Gimzo 2 custom On/Off button?

Check out this post where I added an external power and reset button: http://www.element14.com/community/community/designcenter/single-board-computers/gizmo2/blog/2015/01/28/gizmo2-adding-external-pwr-and-rst-buttons

Oh wow, so much great tutorials I'm having hard time finding

So you didn't use a resistor?

Is there any requirement for what button can be used. All I know is buttons have a maximum current rating, this shows how little my electronics knowledge is. But it's going to be fun programming the Gizmo after I get this figured out.

PS. Is that a 3d printed enclosure? That's another hobby of mine.

Hello Mark,

the on button (generically any switch of this kind) when it is pressed it put the signal from the I/O to the GND generating the logic signal for the device. So take a look to the next image showing a piece of schematics that is what you need:

The GND signal is in common with the Arduino ground and the GND side of your power button (check on the schematics of the Gizmo2 where it is).

The other side of the button is connected to the collector of the transistor (that is, the pin 1 of the connector JP10 in the schematics above).

The Arduino control pin (one of your choice, no matter if this is PWM or not) is connected to the PB1 signal on the schematics.

When the Arduino pin (PB1) goes low, the JP10 Pin 1 goes low too shortcut to the GND signal, the same what the push button do.

The Arduino setup() you should set is the following:

void setup() {

  pinMode(OUT_FLASH, OUTPUT); // Flash

  // Your initialisation code here

}

Then, create a function to switch the pin in the desired mode (e.g. simulate push button for 4 seconds)

void lightFlash(int duration) {
  // Simulate button press
  digitalWrite(OUT_FLASH, true);
  // Wait the nmber of ms needed with the button pressed
  delay(duration);
  // Release the button
  digitalWrite(OUT_FLASH, false);
}

And call the function where you need only when the arduino starts (maybe as the last instruction in the setup() function.

Enrico

I suggest that you DON'T assume the question answered until you have not solved the problem by yourself or someone has not got you a correct answer.

Enrico

There's a bit of language barrier but you're giving a great illustration and explanation. I hope I understand it all. So the main difference between a relay and the transistor is transistor uses the same Ground as the controlled current?

I just dont get one thing, what about the pico projector button emulation?

As I understood the ground for all has to be the same for some reason, right? Will I need to check the PCB of the pico and maybe post a close up photo so we can guess from where it flows?

I don't really mind using a relay right now as I don't have much time left. You're teaching some interesting stuff which I'll probably need to know in the future, but for now if a relay could work, how about just using that?

Just one thing, the device the switch is on is 12V DC.

Does that matter for relays if the controlled power is AC or DC?

I have a typical 1 channel relay shield right now: http://www.ebay.com/sch/i.html?_odkw=arduino+relay+shield&_osacat=0&_from=R40&_trksid=p2045573.m570.l1313.TR0.TRC0.H0.Xarduino+relay+shield+1.TRS0&_nkw=arduino+relay+shield+1&_sacat=0

However, if you think I better go with the transistor route, I'm for it and thankful either way. I just don't want us to waste our time if the relay solution is simply only less practical way for doing this.

Again, thanks for all this.

As I told you before, the transistor is equivalent to the relay. If you should manage 12 VCC use the realy. If you have no time and you already have the relay shield use the relay for the projector. The function is the same, nothing changes at all. But as you have so few time, why don't try to study two hours what I wrote and the link that we got you? Maybe you get more clear ideas instead of trying to copy and paste and nothing else.

Enrico

I did read the link, I'm trying to understand everything honestly. I posted what I understood above, is it right?

Yes it is correct. As following the schematics and using the relay in the case of the high current (that you already have) I think you don't risk to make damage to the boards. Pay attention to the polarity and make the breadboard circuit then you can try to add the software and test what is working and what is not. If you have a tester, as 4 seconds is already a long time, you can see if the button simulator is pressed simply checking the voltage between the two pins of the signal and GND. When voltage goes to zero, it is sure that the shortcut is done. The same with the relay that you can hear distinct "tick" when the contact is closed.

Let me know your progress. Enrico

Thanks. I was about to test it out and post a response but remembered that Arduino is 5V and I've got a 12V relay *facepalm*. I'll look for a 5v one.

You mean that you have a relay driven by 12V? If so, and you can't use / find the transistor you should find a relay driven at 5V else when you power it for switching nothing happens.

Enrico

Yes, it seems I need a 5v relay shield for Arduino to use a relay.

Arduino+relay is getting complicated option itself.

Maybe it will be easier to jut use the transistor with the arduino after all.

It's just two thing I don't get: how would I find out the ground side of the button of the projector? Voltmeter and checking if it shows positive or negative voltage?

If the projector and arduino have a common ground, isn't it dangerous if one uses more current then the other can handle? (Arduino has 5 buttons connected and controls a servo motor). Or is connecting more stuff to GND not dangerous.

how would I find out the ground side of the button of the projector?

Just check with the voltmeter and see where is the negative it's the GND. On Gizmo2 schematics are distributed for free and are very helpful to find also where ground pins are on the board connectors.

No matter about GND, all ground should be connected. voltage does not interfere at all, if you connect things correctly.

how would I find out the ground side of the button of the projector?

Just check with the voltmeter and see where is the negative it's the GND. On Gizmo2 schematics are distributed for free and are very helpful to find also where ground pins are on the board connectors.

No matter about GND, all ground should be connected. voltage does not interfere at all, if you connect things correctly.

I know about Gizmo, the video projectors ground is not known thats why I asked.

I supposed, so you should check with a voltmeter the negative should be GND

Will do and report back.

Ok.

Oh forgot this. The GND from the Arduino is 5V, from projector its 12V. Is that an issue?

I understand, no offence taken. However, most of this is electronics, not electricity. You now mentioned diodes for return current protection, I didn't know about them. So if GND taking 12V and 5V wasn't a problem for the respective devices that wouldn't be needed, right?

It is the worth to use diodes, in my opinion