So what does a cat toy and a PCB have to do with UAVs?
Very easy: One of my dogs had taken my cat's pole toy and left little but the handle stick. I was wondering what to do with that now. At that time, my MF450 frame was on my desk waiting to be completed and I shortly before read about external LED indicators. I also mounted my APM on top of the frame and was worried about damages in case of a flipover.
So - I cut the stick in halves - well somewhat half... Then I soldered suitable resistors for 5V to the LEDs and short cables with 3p jumper plugs. After that I filled the respective parts of the stick with heat glue - pretty much completely to give some additional stability. For mounting, I pushed an M3x35 bolt into the still soft heat glue.
As a result, I have two little masts which carry the external LEDs for GPS and ARM as well as double as some kind of "roll cage" to protect the APM in case of a crash.
As for the PCBs, I did have massive stability problems with my quad in Alt Holt mode and was advised that vibrations might be the cause. The MF450's gimbal comes with rubber balls which are a good bit too soft for that gimbal construction (the gimbal shakes badly) so I mounted the roll servo to the frame with double-sided tape and had the rubber balls as a leftover. I also recently bought a 50 pack of small PCBs from eBay, so I made a quick-and-dirty (and cheap) anti-vibration mount from 4 rubber balls and 2 PCBs.
That's the final result:
The anti-vibration mount will be tested soon when I got my new props.
Comments
Found great solution! I found driver modules for 3x3W LEDs from a German company on eBay. Those have a wide range input (9-18V). When I emailed the seller if those tolerate being PWM'd from the supply voltage, he replied that the driver ICs actually have an analog/digital modulation input and he sent me the datasheet. According to the datasheet, that modulation input directly accepts 5V, which means, it could be directly connected to the APM's ARM LED out. I'm waiting for delivery at the moment. As soon as I got the stuff, I will blog.
Yes, I have played with the ULN2003 before. Problem is driving the high-power-LEDs without using a resistor :).
Besides, 500mA might be not even enough for one 3W LED... They run on close to 1A IIRC.
The JD-IO Board uses a ULN2003A 7 way darlington array and it is rated up to 500mA per channel. So just use that chip connected to the APM directly. You can connect it to the flight battery direct fro the power source. @ ~$0.50, cheap! ;-)
I recently posted in the forums about that because I'd like to use 3W LEDs for that. But I somehow got stuck at how to drive them because a resistor solution would require a monster-resistor and would burn a ton of energy...
Basically, I'd like to use 4x3W for the ARM signal (the NAV lights) and 1x3W for the GPS signal.
Somebody suggested the jDIO board which seems to be almost a reflex-reaction here - if somebody asks LEDs, somebody else writes jDIO board... However, that is relatively useless here as it doesn't include a suitable driver for high-power-LEDs plus it doesn't display ARM/GPS status - just flight modes...
Besides, the LEDs on the poles are standard superbrights running on 15mA (oversized resistor).
When adding LEDs to the A Outputs directly you need to be careful that you do not exceed the chip maximum current ratings.
A typical LED takes about 25mA (Supper bright LEDs are much more). The A signal pins are rated 40mA current sink max (nominal 20mA @5V recommended). Sink means you need to connect the LED resistor to 5V (Vcc) and the negative pin to the signal line. The A group of signal lines A0-A8 can sink max 100mA combined. you get about 4 LEDs (or 3 LEDs and a buzzer and you are near capacity)
If you connect the other way with Signal to Resistor and negative to ground, you are limited by the 200mA max current that can go through an AMTEL2560 chip. the APM takes about 80mA with nothing connected. Add an extra 100mA and it getting close.
The above are consistent current draw, if the lights flash, you can get away with a bit more. Another solution is to use a bigger resistor and limit the current in the LED to more like 15mA, but you sacrifice brightness (not good when in bright sunlight)
A better solution is to use FET (switch), or if you want more than a few LEDs a darlington array (a high current switches). This is essentially using the signal line to turn an external power source on and off to power the lights. Current is then not limited by the AVR chip.
Here's an old article on the STAMP microcontroller that explains how to use a darlington array I am thinking of using to power LEDs & Buzzer with 12V http://www.parallax.com/dl/docs/cols/nv/vol1/col/nv6.pdf
There's another issue as well, and that that the 5V line on the A channels is limited by the 500mA fuse. With GPS/APM/TRADIO/RCRADIO that's about 250mA, adding more current draws also pushes towards this limit, which is brownout territory.
It should be easy using a some prototyping board to make a small board using darlington array to power a range of LEDs and buzzer connected. That can be as loud and bright as you need them... :-D
You still have to solder the cable to the LED... Soldering the resistor between the cable and one LED-leg isn't much more difficult...
No, that's included functionality. See http://diydrones.com/xn/detail/705844:BlogPost:1030922
That's great and simple. I see you connected the led poles to A6 and A7. Did uou have to modify the APM code to allow these led ouputs ?