Open Source 3 Channel Frequency Generator

[Yucca]

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.

[Yucca]

I'm housing it in an old computer power supply box.

[Yucca]

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]

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]

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.