OMM Rx Converter Rev2

The converter board you see above is the second revision of a clever design by Mike Cook, alias Old Man Mike. His design allows several of the Futaba FASST receivers to be used with quadrocopters that require a single PPM composite signal. It plugs directly into the receiver outputs, then generates a single PPM composite signal. There's a jumper that allows you to set 6 or 7 channel output as with the Rev1 version, but this Rev2 version has a new jumper position, to add a new mode for the Spectrolutions folks. The new mode allows you to control Ti on/off, and sensitivity with channel 5 alone, which means that channel 6 and 7 can be available for use with other servos. The LED shows the channel mode on initial power-up, and also flashes to show an active signal being received.

The Rev2 board also provides connectors to access channels 6 and 7, where the Rev1 did not. If you wish to use servos on channels 6 and or 7, you must make sure you have sufficient power to drive them. I believe the Spectrolutions board is the only board with this issue, but there could be others. There is also a separate plug that will allow an ESC BEC cable to be plugged into the converter if needed.

Mike is one of those guys who just builds what he needs, because he needs it, or because it's fun to build. After that, he's on to something else. Since it's such a neat design, and since I love the Futaba FASST system so much, I volunteered to make them available to anyone who wants one.

The price is $40, plus USPS Priority Mail shipping for a fully assembled and tested unit. Please read the common sense disclaimer at the bottom of the page. PayPal is preferred, and shipping in the US is $4.80. Contact me for Priority Mail International shipping rates if you're outside the US. If you'd like to purchase one, email me at- rusty@radrotary.com

What will it work with?

The converter is currently known to work with the following combinations of receivers and copter electronics. Others will be added as they're tested. Note that R607FS and R617FS receivers are both 7 channels, but the timing of channel 6 and 7 is not the same. This converter board only allows 7 channel operation with the R617FS receiver. Note that the converter will not work with the 8 or 14 channel FASST receivers .

Failsafe note- The Futaba FASST receivers hold the last known good signal, so if you lose your radio link the receiver will still provided the last known signal to the quad. This is a good news/bad news sort of feature. It's good because a brief signal loss won't be much of an issue, but it's bad for systems that have a failsafe which depends on being able to recognize a lost signal. As far as the quad will know, you are just not moving the sticks, but the signal will still appear valid, so the failsafe will never kick in.

Spectrolutions Experimental Brushless board (OMM's Kquad Thread)

- Spectrolutions mode with R606FS, R607FS, and R617FS receivers.

- 6 channel mode with R606FS, R607FS, and R617FS receivers.

- 7 channel mode should not be used with this board.

If you don't plan to drive servos, the Spectrolutions board provides enough power for the receiver and converter. In this case, the cable needed to connect the Spectrolutions board to the converter is a simple 3 wire cable. A servo extension wire works well. The female end plugs into the converter. The male end has a protective plastic shell around the pins, which needs to be removed before you can plug it into the Spectrolutions board as shown (install photo).

If you plan to drive servos with channel 6 and or 7, you must provide additional power to the converter from an ESC. If you try to drive a servo using only the power provided by the Spectrolutions board, there's a very real chance the signal will become disrupted, and the Spectrolutions board will shut down. As you can imagine, this wouldn't be a good thing to have happen in flight. A standard Y splitter cable from one of the ESC's should do the trick. It will be plugged into the aux power connector. When using this cable for power, you should cut the red (center) wire on the cable that goes from the convert output to the Spectrolutions board. This prevents the two power sources from interacting. The ESC will now be powering the receiver, converter, and any servos.

Unless you absolutely need to use channel 6 for something else, I would recommend using the normal 6 channel mode for the Spectrolutions board. The clever new Spectrolutions mode allows the converter to create channels 5 and 6 using only the channel 5 input from the receiver. Support for setting this mode is best requested on the OMM Kquad thread, since Mike has the most experience with it.

Mikrokopter

- 6 channel mode with R606FS, R607FS and R617FS receivers. Most people seem to want more channels, so I don't imagine this will be a popular mode.

- 7 channel mode with R617FS receivers.

UAVP

- 7 channel mode with R617FS receivers.

This is only needed if you wish to use the gyro stabilized output for camera tilt and roll, AND also want to manually control tilt and roll.

UAVX

- 7 channel mode with R617FS receivers.
- 6 channel mode with R606FS, R607FS, and R617FS receivers.

Draganflyer

- Not tested, but it can be made to work with a very simple modification to the board. Contact me for details if interested.

How does it work?

The above photo was posted by Mike on the OMM Kquad thread. It shows all the connections and jumper positions. Ignore those extra 3 programming pins, since they aren't on the converters that I made.

The 3 pin RX Serial Output plug connects to your quadrocopter electronics via a normal servo connector. Orientation is marked by red and black dots on the edge of the converter board. Power and ground are from the quadrocopter, and the signal pin is PPM composite signal output from the converter to your quadrocopter.

Power and ground for the converter, and your receiver is normally supplied by the quad electronics through the red and black pins on the RX Serial Output plug. This should be typical receiver voltage of around 4.8V. The PIC processor chip has a max voltage rating of 6.5V, so don't exceed that. If you plan to drive servos from the converter, make sure you're quad type supplies enough power for this. The Spectrolutions board does NOT, so additional ESC power is required at the Optional Power Input plug, using a standard Y splitter cable from any ESC. When connecting this, it's a good idea to cut the power wire on the RX Serial Output connector, so the two power sources don't try to interact.

The jumper selects 6 channel, 7 channel, or the new Spectrolutions (5 in/6 out) modes of operation. See the diagram for jumper positions. This is read during power up, and will not change afterwards, even if the jumper is moved, or removed.

The LED confirms channel mode. Apply power without the transmitter on and the card will tell you which mode it is in:

-One flash is 6 channel mode (R606FS, R607FS, and R617FS receivers)

-Two flashes is 7 channel mode (R617FS receiver only)

-Three flashes is Spectrolutions mode (R606FS, R607FS, and R617FS receivers)

There's an additional caveat to using 7 channel mode with the R617FS. Due to the timing that Futaba set for the output of the pulses, if channel 7's pulse width is near the max, it starts to interfere with the beginning of channel 1. For this reason, you will need to set your EPA for channel 7 to less than 100%. On my 7C, the magic number is 83%, but I'd go for 80% to be safe. Since channel 7 is a switch, this should not cause any problems.

If you don't reduce your channel 7 EPA, you will find that it works just fine with the channel 7 switch in one position (shortest pulse width), but when you flip it to the other position, your roll axis (channel 1) will appear to have a large trim change. If you trim it out, then flip channel 7 back to the other position, the large trim change will be in the opposite direction, back where you started from.

That's about all I can think of at the moment. Let me know if you have any questions.

Rusty- rusty@radrotary.com

Common Sense Disclaimer- These converters are tested before I ship them, and if you have problems, I'll help you get it working, or will refund your money when you return it. You will be responsible for making sure it works properly with your quad, before you fly it. Flying R/C models can cause injuries and property damage, and neither I, nor Mike will accept any responsibility for injuries or damage resulting from the use of these converters. Purchasing a converter acknowledges that you accept this responsibility.