Whats broken

 

Today's casualties:

• Bottom right boom was bent
• Propellers spent as you can see
• One motor with strange sounds
• Ultrasonic range finder is MIA
• Few nuts and buts are spent

I found all electronics including flight controller, GPS, radio and ESC's to seem to work as usual.

Next thing I'll buy is the telemetry radio :).

Ultrasonic range finder part II: how it works

The now famous URF (ultrasonic range finder) has a bit more to tell than I wrote in my last post. One of my big questions was how it would interact with the on-board barometer. As any technical person would understand, is that at some point there will be some kind of conflict as these sensors will indicate different measures.

The URF is rather exact but only has a range of five meters. The barometer on the other hand has unlimited range but isn't that exact. In fact, its quite noisy and differ +/- 1-2 meters.

My experience is that the flight controller handles this in the way that, if the URF indicates different than last measurement then, it's the current height. Otherwise, the barometer is used. This way the URF is disregarded if it's too far from any object and the barometer takes over but also acts as an anti-collision sensor when coming in proximity to the ground.

What I'm still to experience is: What happens if the quad flies over trees? The barometer may indicate 20 meters, while the URF suddenly indicates 3 meters. What happens if it's programmed to hold at 20 meters? Does the quad bounce up 17 meters further? Interesting question.

Issues that I've experienced installing the sensor is that on my device, the Echo and Trigger labels are the wrong way around. On the flight controller that I'm using, the Multiwii MegaPirate board I'm supposed to connect echo to pin 9 and trigger to pin 10. That didn't work unless I connected them the other way around ;).

Ultrasonic range finder and stuff

My trials with the ultrasonic range finder shows that it doesn't get too much interference from the other electronics that are located close by. I still made the rookie mistake by connecting the Echo and Trigger cable the wrong way around and spent much time trying to figure out what was wrong until I figured it out. I've also tried to activate AltHold while having the range finder activated. Didn't see much difference in it's behavior but it'll be essential for automatic landings.

Also, yet another motor has started showing signs of problem. It's slaming back and forth before spinning up but doesn't seem too big of an issue with that. However, after running for a while, 5-7 minutes, it gets really hot while the other three motors stay cool. I'm wondering why I'm having these problems with the motors all the time :(. Therefore I've made another order for more spare motors and I also threw in some more propellers. This time 8 inch x 4.5 propellers. Will try and see if these propellers are more suitable for the quads weight.

Sensors, sensors

 

This is how I've mounted the ultrasonic range finder. It needs to be mounted some distance away from other electronics to avoid interference. I still don't know if this will work but it's a first try. Otherwise I'll have to find another solution. The range finder has a maximum range of five meters and should be pretty exact. I still have no clue how the flight controller will treat it's information in conjunction with it's on-board barometer. That's for the future to tell.

The other sensor, or should I say alarm, is a lost signal alarm. It reacts by emitting beeps after one minute of no change to the servo I've attached it to. It's currently attached to the throttle and so, if I don't change the throttle for one minute, it'll start beeping. I'd say the theory is that if you don't move the stick for more then a minute, your signal should probably be lost. Anyhow, then after another minute, it'll sound a more than 85dB beep until it's regained signal. In theory you should then be able to find your model if it's crashed somewhere out of sight. Cheap insurance policy.

Schematic drawing

This is the way that I see that my quad will be hooked up. As I'm new at this, I will keep this drawing up to date as well over time.