external oscillation

[lerameur]

Hello,

I would like to know if it possible to create 20KhZ external frequency with Pic chips, lets say the pic16f88. I did not find anything on google on such a thing.

thank you

ken

[sayzer]

If what you want is to generate 20Khz frequency using 16F88, then sure you can do it by using PWM feature of this PIC.

For 20Khz at 4Mhz, using 1:1 prescaler, PR2 should be 49.
At 20Mhz, 1:1, PR=249.



mister_e, pls correct me if I am wrong

[mister_e]

Yup PWM is the way to go. You can use the PBP HPWM or setting the PIC register as Sayzer said.

mister_e, pls correct me if I am wrong

I got the same results

[lerameur]

I got it going with a 4Mhz oscillator. Here is the program.
I wanetd to use the 20Mhz oscillator. and it do not work. I change the 4 to a 20 in the program and changes the crystal and the capacitor to 22pF and it is not oscillating, anybody knows why. is there a command I nee to do ?


Define LOADER_USED 1
DEFINE OSC 4 'Using 4MHz oscillator
TRISB = 0

loop: FREQOUT PORTB.1,10000,20000 ' Turn on PORTB for 1- sec at20Khz
Pause 100 ' Delay for .5 seconds

Goto loop ' Go back to loop and blink LED forever

[lerameur]

ok added this line :

@ DEVICE HS_OSC

and now it works

[lerameur]

I am trying ot get a sin wave at the output. From the manuals of picbasic pro, they say to add a low pass filter, I did this, it dos remove the extra noise, but it does not make it a sinwave. Anybody know how to make it a sin wave ?

ken

[sayzer]

Did you check this post?

http://www.picbasic.co.uk/forum/showthread.php?t=718



-------------

[mister_e]

If it's for a single frequency with a 50% duty cycle you could still use a pair of integrator made with Op-Amp.

[lerameur]

I need 6 frequencies.
maybe using an analog circuit using amplifiers to make the oscillation and the pic to control + / - a few kilohertz to get lets say between 20 to 30 khz ??
The goal of this is to create an ultrasonic bird repeller, maybe the square waves (although noisy) can scare them off.

k

[sayzer]

... maybe the square waves (although noisy) can scare them off.
k

Make sure it won't attract the big insects if not small birds!

[Archangel]

Hi lerameur,
I need one of those too, to repel pidgeons, and neighbors with BIG STEREOS!
About 300 watts ought to do it! Someone on eBay is already selling PICs programmed to do this and he sells tranducers too!
Good luck with the birds, let us know how it works.
Joe

[mister_e]

Some DDS synth may do the job.

some DACs to control some VCOs too.

Tons of different way. A single PIC.. maybe good for low frequency.

Do you have all frequency values? It could be possible with some effort...

EDIT: you said 6 frequency... All together or what?

Be carefull some birds are much intelligent than others...
<img src="http://www.picbasic.co.uk/forum/attachment.php?attachmentid=1119&stc=1&d=116054050 2">

[lerameur]

well I thought this thing could be battery operated, at 300watt forget that..

here is the code I would like to use:
Also, one freqnecy the output looks good, but more then one the frequency varies from 11k to 31khz and very unstable.

@ DEVICE HS_OSC
TRISB = 0

loop: FREQOUT PORTB.1,10000,20000
' Pause 100 ' Delay for .5 seconds

FREQOUT PORTB.1,10000,26000 ' Turn on PORTB for 1- sec at 26Khz
Pause 100 ' Delay for .5 seconds

FREQOUT PORTB.1,10000,21000 ' Turn on PORTB for 1- sec at 21Khz
Pause 100 ' Delay for .5 seconds

FREQOUT PORTB.1,10000,27000
Pause 100

FREQOUT PORTB.1,10000,22000
Pause 100

FREQOUT PORTB.1,10000,28000
Pause 100

FREQOUT PORTB.1,10000,23000
Pause 100

FREQOUT PORTB.1,10000,29000
Pause 100

Goto loop ' Go back to loop

[Acetronics2]

A look here ???

http://shop.elv.de/output/controller...&detail2=10617

...

no comment !!!

[mister_e]

Depending your osc frequency (wich you should define at the top of your code) this shoud produce the freq sweep from 11 to 41KHz

Freq var Byte
Duration var Word

Start:
    For Freq=45 to 16 step -1
        For duration = 0 to 10000
            High PORTB.1
            PAUSEUS Freq
            LOW PORTB.1
            PAUSEUS Freq
           NEXT
         NEXT
    GOTO Start

[lerameur]

hello Steve,

tu dois parler francais ?
J,ai regardé ton site l'autre jour
moi je suis de ste-julie.
le monde est petit

ken

[mister_e]

Effectivement le monde est TRES petit. Ici on a donc
1. Ste-Julie
1. Saint-Hubert
1. Saint-Amable

Pas de quoi faire un gros G.T. encore mais bon