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Forum Index : Microcontroller and PC projects : Audio from junk
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brucepython Regular Member  Joined: 19/06/2011 Location: AustraliaPosts: 64 |
I hate trailing wires all over the bench so scrounged some bits from the junk box for on-board audio. It need two capacitors, a resistor, an LM386 and a scrap of circuit board. The speaker was chiselled out of an old laptop. Not rocket science. Works. Might be handy if you're desperate. 
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Gizmo Admin Group  Joined: 05/06/2004 Location: AustraliaPosts: 5078 |
Nice Bruce, bit of a squeeze in there isn't it. Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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| brucepython Regular Member Joined: 19/06/2011 Location: AustraliaPosts: 64 |
Yes, Glenn, my eyes certainly appreciated two pairs of specs while nailing it together. BTW... In the circuit diagram the watermark has obscured the resistor value. It's 150R, more or less (or not at all) depending on how many neighbours you want to wake up. |
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donmck Guru  Joined: 09/06/2011 Location: AustraliaPosts: 1313 |
Or read the color code. :-) How many laptops does it take to make a Maximite? It is nice to see the mods already appearing. Some users started off doing this sort of thing with the ASUS EEE-PC 7" units, but it petered out fairly quickly, when newer, more fully featured ASUS EEE-PC netbooks came along. These incorporated most of the mods that users were looking for. I had a herd of about 8 of them at one stage, both 7" and 10". I still use the 10" for traveling and running the business when I am on the road. Cheers Don... https://www.dontronics.com |
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| brucepython Regular Member Joined: 19/06/2011 Location: AustraliaPosts: 64 |
Don, My daughter is about to travel overseas for a year or so and was looking for a very small flaptop. She spotted one that costs exactly the same as a Maximite kit, complete with Windows 7 and every known Microsoft application imaginable. Having grown up with a father who's been a software developer all her life, she decided that wasn't quite a bargain. Nor very likely to be much good. Oh yes, and the price included freight from downtown Guangzhou. THe EEE-PC is looking better every time she thinks about the "bargain" one. |
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| donmck Guru Joined: 09/06/2011 Location: AustraliaPosts: 1313 |
Yes Bruce, I figure the EEE-PC 10" is not a bad way to go. Ebay ones are dirt cheap, and windows CE, yes, you can't do much with them: http://www.dhgate.com/wholesale_Netbook.html?f=bm|16060200%2 0Netbook%20Cheap%20PS%20AW|7628923991|paid_search|adwords|ch eap%20netbook|16060200%20Netbook%20PS%20AW|WX||&gclid=CMvovb 2d-6kCFdANHAodNkemVw I was carrying a larger Vaio 12" when they were bloody expense, but it was a little too heavy, then I got a 7" which suited me for a while, but then I found out that it was really too small, so I got a 10" and found that it was just right. Just like Goldilocks. :-) However now when I use the 10", it is mostly on my visits to children and grand children in Darwin, so I have a spare big LCD up there. An old bugger like me doesn't mind lugging the 10" around, and I can run the business, and get some useful work done as well. Cheers Don... https://www.dontronics.com |
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| brucepython Regular Member Joined: 19/06/2011 Location: AustraliaPosts: 64 |
Thanks Don. I'll pass that info along. And there's nothing quite like having a 24" LCD or two on hand. Don't leave home without one - preferably waiting at the other end of your trip. I shift house twice a year to keep warm and have a pile of basic peripherals at each place that enjoying six months holiday each year. Sure beats squeezing them into the Corolla! |
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| donmck Guru Joined: 09/06/2011 Location: AustraliaPosts: 1313 |
I shift four times, but only for 2 weeks at a time. Be nice to do it on a six months basis. I remember Harold Holt's wife used to do it from Toorak to QLD. Zara? Too long ago to remember. I am wondering how long it will be before places like tech-rentals will hire you an LCD and wireless keyboard-mouse, even if they were available at hotel-motel receptions, as PCs and similar are getting smaller, people are getting larger. Well, I am
BTW In the link I gave in the previous message: Imagine that $68 (including delivery) netbook with a PIC32 and MM-basic on board, plus a 20 pin IDC header out the back? Cheers Don... https://www.dontronics.com |
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| donmck Guru Joined: 09/06/2011 Location: AustraliaPosts: 1313 |
Bruce, a supplementary question, that I hope you can answer. You no doubt know more about LM386s that I do, so to save me chasing it up, I am thinking of adding small audio circuit, to one of the boards I am designing. The idea is to drive a white RCA female socket for standard audio out. This would be the standard input to a TV. This is of course, is to pipe audio and video into the usual yellow and white RCA connectors that most TVs have these days. Would the gain and impedance you have set, match this setup? If you or anyone else can give me the answer, it would be appreciated. Cheers Don... https://www.dontronics.com |
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| aargee Senior Member  Joined: 21/08/2008 Location: AustraliaPosts: 255 |
Don, The LM386 is a very robust and forgiving little amp, You could just modify the resistive divider Geoff has on his board to both drive the LM386 as well as the audio out socket, or even run the two in parallel! On that note... yesterday we were scrapping a few ancient PCs at work and, amongst other things (including a couple of PS-2 keyboards), found that they had neat little powered speakers inside. Attached to the back of the speaker frame was a little amp board with a long multi-wire lead. I'll post some pics up later... - Rob. For crying out loud, all I wanted to do was flash this blasted LED. |
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| donmck Guru Joined: 09/06/2011 Location: AustraliaPosts: 1313 |
Thanks Rob, and resistor value for the application in mind would be adjusted to, uhmmm 149.25 ohms? Only kidding, would you have a value in mind? Cheers Don... https://www.dontronics.com |
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| brucepython Regular Member Joined: 19/06/2011 Location: AustraliaPosts: 64 |
Sorry about the delay replying. A family member needed some TLC after a short time in hospital over the past couple of days. All OK now. That infamous, colourful 150R resistor was no more than a quick'n'dirty fix to reduce the input level and avoid my beloved in the next room having broken sleep. A better way would have been to use the "official" gain control facility, which is a resistor and capacitor in series between pins 1 and 8. That would have required me to stuff more bits on the component side of the board and such contortions were already getting beyond my eyesight's capacity so I cheated. As Aargee says, it's a tough chip and can take evil treatment in its stride. Just as well because when I tested it I had it running (very unsuccessfully) with -5V across its power pins and it took a while to work out what was making the smell. 
So, to answer your question, I suggest taking each input via a capacitor from the existing audio connector and adjust the gains of each amp using the components across pins 1 and 8. The data sheet is available from National Semiconductor's website (http://www.national.com/ds/LM/LM386.pdf) and there are some examples of various gain configurations on page 5. Good luck! |
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| donmck Guru Joined: 09/06/2011 Location: AustraliaPosts: 1313 |
Thanks very much for going to the time and trouble to answer this for me Bruce. Cheers Don... https://www.dontronics.com |
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