Make this so it is constantly on please

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jaygee007

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I have a fan that works off a USB. To switch it on you press the button, and each press makes the fan faster X 3 levels.

The 4 pin connector powers LEDs.

I need the fan to be powered on constantly so I can use a plug socket timer. At the moment, when the timer switches the fan off it doesn't switch on again when the timee switches on because I have to press the power button.

I want to over ride that and if possible keep the option for fan speed as well.

I hope you can help .







Thanks
 
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It's unlikely that this is possible. The circuit is in standby mode at power up and successive pushes of the power button select a different power level. This might be possible but with a fixed speed by using the USB as a simple power source.

Mike.
 
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What does each button do?

It MAY be possible to just connect a small capacitor across whichever one switches it on; eg. a 1uF cap (with a 100 ohm series resistor, so the button contacts are not damaged by shorting that)?

Try holding the button as you turn power on, first. If that causes it to switch on, adding the capacitor should work.

If the button must be pressed after power is on, it gets rather more complex!
 
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I would be happy with it just powering on.

Even if I hold the power button it doesn't start up again.

The lights do.

The buttons are in the image too. I think they are opposite to each other in function.

 
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Pommie said:
It's unlikely that this is possible. The circuit is in standby mode at power up and successive pushes of the power button select a different power level. This might be possible but with a fixed speed by using the USB as a simple power source.

Mike.
Click to expand...
How could I do that please?
 
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The simplest thing I can come up with for a delayed press is a 4017 decade counter/decoder, clocked by a slows oscillator using eg. a section of a 40106 or 4093.

With a power-on reset for the 4017 and the oscillator set for around 1 - 2Hz, it would slowly step through the outputs. Use the last output as a clock inhibit and it would only run once at each power on.

Any of the other 4017 outputs could be used to imitate a switch press with a delay of anything up to several seconds after it was powered up.
 
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You really need a schematic - presumably U5 is a micro-controller that controls everything, and U1 is a switch-mode power supply feeding the fan, and is controlled from the micro.

U1 looks to be a B628, datasheet available here:


With that information you could disconnect (or remove) the micro, and wire U1 to be permanently ON with whatever speed out you wanted.

However, if speed isn't an issue, you could just unplug the fan and supply a voltage directly to it? - presumably between 5V and 12V or so?.
 
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Nigel Goodwin said:
However, if speed isn't an issue, you could just unplug the fan and supply a voltage directly to it? - presumably between 5V and 12V or so?.
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Thanks for the responses everyone. Most of it zipped over my head I'm afraid.

Is there a part I need to buy or should I just buy a new fan?

I did think I could just hotwire it, but that is because I haven't a scooby about this. sorry.
 
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jaygee007 said:
Thanks for the responses everyone. Most of it zipped over my head I'm afraid.

Is there a part I need to buy or should I just buy a new fan?

I did think I could just hotwire it, but that is because I haven't a scooby about this. sorry.
Click to expand...
It's not a trivial issue I'm afraid - but the fan just plugs in with a two pin lead (top of the picture in post #7) unplug that and provide power directly to the fan.
 
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Can you do micro soldering? I might be wrong but I think it can be done.
Bottom right of the picture short Q1, red arrows. Q1 disconnects the fan for off. This will keep the fan running even when the computer thinks it is off. Probably will run slow. Do not know.
Center of picture is the Enable Function. The power supply increases the 5V to 12V and unknown_V to set the speed. When the point "EN" is high the voltage to the fan is 4.5V. Short where red arrow is and the voltage will be larger than 4.5V. (12 or ? voltage)
R4 sets the supply voltage.
 
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