please help- output level indicator mod

K

Kerri Ann

Limp Gawd
Joined
Feb 28, 2004
Messages
393
i have an old output level indicator that used to be part of a stereo system... it has 2 input connectors and 2 output- 8 ohms. i get so confused about all this ohm voltage wattage stuff...
i'm trying to hook it up to the hdd led... and im not sure yet what other component, and somehow get output level readings on them.
there are 20 leds for each set, if that helps, and they are 1.5 V red leds.
can anyone help me?
 
I think what you are talking about is called a VU meter. A pick of it would help. Unfortunatly the only real way to get the numbers you need to hook it up to your computer is to hook it up to rather expensive lab equipment. I have done it a couple times with stuff since I'm in college but it may not be that easy if you don't have access to an electronics lab.
 
"pic"

Internet lingo for picture :)

Take a picture of the front and back and post them so people can see what the VU meter looks like. Someone may know what you want.
 
vumetermod1.jpg

vumetermod2.jpg

i already took it apart... :D it's my nature. but this is the whole thing.
 
If you have the pics already, find a good host for a website, usually most isp's include free webspace that you can upload pics to. Once you have them uploaded, click on the IMG button above the text box, input the url *something like: http://www.isp.com/username/pic.jpg* That will insure the pic is shown in the post
 
ummmm... thats what i did. i have sbcyahoo and i used my briefcase... i can see the first link fine, but the second one is dead. let me try to post them on my webpage.
brb,
 
Ask to have this moved to the Electronics forum. The people there know a lot more in terms of electronics.
 
Alright you do have a VU meter there. What you need to do is find the voltage that is needed to drive it. The easiest way to do this if you still have the sterio is with a multimeter.


What you need to do is take the original sterio and hook a multimeter set to read DC voltage accross the lines that were originally attached to the VU meter. Crank the sterio playing static so the bar graph is just barely maxed out and then attach the multimeter. The voltage is probably going to be rather low. You then need to hook the multimeter up to the sterio again and read the current. The multimeter will be hooked up differently for this.

Voltage:

sterio -->multimeter-
^---------------------


Current:

sterio --->multimeter --->VU Meter
^--------------------------------------

Once you have these two measurements you need to find a resistance that will drop the voltage driving your HDD LED to the voltage driving the meter. In the pick you took (on the right side) you will see a round purple thing. That is a capacitor. It will hold a mild charge so the meter will not jump to maxed and drop back to nothing instantly (assuming it is part of the VU Meter).

You can use the same formula for dropping voltage here as for dropping it on an individual LED.

R=V/I

THe resistance you need is the difference in voltage (voltage feeding your HDD LED - Voltage needed to drive the VU Meter) divided by the current needed to run the multimeter. Don't be surprised if this is a large number. On a recent analog (needle) VU meter I got the numbers of

R=(3-.33)/.00027 = 10K ohm Resistor. You shold be able to find the resistor at any radioshack or online electronics store. If you have any more questions let me know. If you don't have the sterio any more you are going to have to find some of the lab equipment I talked about in my last post.
 
thank you so much! i have more questions.. but i think i'd like to research them on my own first... i don't unfortunately have the original stereo, it was a very old montgomery wards stereo, and this was the only piece that didn't make the trip to the trash...
i do have one question.... is there any type of trial and error method that i can use to figure out the voltage? maybe starting at the bottom to minimize the chance of overloading it and ruining it?
if not, ill probably just use this one for its intended uses, except hook it up to my pc's sound system and change the leds to blue...

oh yeah- im not sure if this is of any importance at all- but it does work well when i hook it up to my pc's sound card and speakers.... just thought i'd mention it...
 
You could possibly use a rheostat. Set it very low and slowly adjust the voltage up. But Im not sure how safe that is, might blow it out.
 
Originally posted by Kerri Ann
ummmm... thats what i did. i have sbcyahoo and i used my briefcase... i can see the first link fine, but the second one is dead. let me try to post them on my webpage.
brb,
Click to expand...

PM me and ill give you pic hosting
 
Originally posted by xonik
Ask to have this moved to the Electronics forum. The people there know a lot more in terms of electronics.
Click to expand...

its a CASE MOD, this has been done before, its much better here


yes it can be done, no its not going to be fun if you want to display CPU usage or stats. as in youll have to get a DAC (digital to analog converter) circuit to get it to work, and unless you want to really, really overpay, youll have to do it yourself. its not easy but its not difficult, its just soldering and the like.
 
yeah, iwas kinda thinking about the cpu meter... i might try it out on something else instead. im not sure what yet though.... maybe a temp sensor... ???

as for using a rheostat... can a potentionmeter be used? i was trying to find a rheostat in my junk around here (to use on my case fan), and i think what i ended up finding was a potentionmeter instead.
 
if it works when you hook it up to your computers sound card just take the voltage and current readings from there. If you do decide to test using a potentiometer you need to know the resistance it has. I would start with at least a 15000 ohm pot/rheostat(same basic idea in this case)
 
That board is designed for indicating the power level of speakers; making it work with your soundcard would require a full understanding of how the thing works.

I'd sooner build something from scratch, ala:

http://sound.westhost.com/project60.htm
 
Originally posted by eternalspire
He said he already tryed hooking it up to his sound card and it worked.
Click to expand...
im a She :D
and yes, it does work with my onboard sound...
i will see what i come up with and post back.
thanks everyone so much for all your help.
 
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