Hobbyking Mini DLG Pro 990mm durability fix

Entry level DLG (Discus Launch Glider) from HobbyKing has a quite important flaw for a “entry” level model: it is not durable. As a matter of fact, it is quite fragile, specially where plastic nose section is attached to composite fuselage tube. It is attached only with 3 small screws, and I can guarantee: every harder landing will result with something broken. During 3 first weekends with my Mini DLG Pro, I had to glue it back together every second flying session.

Those 3 screws are just not stron enough to keep everything together, so I’ve decided to fix it with epoxy glue and I suggest all new owners of this DLG do it at the beginning. Thin layer of epoxy put everywhere where plastic meets fuselage tube is enough. It make glider strong like it should be from the beginning.

hobbyking dlg pro 990mm epoxy reinforcement 2

hobbyking dlg pro 990mm epoxy reinforcement

There is a penalty of course: nose section no longer can be detached. Since HobbyKing does not sell replacement parts for this model, this is not a big problem after all…

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UART1 and PPM on Airbot F4 / Flip32 F4 Flight Controllers

Today I've discovered another small but irritation limitation of Airbot F4 / Flip32 F4 also known as CC3D REVO for unknown reason. Looks like, by default, this board is unable to share UART1 RX line and PPM input. So, if you would like to connect, for example, OSD or GPS to UART1, you would have a problem. I've discovered that PPM input does not blocks UART1 totally, but makes UART1 transmission erratic and unreliable.

This is because PPM input pin is connected to both UART1 RX (pin PA10 of STM32F405) via inverter and PPM input pin (PB14) without inverter. Any electrical signal applied to PPM input would also be sent to UART1 RX.

Airbot F4 and Flip32 F4 PMM and UART1

Luckily, there is pretty simple, hardware, solution to allow UART1 and PPM input function simultaneously. Jumper called SBUS located near SBUS/PPM input has to be removed with soldering iron. This operation breaks the connection between PPM/SBUS input and UART1 RX.

There is a drawback of this solution too. If jumper is removed, SBUS will not work. To make SBUS works again, jumper would has to be closed again. With a blob of solder for example…

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Tip: how to secure XT60 plugs

I had a problem with my SkyZone goggles: I was constantly breaking battery cable near XT-60 plug. One not careful enough grip and cable was ripped away. I've decided to fix it and permanently secure the cable with epoxy glue.

Sure, I could use hot glue (that looks ugly) or Sugru (that is expensive), but since few weeks ago I've bought HobbyKing Mid-Cure Epoxy glue, I've decided to use it instead. It worked fantastically!

HobbyKing Mid-Cure Epoxy glue

Solder cables to XT-60 plug pretty close to external coating as possible.

XT60 plug

Now, prepare a "mold" using electrical tape. Just wrap it around plug and cable leaving empty space inside. Prepare epoxy glue and pour it into "the mold".

puring epoxy into mold

After and hour or so, epoxy glue will be hard enough, that electrical tape can be removed. There is no chance I could ever rip this cable from the plug by accident!

protected XT60 plug

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Micro MinimOSD stops overlaying in flight: solution

Both MinimOSD and Micro MinimOSD suffers from irritating technical problem. In some setups, they stops overlaying data during hard maneuvers or even right after arming. Problem is very simple: chip MAX7456 is extremely sensitive in terms of supply voltage quality. Working motors and/or servos, can introduce enough power supply noise to occasionally force MAX7456 to reset.

Luckily, solution is simple: separate LC power filter or big enough capacitor connected in parallel to 5V pads of MinimOSD.

Almost any big enough electrolytic capacitor will do (> 100uF, the bigger the better) but best results can be archived with low ESR > 500uF capacitor.

In my case symptoms were not very strong, usually only very fast flips caused MAX7456 to reset, but I’ve decided to go big: 1000uF low ESR capacitor.

Low ESR 1000uF Capacitor

Micro MinimOSD has 5V pads on a side and they are the best place to attach capacitor.

Micro MinimOSD

As you can see below, capacitor is bigger than MinimOSD itself and I had to think a little how to place it inside my Reptile X4R 220 frame.

Micro MinimOSD with capacitor attached

Results are great: no more MinimOSD problems. OSD stays on all the time, no matter how hard I use the stics.

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How to measure gyro noise frequency with Blackbox

Cleanflight / Betaflight / INAV lowpass filter tuning can be a hard thing to do if you have not idea what is noise frequency you want to cancel. Sure, you can blind test or read tutorials. But what if I tell you, you can measure it quite precisely using only Blackbox logs? Or measure rotation speed of motors? That would be nice, isn’t it? The only requirement are few seconds of Blackbox log with visible gyro (it can be also motor output or Pterm or even ACC reading) noise.

blackbox measure frequency 1

Continue reading “How to measure gyro noise frequency with Blackbox” »

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BLHeli firmware for ZTW Spider 40A OPTO Small ESC

ZTW Spider 40A OPTO Small ESC with stock SimonK firmware can be easily flashed with BLHeli using Cleanflight interface. I just did it, the whole process took few minutes. To be true, it took me more time to find out which firmware should those ESC be flashed with, than to flash them. For unknown reason this information is well hidden in the internet! So, here is short guide:

  1. We will be using Cleanflight BLHeli passthrough interface. It is build in in laster Cleanflight / Betaflight / INAV firmwares
  2. Use latest BLHeliSuite. I used 16.3.14.7.0.0
  3. Connect ESC to flight controller
  4. Connect flight controller to USB port
  5. Run BLHeliSuite software
  6. From Interface menu select ATMEL BLHeli / SK Bootloader (Cleanflight)
  7. Select COM port and click Connect
  8. Connect ESC to battery
  9. Click Check to detect connected ESCs
  10. BLHeliSuite will detect unknown firmware with SimonK bootloader
  11. Select ESC (1, 2, 3 or 4) and click Flash BLHeli
  12. Here comes funny part. There is no ZTW Spider 40A OPTO Small formware! Documentation states that ZTW Spider 40A should be flashed with BlueSeries 30A firmware. But images in docs and mine ZTW Spiders differs a little. But, looks like it is not a problem. Select BlueSeries 30A MULTI firmware and flash
  13. BLHeli 14.x enables Damped Light by default. That might not be a best idea for big (> 8″) propellers so you might want to disable it

blheli on ZTW Spider 40A Opto

ZTW Spider 40A OPTO Small ESC running BLHeli

Bottom line: ZTW Spider 40A OPTO Small ESC should be flashed with BlueSeries 30A BLHeli firmware!

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How to dispose / utilize LiPo batteries

LiPo batteries that run RC hobby are potentially dangerous devices. When not handled properly they can ignite or even explode. And they do not live forever. Even the best battery, no matter how taken care off, loses capacity, swells and has to be disposed. When we combine both facts we face a problem: how to dispose old LiPo batteries if they can catch fire? It’s extremely hard to find a place that accepts them for utilization. Throwing out with garbage is not a good idea. Disposing with popular alkaline batteries might sound as a good idea, but it is not either. So, how to utilize old LiPos? This is quite easy…

  1. Build a LiPo discharge device using 24V halogen light bulb. No high-tech here, just a way to connect light bulb to a battery. 12W halogen is generally a good option for both 3S and 4S LiPos
  2. Put a battery inside ceramic pot with some sand (not flammable if thing go very very wrong for any reason), connect “discharge device” and let it do its job. Light bulb limits discharge current, so LiPo should discharge nicely without extra swelling or overheating Magical LiPo tree Continue reading “How to dispose / utilize LiPo batteries” »

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How to print PLA on glass?

When I got my first 3D Printer (Malyan M150) and got into 3D printing I was surprised how consumer not-ready technology this is. Sticking, not sticking, overextrusion, underextrusion, Kepton, blue painters tape, clogged extruder… Over the time, at least, I was able to get the whole 3D Printing process somehow repeatable. I think one of the most important changes I’ve made in my 3D Printing experience is to ditch Kepton and blue painters tape in favor of printing PLA on heated glass. Process got simpler, faster and with better results. Also, not counting initial investment, cheaper.

Malyan M150 printing PLA on glass Continue reading “How to print PLA on glass?” »

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How to reverse motor direction

You finished your build, you connect LiPo, power up flight controller, apply throttle (no propellers of course) and you see that one or motors are spinning in wrong direction. How to fix that? You can not do it, for example in Cleanflight Configurator. ESC communication protocol does not allow to change BLC motor direction.

There are 4 ways of dealing with this problem:

  1. Hardware way that works all the time: swap any two motor wires. Does not matter which, just take any two and swap them between motor and ESC: A with B, B with C or A with C. If you have bullet connectors, it's simple. If you soldered wires to ESC pads, you would have to resolder them. How to change motor direction
  2. If you have BLHeli ESC software, BLHeliSuite allows to change motor direction without swapping any wires. Connect to ESC with BLHeliSuite, and change Motor Direction option. blheli motor direction This works only with BLHeli enabled ESC, and only on Windows.
  3. Most of ESC allows to change options like motor direction via transmitter. Exact procedure differs from manufacturer to manufacturer, but usually it looks like below. For exact procedure and possible options refer to ESC user manual!
    1. Connect ESC to radio receiver throttle channel or use flight controller configurator software Live mode. Remember to remove propellers!
    2. Throttle UP
    3. Power ESC, it will start to beep signaling number of cells
    4. Keep throttle up until you hear a sequence that confirms programming mode has been entered
    5. Wait to hear beeping sequence indicating Motor Direction option
    6. Throttle DOWN
    7. Wait until you hear beeping sequence indicating desired rotation direction (normal or reversed)
    8. Throttle UP
    9. Setting will be changed and after next power cycle rotation direction will be changed
  4. Sometimes special programming cards for ESC can be acquired. They somehow automate procedure from point 3 but work on the same principle. For exact programming procedure refer to programming card user manual.

EMAX esc programming card

EMAX programming card photo [1]

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How to cut Depron

Depron is an amazing material. Light, cheap, waterproof, easy to process and quite durable. Almost everything in RC world can be made from Depron. All one needs is imagination, glue and proper knife. Like I mentioned few times before, I’m cheap, so at the beginning of my adventure with Depron, I was choosing cheap modeling knives. Usually no-name. They had one very serious flaw: knife’s blade had to be replaced every few cuts. And even so, cut was far from perfect.

olfa knives SK-9 and SKB-2

Luckily, I’ve found a perfect, more expensive but cheaper on a long run, solution: Olfa Knives. Especially Olfa SK-9 Knife with SKB-2 Blades. They are sharp, strong and lasts for a long time. When needed, SKB-2 blade can be used without a knife. SK-9 has one disadvantage: there is no lock, so keeping blade extended all the time requires thumb to be used. And that make it hard to switch knife between hands.

But the bottom line is: I love Olfa knives. Not only when working with Depron. They are very useful with dealing with cables, unpacking and so on…

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