Wireless power on / reset button

11 posts
by shadowofdarkness » Fri Jan 11, 2013 10:09 pm
I have a idea for my pi that I have previously done on a original X-Box and need a little tech advice from people that are more technically inclined then my ability to just follow good instructions.

Here is the original X-Box tutorial I followed (I even plan on extracting the hardware from the X-Box since I don't use it anymore.

Here is a reset/power on button tutorial for the pi itself
http://raspi.tv/2012/making-a-reset-swi ... spberry-pi

A unrelated tutorial but used for the gpio info so I know where to get 3.3v

So my guess is that I know that the power line goes to the gpio pin specified as 3.3v
But I am not as sure on the others should ground go to the gpio ground pin or is one of the two reset holes a ground. making one wire go to one and the other to the other. If so which would be which since I could not find a more technical explanation of how they work then just short them together to use.
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by Peter247 » Fri Jan 11, 2013 11:56 pm
Not totally sure if I have you right .
If you are asking what should you do with the two reset pins t .

Just short them out !!

Without looking and a big guess here .
One pin will be the reset pin with a resistor pull high most likely and the other pin connected to ground , so will reset when shorted .... or the other way around.
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by shadowofdarkness » Sat Jan 12, 2013 12:15 am
I think you are missing the point of making the button wireless. I know just shorting those together works, but I want to use a wireless doorbell from across the room to do it. I need to know how to connect the doorbells receiver into the pi.

This is so my bedrooms pi running XBMC can be started without me getting out of bed.
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by Demonic69 » Sat Jan 12, 2013 11:35 am
I'd recommend using a transistor with the collector to one of the reset pins, emitter to the other, with base connected to the doorbell. That way you're not going to put any errant voltage into the Pi, just using the transistor as a switch. Very cool idea though, pretty cheap too.

Another option would be some kind of infrared device that could learn a code and activate a transistor or relay. An MSP430 would work brilliantly and they're stupidly cheap, would just require a bit of code and a couple of components

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by shadowofdarkness » Sun Jan 13, 2013 6:19 am
Thanks for the info, I will look into the transistor. Hopefully I can figure it out since I really don't know this stuff.
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by Demonic69 » Sun Jan 13, 2013 7:05 am
I'm happy to help if I can, I'm better with the electronics than the coding side.
If you can get hold of one the tip120 is a fairly forgiving transistor.
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by shadowofdarkness » Sun Jan 13, 2013 11:26 am
OK I should be able to get the tip120 in a couple days since I found a local place that carries them using Google.

I have the exact doorbell from the X-box tutorial and here is what I am assuming will be the connections based on your info. Feel free to correct any problems considering I literally had to Google what a Transistor is.

doorbell 3.3v connects to GPIO 3.3v pin
doorbell ground connects to GPIO ground pin
doorbell negative speaker line connects to tip120 base pin (hopefully negative because I had cut off the positive like suggested in the tutorial and I am not good enough to reconnect a line)
tip120 collector and emitter pins to separate Pi reset pins (I hope it does not matter which one goes were or that someone who knows better will clarify for me)

Do I need anything like Resistors in any of the lines? When Googling what a Transistor was lot of the diagrams for different uses them.
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by Demonic69 » Sun Jan 13, 2013 11:51 am
Ah, the base needs a positive voltage, there are ways around that but they can be fiddly.
Just checked mine and the square pin hole is 3.3v, the other is gnd. Giving the gnd 3.3v or shorting the 3.3 to gnd both cause a reset of the Pi, not sure which id the safest though. If you connect the black wire of the doorbell to the 3.3v reset pin it may pull it low and cause the reset, should be safe enough as you're only grounding it briefly.
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by Demonic69 » Sun Jan 13, 2013 11:52 am
Also, google "transistor as a switch", that will give you some more usable results.
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by shadowofdarkness » Sun Jan 13, 2013 12:32 pm
Wow thanks for your help, I may of been rash but I using you info about the reset pins I did a test and it seems to work perfect. I can power on after a halt and if needed do a hard reset.

I just connected
doorbell 3.3v to GPIO 3.3v
doorbell ground to GPIO ground
doorbell negative speaker to square reset pin

nothing else the circle reset pin is not used.

Using your info from the pins and this section of the X-box tutorial let me feel safe enough to try this.
Normally, when you press the power button on your XBox, all that is happening is that a signal is being grounded, thereby telling the XBox to turn on or off. So by connecting the - speaker lead to the GND side of the power button, we're essentially giving the XBox an alternate, hands-free GND source.

I will make a Youtube video to show this working as soon as I get time.
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by shadowofdarkness » Sun Jan 20, 2013 3:49 am
I gave up on the Youtube idea because i couldn't get good lighting to make it look decent. But after a week and I have had no problems with it. Other then it increasing the times I lay in bed watching TV since I don't have to get up to turn it on.
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