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Topic: Amplifying the output of a ISD1820 (Read 2665 times) previous topic - next topic

elac

#15
Sep 05, 2013, 01:41 am Last Edit: Sep 05, 2013, 04:44 am by elac Reason: 1
Hey Dustin,
Glad you got it to work.

To have it be louder try building this LM386 based amp, and power it between 9v and 12v instead of 5v.
http://www.instructables.com/id/LM386-Audio-Amplifier/

Make sure you have a speaker that can handle the output of the amp.

The output of the ISD1820 is pretty decent on its own, the LM386 being powered at 5v really cant amplify the 3.3v or 5v signal from the ISD1820 much more.
Running the amp linked above at 9v or 12v will give you more amplification.
For even more power you could feed the 5v LM386 module you have into a larger amp, using the LM386 module as a pre-amp.
It's all about the skills

TwoChain

Hi Elac,

I finally got around to trying what you suggested, and it worked great! I finally have my ISD1820 screaming through my speaker. The final result was actually even louder than I had anticipated, and I am thrilled with the result. Thanks again for your extremely thorough replies to all of my questions. This problem has been bothering me for months, and it is very satisfying to finally have it working.

Thank you!

Dustin


elac

Your welcome Dustin.
What's your project? If you don't mind telling.
It's all about the skills

TwoChain

Hi Elac,

After all your help, I think you're going to be disappointed with my project...

Basically, I am using an ATTiny85 (programmed using my Arduino) to control both my ISD1820 (connected to my LM386) and a modified single to triple wall socket adapter. I cut open the adapter, and soldered in a 5 V relay so that I can control it using my ATTiny85. I also have a photoresistor monitoring whether the lights are turned on or off.

What is the point of all this you ask? Well... it is really just to be annoying. When the lights get turned off (light level is determined by the photoresistor and a poteniometer I have installed to allow the 'trigger level' to be adjusted), the ATTiny starts counting down (I have another poteniometer that controls the time delay). After a preset time, the ISD1820 starts screaming through the LM386, while a lamp (plugged in to the wall socket adapter) starts flashing on and off. It is all constructed, and works beautifully. The plan is to set this up in my friend's/family's bedrooms to have it go off in the middle of the night when they are fast asleep.

What do you think, sound like a good plan?

Dustin

TomGeorge

Hi,  a gain of 200!!!. you are asking too much, try a gain of 20.
If the output of the recorder is producing speaker level audio, you do not need a gain of 200. This will put LM386 possibly into self oscillation.
Definitely run the LM386 from 12V, just amplifying with a 5V is of no gain. The output would cutoff with very little input from your recorder.
So try 20 or lower gain.
Tom.... :)
Everything runs on smoke, let the smoke out, it stops running......VK3DMK

TwoChain

Hi Tom,

With a gain of 200 I am getting excellent sound. Why do you suggest a gain of 20? Actually, when I was reading the data sheet, I couldn't figure out why you would want a gain of 20 vs. 200. Isn't a gain of 200 always going to be louder than 20? How would a gain of 200 put the LM386 into self oscillation?

Thanks,

Dustin

elac

That sounds like a good prank, should cause a bit of excitement.  ]:D

If the gains to high the amp feedbacks to it self creating oscillation.
200 gain is good for a very weak signal.
If you turn the gain up of your module then no sound will come out, or just noise.
You adjusted the pot on the module to find the right gain (sweetspot) so you could get a sound coming out.
Did you try the building amp I linked to?
It has a good sound.
It's all about the skills

TwoChain

Hi Elac,

Sorry, I didn't see your last message. I did try the circuit you suggested, and that was the only way I got this to work. Both circuits are not powered by the same source, but I have connected the grounds. I have used a 5 V regulator to power the ISD1820, but I am running ~ 12 V to the LM386. This is working very well for me at the moment.

I do have another question for anyone who is familiar with the LM386 chip. I am now comfortable in making a small amp for my mp3 player, but I would like to make a stereo configuration using two LM386 chips. I was wondering how I could control the volume from both LM368 chips using only 1 potentiometer. Using the circuit posted by Elac, it would appear to me that if I prepared a stereo configuration, I would need two potentiometers which would independently control the volume of either speaker. I would prefer the volume from both speakers to rise and fall with a single potentiometer. Does anyone know how to do this?

Thanks,

Dustin

elac

You can use a dual taper potentiometer like this one.
It's all about the skills

TwoChain

Thanks again Elac, you always seem to have the answer!

Dustin

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