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Author Topic: Having problems with finding parts for the HDD VU meter.  (Read 7954 times)

REK636

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Re:HDD VU meter PCB.
« Reply #10 on: April 30, 2007, 02:51:26 PM »

I was making a pcb  for the meter and I thought that didn't look right.

This is what I've got.
I think it looks correct in function but looks like a mess. Yellow lines are jumpers. Top + is 5v. Needs a little work still.


Not actual size.
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REK636

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Re: Having problems with finding parts for the HDD VU meter.
« Reply #11 on: May 06, 2007, 12:22:02 AM »

Can some one check me on this. I think it is correct by flowing the lines.

If it will work I will throw a pdf up of it if some wants to give it a go or interested in it.
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trials_modder

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Re: Having problems with finding parts for the HDD VU meter.
« Reply #12 on: May 08, 2007, 11:21:15 AM »

hopefully you've already read over the product data sheets http://www.national.com/pf/LM/LM3914.html there's an example on that page on how to set up a circuit. i don't know why you need the 4n2x opto isolator (input from parallel port?) and something tells me its not as easy as hooking up a series of LEDs to the output of that LM3914 chip. i think the chip's output should go the the base of a TIP 31C/41C. emitter of that goes to ground. collector goes to the LEDs with appropriate resistor, which in turn connects to V+. I also don't know about the purpose of that resistor in parallel with the capacitor, i know the capacitor is there to smooth out the voltage from this presumably unstable power source, but I think you need to put the resistor in series with it to make it effective.
on further look at the LM chip, it seems like it varies how many outputs are turned high by the variance in input voltage. your set up seems to suggest (if the 4n2x is acting as a switch, i'm not sure how it works as an amplifier) that there's just an on and off state.
i'd try prototyping all of this on a breadboard before going out and soldering anything
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trials_modder

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Re: Having problems with finding parts for the HDD VU meter.
« Reply #13 on: May 08, 2007, 11:23:01 AM »

ignore the part about LEDs and using a transistor (unless you're planning on running some higher current drawing components), i got confused with the other post about the other post with the IR array
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