Author Topic: The 5MHz $46 DDS sig-gen/counter  (Read 9111 times)

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Offline RCMR

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The 5MHz $46 DDS sig-gen/counter
« on: September 15, 2011, 10:05:47 pm »
After a loooong wait for GLB to ante-up with the missing items in an order I finally received this:

SG1005 5MHz Signal Generator Source Module w/ DDS Function.

I have to say, it seems to work as advertised and will probably be all I need 95% of the time.

If anyone wants a more comprehensive review let me know.

There's little point in doing a tear-down since it comes in a torn-down state -- no case, just the PCBs and wall-wart as pictured on the GLB website.
 

Offline nukie

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Re: The 5MHz $46 DDS sig-gen/counter
« Reply #1 on: September 16, 2011, 12:48:39 am »
I have it for a few months now, looking for a case for it, nice little kit. There are also slower mhz models make sure you get the right one. This design is copied from somewhere just do a search for dds function generator.

My firmware always reset the setting whenever I power up. which is annoying. There are 10 or so space for saving signal output setting but the interface take quite a while to get used to. Dont expect great documentation.
« Last Edit: September 16, 2011, 12:51:42 am by nukie »
 

Offline RCMR

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Re: The 5MHz $46 DDS sig-gen/counter
« Reply #2 on: September 16, 2011, 01:46:30 am »
Yes, I got the 5MHz one.  The documentation was in Chinese but it was easy enough to work out how to drive it.

I will put mine in a case eventually -- when I get a round tuit.
 

Offline saturation

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Re: The 5MHz $46 DDS sig-gen/counter
« Reply #3 on: September 16, 2011, 10:47:37 pm »
I noticed this toy looking FG that has very similar, if not identical functions.  For $25 you get a decent case, some cables, jacks and knobs; save you the work and cost of adding it.

http://www.ebay.com/itm/5MHz-Signal-Generator-Counter-DDS-Function-5V-Power-Kit-/260821733246?pt=AU_B_I_Electrical_Test_Equipment&hash=item3cba2fcf7e

Best Wishes,

 Saturation
 

Offline metalphreak

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Re: The 5MHz $46 DDS sig-gen/counter
« Reply #4 on: September 17, 2011, 12:19:45 am »
I noticed this toy looking FG that has very similar, if not identical functions.  For $25 you get a decent case, some cables, jacks and knobs; save you the work and cost of adding it.

http://www.ebay.com/itm/5MHz-Signal-Generator-Counter-DDS-Function-5V-Power-Kit-/260821733246?pt=AU_B_I_Electrical_Test_Equipment&hash=item3cba2fcf7e



$20AUD.................. +$53 delivery  ::)

Offline Zad

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Re: The 5MHz $46 DDS sig-gen/counter
« Reply #5 on: September 17, 2011, 04:12:52 am »
Or make yourself one of these: http://midnightdesignsolutions.com/dds60/index.html

I suspect the Ebay one has DDS generated by the processor, rather than being true hardware generated DDS.

Offline Lightages

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Re: The 5MHz $46 DDS sig-gen/counter
« Reply #6 on: September 17, 2011, 04:47:21 am »
I noticed this toy looking FG that has very similar, if not identical functions.  For $25 you get a decent case, some cables, jacks and knobs; save you the work and cost of adding it.

I was wondering about this thing too. I have almost pulled the trigger on buying this a number of times to see what it can do.
 

Offline saturation

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Re: The 5MHz $46 DDS sig-gen/counter
« Reply #7 on: September 17, 2011, 12:40:19 pm »
Sorry metal, what I meant is the OP link of $47 and just add $25 you get the same thing fully assembled plus extras.

You can find other vendors that sell the whole thing for the equivalent $US 60-75.

Some sellers flip the price, high ship low item cost, to reduce any potential custom charges to your country, since its based on the 'value' of the item not the shipping.

I noticed this toy looking FG that has very similar, if not identical functions.  For $25 you get a decent case, some cables, jacks and knobs; save you the work and cost of adding it.

http://www.ebay.com/itm/5MHz-Signal-Generator-Counter-DDS-Function-5V-Power-Kit-/260821733246?pt=AU_B_I_Electrical_Test_Equipment&hash=item3cba2fcf7e



$20AUD.................. +$53 delivery  ::)
Best Wishes,

 Saturation
 

Offline PsI-On

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Re: The 5MHz $46 DDS sig-gen/counter
« Reply #8 on: September 17, 2011, 05:05:35 pm »

Some sellers flip the price, high ship low item cost, to reduce any potential custom charges to your country, since its based on the 'value' of the item not the shipping.

Hmm, this is not the case in Ireland, import duty/vat is calculated on the total cost including shipping :(
 

alm

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Re: The 5MHz $46 DDS sig-gen/counter
« Reply #9 on: September 17, 2011, 07:47:15 pm »
It does reduce Ebay fees for the seller though, which is probably their main motivation for doing it.
 

Offline ciccio

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Re: The 5MHz $46 DDS sig-gen/counter
« Reply #10 on: October 02, 2011, 01:25:44 pm »

Some sellers flip the price, high ship low item cost, to reduce any potential custom charges to your country, since its based on the 'value' of the item not the shipping.

At least in Italy, it is not true.
I can confirm what  Psi-On writes.
I believe it's an EU regulation, because I've checked with Italian Customs about duties on Ebay items from China and I was told that Customs duties are based on "delivered value", that means  value (not cost) of item + delivery cost.
In effect, if you buy a 100 Euros multimeter for 25 Euros, Customs will assume that it's value is 100 Euros.
Items with a delivered value less of 30 Euros may be declared as "no value samples" or "gifts", and be exempt from duties.
This led many Chinese seller to declare a 30 Euros value for everything they shipped, resulting in annoying controls at the Customs offices (who are not dumb, in fact), with requests for original invoices, written in ITALIAN or another EU language (that these sellers usually do not provide), time lost in sending documentations and the item held in hostage by the Customs for months..
My wife bought 2 dresses and a pair of shoes from China: the box was marked:
- 1 gift : dress : 10 Euros + 1 gift : dress : 10 Euros + 1 gift : 1 pair of shoes :10 Euros 
but in effect she paid a total of 68 Euros, with free delivery.
We received the box after 19 weeks of faxes and phone calls with the Customs office,  with me editing a fake invoice and paying 15 Euros of duties.
Many Chinese sellers do no ship anymore to Italy (or other European countries, such as Spain).
Regards
« Last Edit: October 02, 2011, 01:39:57 pm by ciccio »
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Offline Bored@Work

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Re: The 5MHz $46 DDS sig-gen/counter
« Reply #11 on: October 02, 2011, 03:33:28 pm »
I can confirm what  Psi-On writes.

So do I. In fact, when I reported it here last time, I got laughed at.

And the other way, free shipping, also doesn't help. My local customs does not believe in "free shipping". So they regularly assume an attempt to cheat.

And when they have reason to suspect a cheat they are legally allowed to estimate the value, i.e. they invent shipping costs which they then add to the value of the goods. They of course take the shipping costs of the really expensive carriers, not the magic discount shipping costs some sellers in China seem to get.

I therefore avoid sellers with "free shipping" because they cost me extra. I tend to use sellers where the cost of the goods and the separate shipping costs look reasonable in relation. Then, when customs stops the delivery, and they almost always do, due to the stupid fake "gift, $10 value" CN22 declaration, I can show reasonable values. They in turn perform a reasonable calculation of the duties due, I pay and be done with it.

Quote
This led many Chinese seller to declare a 30 Euros value for everything they shipped, resulting in annoying controls at the Customs offices (who are not dumb, in fact),

My words exactly.

Quote
with requests for original invoices, written in ITALIAN or another EU language (that these sellers usually do not provide), time lost in sending documentations and the item held in hostage by the Customs for months..

I usually manage to convince customs by showing them a printout of the eBay auction (and they do occasionally check the auction online to make sure I am not showing a fabricated printout), and a printout of the eBay payment page for that auction, with the sum, purchase data, my name and address on it.

What I have learned it that all they want is something reasonable, that doesn't insult their intelligence, which they can legally process, especially so their supervisors wouldn't scold them, and that doesn't take much of their time.

Quote
and the item held in hostage by the Customs for months..

I avoid having stuff hold by customs for month, because they start to charge for storage after a few days already. I often already have my application for release from customs and printouts ready before I get a note from customs.

Quote
Many Chinese sellers do no ship anymore to Italy (or other European countries, such as Spain).

I think this is because people are quick to open up an eBay dispute when they don't get the item, while the item is hold by customs. And then refusing to deal with their local customs, so customs destroys the goods. It is in fact their fault, but they want to get their money back from the eBay seller. Would I be an eBay seller I would also stop selling to those people.
« Last Edit: October 03, 2011, 08:37:49 am by BoredAtWork »
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Offline RCMR

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Re: The 5MHz $46 DDS sig-gen/counter
« Reply #12 on: October 02, 2011, 11:33:35 pm »
I am so glad that this country (New Zealand) allows a tax/duty-free import of up to US$300 or so (including shipping).

The exact amount varies from day to day (because it's based on the landed NZ dollar value) but it means that most things just arrive in my mailbox, unhindered by the attentions of the customs officers.

However, if you're ordering something that would normally attract the attentions of Customs (ie: >NZ$400 worth) then it pays *not* to use any of the major carriers such as FedEx, UPS, DHL etc as they will declare the value to the Customs in order to charge you (the recipient) a handling fee for processing the payment of those taxes and the clearance.   The same goods sent via the postal system (or EMS) almost always escape the attentions of Customs, regardless of their value.

I've seen guys get huge 50cc RC model planes worth $1K+ and which come in a box which is over a meter long and 600mm square delivered via EMS without any attention from NZ Customs.

I pitty our European friends who have to go through all that bureaucracy every time.

However, I envy our Aussie cousins who have a $1,000 tax-free import allowance and who pay a lower rate of tax if it's applicable anyway.
 

Offline nukie

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Re: The 5MHz $46 DDS sig-gen/counter
« Reply #13 on: October 03, 2011, 12:53:06 am »
Back to the topic. This DDS generator does not have hardware DDS, it has a Altera EPM240 and a STM for I/O controls.

There are other DDS gen with true hardware, search for those with Analog chip numbers they are plenty on ebay. Dave already got one if you DIY http://www.alternatezone.com/electronics/dds.htm
 

Offline RCMR

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Re: The 5MHz $46 DDS sig-gen/counter
« Reply #14 on: October 03, 2011, 03:01:46 am »
Despite the lack of true DDS, this little board does all I need right now and had the right price.

I've checked and the frequency output is pretty much spot on and doesn't drift.  I'm using it for testing some rotor-alarms which basically have an upper and lower RPM (frequency) setting.

Sure beats the old 555 and a pot I was using before ;-)
 

alm

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Re: The 5MHz $46 DDS sig-gen/counter
« Reply #15 on: October 03, 2011, 08:55:44 am »
Just because it doesn't have a dedicated DDS IC doesn't mean it can't perform true DDS. This was the only way to do it before the DDS chips appeared. It is surprising that implementing one from scratch is cheaper than an easy-to-use IC, however.
 

Offline Mechatrommer

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Re: The 5MHz $46 DDS sig-gen/counter
« Reply #16 on: October 03, 2011, 10:35:39 am »
maybe we shouldnt call electrical or hydrogen car, a "car". a "car" only has gas in it.
if something can select, how cant it be intelligent? if something is intelligent, how cant it exist?
 

Online Zero999

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Re: The 5MHz $46 DDS sig-gen/counter
« Reply #17 on: October 03, 2011, 09:51:05 pm »
Just because it doesn't have a dedicated DDS IC doesn't mean it can't perform true DDS. This was the only way to do it before the DDS chips appeared. It is surprising that implementing one from scratch is cheaper than an easy-to-use IC, however.
Yes, the old method used clock connected to a counter which was fed to a ROM containing the wave values which were passed into an ADC. Because memory was expensive, often only sin 0 to 90o were stored in the ROM. The counter would then count up and down with another divide by two connected to a programmable analogue inverter to invert the output every 180o.

The gain of the output amplifier was also often digitally controlled so the output could be controlled fairly accurately.

This used to be done with loads of ICs but now it can be done all in one.
 


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