Need a circuit

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Mike
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Need a circuit

Post by Mike » Wed Aug 13, 2003 5:05 am

I need a circuit that is like an electronic switch. There are 4 inputs, and 1 output. On each input, a positive and a negative wire connects. The same on the output. There will be 4 NO Pushbuttons, to select each input, and send it to the output. I need a led to light up above whichever input is selected, and the button needs to be pressed and can be released, not held down. I guess this, in function, would be like the selector switches on a stereo system. They are pressed once, released, the display changes to the corresponding selection, and the selected input is connected to the output.<p>Thanks, Mike

rosborne
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Re: Need a circuit

Post by rosborne » Wed Aug 13, 2003 6:54 am

My initial response is to suggest a 4:1 differential mux and some logic to drive LED's but I have a feeling your playing with analog signals.
-Rick

russlk
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Re: Need a circuit

Post by russlk » Wed Aug 13, 2003 12:39 pm

Since all 4 negative input wires connect to one output wire, why not connect them all together and only switch the positives? Is there a reason the input A cannot have a common with input B etc.? If the signals are analog, a quad analog switch and quad flip-flop would do the job.

Mike
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Re: Need a circuit

Post by Mike » Wed Aug 13, 2003 7:16 pm

Yes, the grounds of the inputs can be tied together. It is an audio switch, but would like to have the LED effect and avoid mechanical selector switches as found in old car stereos. <p>-Mike

scm6079
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Re: Need a circuit

Post by scm6079 » Thu Aug 14, 2003 12:48 am

How much power are you running through this 'switch'... is it line level? And are the switches SPST momentary, or DPDT momentary? You could always run a relay array with some basic logic to do a 'physical' type switch if it is speaker level power. <p>Also, what did you want to spend on it-- although not the cheapest solution, if the purpose is impressive car audio, you could use a PIC (or basic stamp, etc) to do some logic, or even drive a screen... all depends on the level you are looking for.<p>_Scott

Mike
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Re: Need a circuit

Post by Mike » Thu Aug 14, 2003 7:04 pm

I am running line audio through it, and I forgot to mention that it needs to be stereo. It is for a small home power amplifier. I will have 4 inputs, tape, cd, tuner, and aux/video, and each will have left and right. I have some chips sitting around, and I know that some are logic. The are listed below. I just don't know which ones, if any will work, and how to use them. I do not need any displays, I just want to keep it as simple as possible. I would like indicator LEDS that light up cooresponding to the selected input. <p>Chips I have:
CD4009
4050
74LS138
7495
74LS471
CD4011
4049
74LS42
7417
7609
7497
4449
74LS125
74LS00
7493
74LS139
74LS86
74126
AY-3-8112
TMS-6011
74LS373N<p>I know I have more, but those are the chips I have easy access to righ now. I have no idea what any of them do, though.<p>My switches are Normally Open spst pushbuttons. <p>Thanks, Mike

russlk
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Re: Need a circuit

Post by russlk » Thu Aug 14, 2003 8:23 pm

The CD4011, quad 2-input NAND, will be useful to make set-reset flip-flops. I don't recognize any of the other chips as analog switches, so you will need to buy some CD4066 or similar. You will only want one stero channel on at a time, so turning on one channel should turn off the other 3. I will see if I can come up with a schematic.

rosborne
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Re: Need a circuit

Post by rosborne » Fri Aug 15, 2003 10:25 am

I drew a partial schematic yesterday and here is a url for the picture.
http://makeashorterlink.com/?X5B165A95
I don't get the url and image thing for this list. :-/
I had trouble figuring out how to post the picture. It's incomplete, but I think you'll get the idea. It's also never been simmed so there is probably some bonehead error. I'm somewhat comforted that Russ had the same basic idea.
-Rick

rosborne
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Re: Need a circuit

Post by rosborne » Fri Aug 15, 2003 10:26 am

I drew a partial schematic yesterday and here is a url for the picture.
http://makeashorterlink.com/?X5B165A95
I don't get the url and image thing for this list. :-/
I had trouble figuring out how to post the picture. It's incomplete, but I think you'll get the idea. It's also never been simmed so there is probably some bonehead error. I'm somewhat comforted that Russ had the same basic idea.
-Rick

rosborne
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Re: Need a circuit

Post by rosborne » Fri Aug 15, 2003 10:47 am

I don't know how I double sent that. Sorry.
http://makeashorterlink.com/?T48424A95
is a link to a cheap place to post pics with readable closeups of some of the schematic. Can anyone advise me on how to better post pics like this?
Rick

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Edd
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Re: Need a circuit

Post by Edd » Fri Aug 15, 2003 12:59 pm

Sir Michael:
Looks like another branding iron is in the fire.
Looking thru my circuit archives, see if this one might fulfill your needs, Four AF inputs with the individual center LED’s indicating the switched signal source and its your option if you want to gild the lilly with the audio “VU” chip circuitry add on at the right end.

http://electronicsworld.tripod.com/audioimages/1.html <p>Addenda: Waaatcch out for flying pop-ups, at that site, or U might want to cut and paste that small schem image to Wordperfect/Word wherein you could zoom it up.<p>
73's de Edd
[email protected].........(Interstellar~~~~Warp~~~Speed)
[email protected]........(Firewalled-Spam*Cookies*Crumbs)<p>
;)<p>[ August 15, 2003: Message edited by: Edd Whatley ]</p>

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