Unintended Adventures

Tag: Circuit Breaker

Mad dash to the finish

The summer for students has come to an end and I’m back in Iowa. Summer job was fun, I learned a lot, and met some great people. Alas, it is now time for airplane building once again. A lot happened since the last update in March, so I’ll try to cover all of it.

I made a crazy work week before leaving for Denver in May to get a lot of stuff done. I accomplsihed most of what I wanted to do. I mounted the ailerons/flaps, fitted up the windshield, completed the second seat (that had been waiting since Thanksgiving of 2016), and prepped the hangar in case I got a hangar spot closer to home. The last bit did happen which was great. The plane now resides a mere 15 minutes from home compared to the 55 minutes it was for the last year. Still not quite as good as just being in the garage, but it’s too big now anyways. This should allow me to get a lot done on the plane these next 4-6 months (or until I convince someone to give me a job 🙂 ). I only have one class to finish up my fancy-pants degree and I will be doing some flight instruction, but I should be able to go full airplane build mode for most of the time.

The second great news is that we finally committed to finish the project and have purchased the avionics and the engine. The plane will use a Rotax 912ULS (100HP) engine. I started to become nervous about this before the decision since there was and still may be a chance we will move to higher elevations. The Rotax 914 would be the safest bet and make an awesome airplane, but in the end I couldn’t find any reason at this point in our lives to drop another $11k-13k on an engine to get a turbocharger. Maybe the next plane or when this 912 gives up.

The avionics are pretty bare bones. I’ll go into more depth when I get to wiring stuff, but I’ll have a Garmin G5 for primary flight information, a Appareo ESG transponder (RST Engineering has a great deal for EAA/AOPA), a Garming GTR200 radio, and my homegrown engine monitor (also looking at purchasing something from MGL as a backup and to reduce the risk that my engine monitor doesn’t want to work; I don’t want to delay flight testing for an engine monitor). The wingtip lights are the AeroLEDs Pulsar NSP variety. The other big (maybe controversial) decision was to forgo circuit breakers for most of the electronics. I will be using fuses for all of the equipment in the plane and then circuit breakers for the master and generator circuits. With my desire to fiddle with electronics, I couldn’t devise a plan that would let me hack the electrical system as easy as having banks of fuses with available slots. More to come as I get into wiring.

As I get further into the build, I find I have less and less to say about the specific tasks I’m doing. I wish I had more to say to help others, but I have been putting off writing these for too long after doing the tasks. I hope to change that moving forward.

One thing I will say about the boot cowl sides. For us tailwheel builders, you have a choice. You can either install the boot cowl sides with the gear off or you can trim the boot cowl sides to go around the gear blocks. I did the latter and ended up trimming off too much of the boot cowl and now I have a gap. I plan on getting some thin aluminum to extend the area I trimmed and make it a more flush finish with the fuselage. So if you’re tailwheel and don’t want to remove the gear to install the boot cowl, go very slow and check often. I think it would have gone better with another person to help me hold the boot cowl up and check interference. With only two hands, it gets difficult to check and trim quickly.

Some other small items being completed are on the firewall. This includes the battery box build up, and mounting the coolant overflow bottle. I had a very annoying spat with some stainless steel rivets on the battery box. The stem would pull completely out of the rivet on most of my attempts. I took a break, ordered some more rivets, and used some rivet backing washers. That solved the issue. Not sure what was wrong, but my casual internet reading (very dangerous) leads me to believe it may have been the rivets themselves, but I don’t know enough to say how much belief to put into that thought.

In general shop news, after 3.5 years of building I finally bought some shelves and a work table to supplement a small workbench. Not sure why I didn’t do it sooner, but I was younger then 🙂

The panel is off to the laser cutter in town and some more orders to Spruce and Digikey are inbound. I’ve attached a picture of the cutouts I’m making for the panel. Hopefully it works well. I think I could do much better from a human factors stand point, but we shall find out when it is flying.

I’ve been adding to this for a few weeks, so I’m pushing it out and I’ll be getting some more updates in the coming few days.

Long time no update

The Spring 2018 semester is almost ready to start. This weekend I will be wrapping up some painting for my rudder, doors, and a few fairings around the tail area.

Not much work was done over the Fall mainly because of me taking on quite a few projects at school. Sort of depressing, but projects are good and they provide me with things to talk about during interviews when I’m not talking about the RANS :-).

The big task going on since the last update is painting. Although it has only taken place over two weekends, that is the big project for the last 4 months. I finally painted the landing gear and as mentioned above will have completed the rudder and doors. The bigger task before that was completing the door trim. That was a fussy task, but as with all other things, it has passed. If you have questions or want some tips, get in touch with me. I would like to write a detailed process, but it was messy haha.

Other little things were getting the tail brace wires installed, some hardware installed on the ailerons, attaching some interior fabric, and starting to fit up the wing tips.

In other big kit news, I ordered the firewall forward kit back in mid-November. I’m hoping that will keep me busy for a while. I will be out of town for 3 months over the summer, so I won’t have any airplane work going on although I do plan on working with some of my electronic projects.

On the electronics side, the Engine Monitor software is pretty much where I’d like it. It is really ready for some higher level testing. I’m preparing for this by working on some circuits to help protect the electronics from voltage surges and other things.

For some new ideas, I am beginning to toy with some components that would provide a means for an electronic circuit breaker and provide current monitoring for individual loads. My idea is to somewhat emulate other commercial offerings that provide electronic circuit breakers. I’m going to go slow with this one and test as much as I can. Even if I do put it in the airplane, I am planning on some standard fail safe circuit protection devices.

Here is an example of the circuit that I am going to play around with for the circuit breaker. The green line in the graph shows a simulated current draw. The system senses a voltage drop across a resistor. By changing the value of that resistor, the device will trip at the specified current. This example is using a resistor that should trip at 2A. The simulation shows it being tripped at 1.8A, which is caused by an additional resistor on on of the sensing pins of the chip. I need to do some researching on why they have used a resistor in that location.

Example current trip.PNG

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