m3pi "lighted antenna"

If one does not use the USB A connector at this time, I did this:
Find a short piece of thin USB cable that in not needed.
At the end that plugs, into the USB A, cut off about 5-6 inches.
Strip cable and dig out the red and black wires, which carry 5 volts.
Trim off the other 2.
Now attach a small LED in series with about 330 ohns.
Connect resistor end of LED to red wire, other LED wire to black wire. Solder carefully.
Slip a small piece of heat shrink tubing over the connection.
Take it to the fire to shrink the tubing.
Now you have a lighted radio beacon. For more WOW, use a RGB LED changing every few seconds.
If you want a bit of rear counter weight for the robot, slip a few large nuts over the antenna. I use three, taped together. :slight_smile:

Hi, Donde.

Cool ideas. Doing a single color LED is certainly a lot easier than an RGB one. Do you have any pictures of your antenna?

- Ryan

Will do, showing “antenna” and other stuff on my m3pi. Got Bluetooth working very well under WiiRacing. But, very interesting it fails to sync at some hotspots. Apparently RF interference from cash registers or other data noises causes problems. Just came from Mac Donalds with strong Wi-Fi there. No problem. Fun to steer robot on big round table.

Are you going to carry the new low power mbed just coming out? The m3pi does draws lots of current with stuff on it! The 4 AAA batteries feel if fast.

Do you have any surface mount green LEDS. Would like to replace the one that was sacrificed for Serial comm.
And just connect it to 5 volts through 1/8 watt resistor, maybe 470 ohms.


Sounds fun. We are looking into carrying the mbed NXP LPC11U24. Unfortunately, the maximum input voltage on VIN appears to be 9.0V and the m3pi connects 9.25V to that pin, so it probably will not be compatible.

The green LED line on the 3pi is not also used for serial communication, the red one is. The green LED control is not available because there is no serial slave command for it (You could add one). As for the LED you are losing out on, I do not really know where you want to put it, but you could always desolder it and use it elsewhere. Unfortunately, we aren’t really set up to handle special orders/requests for the surface mount components, and we don’t have any plans to start selling them.

- Ryan

Thanks for the update. That’s too bad about the NXP LPC11U24 voltage difference. Maybe, a work around could be possible, like a couple of series diodes to drop voltage.

OK on the correction of the 2 LEDS. The underside green LED is very very dim. but the red is OK. So, I could re-light the green LED if I wrote a serial slave command? That would be neat. Maybe a hint on how to?

No problem on the surface LED not available from you. I didn’t think so.

Been reading about Bluetooth interfered with. Apparently quite common. At least it works! One arrow key on the Wiimote spins the beast around at warp speed. Glad it stops after a few seconds!

Have a good one, donde

You can modify the source of the serial slave program by adding a case statement to the switch statement in the main loop. Your code could be something like:

        case (char)0xC7:

Be sure to pick the case byte to be one that is not already in use. Then in the mbed you would make a function that sends that command byte, which you’ve already done before.

- Ryan