My quadcopter has been grounded for over a week now. The last warm sunny day of October I went for a normal flight session only to find that the front right motor was not spinning. No spinning motor, even one, no fly. Back at the workbench I discovered that the ESC had given up on life and quietly died. I had one spare ESC but in a puff of magic smoke discovered that something else was wrong.
I probed around with the oscilloscope and the only thing I could find different was that the signal line going to that particular ESC would remain at about 3V for a few nanoseconds longer than the other three motors when first powered up [I just tried to repeat this testing to capture oscilloscope traces for this post and was unable to recreate what I described] I still suspected something was wrong with the power distribution board but was not confident what the exact problem was. I figured the rainy cold weather of upstate NY in the fall would prevent me from flying anyways so I might as well order a new power distribution board along with a few more ESCs and upgrade my quadcopter. Enter the Matek HUBOSD Eco H-Type.
Through a roundabout way I was made aware of the HUBOSD watchin a review by UAVfutures and his review of the Realacc HUBOSD Eco X-Type. I had been looking to upgrade my ZMR250 with an on screen display for a while and being able to combine that with a power distribution board sounded great. Not wanting to wait for up to a month that Banggood may take to delever the Realacc from China I went to getfpv.com and found that there is either a clone or the original avalible right here in the USA within 3-10days of shipping for about the same price.
Before receiving the HUBOSD I started the preparations for the upgrade. This included removing the existing power distribution board and replacing the damaged ESC. The old power distribution board was part of the ZMR250 base plate so required that the quadcopter be fully disassembled.
So far in my few months of flight I have damaged 4 ESCs. I have held onto them in the hopes that I would be able to repair them. I was able to repair one of them by replacing the damaged mosfets, I will be sure to write a post the next time I have an ESC to repair.
With the quadcopter broken down into individual components it was time to wait for the HUBOSD to arrive.
Before assembling the HUBOSD into my quadcopter I decided it would be useful to set up the onscreen display and check for possible firmware updates. Fortanatly Matek makes this simple with there software tool avalible on thier website: http://www.stosd.com/. The only additional piece of hardware required is a USB to serial connection. I used the SparkFun FTDI Basic Breakout that I had purchased for various electronics projects. Connecting it to the HUBOSD is simple as shown in the connection diagram below. In addition the the FTDI breakout an external DC power supply is required. I used an adjustable power supply set to 12VDC. I would advise against using a LiPo due to the risk of shorting out the board and damaging the battery or your computer. An old wall wart power supply would work if an adjustable power supply is not available.
I ended up soldering a right angle three pin header to the HUBOSD so that I will be able to update the OSD settings and firmware even when the quadcopter is assembled. I also used the cutoff servo connectors from the ESCs and jumper wires to connect the HUBOSD header to the FTDI breakout.
With the firmware updated and the OSD settings as I want them it is finally time to assemble my quadcopter.
Installation of the new power distribution board was as easy as following the connection diagram in the user mannual for both the HUBOSD and the Naze32 flight controller. The only tricky part was that the power and signal cables for the ESCs were cut to length for the previous PDB so a few of them had to be replaced. Since the new PDB has a built in 5V regulator (BEC) I did not need to connect the 5V output from the ESCs to the flight controller.
Hopefully there will be a break in the weather soon that will allow me to go for a test flight.