Go Down

Topic: DUE DAC...Safe to test with oscilloscope? (Read 910 times) previous topic - next topic

Mubase

Hi all.
I have just recieved an arduino DUE which I am very excited about. My initial reason for getting it is for synthesis/audio applications.
I haven't touched the DAC yet as I have heard some baaad things about what can happen to it if you connect speakers or amps straight.
Could someone please help me with the best approach to using the DAC0 and DAC1 without blowing it out?
I have seen some reference circuits using an LM386... Are these definitely safe?
Could I use an op-amp circuit such as a TL072 summing amp?
And also, if I wanted to do a simple test running a loop through the DAC to create a triangle wave for testing purposes like this:
Code: [Select]
void setup()
{
analogWriteResolution(12); // 12-bit!
}
void loop()
{
for(int x=0; x<4096; x++)
{
analogWrite(DAC0, x); // use DAC1 for ... DAC1
}
for(int x=4095; x>=0; --x)
{
analogWrite(DAC0, x);
}
}


Could I then connect DAC0 and GND straight to an oscilloscope probe with no fear of retribution??

Any help greatlt appreciated,
Thanks,
STeve (Mubase).

Smooberry dooberry.
Smooberry Dooberry.

Kibabalu

#1
Oct 01, 2013, 06:42 pm Last Edit: Oct 01, 2013, 06:47 pm by Kibabalu Reason: 1
Inputs of oscilloscopes are high resistive, so it will strain the DAC output with just a low load current. Or with other words: You are save!

Gericom

I have had a 75 ohm input connected to the dac output, and it still works. (and an oscilloscope too)
Subscribe my youtube channel: http://www.youtube.com/user/MKDS3

Mubase

Thanks Kibabalu. 8)
Works like a charm. Tested with code for triangle wave and sawtooth.
So do you know what size resistor I would need as a limiting resistor or a link to a safe Amplifier circuit so I can use it for sound??


Smooberry Dooberry.

Kibabalu

#4
Oct 02, 2013, 06:43 am Last Edit: Oct 02, 2013, 06:45 am by Kibabalu Reason: 1
I wouldn't strain the DAC output direktly with a speaker. A 'resistor solution', whatever it means, will not work. It would change the impedance and also influence the bandwidth. Maybe this would save your DAC output, but it will cause at least a poor sound quality and a very very low audibility. What you need is a cassical output stage resp. a power amplifier.  







Mubase

Hi. I've had success connecting the DAC to my mixing desk via a 4.7K ohm resistor with no bad effects.... The output level through the desk (Mackie 12 track) was OK! Im still going to work out an amp for it though...
Smooberry Dooberry.

Go Up