Remote USB/Audio/switch panel

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Blagard

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I am rearranging my gear and decided to stick the PC case out of the way, I rarely use the DVD drive but it is accessable if I need to.

So I have set up a panel with a couple of USB ports, Mic and Headphone Sockets. All good so far as these are simple extension leads. What I fancy doing next is adding a remote power switch and power on LED.

I believe it is just a momentary push to make switch for power, so I can wire one in parallel, I'm just checking if this is correct.

The LED is an unknown to me and while I could do likewise, wire another in parallel, I am not sure about this at all for a number of reasons. Would the additional load on that circuit be so minor that it would not matter? I have not looked it up yet but what value are the power LED's anyway?. Next, from my schooldays (over 40 years back) if I recall correctly, the resistance the LED's have on the circuit is going to change with two in parallel so will I have to add a resistor in series when the remote LED is connected, or will this not really be necessary?
 
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OwainDIYer said:
why not disconnect the existing case LED, then you won't have two in parallel
Click to expand...

It's a vaid statement but I want to see the PC in normal operating mode. The LED on the PC is a positive indication it is on when I am not looking at the remote panel. - So I will not put a LED in the panel if it means compromising the PC itself.
 
Blagard said:
I believe it is just a momentary push to make switch for power, so I can wire one in parallel, I'm just checking if this is correct.
Click to expand...

Yep, that's no problem at all.

The LED is an unknown to me and while I could do likewise, wire another in parallel, I am not sure about this at all for a number of reasons. Would the additional load on that circuit be so minor that it would not matter? I have not looked it up yet but what value are the power LED's anyway?. Next, from my schooldays (over 40 years back) if I recall correctly, the resistance the LED's have on the circuit is going to change with two in parallel so will I have to add a resistor in series when the remote LED is connected, or will this not really be necessary?
Click to expand...

The LED should be a pretty normal one, but I'm not actually sure of the existing circuit. I can check on a couple of spare/scrap boards and see what's going on..

You could just run one off the USB ports easily enough, though. It's not like 10mA will cause problems.
 
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Monkeh said:
You could just run one off the USB ports easily enough, though. It's not like 10mA will cause problems.
Click to expand...

I think there may be enough power available to the USB circuit to keep the LED on even when the PC is "off". I know a fair few deivces I have still draw power when the PC is off as they have different LED's that illuminate in the off condition. (These devices do not have seperate power supplies)

I have not tried but it may work with the LED's in series. The problem is I know next to nothing about electronics, so I have virtually no idea about anything that has an impact on circuit component values. - I am aware that sometimes impact can be negligable which I am hoping is the case situation here.
 
Blagard said:
Monkeh said:
You could just run one off the USB ports easily enough, though. It's not like 10mA will cause problems.
Click to expand...

I think there may be enough power available to the USB circuit to keep the LED on even when the PC is "off". I know a fair few deivces I have still draw power when the PC is off as they have different LED's that illuminate in the off condition. (These devices do not have seperate power supplies)
Click to expand...

Hmpf, so it powers USB off the +5VSB rail. I hate it when boards do that.

I have not tried but it may work with the LED's in series. The problem is I know next to nothing about electronics, so I have virtually no idea about anything that has an impact on circuit component values. - I am aware that sometimes impact can be negligable which I am hoping is the case situation here.
Click to expand...

Putting them in series may well not work at all. Either way, two LEDs is likely to end up quite dim.

Could run +12V out and use that though.
 
I think I have the answer!

Just wire a LED to a molex supply (Like a case fan) That should be no problem at all as power is direct from the PSU, re-reading your reply I think that is what you are saying!
 
Blagard said:
Monkeh said:
Don't forget the resistor.
Click to expand...

Good point, fortunately there are plenty of 12V LED's on ebay with either intergal resistor or supplied with resistor for 12V - Saves me having to use a web calculator!

Cheers
Click to expand...

470R to 2k2. Pick any value. You can vary the brightness to suit you if you don't fork over silly money for one with a supplied resistor.

If you want red, green, or yellow/orange, you can HAVE ONE and a range of resistors for the price of a second class stamp..
 
I have actually found an illuminated momentary push to make switch on Maplins site for £2.69. The LED in it (which has seperate terminals) is rated at a forward voltage of 2.2V 25mA so the resistor according the Web calculator will be 470 ohms. Also available from Maplins for 29p. (0.6W and 1% Tolerance)
In the end I could not find what I liked on Ebay, plus Maplins are cheap enough on this (makes a change).

http://www.maplin.co.uk/illuminated-push-to-make-switch-34861
http://led.linear1.org/1led.wiz

I played around with the values on the Web Calculator and if I use 11.75V it came out at 390 ohms likewise for a number of other values.

Maplins are just down the road from where I am so it will be just a drop in visit.

After a bit of reading I found that a genuine 12V LED does not need a seperate resistor. But since most LED's are near 3V they need one to stop it burning out. So really the Ebay 12V ones are probably 3V with a resistor!
 
Blagard said:
The LED in it (which has seperate terminals) is rated at a forward voltage of 2.2V 25mA so the resistor according the Web calculator will be 470 ohms.
Click to expand...

If you want 25mA. You may find it very bright.

Also available form Maplins for 29p. (0.6W and 1% Tolerance)
In the end I could not find what I liked on Ebay, plus Maplins are cheap enough on this (make a change).
Click to expand...

29p for a resistor? That is not cheap...

I played around with the values on the Web Calculator and if I use 11.75V it came out at 390 ohms likewise for a number of other values.
Click to expand...

Well, yes, dropping the voltage would require dropping the resistance to maintain current.

After a bit of reading I found that a genuine 12V LED does not need a seperate resistor. But since most LED's are near 3V they need one to stop it burning out. So really the Ebay must be just that!
Click to expand...

There's no such thing as a 'genuine 12V LED'. That's not how they work. They're diodes, not bulbs.
 
Check out

http://www.maplin.co.uk/5mm-12v-leds-35782

Edit: Oops reading the small print I apreciate the resistor is built in!

As a switch illuminator I am guessing the LED will not be that bright, but to drop the brightness I assume the resister is increased in value. The LED is built into the switch so I don't get a choice on the 25mA

29p for a Resistor LOL yes I know it is expensive as resistors go, but I only want the one, and its less than the cost of a stamp.

Last Edit

Ah! - The penny drops again, by using a 1k ohm resistor it will only be drawing around 10mA. I might get one to compare.
 
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