Sound on my Teensy 3.x Carrier boards...

[KurtE]

I have been thinking about making a simpler rev for the Teensy LC... But wondering about what I currently do for sound output.

My boards typically have a simple speaker. (http://www.digikey.com/product-search/en/audio-products/buzzers/720967?k=102-1155-ND), which I have a jumper that I optionally connect up to IO pin and use code like tone to make sounds. I like this with my robots as to know state changes and the like.

The buzzer is hooked up like:


Wondering if I rev board, would it make more sense to optionally connect to DAC? Could I then use some of teensy sound library? On setups with Linux boards, I at times generate PCM sounds or use Espeak...

If I do hook up to DAC, should I change the sound circuit?

Thanks
Kurt

 

[KurtE]

For now I will assume a simpler setup (RC) like in: http://www.pjrc.com/teensy/td_pulse.html

 

[robsoles]

option to connect to DAC easily worthwhile; Audio Library makes fine (excellent even, perhaps) use of the DAC as an output.

 

[KurtE]

As I mentioned yesterday (https://forum.pjrc.com/threads/2806...ield-with-color-TFT-display?p=72553#post72553) , I built the first of a smaller shield, for the T3.1/LC that I assembled the first one of yesterday...

With it, I am trying a simpler Speaker hookup as shown in http://www.pjrc.com/teensy/td_pulse.html (330 ohm Resistor and 100uf cap). Luckily I made the hook up to which pin be a jumper. By default I was hoping to try it out with the DAC (so setup, that can just use shunt to connect), but with this hookup, I am not getting really any sound out. If however I jumper it to lets say D6, I do get sound. (Not as much as when I had a transistor circuit, but enough).

Currently using the speaker/buzzer (http://www.digikey.com/product-search/en/audio-products/buzzers/720967?k=102-1155-nd), which I have used on other boards. I can use tone and the like to make notes...

If I wish to maybe use the audio library, suggestions for small onboard speaker and circuit would be appreciated... I really don't need much sound on these boards, mainly used for things like knowing when the voltage is getting too low, or some form of acknowledgment that a new command/mode was accepted...

thanks again
Kurt

 

[robsoles]

I could attempt to parley any amount of stuff I have seen for single supply audio amplification but you and I are both better off derferring to such as https://www.google.com.au/search?q=single+supply+amplifier imho.

If you even have half an inkling of schematics then switch to pictures mode and look at them, look for something you could see yourself willing to deploy and click away for the page the picture comes from - 'middle' clicking on links (in decent browsers) opens the link in a new tab, dunno why I choose now to mention.

I'm fairly sure I could draw a (almost-passing-for-reasonablish) single supply amplifier that might suffice but I sure would make the EE at work look at it properly before posting anywhere anyone but he might see - half the results from Google will be rubbish (or practically advert for spec'd device) but half the remaining results (I) should (hope) range from as good or heaps better than I would draw.

Basis of a good single supply amplifier will be making a virtual ground halfway between 'supply neg' and 'supply pos' with reasonable attempt at stability (pair of [strikethrough]100K[/strikethrough] matching (prefer higher-ish value to decrease supply drain) resistors with a 22uF electro from node/VGND to GND is OK, opamp driven VGND is better if near digital circuitry imho (but gaurd against coupling digital noise to basis of VGND)) and then referencing the actual 'audio signal' to that alone should be great.

If you post back indicating a circuit you are considering deploying to amplify for small speaker I will notice within a reasonable time and if so confident you won't complain after I recommend it I will, otherwise I will make EE look at it and pass you ensuing verdict.

 

[PaulStoffregen]

That circuit appears to be designed to couple digital pulses to the speaker, as pulses.

To use the DAC, you'd want a more sophisticated analog circuit to actually buffer the analog voltage.

 

[KurtE]

Thanks Paul,

As I mentioned in other thread, I am going to see what it sounds like through a simple LM386 circuit since I can breadboard it and Radio shack carries part...