[finleyville]

So I found this part in Mouser that I really want to use here.

As you can see the only specs that are available anywhere are:
125VAC/33k Ohm

I understand that it is rated for AC power. Can I use it in the META42 design? The LED is integrated into the part and does not have its own leads. I guess I would have to jumper the LED and R led pads since it seems to have its own 33k resistor? Or does that 33k rating relate to something else? I called Mouser and neither could they answer my questions nor have a data sheet on the part. Your help is much appreciated.

 

[tangent]

That page links to a "spec sheet". If I'm reading it correctly, the switch's internal LED runs directly off of the power running through the switch. Since it has an internal resistor, you can leave RLED unpopulated.

 

[andrzejpw]

nice! I think I might use that. . .

 

[finleyville]

Thanks Tangent.

How I missed that data sheet I'll never know. So even though the sheet only lists 125VAC, I guess I can use it in a DC operation anyway.

 

[tangent]

Andrzej -- don't go shopping just yet. Let's let Finleyville get the part in and try it out first. I may not be reading that datasheet right.

Finleyville -- the reason it gives an AC spec is probably just because it will tolerate 125VAC. Since AC tolerance is harder, due to higher peaks (125VAC is actually 177V peak-to-peak!), that's the conservative spec to give. If I'm right that the LED is powered by the voltage going through the switch, you could still use this switch for AC -- the LED just woudn't light.

Again, I could be wrong -- perhaps you'll find that you need a separate connection from the switch to the LED position on the board. in any case, I _am_ sure you won't need the RLED resistor -- the spec sheet clearly shows an inline resistor.

 

[finleyville]

ok...
So I received the switch from Mouser today and decided I would hook it up to a 9V battery. Even though the spec sheet doesn't show it, there are 3 terminals to the switch labeled 1, 2, and 3. It looks like the 3 post is labeled the +. I tried many different combinations of posts to poles on the battery and couldn't get the built in LED to light. Looking at the spec sheet, it appears that I would use poles 1 and 3. I'm kinda stumped at this point. I am assuming that the 3 poles relate to a +, -, and ground source for an AC supply. Is this correct? I wanted to test this part before hooking it up to my META42 when I do build it.

 

[eric343]

Probably, the LED needs more than it can get with 33K of resistance in series with 9V.

 

[tangent]

Weird.

To make the LED light, you probably need to connect 2 or 1 to the negative terminal of the battery, and 3 to the positive terminal. If the internal resistor is indeed 33K, Eric's right about the voltage issue -- with 9V, you only get a small fraction of a milliamp through the LED, and you need at least 1mA to get an LED to give a reasonable brightness.

But here's the thing: now that I know what the terminals do, I don't think you can make it work with the META42 -- at least, not if you want the LED to light. If terminal 3 is for V+, then terminal 2 (or 1) is for V-. That leaves terminal 1 (or 2) for the other contact for the power switch -- which means that you would need to place this switch on the V- side of the power supply! In the META42, the power switch is on the V+ side -- it's an arbitrary difference -- we just chose one way, and the makers of this switch chose the other.

I hope I'm wrong about this -- can anyone else see a way to make this part work in the circuit? I'm at a loss...