Question about connecting 12 V fan to a digital set top box

[learntofly]

Hello Guys nice to meet you all,

Sorry for asking this really silly question but here goes.

I want to modify my digital set top box by adding a 12v fan to cool the thing. I know i need to tap +12v from somewhere out of the PSU (I have a very basic diagram that should help me locate that).. my question is where does the other lead go.. Does the whole thing share a common ground i.e. everything connect to the one -ve point... can i just connect the negative wire to the case or do I need to find a specific point.

Also not directly related but if someone was to connect up to a +12v and a -12v would that give 24v or does the -12v just denote that it s the other contact for the +12v Thanks

Hope someone can help?

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Regards,

 

[fiquran]

Re: Dumb Newbie Q

hi,

you need to connect one lead to +12V, and the other lead to the common ground of PSU. Just make sure that you do not connect +12V to the ground directly, otherwise the PSU will blow or will just don't work if you are lucky.

You can connect the -12V across a load and the other end to +12V to obtain 24V. Again, make sure that +12V can give enough current. You can get 24V as long as your ground is with reference to -12V.

regards.

 

[learntofly]

Re: Dumb Newbie Q

Thank you for you help on this. It clears this up now. Cheers,

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Regards

 

[rock_win]

Dumb Newbie Q

dude, i would recommend you to connect leads by first checking the V by a DMM this way you wont short it and will be able to detect the common groun and your desired V point.

And there is POTENTIAL DIFFERENCE of 24V between -12 and +12 volt, so in lehman terms -12V is the other equivalent side of +12V for electrons