Setting up your own project constraints

Status
Not open for further replies.

Lord_Nikon

New Member
Hello world,

I'm about to start designing my own signal generator for test purposes. I like to work with audio circuits. So it's intended use is for testing audio filters and the like. Anyway, I've set up a few project constraints for myself to follow. I just wanted yall's input. Is there anything I should add to the list of constraints that would make this a better project? A lot of these are arbitrary and off the top of my head. Plus it's a personal project soo... I'm not too picky as long as the job gets done. I just want to make sure that I design a legit piece of equipment.

Here are my constraints:

-Must produce 3 basic wave forms (1 output with a 3-way select)
-Sinewave
-Square wave
-Triangle wave
-Must have variable frequency within audio range (20Hz - 20kHz)
-Must be able to run off a generic Wallwort for power
-Must have amplitude variation from 1V pk-pk up to 24V pk-pk

If you were building a signal generator what specifications would you add?
 
20 kHz is too low. Go fro at least 50 kHz, preferably 100 kHz. I have professional audio equipment rated 0-100 kHz and my power amp is intentionally rolled off at 40 kHz. The unrolled off -3db freq of that power amp is insanely nuts: 800 kHz.

Low distortion.

If your designing filters, then sweepable, possibly with a marker.
 
What you really are looking for is a function generator. These things are so cheap to buy these days from Ebay, you would save money just buying one.
**broken link removed**
 
Mikebits said:
What you really are looking for is a function generator. These things are so cheap to buy these days from Ebay, you would save money just buying one.
**broken link removed**
Click to expand...

Thanks for the suggestion! I will probably end up buying one, one day. But the purpose of my project is to learn while doing. Thanks tho.
 

Consider having defined output impedances, 600, 150, 75 Ohm etc.

JimB
 
JimB said:
Consider having defined output impedances, 600, 150, 75 Ohm etc.

JimB
Click to expand...


Thanks! all great suggestions. 24V was just a random number. No real rhyme or reason. Just wanted a good range.
What would you base your output impedance on? If I'm designing for audio circuit testing is there a standard value that is used?
 
Lord_Nikon said:
What would you base your output impedance on? If I'm designing for audio circuit testing is there a standard value that is used?
Click to expand...
600 Ohm is in my experience the most common interface impedance for audio circuits and audio frequency test equipment.
I have also some audio test equipment which has the option of switching to 150 or 75 Ohm impedance.

JimB
 
Be aware that a function generator may not generate a very low distortion sinewave if you are interested in doing distortion tests.
 
No need to buy anything.

Your PC can generate 0 to >270 kHz with software. ( enable Tone and Log display) then draw wave or select any waveform. select max playing f and max terms. Java based arbitrary waveform generator , or arbitrary spectrum with draw of std. wave form
https://www.falstad.com/fourier/ Each button selects a wave or processes existing wave ( e.g. High pass , rectify etc.

Then Audacity has Sweep Generator and Mic input record. or Speaker and Aux in., with Analyze Fourier spectrum, etc. use it as a sig gen, scope and spectrum analyzer/
 
Last edited:
You do not want a measurement of the harmonics (distortion) when you test the rolloff of an audio filter. Some function generators make a funny looking sinewave full of harmonics. The ebay function generator does not spec its amount of distortion or its level variation so maybe ebay does not want you to know how bad they are.
You also want the output level to stay the same when it is set at different frequencies.
 
For 15 bucks, I would not expect much, but for someone just starting out in electronics, I am sure it would be adequate. I think for someone just learning, they would not have the knowledge nor the equipment to discern the shortcomings of the instrument anyways. As their knowledge progresses, then a larger investment would be justified.
 
You can also use a CD4046 PLL which has a VCO that spans up to 2MHz or more at 15Vdc with by R or C selection.
using counters to scale many decades with precision.

Or you can make your own sine gen
Or a FM sweep gen

Or just a simple Triangle, Square wave gen.


adjust cap for 20Hz ~20kHz
 

Attachments

  • upload_2015-9-7_16-15-40.png
    83.9 KB · Views: 148
YOu can even use an MP3 swept freq. sine wave with >70dB SNR from your speaker or Aux out and Audacity to capture the response.
 
Status
Not open for further replies.

Similar threads

T
  • Question
4029 and 4511, 2 digit up down counter
Replies
1
Views
337
sarahMCML
S
S
  • Question
Help onStar Wars Prop Project how to use 12 and 24 illuminated switches with 3 PP3 9v batteries without the batteries burning up
2
Replies
23
Views
4K
Pommie
P
E
  • Question
Help with my project please
Replies
13
Views
3K
danadak
S
  • Solved
Help with bus dash project
Replies
3
Views
1K
Stefan22
S
W
  • Question
PSU choice for Micro project
Replies
5
Views
1K
Pommie
P
Menu
Log in
Register
Cookies are required to use this site. You must accept them to continue using the site. Learn more…