timxirish

To explain in brief, I'm wiring some transistors and LEDs in an Xbox 360 wireless controller, and have had multiple ideas tossed at me on how to wire it... And now I want to try and do a hybrid wiring design.

I'm going to be using four 4.5v high intensity white LEDs and one 3.3v (?) RGB cycling LED in this controller, and I only have a few options for powering them.

In an "always on (when device is on)" configuration, I can wire them to a 2.7v power source, which would mean I won't be using a resistor. Of course, that means the LEDs would be kinda dim.. The white ones will be backlighting the ABXY buttons, and the RGB will be backlighting the Xbox 360 guide button dome. I need a transistor for this because the 2.7v is not a switched power source. I'm using an NPN and a 2k OHM resistor between it's base pin and a lower, switched power source on the controller's board. Since the base would be getting low power, electricity would flow free from the collector to the emitter, powering my LEDs and making my 2.7v source "switched".

Now because the LEDs would be dim, I was told it may be better to try wiring to the 5v pin of the Play and Charge connector (ie. LEDs would only be on when P&C cable is connected). This sparked an idea.

I very much still want the LEDs to be lit when not connected to the P&C, no matter how dim they are.. But a 5v source would make the LEDs really shine. I use the P&C cable on occasion, so I thought I could wire it both ways in the same controller, then switch between the power sources with a small SPDT switch.

...But if transistors can technically be "automatic" switches, couldn't I wire it in a way where when the P&C cable is plugged in, the transistors automatically do the switch for me? There's another power source on the P&C cable, and it's 3.3v. I started thinking maybe I could use that source with a PNP transistor to cut the connection of the 2.7v source from way above to form my second "auto switch".

The biggest problem is I'm new to the concept of transistors and do not understand now a PNP transistor would need to be wired to acomplish this (or if it even can! but reading stuff on how these types of transistors work leads me to believe it might be possible?).

If anyone can shed some light on this for me, it would be GREATLY appreciated. All helpful posts will be rewarded.

If you require a few visuals, I'd be happy to provide them.

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keith27

I'm afraid I don't understand. I can help, transistors are something I understand a lot, but you need to explain it better.

timxirish

I'll provide visuals in that case. Here is the original schematic for wiring switched LEDs in a wireless controller:


(image by g0t m4xx 21)

Here are the points in question:


(image by RDC)

Red is 2v switched, and is what would be wired to the base of the transistor seen in the schematic above. g0t m4xx uses a 1k ohm resistor there, but apparently a 2k ohm works just as well. Black pin is ground.


(image by RDC)

The black wire here goes to the collector on the first NPN transistor, and the red wire there is attached to the 2.7v source I've spoken of. Installing the NPN transistor this way will technically make that 2.7v source switched (ie. the LEDs I plan on wiring will only be on when the controller is. without the transistor, the LEDs would remain on even when the controller is off-- the 2.7v source taps into the rechargable battery pack).


(image by RDC)

This is the other spot I've considered for wiring LEDs-- The Play and Charge cable connector. The 5v and 3.3v are only active when the cable is connected to the controller (to charge the battery pack).

What I want to do (and am led to believe it may be possible to pull off) is use more transistors to switch from the 2.7v source to the 5v source when the Play and Charge cable is connected. I could certainly use a SPDT switch to change between them, but if it's possible to use transistors to auto switch power sources when the cable is connected, I would prefer that route.

Thanks for your help, and sorry for my first explanation.

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radodrill

I'd suggest using a relay to auto-switch between power sources rather than trying to do so with a transistor.

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timxirish

Something like this?

That's the smallest one I can find, and most of the controller's insides are cramped.. So I'm uncertain as to if it would fit. Another concern is that particular one says it's 18mA... Would this be a problem if my LEDs are 20mA?

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grishkathefool

It would be kind of cool to use an illuminated Toggle switch... make it a mechanical choice of Power sources.

For that matter could you find a really small CT and wire it to the 2.7v source to make it produce 5v output?

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radodrill

That relay will not work since the control voltage has to be at least 7V to throw the switch; you'd need a relay with a lower coil voltage. the listed coil current rating does not have any affect on how much current can pass trough the switch (that specific relay is rated for 12A through the switch). So you'd need a SPDT relay with ~5V (0r 3V depending on what voltage from the external source you use as a control) coil voltage rating.

Basically you'd connect the coil across the control voltage (to ground) and then connect the NO to the external power, the NC to the internal power source, and the Common would provide the power to your LED circuit.

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keith27

Don't use a relay.

I'm on too many pain meds to understand this. I'm sorry man.

timxirish

CT? Not familiar.

Well unfortunately space would still be a bit of an issue.. I have a lot of respect for Microsoft's design on their controller (still to this day is the most comfortable one I've ever held), but the sleek and compact package really took a toll on what you can manage on the inside.

If I were to use the relay I linked above or use an illuminated toggle switch, I would likely have to remove the rumble motors or the D-pad.. Neither of which i'm too fond of doing right now.. but i'd consider it for an auto switch setup. Possible switch locations (should I give up and go to a mechanical SPDT switch) would be on the top or bottom of the controller.

Here are some more pictures, this time taken by myself. It'll give you all an idea of what I'm working with.



Alright, I believe I'm following you. I'd be using 5v for my external power, so coil voltage rating would have to be 5v, and then when I plug in the cable, the switch flips and I'm using 5v instead of 3.3v.

Do you have any websites in mind that may have a small one with 5v coil voltage rating?

It's no problem, but thanks regardless. Is there a specific reason in mind why a relay would be bad?

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keith27

The inrush of current may to be great and cause other items to burn out. A transistor is the best option here.