series with a resistor. My only concern is that the leds are rated at 1.2 V (forward voltage) and 100 mA (forward current). Might the usb fry the leds if I put everything in series? Or should I also add another resistor in parallel to the leds to divide up the current? Thanks again.

Booze23
tristan68 #9 01/06/2008 - 17h29

Electronicien en chef
Class : Electronicien en chef
Posts : 651
Registered on : 10/07/2007

Off line

Hello Booze23

1)
NEVER use leds without a resistor.

2)
Be careful if you plan to power your setup using USB power. If you do something wrong, you can :
- fry your leds
- damage your motherboard (uh oh)  :blink:

3)
If you really want to power your leds by USB , use a PTC fuse too, to protect your PC.

4)
Don't drive SFH485 at 100mA, they're rated for 75mA max if you solder them on wires.

5)
SFH485 forward voltage is 1.5v, not 1.2v.

6)
the led wizard has a calculation mode for USB setup, just use it and you'll get the correct resistor value.

Cya
booze23 #10 01/06/2008 - 19h36

Class : Apprenti
Posts : 6
Registered on : 05/05/2008

Off line


3)
If you really want to power your leds by USB , use a PTC fuse too, to protect your PC.



Hi Tristan68, could you maybe refer me to a proper PTC fuse? I don't really know what that is...Also, would it be okay to temporarily work with the Usb without the fuse? Thanks.


4)
Don't drive SFH485 at 100mA, they're rated for 75mA max if you solder them on wires.



So if that is the case, should I also add a resistor in parallel to the Leds to divide up the current? I'm not exactly sure how to set up the circuit.

******
Just a little addition to my post here:
I went and bought a USB A-B cable, thinking I could cut off one end and wire the LEDs to it. Here is a link to the cable:

http://www.thesource.ca/estore/Product.aspx?language=en-CA&catalog=Online&category=USB&product=2611235

Could I maybe use this in some way to wire the headset? If not, I think I have a power supply hanging around that I could use.
Edited by booze23 on 01/06/2008 at 20h13.
tristan68 #11 02/06/2008 - 10h59

Electronicien en chef
Class : Electronicien en chef
Posts : 651
Registered on : 10/07/2007

Off line

Hello Booze23



could you maybe refer me to a proper PTC fuse? I don't really know what that is...Also, would it be okay to temporarily work with the Usb without the fuse? Thanks.




If you aren't familar with electronics (and even if you are  :p), you shouldn't power your setup on USB without protecting the setup and your PC with a PTC fuse.


A PTC fuse is a little component acting like a fuse but :
- its much faster than a fuse
- it rearms automatically once the probleme is solved (it doesn't burn).

You should ask for a 100mA PTC fuse at your location. Try to find an electronics shop, they should have or be able to order.






So if that is the case, should I also add a resistor in parallel to the Leds to divide up the current? I'm not exactly sure how to set up the circuit.




NO !

Always put resistors in serial with the leds they're protecting.

It's not easy to calculate the values of a voltage divider based on resistors, with a led in parallel of one resistor.

So please stick to a "standard" schematic.

Use the led wizard, it'll provide the resistor value you need to use.




cya.
booze23 #12 02/06/2008 - 23h05

Class : Apprenti
Posts : 6
Registered on : 05/05/2008

Off line

Hi again,

Okay, I will opt out of using a usb cable for power. Instead, I have an old power adapter for a zip drive that I don't use anymore. The output written on it is 5 V and 1 A.

My question is this:
I want to cut the end of the power cord, and solder the wire tips to the led circuit. My only concern is over-powering the leds. The leds are SFH 485 (1.5 V forward voltage, 100 mA forward current). If I use a single series circuit to connect the leds to the power supply (as suggested by the led wizard), won't they burn? How do I reduce the current to about 50 mA or 70 mA? The led wizard does not have a criterion for power supply current. Is this not important? Also does a zip power adapter count as an unregulated power supply? Thanks for the feedback.

Booze23
tristan68 #13 03/06/2008 - 01h26

Electronicien en chef
Class : Electronicien en chef
Posts : 651
Registered on : 10/07/2007

Off line

Hello Booze23

First , i'm glad you finally choose a power adapter, instead of using USB cable. It's far much safer for your computer  :)

Now about your power adapter (PA) :

It's a 5V 1A model.
That means : It will deliver 5V output voltage , and is able to drive UP TO 1A current.

The power supply will provide as much current as your setup need to, until your reach the power supply max current (well thats not totally true , especially in case of unregulated power supplies, but we can live with it).

Since your power supply outputs 5v, chances are it's a regulated power supply.

About the Leds :

The SFH485 are rated 1.5V 100mA.
That means : you can drive them up to 100mA. In fact thats more 75mA than 100mA.

When driving them with 100mA, they'll show a voltage drop of 1.5V.

If your try to directly connect the leds to the PA, you'll overpower them and fry them (or your PA, whatever fries first).

That's why we need the resistor. It's purpose is to limit the current in the setup.

Just enter the values in the wizard and it'll calculate the resistor value for you.

Power supply : regulated
PS voltage : 5v
Led forward voltage : 1.5v
Led forward current : depends of your needs, but not more than 75mA
Setup type : 3 points cap



The led wizard does not have a criterion for power supply current. Is this not important?



It doesn't because it's usually unnecessary, and would confuse people. As long as your PS is able to deliver more current than your setup needs, its ok (and thats usually the case).


cya

 >  Fast reply

Message

FreeTrack Forum > FreeTrack : English Forum > Support : Tracking System > Led's and webcam to be used

 >  Stats

1 user(s) connected during the last 10 minutes (0 member(s) and 1 guest(s)).