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Author Topic: Open Source 3 Channel Frequency Generator  (Read 38873 times)

Yucca

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Open Source 3 Channel Frequency Generator
« on: September 26, 2008, 11:18:09 PM »
Hello All,

I blew my lab budget this year on a second hand Tektronix 2431L Digital Storage Scope. And I now want/need a signal generator or 3 so I've decided to build my own.

The current secifications for the unit are as follows:

1 channel DC ... 1MHz with variable PWM.
2 channels 10kHz ... 133MHz Square waves using programmable DS1085 oscillators.
Unit actually gates external supply voltages, you feed your lab PSU in and it gets gated.
The unit is all controlled by one knob, it's a jogwheel with push and click.
All controlled by Freeduino board.

This thread will document my progress. I will post photos and descriptions in seperate posts because sometimes I lose what I'm writing when the browser hangs on me and it wastes my time.

Below is a picture of the prototype unit so far.

« Last Edit: December 11, 2008, 03:27:09 AM by Yucca »

Yucca

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Re: Open Source 3 Channel Frequency Generator
« Reply #1 on: September 26, 2008, 11:21:49 PM »
I'm housing it in an old computer power supply box.

Yucca

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Re: Open Source 3 Channel Frequency Generator
« Reply #2 on: September 26, 2008, 11:24:23 PM »
Inside the box so far. Note the mains conditioner and switch is retained from the PSU. I will feed this into an old nokia phone charger, it's a nice little switch mode 5v supply, you can see it at the back right. At the front you can see my 3 board controller stack, microcontroller board at the back, custom board in the middle and LCD board at the front.

Yucca

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Re: Open Source 3 Channel Frequency Generator
« Reply #3 on: September 26, 2008, 11:26:53 PM »
These are four DS105 programmable frequency generator chips that I got for free by requesting a sample from Maxim. They are in SOIC package and I had to solder them onto DIL adapters to make them more manageable. The caps are two stage decoupling across +V and GND.

I will only be using 2 of these in this unit but you could add another board to the controller stack and put another 2 in because I've written the software so that you can change the number of oscillators in the system just by changing one line in the code.

Yucca

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Re: Open Source 3 Channel Frequency Generator
« Reply #4 on: September 26, 2008, 11:31:32 PM »
Heres the middle custom board for holding the oscillators and FET drivers. The piezo gives audio feedback for the GUI and also plays a little tune on bootup. I've got quite a bit more work to do on this board yet.

These controller boards are called "shields" in the world of Arduino/Freeduino. This shield has vero strip like connectors underneath and allows the experimenter to populate with whatever. All shields stack on top of one another and all the microcontroller signal lines are available to every shield. It's a nice flexible system for building things with.

Freeduino boards can be purchased at http://www.nuelectronics.com

The development environment for freeduino is completely free to download, just write you program in C or C++ and then download it to the freeduino board using a normal USB cable on your PC.

Yucca

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Re: Open Source 3 Channel Frequency Generator
« Reply #5 on: September 26, 2008, 11:37:49 PM »
Here's the current bezel artwork. I just print it onto paper and then sandwich it between the case and a piece of acrylic. I have a high res image and when it's finished and stable I'll ZIP it and attach it to this thread.

Note that the bezel says max frequency is 40MHz, because my FET drivers (UCC27322) will only go up that high. But the core of the unit, the programmable oscillators are good for up to 133MHz.

Yucca

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Re: Open Source 3 Channel Frequency Generator
« Reply #6 on: September 26, 2008, 11:47:59 PM »
Will post source code here as a saved txt file soon

Shame this forum hade the CODE tags removed, load of characters got converted into unknowns and even a smilie ;) appeared in it halfway. No wonder people were unable to compile LOL.
« Last Edit: December 12, 2008, 11:30:20 PM by Yucca »

Yucca

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Re: Open Source 3 Channel Frequency Generator
« Reply #7 on: September 27, 2008, 12:01:44 AM »
.
« Last Edit: December 11, 2008, 03:25:18 AM by Yucca »

Yucca

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Re: Open Source 3 Channel Frequency Generator
« Reply #8 on: September 27, 2008, 12:33:06 AM »
I forgot to mention in the first post, If anyone wants to build one of these for their own home lab then I'll be more than happy to help them do it, the total cost of the project is probably going to come in below €100.

The only difficult part to source is the jog wheel, but a jog wheel is not necessary because I've written into the code the ability to use the 5 mini push buttons that are already included on the LCD board from nuelectronics:

http://www.nuelectronics.com/estore/index.php?main_page=product_info&cPath=1&products_id=2

(http://www.nuelectronics.com/estore/images/nustore/lcd_shield.jpg)

Yucca

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Re: Open Source 3 Channel Frequency Generator
« Reply #9 on: September 28, 2008, 12:56:00 PM »
I will also post a youtube video of the user interface in action sometime showing how you can select which decade to adjust and then just sweep through that decade and how you can select which oscillaotr to adjust and adjust PWM.
« Last Edit: December 11, 2008, 03:23:32 AM by Yucca »

Yucca

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Re: Open Source 3 Channel Frequency Generator
« Reply #10 on: September 28, 2008, 02:54:34 PM »
A short youtube video of the unit in action, a bit blurry because it's shot with a USB webcam:

http://www.youtube.com/watch?v=XXJbskeYq-s

z.monkey

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Re: Open Source 3 Channel Frequency Generator
« Reply #11 on: September 28, 2008, 03:04:31 PM »
Howdy Yucca,

Cool!  DIY Freq generator.  My favorite kind of project.  So you get to hardware, software and mechanical.  Are you doing any PCB designs or are you using protoboards?  I build test equipment at work on a as needed basis.  I usually don't put it in a pretty box like you have.  Mine get mounted on a chunk of wood (don't have the budget for pretty boxes). 

Have fun!

Blessed Be...

Yucca

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Re: Open Source 3 Channel Frequency Generator
« Reply #12 on: September 28, 2008, 03:21:48 PM »
Howdy Yucca,

Cool!  DIY Freq generator.  My favorite kind of project.  So you get to hardware, software and mechanical.  Are you doing any PCB designs or are you using protoboards?  I build test equipment at work on a as needed basis.  I usually don't put it in a pretty box like you have.  Mine get mounted on a chunk of wood (don't have the budget for pretty boxes). 

Have fun!

Blessed Be...

Hi Z.Monkey,

Yep, as you well know it is good fun to realise your ideas. Software's my favourite bit of it all, I'm not doing any PCB design on this project, I'll be using proto board and flyleads to the FETs. The pretty box was zero cost, old salvaged computer PSU steel case with acrylic bezel salvaged from a broken shop sign discarded on the street. I don't think it'll look as cool as your infinity coil though ;).


Yucca

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Re: Open Source 3 Channel Frequency Generator
« Reply #13 on: October 03, 2008, 12:04:28 AM »
I've got the FETs working OK now, the FET drivers make it all very easy, you just hook them straight up to the gate. I'll be changing the FETs to P-Channel, which will reduce my max freq. down to ~20MHz, still fast enough for me though.

Cascading will be possible with the unit for gated waveforms.

I will also be adding two BNC ports to the back that will accept analog (0...5v) signals, these will go through optoisolators and into the ADC of the microcontroller. This will enable the unit to perform automatic 3D sweep searches for maximum or minimum with the option of logging the data back to a PC over a USB cable.

Basically the unit will be able to do lots of different jobs just by changing the software, a kind of swiss army knife for the lab, not bad for 50 euros worth of kit.

NOTE:
It's progressing at a slowish rate because I work in the day and spend time with family in the evening.

innovation_station

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Re: Open Source 3 Channel Frequency Generator
« Reply #14 on: October 09, 2008, 04:24:49 PM »
wow!!  awsome job bro 8)

i would just love to get my hands on somthing like that....

might you be intrested in designing some pwm's  i would be intrested in re selling your kits..or compleated units my web page in in the works and can easly be expanded should you be intrested ...

agin great work!!

ist

i would really love a TUBE unit   ;) ;)