The guy on an other forum had this issue. After going around and around with Mk in Germany they discovered that it was the connector in the falling brick incident. I saw this twice when I had the bird on the bench and lost communication with MK Tools and discovered in fact it was the molex connector not make correct contact between the BDB and FC. Gave it a nudge and it reconnected. Consequently this made me think what would happen if this occurred while in the air? Answer: It falls to the ground like a brick.
On second thought I think it would be better to ditch the molex and solder the buzzer to the FCB because the solder pad on the PDB is ultra small. What size wire did you use for the power, just curious?
Hello Mark, If you are hard wiring in the C/D buss and +/- from the PDB to the FC and then use the molex for the buzzer you may create a double ground (if I am following your procedure properly). +1 with Dave here on the connection to the MK FC for the buzzer. Greetings, Adam
I think the guy who made that assertion said that he saw a cable falling away from the copter -- or that the cable was disconnected when he inspected the wreckage. I'm not sure I'd be persuaded by the latter assertion, myself. It could have become disconnected on impact. Connecting up the Molex as well should not cause any problems. Note my use of the word "should." All you're doing is providing a second electrical path for the same signals between the boards. On the other hand, if I see a bright flash to the East, I'll know I was wrong. Andy.
Hi Bill: Over such short distances I very much doubt that you'd actually see any bad effects from apparently creating a ground loop. Those typically cause problems in situations where the ground wires have some noticeable resistance and there's a potential difference between the two "grounds" causing current to flow. Given that the boards are already connected to the same ground (the PDB directly to the -ve side of the Lipo, and the FC board connected via the -ve side of the input to the on-board DC/DC converter (aka Recom), they're really already in a "ground loop" when you add the ground coming along the Molex. Add to that, there really isn't any "ground" on an aircraft. It's more than everything's connected to a common -ve terminal on the LiPo. However, I must say that the first rule of being a forensic expert is that you always have to have a valid reason for being wrong. So try it: 1. Smoke stays in the wires. I was right. 2. Smoke comes out of the wires. I was wrong. Seriously, before you make the ground connection, put a voltmeter across it and see if the "grounds" have a voltage between them. If they do, then don't connect'em! Andy.
HI Bill I have a degree in electronics and have been an electronic tech for 20 years. No you wouldn't be creating a ground loop, all you would be doing would be to put a wire in parallel to the connection you are making. A ground loop is a difference of potential between two ground points. Usually you see this if you have a loose ground, or bad component such as a leaky capacitor. For the purpose of the molex connector. Let's use the ground wire. In the electronic circuit of the flight control board and PDB, ground is ground. IF you took a meter and went across any 2 ground points anywhere on either board you should have no resistance no matter where you went. So by adding the molex connector back into the circuit, all you are doing is putting another wire in parallel to the one you just created when you hardwired it. A wire has very little resistance, should be less than one ohm for this size and length. When you put a resistance of less than one ohm in parallel with a resistance of about the same amount, you will end up with essentially no resistance which is what any two points of ground should measure when you put a meter on them. See picture attached.
I did the wiring mod last night and it worked fine. It took me about 2 hours because I took my time and I removed the PCB so I could solder the bottom side of the board. FYI: The c and d pads on the PCB are in several places on the board for easy accessibility. The plus and minus pads are also in several spots on the PCB which allows flexibility to wire as you need. Right now I have the molex cable off for functionality testing. I wired the buzzer straight to the pads on the FCB. Everything tests good.
Wow!!!! I had no idea when I posted this that it would be such a hit. Not bad for a complete and utter NEWBIE!!!
If often takes a newbie to show up and ask the question: "Why are we doing it this way?" to provoke a "Yeah, why are we doing it this way." So "newbie" is not a perjorative term.....any the more than "geek" is. Keep asking questions! And trust nobody under version 3.0. Andy.
Good to know you're background, Dave. I'll defer to your answers on questions about volty and ampy thingies to you! Andy.
+1. This is awesome Dave. Good to know. Like I said I have no use for the molex connection czuse I am using different esc's but good to know, now plug the molex in and report back please. Bill
So whats the conclusion? Hardwire cables to the PDB? If so keep the molex? Keep the molex and hot glue it? G
Gustav I did the hardwire but not have connected the molex. The hard wire is rock solid! You can pull on it and does not come free. I have peace of mind knowing the connections will not fail. I don't trust that little connection too keep $20,000 in the air.
I think either way is fine provided you apply the hot glue on the molex connector properly to ensure the connector isn't coming off. I did hardwire it myself and kept the connector off just on the one and a million chance there is a problem with the connector losing connect with connector holder that has the pins or issues with connections on the board. I think its a very small probabilitiy that there is an issue if you use hot glue but I didn't want to chance it with my $7000 plus investment.