DDS 20 Function Generator Kit

[MeggerMan]

The DDS 20 function generator is available in kit form or assembled from ELV in Germany:
http://shop.elv.de

Kit (without AD811 for sine wave output):  61 EUR
Build (including AD811): 90 EUR

The AD811 op-amp provides a true AC sine wave (+ve and -ve signal). But even without the AD811 you get a full sine wave but it sits above the ground rail (+ve only) and it's amplitude can be controlled by the potentiometer.
Using this signal you can feed to a less expensive external op-amp without voltage follower to give you a variable pulse width output.  This can be used to feed a mosfet driver and mosfet for the ECD/TPU project.

Note:When building the kit I have found an issue with the LCD display not displaying all the segments because of the clamping frame tabs do not contact the clear cover.
You need to screw in the screws very carefully and do not over tighten them, just enough to move the frame to touch the board and no more.
ELV sell spare frames I think for this purpose - people over-tighten the frame screws.
Remember you must set the configuration defaults on it before it will start working, press the "Prog" button for more than 2 seconds and just accept all the defaults. I was scratching my head for about an hour before I realised this.

Note: power on the +12V rail is about 90mA rising to 110mA with the outputs loaded and the freq. at 20Mhz.
Power on the -12V rail is about 15mA rising to 23.7mA at 11MHz(peak load frequency) with the AD811 output loaded with a short or capacitor. With such low power requirements lends itself to a low power inductor based inverter using the TPS6735 plus the following:
C1 44uF, C2 10uF, C3 1uF, C4 ~44uF, C5 22uF, D1 1N5817 (schottky 1A 20V), L1 10uH, L2 22uH
The whole board will be about 17mm x 43mm and plug into the two 100uF capacitors pads on the DDS 20 board, one capacitor is transfered to the new board.
http://focus.ti.com/lit/ds/symlink/tps6735.pdf




I have included the original German manual and my translation.
I recommend you buy the kit as it is so simple to build and because you still need to add a case and PSU anyway.
I will update this message with a more complete manual when I get more time.

[Gregi]

Its really great you posted this, cause I'll probably buy it.
Do I need the AD811 for ECD purposes?
Thanks,
Greg

[giantkiller]

@Meggerman,
I was looking at getting one of these but I remember some noise about the Deutsch site not selling in the U.S. How did you overcome this?
Thanks.
--giantkiller.

[MeggerMan]

I was looking at getting one of these but I remember some noise about the Deutsch site not selling in the U.S. How did you overcome this?

Simply by living in the UK and not the U.S. 

I think its the cost of sending the large glossy catalogue (also in German) with your order that may make it too expensive to cross the pond.
What you need is someone in the UK or EU who will post it on to you.
Regards
Rob

[Gregi]

I received my kit and there is a warning that comes with the manual saying that there is an error in the inscriptions of the board concerning the C24, C27, C34 and C40 capacitors polarity. But as I compare the schematics in the manual and the drawing on the board indicating the polarity, its the same.
So where is the problem? Do I trust the board's and schematics' drawings or do I change polarity as its stated in the warning paper?

Thanks
Greg