i need a switch that automatically turns on a 220 volt when

hi
i strand in a situation
a computer turns on automatically and i need to run an 220 volt fan when its turns on
fan can not run constantly
i want to know if anyone knows a circuit that switch fan on when computer turns on an switch off when computer shut down
gracias

Hi,

If your computer has USB port you can do it.

Connect one end to computer and other end to a transistor(BC547/548) via resistor (1Kohms) to control a relay, which in turn connected to the FAN

So it will work in the same way explained by you

Re: i need a switch that automatically turns on a 220 volt w

This is what suresh meant :

Hi eXnol,

he needs 230v fan, you can use the relay switch NO and Common as fan switch, but the above circuit wont work correctly because the new boards will have usb supply when the board is in off state, instead of usb you can use 5v supply of the computer connector.

Re: i need a switch that automatically turns on a 220 volt w

I also forgot to connect the freewheeling diode.

Hmm. I think there will be USB supply only when the board is 'sleep'ing not while its off.

So here it is again.

Or you can connect the power LEDs supply through a 1K to the base of a BC547 as the first circuit and then use it to drive the relay given in the second circuit.

The diode can be 1N4007, cap can be 100uF/25V

Re: i need a switch that automatically turns on a 220 volt w

Hi,

First I thank eXnol for picturising my description.

When you switch on the system then the USB ports will also get supply.
I dont think there will be any problems

rajudp said:

Hi eXnol,

he needs 230v fan, you can use the relay switch NO and Common as fan switch, but the above circuit wont work correctly because the new boards will have usb supply when the board is in off state, instead of usb you can use 5v supply of the computer connector.

Click to expand...

My second circuit it uses the CD power connector.

BTW I have not yet found a board that supplies USB power while switched OFF. (Also my second circuit does not use USB power for that matter)

Re: i need a switch that automatically turns on a 220 volt w

Dear, All PC power supplies, when plugged in and supplied with power, produce a +5 volt standby (2 A Max) even with the PC shut down.

If you need +5 Volts with the PC turned off then a usb connector tapped into that source shall provide you power with the PC off.

If you want to start something as soon as the pc is started then use the Power Good / Ok signal (from PC TO ATX Supply) which needs to be buffered using the USB by eXnol above.

You can find out the details by googling "ATX Power Supply Connector / Pinouts.

here is a link **broken link removed**

Maybe I can do an Instructable Article on that one

Re: i need a switch that automatically turns on a 220 volt w

Yes, there is a 5 volt available, but it cannot be tapped from any USB port. It is for the MB. You cannot get it from a USB port when the system is OFF.

And POWER OK is always present, whenever the PC has input power. It DOES NOT go off when you shutdown the PC. Only on removal of AC would it go down.

It is not advisable to use this Power OK line for any other purpose. This is because this line, ifnot active high will keep the processor in Reset state. Only a high signal on this line will allow the processor to come out of reset. If you use this line for an external use and by any chance it gets shorted, your computer will be reset.

Since the signal is generated by the PS for use by the MPU, the PWR_OK (gray) wire should not be grounded, attached to any of the other output lines or tied to a resistor. It is not required for the PS to function -- its sole purpose is to allow the motherboard to initiate the boot process and to continue to function in the absence of unstable or improper power levels.

Click to expand...

- http://web2.murraystate.edu/andy.batts/ps/POWER_OK.HTM

The best bet is to use the CD power connector as I mentioned. It can provide good power output, has stable 12V supply and does not interfere directly with Processor.

depending on the fan, it's power supply etc, it seems that one possiblity - and i know it's not a project build, just a product that you buy, is one of those 4-way power extension leads, with one master socket (that you plug your pc into) which turns the others on and off in sync.

If the master socket draws current then the other sockets are turned on. If it doesn't, they're turned off.

It's designed for turning power off to peripherals either with a computer, or a hi-fi amp etc.