Author Topic: Too good to be true? Fake AD9850?  (Read 15687 times)

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Online tom66

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Too good to be true? Fake AD9850?
« on: May 27, 2012, 10:34:53 pm »
I am seeing a lot of these pop up on ebay:

http://www.ebay.co.uk/itm/New-AD9850-DDS-Signal-Generator-Module-0-40MHz-Test-Equipment-/180820399452?pt=UK_BOI_Electrical_Test_Measurement_Equipment_ET&hash=item2a19bc555c#ht_3702wt_1189

£4.82 for a complete board, including crystal and AD9850, and shipping from Hong Kong seems too good to be true - the AD9850 is at minimum $12.14 in 1ku (£7.75).

So, what's the catch... Fake chips, production rejects...?

I was thinking of building a 25 MHz sine generator with one of these modules. One issue seems to be the lack of pin out diagram, although there could be some with the unit.
 

Offline amspire

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Re: Too good to be true? Fake AD9850?
« Reply #1 on: May 27, 2012, 11:22:41 pm »
It can be genuine. Once a company has enough requirements for quantity to negotiate a scheduled delivery from the manufacturer, prices can be very much lower then the prices from the stock of a distributor. Manufacturers love customers who commit to a long term scheduled delivery.

These board could be using up some excess stock of a manufacturer who uses very large number of these chips.

Richard.
 

Offline codeboy2k

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Re: Too good to be true? Fake AD9850?
« Reply #2 on: May 28, 2012, 04:08:39 am »
It can be genuine. Once a company has enough requirements for quantity to negotiate a scheduled delivery from the manufacturer, prices can be very much lower then the prices from the stock of a distributor. Manufacturers love customers who commit to a long term scheduled delivery.

These board could be using up some excess stock of a manufacturer who uses very large number of these chips.

Richard.

could be fake.. could be real.. that's the risk. But at £4.82 and free delivery, it's not a big risk.
The crappy printing and bad logo is a red flag to me. Compare it to this one from itead studio

    http://iteadstudio.com/store/index.php?main_page=product_info&products_id=414] [url]http://iteadstudio.com/store/index.php?main_page=product_info&products_id=414[/url]
 

Offline Mechatrommer

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Re: Too good to be true? Fake AD9850?
« Reply #3 on: May 28, 2012, 05:05:27 am »
i recently got one. but never have time to make it work. i'm planning for standalone FG with this module. i hope i can get around it....
https://www.eevblog.com/forum/general-chat/whats-wrong-with-digikey-ebay-and-the-pricing/
It's extremely difficult to start life.. one features of nature.. physical laws are mathematical theory of great beauty... You may wonder Why? our knowledge shows that nature is so constructed. We simply have to accept it. One could describe the situation by saying that... (Paul Dirac)
 

Offline Jon Chandler

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Re: Too good to be true? Fake AD9850?
« Reply #4 on: May 28, 2012, 05:54:23 am »
I just bought a couple of these and they seem to do the trick.  I've only tested them to 100 kHz because that far exceeds my needs but the output is at the expected frequency and reasonably clean (although additional high frequency filtering my be a good idea).

Controlling the module is simple.  I'm using the serial interface.  Shift out 32 bits for the frequency, 8 bits for phase modulation and control (%00000000 is probably the right answer) and strobe the FQ_UL pin.

I couldn't find a schematic anyplace for these, but ebay seller "nooelec" does have a pinout diagram...and stock in the US/Canada.
 

Offline pickle9000

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Re: Too good to be true? Fake AD9850?
« Reply #5 on: May 28, 2012, 06:40:22 am »
If you look at the original datasheet for the chip I think there is demo board (including pcb pattern). My guess would be that is what this board is.

Some of the Ebay boards have the pinouts on them,

http://www.ebay.ca/itm/AD9850-DDS-Signal-Generator-Module-0-40MHz-Test-Equipment-Sine-Square-Wave-/260967834514?pt=BI_Signal_Sources&hash=item3cc2e52392

In the original they controlled the unit with the printer port from a pc.

...mike
 

Offline casinada

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Re: Too good to be true? Fake AD9850?
« Reply #6 on: May 28, 2012, 07:37:53 am »
I purchased one of those cards (they sell 2 different styles). The one I purchased is similar to the one here:
http://www.ebay.com/itm/AD9850-Module-DDS-Signal-Generator-0-40-MHz-2-Sine-Wave-/200646095475?pt=LH_DefaultDomain_0&hash=item2eb7707273
Then I purchased the Parallel card with the buffers:
http://www.ebay.com/itm/New-DDS-Signal-Controller-module-Board-For-AD9850-AD9851-PC-Connecter-Control-/170799180501?pt=LH_DefaultDomain_0&hash=item27c46caad5
Lastly, I tried to use the chinese software but couldn't make it work so I searched on the web and found:
http://www.njqrp.org/dds/waystouse.html
Just make sure you study all the pinouts and make the appropriate connections.
The potentiometer allows you to adjust the duty cycle of the square wave signal output.
The software from Robert Hillard will allow you to change frequencies and even create sweeps.
I hope this helps a little
 :)
 

Offline Neganur

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Re: Too good to be true? Fake AD9850?
« Reply #7 on: May 28, 2012, 03:46:17 pm »
The crappy printing and bad logo is a red flag to me.

I bought a couple of AD9850 from Digi-key a while back, the print looks exactly the same.
 


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