Hey everybody, I figured it would be a good idea to call upon the gurus for this one. Basically I'm looking to make an infrared proximity switch to power on a build I'm planning. I'm pretty much looking to make something with the same functionality as those no-touch toilet flush sensors that you wave your hand in front of. I've looked around for stock implementations but have been met with a lot of over-engineering and pricing. From seeing what other people have done, I guess it makes sense to simply make one from the individual components. This is where I get a bit stuck. I haven't really done much electronics at all since A-level physics, and even that was basic (not to mention my least favourite bit). So trying to navigate places like Farnell or Digi-key for the right bits is nigh on impossible for me. I've seen a few guides around, but I'm not entirely sure how to implement what they suggest. Most switches they make seem to end up as latching ones, when naturally I want the momentary kind. Also, most seem to deal with capacitive switches rather than infrared. So if anybody could point me in the direction of what parts they would buy, and potentially how I would put them together, I would be eternally grateful.
The simplest solution may be a E18 D50NK infrared proximity switch. Cheap, too. The way it works is like this: there are three wires; the red and green wire connect to the + and - respectively of a 5V power source. This is an important detail as you want this 5V source to be present even when the PC is powered off (else the switch won't work, natch), and conveniently the USB 5V supply is always on, irrespective of the status of the PC itself, as long as its PSU is plugged into the mains. So you basically just connect these wires to the + and - of any motherboard USB header. The yellow wire goes to the + header of the PC power on switch (don't worry about the - header of the PC power on switch, as this is a common GND with the - of the USB power supply). At the back of the sensor is a little rotary button that adjusts detection distance from 3cm up to 50cm. There. Simple, cheap.
And that is exactly the answer and info I was looking for, thanks man! Now I just need to figure out where to put the thing so that it's nice and unobtrusive.
There are inductive proximity switches. They work the same way (wave your hand nearby to trigger) but they are often much smaller, and because they work electro-magnetically need no line of sight and can thus be hidden behind a non-conductive (e.g. plastic) panel.
I thought about it, but I have an issue there, I'm using 20mm granite/basalt which is a little much for a capacitive switch. I can hide the infrared one in the stand or someplace instead.
A word of caution with your plan, double check the current draws of the infrared proximity switch and the available current of your power supply. I assume that you are planning to use either the Power On signal or the Standby Power line to power the proximity switch while the computer is power down and both of these lines have limited power available to them. If you want a smaller switch you could consider something like this. I not sure where you could purchase such a device in Europe. As for the look of your case, with either product you could install it behind and plastic cover that is transparent to infrared and nearly opaque to visible. An excellent source is old television remotes.
The one Nexxo linked to only draws 100mA. The 5VSB rail on most PSUs is good for ~3A. The 5VSB is only used for the USB ports and powering the mobo when turned off, you'll be fine.
What about a light sensor? Or a magnetic window switch, just pass a magnet or piece of metal over it.
