Non-Proportional RC Encoder

PRELIMINARY INFORMATION

Non-proportional RC Encoder

The Non-proportional RC encoder is a microcomputer-based digital encoder that simulates reed or single-channel operation. It is designed to utilize, in most cases, modern unmodified proportional flight equipment in the airborne environment. The customer will be expected to construct or modify an antique style transmitter using this encoder to complete the system. The construction skills required are those expected of any radio amateur.

Using a modern flight package allows you to trim and fly your vintage aircraft before committing to non-propo flight. The encoder provides a trainer output compatible with Futaba transmitters so that skills may safely acquired. RF output may be provided using an off-the-shelf 50 mHz Futaba or similar module.

Reed Operation

Reeds were used by modelers for multi-control before the development of modern digital proportional. Reed transmitters, rather than being dominated by two joysticks, were dotted with self-centering Switchcraft-style toggles. Popular channel numberings were two times the number of toggles with six, ten, and twelve channel systems controlling three, five or six servos.

Servos came in two varieties: neutralizing (self-centering) and trim (translational). Neutralizing servos were typically used for the basic flight control surfaces aileron, elevator and rudder. Trim servos were used for throttle, auxiliary functions and trim. The modeler would link a trim servo mechanically to a neutralizing surface servo (usually elevator) in such a way as to provide a summed output to the pushrod. The common ten channel system would thus have three neutralizing servos and two trim servos. This 3+2 setup was called ‘Full House’ in reference to the poker hand. Four channel propo systems were later on referred to as ‘Full House’ also since they provided the standard flight pack, but the expression lost its whimsy.

The ten-channel reed transmitter had laterally moving switches on the right side for rudder and aileron and vertically moving switches on the left side for motor, elevator, and elevator trim. A residual of this arrangement may be seen today in propo systems that are Mode 1. The reed transmitter was not capable of total simultaneous control. The right hand switches were committed to one tone oscillator and the left hand switches another. Both oscillators could run at the same time, but only with one frequency or switch deflection each. Complex maneuvers such as slips were virtually impossible.

A number of Vintage experimenters have tried to produce reed RC functionality by either cleaning up old systems or mixing them with digital proportional systems to some degree. This encoder concludes the task.

Reed Installation

Before handling the encoder board, be advised that it is static sensitive and should be handled using ESD procedures and equipment.

Preset the dipswitches (SW1) to the default settings:

1-ON

2-ON

3-ON

4-ON

5-ON

Refer to the diagram to make any further adjustments of the dipswitches.

Switch 5 will remain ON for any reed system. Switch 5 is turned OFF for single channel operation only.

Switches 1 and 2 reduce the servo speed to the lowest level, approximating that of a middle-aged Bonner Transmite. This speed was used in all the prototypes and is selected for smoothest flying with an aircraft set up for normal proportional flight. Increase the speed if desired after gaining experience with the system.

Switches 3 and 4 set the aileron and elevator channels to have the trims mixed in. Adjust this as required per the diagram. This default assumes the user may be swapping between proportional and reed transmitters. It may be desirable not to have aileron mixing should the ‘aileron trim’ channel be used as an auxiliary function. It is not desirable to have elevator mixing if a separate elevator trim servo is used.

We recommend that you remove the existing electronics. It may be possible to leave the existing PC board in place for appearance reasons, however it would require the removal of most active components so that they do not interfere with the new circuit.

Decide how and where you are going to mount the board, transmit module, and trainer connector. You probably are wiring in new batteries, replacing broken switches, etc., so get your plan squared away. You will want easy access to the board wiring and meter pot. The four holes on the board edge accept standard electronic standoffs and help provide good grounding to the case. However you decide to mount the board, do not omit a good case ground.

Obtain connectors and wire to connect to J1-J10 as required. These may be generic servo pigtails. Radical RC and other shops also sell unassembled connectors and crimp tools should you want to go that route. Use a good quality stranded hookup wire.

Before wiring, note that connectors J7-J9 are polarized as indicated by corresponding dots on the diagram. Observe this polarization!

Wire your batteries, charge jack, on/off switch and connector to J8 first. Meter this circuitry thoroughly before attempting to power the board though J8. At this point, the board may be powered and the modulation checked at the middle pin of J7 if an oscilloscope is available.

Complete the remaining wiring per the diagram. The connector to the transmit module will need to be cut down to approximately 0.65”. Use heat shrink tubing on the opposite side of this connector.

The J11 serial connector is for factory programming the encoder only and not for user access.

One may wish to wire only one front panel control switch and perform a preliminary system checkout before wiring the remainder. Note that channel reversing is performed by rotating the plugs in J1-J6.

Adjust the potentiometer (R37) as required to give the desired meter display with fully charged batteries. If further adjustment is necessary, the user may change the value of R38. When using your meter, be advised that it is a very coarse indication of battery level. Always double-check your batteries with an appropriate meter before flight.

We recommend that you buddy-box fly with a helper or fly a simulator with your vintage transmitter before attempting real unassisted flight. The transmit module may be disconnected or omitted for this kind of flying. Before using the RF module in flight, check your transmitter with a spectrum analyzer and range check thoroughly to assure safe, legal flight.

Good Luck!

Non-Proportional Encoder Specifications (Reed mode)

Power input: 9.6V nominal switched power

9.6V nominal from master trainer Tx

Power output9.6V nominal to transmitter module

Modulation Inputs:One to six self-centering switches, SPDT minimum.

Retrofit Tx type:Up to 12 channel reed

Modulation Outputs:Directly compatible with Futaba, 1.0ms-2.0ms with 1.5ms center

Meter output:Linear voltage, user adjustable by potentiometer

Digital Channels: Six

Receiver output:1: Aileron

2: Elevator

3: Motor

4: Rudder

5: Elevator Trim

6: Aileron Trim

Trims:Elevator and Aileron dipswitch selectable as

standalone channels or 20% mix

Recommended Rx:To match Tx module, four to six channels

Servos speed:Four speeds adjustable by dipswitch

Recommended Tx module: Futaba FP-TP-FM or FP-TK-FM on 50mHz

Recommended TX antenna length: 54”

Trainer connection:Slave only via Futaba six pin DIN

Serial input:9600 baud. Programming use only.

Size:2.5” x 3.0” 63.5mm x 76.2mm

Reed mode wiring diagram.

Single Channel Operation

Single channel manually keyed transmitters were the first type of RC used for controlling models. Input from the pilot consisted of a single spring-loaded push button.

Controls were typically rubber-band powered escapements, though surface vehicles often used motorized actuators. Near the end of the single channel keyed technology period servos became available that would provide similar sequential functions as escapements but giving more power and confidence.

The simplest escapement setups gave alternate left and right rudder outputs with interim neutrals. Compound escapements would give the same result every time, for example, one push for right rudder and two for left.

Some vintage experimenters have antique 27MHz single channel equipment of this type that they continue to use to this day. This encoder allows the vintage flier the opportunity to utilize a modern radio link to fly his single-channel escapement aircraft.

When used in the single channel mode, the Non-proportional Encoder board will deliver four channels to a matching proportional receiver. Channel four provides a direct output servo pulse of 1.0ms.or 2.0ms., depending on the state of the transmit key. This channel is for use with an external relay or speed control to directly trigger an antique escapement package. Such setups may be limited by their speed of operation, so it is up to the user to determine it’s suitability to a particular installation.

The remaining three channels are standard servo outputs to the rudder, elevator, and motor servos. The encoder generates signals to these three servos based on a simulation of two cascaded Bonner Varicomp compound escapements with a three-position quick blip motor. If the user desires a simpler control system, simply omit servos as required. For the truest reproduction of single channel flight, use the fastest servos possible.

In flight, the full system operates as follows:

1)Pressing and holding the key once will cause the rudder servo to cycle to right rudder and stop. Upon release the servo returns to neutral after passing through left rudder. This simulates the circular motion of the escapement output gear.

2)Pressing the key twice will cause the rudder servo to cycle to right rudder then left and stop. Upon release the servo returns to neutral

3)If the rudder is being held at the right position, a quick release and rekey will move the servo to the left position.

4)If the rudder is being held at the left position, a quick release and rekey will cause the rudder servo to go to the neutral position and the elevator servo to move to the up position. Unkeying the transmitter at this time will result in all surfaces returning to neutral, but the elevator servo will pass through the down elevator position.

5)A quick release and rekey while in the position described in 4) will cause the elevator servo to move to the down elevator position. The rudder servo will remain neutral at this time. Unkeying the transmitter at this time will result in all surfaces returning to neutral.

6)To change the motor servo position requires that the operator send a quick-blip while having neutral control surfaces. This is done by a “snap” of the transmitter button such that a pulse 20-60ms. is sent. The motor servo will cycle from neutral to high or high to low or low to neutral each time this is done. At turn-on, the encoder supplies neutral motor.

Single Channel Installation

Before handling the encoder board, be advised that it is static sensitive and should be handled using ESD procedures and equipment.

Preset the dipswitches (SW1) to the default settings:

1-OFF

2-OFF

3-OFF

4-OFF

5-OFF

Refer to the diagram to make any further adjustments of the dipswitches.

Switch 5 will remain OFF for any single channel system. Switch 5 is turned ON for reed operation only.

Switches 1, 2, 3 and 4 reverse the operation of the channels 1, 2, 3, and 4 in that order.

We recommend that you remove the existing electronics. It may be possible to leave the existing circuitry in place for appearance reasons, but if you do so make sure that it does not interfere with the new circuit.

Decide how and where you are going to mount the board, transmit module, and trainer connector. You probably are wiring in new batteries, replacing broken switches, etc., so get your plan squared away. Consider that you may want easy access to the encoder board. The four holes on the board edge accept standard electronic standoffs and help provide good grounding to the case. However you decide to mount the board, do not omit a good case ground.

Obtain connectors and wire to connect to J1 and J7-J10 as required. These may be generic servo pigtails. Radical RC and other shops also sell unassembled connectors and crimp tools should you want to go that route. Use a good quality stranded hookup wire.

Before wiring, note that connectors J7-J9 are polarized as indicated by corresponding dots on the diagram. Observe this polarization!

Complete the remaining wiring per the diagram. The connector to the transmit module will need to be cut down to approximately 0.65”. Use heat shrink tubing on the opposite side of this connector.

The J11 serial connector is for factory programming the encoder only and not for user access.

Good Luck!

Non-Proportional Encoder Specifications (Single Channel mode)

Power input: 9.6V nominal switched power

9.6V nominal from master trainer Tx

Power output9.6V nominal to transmitter module

Modulation Inputs:One spring action push button, SPST minimum.

Retrofit Tx type:Single channel manually keyed

Modulation Outputs:Directly compatible with Futaba, 1.0ms-2.0ms with 1.5ms center

Meter output:Linear voltage, user adjustable by potentiometer

Digital Channels: Four

Receiver output:1: Rudder

2: Elevator

3: Motor

4: Direct output

Trims:None

Recommended Rx:To match Tx module, four channels typical

Synthesis model:Two Cascaded Bonner Varicomps with three-tooth quick-blip motor escapement.

Recommended Tx module: Futaba FP-TP-FM or FP-TK-FM on 50mHz

Recommended TX antenna length: 54”

Trainer connection:Slave only via Futaba six pin DIN

Serial input:9600 baud. Programming use only.

Size:2.5” x 3.0” 63.5mm x 76.2mm

Single channel mode wiring diagram.

Kit Contents

Non-Proportional Encoder board
Trainer connector
Transmit module connector

Disclaimer

No warranty or guarantee, aside from the replacement of defective items, is expressed or implied. This product is experimental and it’s safe use is the responsibility of the customer.

ADDENDUM

Processor, Hardware Changes

Starting at software revision 2.6, the BX24 was replaced with a BX24P.

The BX24P encode output has been changed from pin 12 to pin 27 to improve stability. To achieve this, a shorting wire has been added between pins 27 and 12 of the BX24P module. The encoder printed circuit board remains unaffected.

Some BX24 modules were produced by the OEM with the red and green LEDs in reversed locations. This results in a lit green LED when a red LED should be lit and vice-versa. To date, this will only affects the neutralizing mode.

Neutralization

Starting at software revision 2.6, the users have the ability to slightly adjust the neutrals of each channel. This feature becomes necessary when using a buddy-box as your proportional unit may have centering at 1.50ms, 1.52ms or some other value. This becomes a problem if the non-propo encoder centers are beyond the range of the propo trim.

Adjust neutrals as follows:

Turn on your proportional transmitter and receiver, center the trims and joysticks and measure the pulsewidths at the receiver’s aileron, elevator and rudder channels. This should give you an idea of the neutral values to which you will want to adjust your non-propo encoder. If you do not have a pulsewidth measuring instrument, a reference servo with a long pointer attached will do.
On the non-propo encoder set dipswitch (SW1) #5 to “OFF”.
To enter the neutralizing adjustment mode, you will need at least one switch wired like the front panel switch in the reed mode wiring diagram. If the encoder is already mounted in a reed chassis, you should be all set. If you have a single channel chassis, you will have to fabricate this switch. If a paddle switch isn’t available, two pushbutton switches will work equally well.
Plug the switch from the previous step into J6, the aileron trim channel. (If you have a 12 channel reed system, simply use the aileron trim control.)
Deflect this switch in either direction and hold it while turning on the transmitter. A red LED should light on the BX24P module.
Now release the switch. The red LED should go out and a green LED should light on the BX24P. This indicates that you have entered the neutralization mode.
While in the neutralization mode, switches plugged into J1 thru J6 will be able to adjust the permanent centers of corresponding channels. Observing the receiver outputs using a pulsewidth meter or reference servo, use paddle (or test) switch(s) to match the neutral value determined in step 1. Note that the receiver channel outputs are affected by J1-J6 per the following table:
J1=Ch1
J2=Ch4
J3=Ch3
J4=Ch2
J5=Ch5
J6=Ch6
When you are satisfied with the neutrals, turn off the transmitter. Return the dipswitches to their proper condition. Reassemble transmitter.