Essential Instructions (LM0087X)

Description

The Lemon Rx LM0087 Ten-channel Stabilized Receiver is a full-range DSMX/DSM2-compatible receiver, part of Lemon's Generation 2 line. It combines full-range telemetry functions with the well-proven Lemon rate stabilizer technology to iron out turbulence. The stabilizer is small, light, offers long range and high performance with its "dual diversity" antenna system. A Lemon DSMP satellite receiver can be added for enhanced signal reliability, though it is not normally required. Its slim profile, ten available channels, and built-in barometric sensor make it attractive to glider pilots. It also features isolated inputs for multiple power sources and automatically switches between DSMX and DSM2 modes. The LM0087 is compatible with most Spektrum transmitters (DX, NX, iX series) and open-source transmitters with compatible modules like the RadioMaster TX16S. Telemetry is available if supported by the transmitter. While labeled a 10-channel receiver, when configured as a stabilizer, it typically offers 8 or 9 output channels. Channel 7 is usually for stabilizer ON/OFF, and Channel 8 for Master Gain. Channel 7 can be freed up for always-on stabilization. A ten-channel transmitter with voice capability is recommended for full functionality.

The LM0087X version, introduced in August 2024, features a Text Display for simplified programming, while retaining the older LED and button programming methods.

Connections

The receiver has six sets of pins on each end, arranged in the standard Spektrum order: Channels 1-10 (T, A, E, R, G, Aux1, Aux2, Aux3, Aux4, Aux5). Channel 10 pins also serve as a bind plug connector. Channels 8 and 9 are labeled S.Ch and Mix, useful for setup if Text Display is not used. Optional isolated BEC (separate power source) inputs are labeled BEC1 and BEC2. Connectors for an optional satellite receiver and a voltage/current sensor or voltage probe are also present. Note that Channel 1 is the second set of pins. Satellite and sensor connectors are identical but labeled. The receiver includes a built-in barometric sensor for altitude and vertical speed (vario) data.

Out of the box, the receiver has stabilization disabled and no internal mixes. It functions as a standard ten-channel DSMX/DSM2-compatible receiver. For unstabilized use, changing the default No-pulse failsafe to User-set is recommended.

Setting Up the LM0087X Receiver

Step 1: Powering the Receiver

The receiver requires a power supply between 4.0V and 8.5V. The most common source is an ESC (Electronic Speed Controller) providing 5V, typically connected to Channel 1. The receiver also has isolated BEC1 and BEC2 power input pins for alternative power arrangements. These are input-only and cannot supply power to other components.

Three common powering methods are illustrated:

• Via the Throttle Connector: Using an ESC with an integrated BEC, connected to Channel 1.
• Via BEC1: Using an external battery or BEC. Channel 1 controls throttle via a servo (for IC power) or an ESC without integrated BEC. The power source connects to BEC1.
• Via BEC1 and BEC2: Using both BEC1 and BEC2 simultaneously. An ESC with integrated BEC powers through BEC1, while a supplementary supply connects to BEC2. Channel 1 connection is not needed as throttle signal is routed from BEC1.

Step 2: Binding the Receiver

To bind the receiver to a transmitter model memory, use one of these methods:

• Binding Using the Bind Button: Power ON the receiver. Hold the Bind button (labeled B) for approximately 3 seconds until the red Receiver Status light flashes. If a satellite receiver is used, power cycle the receiver. Proceed with binding via the transmitter. Bind is complete when the red Receiver Status light (and satellite light, if connected) are solid.
• Binding Using a Bind Plug: With the receiver OFF, place a bind plug on the Channel 10 pins. Power ON the receiver (with satellite receiver connected, if used). The red Receiver Status light and satellite light will flash. Proceed with binding via the transmitter. Bind is complete when the lights are solid. Remember to remove the bind plug.

After binding, stabilization is inactive. Adding User-set failsafe is recommended.

Step 3: Setting Failsafe

The default failsafe is No-pulse mode, where the receiver ceases sending pulses upon signal loss, causing servos to hold their last position and the ESC to shut down after a delay. User-set failsafe is often preferred, sending pre-set values to servos and ESC upon signal loss.

To activate User-set Failsafe:

1. Power ON the transmitter and set sticks/switches to desired failsafe positions.
2. Power ON the receiver.
3. Within 60 seconds of powering ON, press and hold the Failsafe button (labeled F) for 3 seconds.
4. Release button F when the green Setup LED turns ON.
5. Test failsafe by turning off the transmitter.

To cancel User-set Failsafe:

1. Power ON the receiver (green Setup light should be ON if User-set Failsafe is active).
2. Within 60 seconds of power ON, press and hold button F.
3. Release button F when the green Setup LED turns OFF (indicating No-pulse mode).
4. Alternatively, cancel via the Text Display Setup menu.

Setup is complete if stabilization is not needed. Stabilization is inactive if none of the red programming LEDs (R1, R2, R3) are lit.

Step 4: Activating Stabilization

This section assumes a Spektrum Generation 2 or later transmitter with recent AirWare. Compatible radios can also be used.

Programming the Receiver for stabilization can be done via Text Display (easier) or using the receiver's LEDs and buttons (refer to LM0087 instructions for details: LM0087 Instructions).

When stabilization is active, specific mixes like Delta Wing (elevons) and V-Tail must be configured in the receiver, not the transmitter, to prevent crashes.

WARNING: Remove the propeller when programming an electric model with the motor connected.

LED Identification: Understanding the LEDs is crucial for verifying receiver setup. The diagram shows programming LEDs (G1-G3, R1-R3), Setup LEDs (blue/green), and Status LEDs (red/green). Adjustment pots are labeled A (Aileron), E (Elevator), and R (Rudder).

Programming Stabilization with Text Display: Text Display allows viewing and changing stabilizer settings on the transmitter screen. It's available for Lemon telemetry receivers (7- and 10-channel) and uses Spektrum's "TextGen" DSMX functionality. Ensure your transmitter has the latest AirWare version. For EdgeTX transmitters (e.g., RadioMaster TX16S), setup involves scripts (see Appendix 1).

Accessing Text Display: Bind normally. The transmitter should establish a telemetry connection. For example, a Spektrum DX8e will show telemetry screens during setup. After binding and configuration, the last telemetry screen should display information like the examples shown (Spektrum DX8e, NX8, iX14).

Initial Screen: Basic Text Display Information: Displays individual gains for Aileron, Elevator, Rudder, and Master Gain (set on Channel 8). These update in real-time. Mixer modes (NT, DT, VT, Rx Only) and stabilizer response directions (Normal/Reversed) are shown. Throttle Lock (TL) is typically ON by default.

Setup Mode Screen: To change settings, enter Setup Mode. Within 60 seconds of powering up the receiver, hold both transmitter sticks in the lower outside corners of the gimbals. The Lemon RX display will change to show setup options.

Navigating Setup Mode: The first line indicates the item to change. Use the Elevator stick (up/down) to change the value. Use the Aileron stick (left/right) to navigate between screens (increment/decrement screen number).

Basic Screens: Change stab reaction direction for Roll, Pitch, Yaw; select single/dual aileron response; Show Config; Exit & Save; Exit without saving.

Advanced Screens: Accessed via "Show Config." and Elevator stick. Options include changing stabilizer mode (NT, DT, VT, Rx Only), ON/OFF switch channel (5 or 7), Always On stabilization, Throttle Lock (ON/OFF), cancelling User-set failsafe, resetting to factory settings, and calibrating sensors.

Step 5: Using Stabilization

This assumes receiver programming is complete and items 1-3 (transmitter setup, binding, testing) are done before mounting.

1. Set up the transmitter: Create a new model or reset an existing one. Disable any transmitter delta wing or V-tail mixing. Set servo Travel to 100%. Assign a switch for Stabilization ON/OFF (default Channel 7, optional Channel 5) and a knob/slider for Master Gain (Channel 8, if available).
2. Bind the receiver: As described in Step 2.
3. Test the receiver: Power ON transmitter and receiver. Red Status LED should be ON. Verify the Stabilization ON/OFF switch works. Green Status light indicates stabilization is ON (e.g., Channel 7 at -100%). Test servos on Ail, Ele, Rud outputs. Power OFF.
4. Mount the receiver in the plane: Mount upright or inverted, aligned with flight direction. Ensure antennas are well separated and not obstructed. Mount securely using supplied tape or vibration-absorbing material. A satellite receiver can be used for extra reliability, placed separately. Ensure access to gain pots.
5. Connect servos and ESC, set switches and wing type: Ensure motor is disconnected or propeller removed for safety.

Table 1: Configuration for Various Model Types details servo assignments for channels 1-8 and stabilizer red LED indicators for different model types (Conventional, Delta Wing, V-Tail) and wing types (Normal, Dual Ail/Flaperon). Channel 5 (Gear) can be used for Stabilization ON/OFF on 6-channel transmitters, but is typically a normal servo output on 10-channel receivers.

6. Verify control directions, adjust centring and servo throws: With stabilization OFF (green Status light OFF), center servos and adjust linkages. Use minimal subtrim. Ensure servo arms are at right angles. Verify transmitter reversing for correct servo response. Set control surface throws to recommended maximums mechanically, as transmitter adjustments won't affect stabilization response.

7. Test stabilization response and directions: Turn gain adjustment pots clockwise (or set Master Gain). Set Stabilization ON/OFF to ON (green Status light ON). Sharply move the model in each axis; control surfaces should momentarily oppose the disturbance. If surfaces move the wrong way (increasing disturbance), switch OFF stabilization immediately and correct the direction via Text Display or LEDs (G1 for Aileron, G2 for Elevator, G3 for Rudder).

9. Set dual rates and expo in the transmitter: With correct control directions and throws, adjust transmitter stick response using dual rates (D/R) and expo. A starting point for D/R is 100% (High), 80-85% (Mid), 65-75% (Low). Expo around 20% softens response near neutral. Stabilization settings may slightly reduce sensitivity.

Adjusting Gains and Flying

10. Adjust the stabilizer gain pots

Gains are normally at the 12 o'clock position. For first flights, set pots to approximately 10 o'clock for noticeable stabilization. Adjustments during flight testing are common for optimal stabilization.

11. Prepare for flying

Check model balance. Verify control directions and stabilization functions. Perform a reduced-power range test (at least 30m/100 feet). Check the stabilization ON/OFF switch operation (green and red lights for ON, red only for OFF). Test failsafe operation by turning off the transmitter.

If using Master Gain (Channel 8), set it to the middle range and ensure increasing it increases stabilizer reaction.

12. Test fly

Start test flights with stabilization OFF (green Status light OFF). After takeoff and trimming, turn stabilization ON at a safe height. If the model behaves erratically (rolls, dives, oscillates), switch OFF stabilization immediately and check gyro directions. For oscillations, reduce gain on the affected axis or lower Master Gain. Explore the stabilizer's action by performing maneuvers and observing its effect. Note that stabilization may reduce responsiveness on some axes. Experiment with dual/triple rates and Master Gain.

13. Fine tune stabilizer gain

Optimal gain is just below the point of oscillation at high speed. This requires iterative flights and adjustments. Master Gain can accelerate this process. If not using Master Gain, adjust rudder, elevator, and aileron pots sequentially, testing for oscillation after each adjustment. Generally, aileron gain is lowest, elevator mid-range, and rudder highest, but this varies by model.

HINT: Perform initial setup in calm conditions to distinguish stabilizer-induced oscillation from turbulence.

14. Restrict Master Gain (if applicable)

To prevent excessive gain causing oscillation, limit Master Gain. This can be done via transmitter's Servo Setup (limiting travel on Channel 8) or by assigning Channel 8 to a switch and using Digital Switch Setup to set specific values (e.g., -20%/0%/10%). Note that these settings may prevent disabling stabilization if Always-ON is used.

Using Telemetry

Telemetry is independent of stabilization. The document “Telemetry with the Lemon Rx 7- and 10-Channel Receivers” provides detailed setup and calibration information (Telemetry Guide).

Lemon Telemetry Receivers send data on receiver voltage, temperature, RSSI (signal strength), altitude, and vertical speed (vario). Flight battery data can be provided via a voltage sensing wire or an optional V/I sensor. Alarms can be set on the transmitter for low voltage or exceeding height thresholds. To use telemetry, turn on the radio and receiver, go to Telemetry, and run "Auto-Config" if parameters don't appear. Settings allow selection of metric or US units. The transmitter can display parameters and set alarms.

The transmitter can record telemetry data on an SD card for review. Recalibration for sensors uses specific advanced screens and the "Telemetry with the Lemon RX 7 and 10 Channel Receivers" document.

Factory Reset the Receiver

A reset cancels all programming, returning the receiver to its basic, unstabilized state. The transmitter is not required.

1. With the receiver ON, press and hold Button B and Button F simultaneously for about 6 seconds.
2. Release buttons when all receiver LEDs flash.
3. Press Button C briefly. The receiver will flash and reboot.
4. Reset is complete. No lights will show.

Note: Reset does not clear the existing bind. The receiver can also be reset via the transmitter and Text Display.

Appendices

Appendix 1: Setting Up Text Display with EdgeTX

For color-screen radios like the Radiomaster TX16S, bind as usual, press SYS, select TOOLS (Wrench/Screwdriver), then "DSM Smart RX Telemetry", and finally "TextGen". For black-and-white screen EdgeTX radios, download the DSM_Telemetry zip file from GitHub (DSM Tools GitHub), extract DSM_SmartRX_Tel.lua, and copy it to the SCRIPTS/TOOLS folder on the SD card. EdgeTX versions 2.8.3 and later support TextGen.

Appendix 2: Meaning of the LM0087X Receiver LEDs

LED Identification: The diagram shows programming LEDs (G1-G3, R1-R3), Setup LEDs (blue/green), and Status LEDs (red/green). Pressing button C briefly identifies the programming lights.

Red Stabilization Option LEDs: R1, R2, R3 indicate stabilization mode: Option A (Delta Wing/Elevons) - R1; Option B (V-Tail) - R2; Option C (Normal Tail) - R1+R2; Option D (Dual Aileron/Normal Tail) - R1+R2+R3; Option E (Dual Aileron/V-Tail) - R2+R3. Text Display is used to choose the option. Dual Aileron Channel is set separately.

At least one of R1 or R2 must be ON for stabilization. When stabilization is ON, the green Status LED is illuminated.

Green Stabilization Direction LEDs: Indicate if control channels (A, E, R) are Normal (OFF) or Reversed (ON). Direction must be determined by physical testing and changed via Text Display.

Stabilization ON/OFF: Controlled by a switch assigned to CH7 (Aux2) by default, or CH5 (Gear). Indicated by the green Status LED.

User-set Failsafe LED: A green Setup LED indicates User-set Failsafe is active.

Appendix 3: Understanding Throttle Lock

Throttle Lock (TL) is a function that modifies User-Set Failsafe behavior. When TL is ON, upon signal loss, the receiver sends a series of Throttle OFF commands (-100%) for 0.1 seconds, then all channels go to logic low. This forces the ESC to zero and stops servo pulses. This ensures the motor stops instantly and control surfaces hold position. If TL is OFF, all channels go to logic low (no pulses sent) upon signal loss. TL is ON by default and is recommended for most electric planes. It can be turned OFF for models where Channel 1 is used for other functions (e.g., gliders) or for IC engines.

Appendix 4: Troubleshooting Text Display

Problem 1: Text Display screen does not appear: Your receiver may not support Text Display. Some early production receivers with the new firmware might not have this feature. Binding may have failed; try reconfiguring telemetry recognition on your Spektrum transmitter by selecting "TextGen" as Active.

Problem 2: Setup Mode does not work: Early Text Display firmware versions may not support Setup Mode. Ensure Setup Mode is available within 60 seconds of power-up. Your receiver or transmitter may not support Setup Mode (check firmware versions for Spektrum and EdgeTX). Ensure stabilization is OFF and channel outputs are correct (check dual rates, servo output/travel, throttle kill/lock, and model configuration).