Well I got some 10 ohm resistors and tried one with my led and just the batteries. It lights but is just too dim. So I've ordered a brighter LED (5500 mcd). I'll see if that helps. Does anybody have a source for low voltage blue LEDs (lower than 3.5v)? thanks!
Ok, I searched for low voltage Blue LEDs and only found (Dim) surface mount types. So we need to do a little more hacking. There is a chip in the schematic above The LM3352 (A DC to DC Convertor) http://cache.national.com/ds/LM/LM3352.pdf It takes in 2.5volts and puts out 3.3volts. It's not 3.5volts but a lot closer than 2.4 volts Try tapping the LED's power off that chip,
Ok, so those diagrams I listed at the beginning of the thread do not match the mx700. The optical chip has 20 pins instead of 16 for starters. Also, there is no sign of a DC/DC converter as large as the one shown (16 pins). But I started metering around looking at some voltages. I found that the white connector that connects the top board to the sensor board has a ground and 3.55V pin (black and white respectively)! I tested hooking the resistor/LED to this pin and it looks pretty bright. I'll have to wait until later to put it all together and see how it looks as I don't have the time now. But this looks promising! Here is the connector I found. Any reason I shouldn't try this out?
hey saber, could you send me an email? I want to ask you a question. I have this same mouse and have used the white and black cables to put a blue LED in. I've found a great location for the LED to shine through the wheel, and also light the bottom up. pizzaeatnmonkey@mchsi.com
What about a MOSFET? The isolated gate won't pull any current (well, not enough to talk about here), and that sould get aroung any current supply problems. Then use one of those small litium cells used in the keychains as an auxillary supply for the LED. The trick is biasing. I'm doing this quick here, so I haven't gone hunting for much on that microcontroller. However, I don't think that pin p3.2 will sink current from 2 LEDs, and I don't know if it goes to groung reference when active. If it does go to ground, I *think* you could connect the battery's negative terminal to it, but connect the positive side only to the blue LED circuit. Here is a (crude) picture: The trick is that the voltage between G and S must be larger than a spec that should be labled as Vt to turn on, and below it to turn off, and in this circuit, that value looks to be very dependant on the voltage of the LED. Looking at it now, I'm not sure it will turn off.... The total circuitry should't be too large including the battery. Not the most elegant, or simple of solutions, but it's is a start on a possibility.
He should have posted that this mod is complete: We already figured out the LED power. http://forums.bit-tech.net/showthread.php?s=&threadid=32710
