Propeller Counters ?

Areal Person

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Hi,
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I’m studying the propeller counters documentation.
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I’m really new to electronics. I’ve managed to build a simple
Colpitts Harmonic Oscillator with a 5MHz crystal on my breadboard
according to spec.
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I plugged it into the FrequencyCounter.spin program on Prop.P7
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It seems to be functioning, but it’s displays a 5 digit number (13000 – 15999) which the spin program sayes is in Hz.
My crystal is 5MHz but 13000 is 0.013Hz· Correct ? not 5000000Hz· (5MHz)
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Anyway, the reading is bouncing from 12000 – 15999
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The sinusoid looks clean on my scopy, but I don’t have a good frequency counter
to double check it with.
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Any advise, why is it only displaying 5 digits ?
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Thanks,
-Areal
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I have a tree growing out of my head, but

what do you expect ? I'm a programmer.

Areal Person

Ok, now as I increase the voltage the value is going up, but it’s taking 6.0 vdc to get it to
5MHz

Wont that kill my propeller ?

Ua... I ran it at 6vdc for about 30-45 seconds before I caught myself [noparse]:([/noparse]

What voltage should I run a 5MHz crystal at ?

-Areal

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I have a tree growing out of my head, but

what do you expect ? I'm a programmer.

Post Edited (Areal Person) : 12/5/2007 4:16:01 AM GMT

Mike Green

You need to post your circuit. It's hard to advise you about voltages or why it might not work properly unless you post a circuit.
Also, have you modified the frequency counter program at all? If so, you'll need to post that as well (as attachments).

Ale

13000 or so would indicate 13 kHz, or 0.013 MHz. With the scope you can tell, looking at the period of the signal the frequency... you know f=1/p... p is the period (in seconds).
A 13 kHz signal has a eriod of ~ 77 us and a 15 kHz signal one of 66

Areal Person

My scope sux [noparse]:([/noparse]


Here's the Colpitts circuit I'm using
http://www.radio-electronics.com/info/circuits/transistor_crystal_oscillator/crystal_oscillator.php

I'm powering the oscillator at 6vdc the output signal is going into P7 of the Propeller which is running at 3.3vdc
However, the Crystal will operate at 3vdc also. (But the output number is droping)

Would the Propeller be syncing 6.0vdc ?

Also, does anyone know of a way that I can use the harmonics·of the fundamental frequency (harmonics being 2, 3, 4, etc. times the fundametal, or 3/2, 5/2, etc. being overtones), using some L and C components to lock the circuit into that frequency.

I need to do that, but I'm a greenhorn.

Just give me the general instructions, I can figure out the details of implementation.

I want to split two harmonic levels out from the fundamental frequency so I can implement FSK
What components would I use to get the harmonic frequencies ?

Can I use the Propeller for this ?

Thx

-Areal


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I have a tree growing out of my head, but

what do you expect ? I'm a programmer.

Ale

You can connect P.7 to a resistive divisor (two equal 10 k resistors for instance).

Sorry for asking, but do you need a sinuoidal wave or square is good enough ?, because the propeller can generate these signals... square I mean.
A maybe more costly but somehow more controllable will be to use a DDS (AD9835 for instance or 9834)... they provide stable sinus outputs... and are not _that expensive_ 5 € each or so.
Are you sure freqcounter.spin can detect so high frequencies ?... I did not look at it...