Hey, I need some expertises, for my current case mod Tri-Box. I am going to have an external box which will sit on my desk with a dvd drive, fan controller and switches. I want to be able to go to lans or etc, with out the external box but when I unconnected the box I want the fans which are normally controlled by the fan controller to be on full power if the "DVD box" is not connected. How would I go about doing that??? Thanks
You could get a big multipin plug & socket for the dvd power & fan wiring to connect to, that way there is just two plugs, the sata & the multi pin. There are different ways to do what you want, you could use the easier option of a mechanical rotary switch, to decide wether the fans are on full power or being run from the fan controller in the dvd box, or you could hook up an automatic setup where unplugging the multi-pin would trigger the fans on full power. This auto setup is more complicated and would probably mean hooking up a few transistors, but definitely do-able.
You could have a few of those rotary switches for your fans and have a cord you used for power and data to the DVD drive. The socket that is attached to the case that goes to your box have a switch near it for your FULL speed.
Hey would you be able to draw a (very rough) digram as I am only able to work out how to use transistors if I have a variable resistor
Yeah, i know, it's the most precise drawing you've ever seen in your life, and you're wondering what expensive piece of cutting edge software was used to create it. Lemme know if you need stuff explained. It should work as long as you are controlling the power to the lights and fans and whatever via gnd, as the diagram indicates, but.... i'm not sure if the transistors will need a little protection, like diodes and/or resistors... but i think it may all be fine. No guarantees as i haven't made this circuit before, if anyone has any cc dont be shy! As for which model of transistors to use, they just need to be able to handle the load placed on them, such as the fan or lights or whatever.
Best bet and easiest would be to use small relays. On the plug that joins up to your "box" you have a jumper that shorts out a pair of wires that provide power to the relays. The relays are wired so that when powered (box plugged in) the fan positive wires go to their respective fan controllers. When the box is unplugged, the relays drop out, and supply raw 12 volts to the fans. I can draw you a diagram if you would like.
I was thinking about doing that but got told by an electriction that is not the best method ie why I asked I do believe that STSP relays would work
it will work fine in this case, low current STSP relays will work perfectly, and also a fail safe, if something goes wrong, the relays drop, and supply full voltage to the fans. You could probably do it with transistors, or more easily, mosfets, but would be a much more complicated circuit.
The problem with doing this with discrete components is that you arent switching power to a device, you are switching a varying signal to a device, which can cause all kinds of fun with voltages that go too low or high. You could use mosfets, with a common "control" line that can go high or low, and using p-channel and n-channel to switch the wanted signal to the fans/lights.
You said relay so I thought about this. When the relay is not energized the fans have the full 12v. when you put your plug in. The relay is now energized and disconnects from the 12v. This will let you use your fan controller in the box.
You are wasting a relay point there. Hook the fan up to the switching contact, put one contact to 12 volt, put the other contact to the fan controller.
Relay's are simpler to wire up, but i hate the sound of those old mechanical things. Transistors would work fine, as you'd be running lights and fans on plenty of volts for the transistors to run, even pwm can work fine, but relays are quick and easy. A solid state relay would be nice, that way you get the simplicity with the electronic benefit and no noise or mechanical wear, at a little more cost. The one benefit of mechanical relay is the fail safe feature though, not that the transistors would be likely to fail anywhere near as much as a relay. If you use two contacts of the relay in parrallel, you increase the life of the contacts in the relay, and have redundancy.
