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PostPosted: 23.11.2002 13:35 
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Junior Modder
Junior Modder

Joined: 01.11.2002 09:18
Posts: 11
Location: Norway
Hey there.

I want to try to connect the switch to the PSU if that is possible.
The AC-DC adaptor I got with the switch delivers (secondary):
7.5V DC, 750mA and 5.63 VA, whatever that means ;p

Anyway.. As I can only get 12, 5 and 7 volts directly from the PSU, I figured I could just hook up a resistor to get 7.5 volts.
I'm not good with electronics, but reading the basic electricity article I figured that I would have to remove 12volts - 7.5volts = 4.5 volts.
Now for the resistance.. R=U/I. R= 4.5V/0.750A = 6 ohms?

Is it even possible to do this mod? To power the switch from the PSU?
And if it is, what am I doing wrong, or how would you go about doing this?

Any answers would be appreciated.

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PostPosted: 23.11.2002 19:26 
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Site Admin
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Joined: 24.01.2002 10:09
Posts: 4683
Location: Finland
That should work. You just have to calculate that power dissipation for that resistor too. P=U*I = 4.5 v * 0.750A = 3.375 W. You have to get resistor with bigger power dissipation value than this.

Because that power need to handle that much power you might want to try if that switch would work with 7 volts. This way you don't need any resistors and this way your case temperature would not rise. Just a thought.


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PostPosted: 31.01.2003 20:52 
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Junior Modder
Junior Modder

Joined: 01.11.2002 09:18
Posts: 11
Location: Norway
Forgot to say thanks...
It's been a long time since I posted this, but I got another question on the subject.

I recently aquired a multimeter, and when I measured the voltage directly from the AC => DC adaptor it gave me around 11-12 volts, instead of 7.5 which is printed as the secondary output on the adaptor itself. This is without connecting the adaptor to anything. I know that I might measure something else once it's connected to something, but my real question is:

Should I try to connect it to the 7V or the 12V from the PSU?

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PostPosted: 05.02.2003 16:43 
*bump*


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PostPosted: 06.02.2003 09:00 
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Super Modder
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Joined: 28.01.2002 10:31
Posts: 941
Location: Tuusula, Finland
Rexxie wrote:
Forgot to say thanks...
It's been a long time since I posted this, but I got another question on the subject.

I recently aquired a multimeter, and when I measured the voltage directly from the AC => DC adaptor it gave me around 11-12 volts, instead of 7.5 which is printed as the secondary output on the adaptor itself. This is without connecting the adaptor to anything. I know that I might measure something else once it's connected to something, but my real question is:

Should I try to connect it to the 7V or the 12V from the PSU?

7V, works...

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PostPosted: 06.02.2003 14:34 
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Junior Modder
Junior Modder

Joined: 01.11.2002 09:18
Posts: 11
Location: Norway
k, I'll try that then :)

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PostPosted: 07.02.2003 18:37 
You shouldn't try that 7V from your PSU. You'll just kill your whole system.


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PostPosted: 07.02.2003 20:52 
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Junior Modder
Junior Modder

Joined: 01.11.2002 09:18
Posts: 11
Location: Norway
Right...
So why will it kill my system, and what should I do then?

I did connect it to 7V from the PSU and the leds lit up. Haven't tried it with traffic yet tho.
Would be nice if japala would answer :|

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PostPosted: 10.02.2003 13:29 
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Super Modder
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Joined: 28.01.2002 10:31
Posts: 941
Location: Tuusula, Finland
Rexxie wrote:
Right...
So why will it kill my system, and what should I do then?

Yeah, why? My Cisco MicroSwitch 10/100 works and I powered it from an ordinary PSU.

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