Modified Spektrum DM8 DSM2 Module for Futaba 18SZ, 14SG, 10J and Others
I made this modified module to work with the following Futaba transmitters equipped with the micro square trainer port:
Note that the power switch on the module works only with the higher end transmitters - the 8FG, 9C, 10C, 12FG, 14SG and 18SZ and will not work with the rest from the above list as they do not provide unswitched battery power to the trainer port.
Here is a picture of the finished product:
Here's the prototype I made originally for the Futaba 8FG transmitter - this was before the 14SG, 18SZ, 10J and 8J had come out:
The module uses its own power switch to turn on power to the transmitter encoder and the DSM2 module. When the radio power switch is left in the off position and the DM8 power switch (soldered between the trainer port and the module) is turned on it powers both the DM8 module and the radio but only the stick encoder/mixer. The internal 2.4GHz RF circuitry is left without power. This is the reason why the extra switch is used. If the switch was omitted, powering up the radio with its own switch will provide power to the module but it will also power up the whole radio, including its own 2.4GHz RF circuit so it will use more power from the battery. Without the module power switch you can still turn on the transmitter without RF by either enabling the throttle stick position warning, moving the throttle stick above idle then power the transmitter and on the warning screen select no RF or by holding the RTN button while powering the transmitter then selecting from the screen no RF.
Here's what happens when the DM8 power switch is turned on:
After several seconds the radio shows the main screen. The right monitor light flashes slowly to show that the internal RF circuitry is not working.
The modded module is mounted in a Spektrum DM9 case with integrated antenna:
The following pictures show the module on the back of some of the compatible transmitters.
Binding and Using a Modified Spektrum DM8 DSM2 Module
Initial Transmitter Setup:
1. Create a new model. Select the new model.
2. If your transmitter is NOT the Futaba 18SZ skip this step and go to step 3. Turn on the trainer port signal output on the Futaba 18SZ (Page 112 of the manual) - in Trainer function:
ACT/INH - Change to ACT
3. Reverse channels 1 through 8. This is needed for compatibility with Spektrum which uses opposite channel reversing.
4. Leave endpoints (ATV) at 100% for now. Later you can tweak this if needed. I never had to change them with UMX models.
5. Set any dual rates and exponential you may want or you can leave this for later when/if you want to tweak the model. I found that UMX models need very little if any negative expo. My "standard" high/low rates for UMX models are 100/70% but most often I fly on high rates.
1. Attach the modified module to the back of the transmitter as shown in the post above. You can use the provided hook and loop material.
2. With the transmitter turned off connect the trainer connector to the transmitter trainer port. If the transmitter turns on automatically, wait for it to finish booting up then flip the switch on the modified module.
3. Put the receiver in bind mode:
4. With the transmitter still turned off, press and hold down the BIND button on the module then turn on the switch on the module. The module will start flashing indicating it is in bind mode. When the receiver no longer flashes rapidly you can release the BIND button on the module.
5. Wait for the bind process to finish - this will be indicated by the lights on the module and receiver coming solid on.
6. Remove power from the receiver and if using a standard receiver remove the bind plug.
7. Turn off the switch on the module.
IMPORTANT: Specific to DSM2/DSMX receivers is that the fail-safe is set at the receiver during bind. Because of this the above binding procedure has to be performed for each model at least twice - once to establish initial connectivity between the module and receiver and a second time after the model set up has been finished. This second bind will set the correct fail-safe. If you make any major changes to a model set up, especially channel reversing, perform the bind procedure again.
Using the Modified Spektrum DM8 DSM2 Module
1. With the receiver power turned off and throttle stick all the way down, turn on the switch on the module. Wait until the module finishes powering up - the light on the module to come on.
When the transmitter power switch is left in the off position and the module power switch is turned on it powers the module and the transmitter but only the stick encoder/mixer part of the transmitter. The transmitter internal 2.4GHz RF circuitry is left without power. This has a double effect - 1) does not pollute unnecessary the 2.4GHz band and 2) saves power. If you use the transmitter switch to turn on the system it will provide power to the module but it will also power up the whole transmitter, including its own 2.4GHz RF circuit so it will use more power from the battery.
When the module switch is turned on while the transmitter switch stays in the off position, the transmitter powers up and in the case of the 8FG and 14SG transmitters "DSC/TRAINER CABLE IS CONNECTED" message is displayed:
After several seconds the transmitter shows the main screen. The RF monitor light on the transmitter (on the right for the 8FG and 14SG) flashes slowly to show that the internal RF circuitry is not transmitting. The 8FG/14SG display shows two little transmitter icons connected with a wire as a reminder that the transmitter is in DSC/Trainer mode:
2. Power up the receiver/aircraft. Wait for a solid light from the receiver indicating communication from the module to the receiver.
3. Perform a pre-flight check to make sure all control surfaces move in the desired direction.
4. Before the first flight for the day on that model do a range check. Place the aircraft on a surface at least 2-3 feet above the ground. Press and hold the BIND button on the module and walk 20 paces away - you should have control over the aircraft.
5. If the pre-flight and range checks are good, enjoy flying the aircraft.
6. After landing, remove power from the receiver.
7. Turn off the switch on the module.
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