I don't have a clue how they sell so cheap but the ones I've bought=20
(including some that I suspect were mispriced at =A32 each delivered from=20
China for the full module) have all worked perfectly.

They may be out of spec chips as has been previously mentioned but for your=
=20
frequency range they should be fine.

I always treat any items bought from the cheaper Chinese "outlets" as=20
disposable toys rather than a long term investment but occasionally you get=
=20
stuff that is properly designed and works well.

Dom

-----Original Message-----=20
From: Neil
Sent: Tuesday, September 16, 2014 11:08 PM
To: piclist@mit.edu
Subject: Re: [EE] Digitally-controlled oscillator

Argh!  Looks awesome, but how do they manage to make these and ship at
these low prices, when the Digikey 1K+ pricing is at $16 for the chip
alone?  Unless these are knock-off chips, I can't understand it.

Cheers,
-Neil.



On 9/16/2014 4:44 PM, Dom S wrote:
> Neil - have a look at the Chinese AD9850 boards on eBay - around a fiver
> delivered and range from 0.something to lots with plenty of resolution an=
d
> accuracy.
>
> Sine wave output with a comparator onboard for square wave. Not a perfect
> design but adequate for the majority of messing about. Can be accesses by
> serial or parallel loading depending on how quickly you want to change th=
e
> frequency.
>
> Bang in the right number for the frequency you're after and you're there.
> I've been quite impressed with the unit I've been playing with.
>
> Dom
>
> -----Original Message-----
> From: Neil
> Sent: Tuesday, September 16, 2014 8:45 PM
> To: Microcontroller discussion list - Public.
> Subject: [EE] Digitally-controlled oscillator
>
> Hi all,
>
> I need to build a small test device that can generate, among other
> things, pulses of specific frequencies.  And I'd like to control this
> digitally (from a central PIC).  Specs would be basic 0-5V pulses, freq
> from about 1Hz to 500Hz (higher is fine as I can divide with some
> gates), and resolution of about 1Hz across the full range.  1% accuracy
> should be fine.  And I need to be able to change frequencies very
> quickly (say at least 20 times a second).
>
> Any recommendations on chips that can do this easily?  Yes I can use a
> PIC for this, but I just need a few of these and would rather just get
> something off the shelf.
>
> So far I've found the DS1077, but at a quick glance, I have to give it a
> divisor rather than a frequency and in the low range of divisors it
> seems I may not get good resolution.  IE: changing divisor from 2 to 3
> would mean a 50% change in frequency.
>
> Cheers,
> -Neil.
>

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