Subject:
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Re: 6.8nF Capacitor
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Newsgroups:
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lugnet.robotics.handyboard
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Date:
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Wed, 12 Jul 2000 14:27:07 GMT
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Original-From:
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John Hatton <john.hatton@uk.!ihatespam!airsysatm.thomson-csf.com>
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Viewed:
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3778 times
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I don't suppose you know what the formula is for calculating the value of the
frequency ?. 1/(R4*C6) possibly ?. This equation gives 38396Hz (38.4KHz) which
means that my 6.6nF caps give 39560Hz (39.6KHz) which is closer to 40KHz than
the 6.8nF value listed. I would appreciate confirmation of this before I decide
which component to use.
Thanks for your help
John Hatton
johnhatton@email.com
JR wrote:
> Greetings:
> The capacitor used on the handy board (c6) and resistor r4 set up an
> oscillator for infrared output frequency. This signal does not have to be
> an exact frequency. IE most infrared demodulators have a center frequency.
> However the demodulator will operate within a range of a couple of kHz. You
> can change the values (of course within reason) of c6 and r4 to yield the
> frequency that you desire.
>
> Issue this command to start the Ir transmitter circuit:
>
> poke(0x1000, 0x40);
>
> this will start the transmission circuit. LED 9 will light.
> use an oscilloscope to measure the signal at pin 2 of U9. This should be a
> square wave of about 40kHz (39,000 Hz to 41,000 Hz will work).
>
> Issue the command from IC:
> poke(0x1000, 0);
>
> This will turn off the transmission circuit and LED9 should go off.
>
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