Adjusting infraout/irout freqency

[Pauldesign]

Hi

I'm having problem establishing infrared coms between a 40x1 Tx and a 18X Rx.

I've done the following:
- Used wired link and it works just fine.
- Keep them in rectilinear sight and in close proximity and in a dark corner but not still working.
- I've checked the IR led using a digital camera and it's flickering.
- Scoped and FFT the IR Tx pin and is centered at 42 KHz instead of 38KHz.

My approach now is to:

- But first will calibrating the center frequency (with the setfreq command) close to 38KHz helps as i'm not very comfortable playing with the internal clock.
Does anyone knows of what the 38KHz Tx carrier freq bandwidth has to be, to create COMs with the 38 KHz receiver? Any previous success using this setfreq approach with IR?
- Use a 555 timer circuit and troubleshoot it with but i'm too lazy to built one :rolleyes

Thnx

 

[SAborn]

From the data sheets i read and my own playing with IR between 30 and 40Khz should be in the range of Ir module operation, but closer to the 38khz is optium.
I found outside of 40khz no signal reception.

 

[rolfi@tisco.no]

What IR detector are you using? If using the LED020 from TechEd (TSOP1838 from VISHAY), the center freq is 38kHz with a -3dB bandwith of 5,5 kHz. Which means that your 42kHz is a little too high. However, held close, it should still work, though with a mere 50% sensivity. But a slight pwm-command ajustment is a good idea.

There are, however, a few more things to be aware of.. I qoute from the datasheet:

The data signal should fullfill the following condition:
• Carrier frequency should be close to center frequency
of the bandpass (e.g. 38kHz).
• Burst length should be 6 cycles/burst or longer.
• After each burst a gap time of at least 9 cycles is
neccessary.
• The data format should not make a continuous
signal transmission. There must be a Signal Gap Time
(longer than 15ms) at least each 90ms

I have used the chip successfully with an 8M based IR source, giving 1.5millisec bursts, and 3 millisec pauses btw bursts. The frequency was 38,3 kHz (pwmout 2,26,52).

 

[hippy]

Details of what you are actually using, IR LED and IR Receiver, will help.

You can put an IR LED on PWMOUT and tweak that or use CLAIBFREQ to get an exact frequency you want which may help in testing. Turn the PWMOUT on and off and check what is seen by the IR Receiver.

 

[Pauldesign]

Thanks for the replies and troubleshooting with pwm commands and adjusting the center frequency to 38 KHz should do the trick but more advice are still welcome and by the way all the parts that i'm using were bought from Tech Supplies.

 

[hippy]

To help people help you it helps to say exactly what you have as they may not be familiar with all the parts Tech Supplies stock - I'm guessing you're using the LED021 or LED023 IR LED plus LED020 IR Receiver (TSOP); is that correct ?

 

[Pauldesign]

Sorry for that Hippy and your guest is right.

I'm using LED021 IR LED and LED020 TSOP IR receiver.

The info supplied so far will suffice for now, i'll experiment and i'll feedback if successful or not.

And for interest sake what is wrong with Tech Supplies web link. (www.techsupplies.co.uk). It's doing this cycle game sort of thing.

 

[hippy]

I'm not seeing any problems with www.techsupplies.co.uk - what behaviour are you seeing ?

 

[Tooms]

Maybe there is a issue with the hosting/dns...

www.picaxeforum.com does not redirect to www.picaxeforum.co.uk as it dit some days ago, not www.picaxeforum.com just gives a 404 error.

 

[Pauldesign]

Hi Hippy

Attached is the problem i'm experiencing both with Mozilla Firefox and Internet web browsers.
When i browse the link www.techsupplies.co.uk, it took to the top screen shot and when i click on it, it took me to the bottom screen shot and when i click to enter store, it took back again to the previous page (the top screen shot).

Clicking on the same link in your reply, does the same scenario.

 

[MartinM57]

The 81.134.... IP adress based site is obviously deprecated now - and www.techsupplies.co.uk works fine for me. But me and Hippy are both in the UK, so maybe the inter-continental wires are a bit crossed at the moment...

 

[hippy]

You seem to be accessing the old site and the old site home page. Not sure why this is happening as the DNS routing details should have propagated globally by now.

Pressing F5 in your browser should flush your cache, and you can also try going to www.techsupplies.co.uk?xyzzy which should also force that.

If that doesn't work try powering off all PC's on the network, all NAS's, hubs, switches, routers and modems. Then power them back on, modem first, PC's and NAS's last.

 

[Pauldesign]

Thanks for the replies and www.techsupplies.co.uk?xyzzy did the trick (takes me to techsupplies store and works fine) but the normal link still doesn't work.

Will power cycle my network tonight and see if problem persist.

Rgds

 

[hippy]

That's good news as it means DNS resolving for www.techsupplies.co.uk is working correctly.

Any 'old pages hanging around' will be somewhere between the internet backbone, your ISP and your PC so hopefully a power-cycle will fix things. If not there's probably not a lot we can do from this end.