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LANDTASTIC
The Ultimate R/C Model Retract Controller

The GWS Formosa is a good looking model that uses retracts.


This low cost project is used to slow down retractable landing gear. It also adds remote activated Landing Lights and a Lost Model Finder feature.

Wish to see it in action? Just click the photo on the left to see the short demo video.


A big parkflyer crowd pleaser has got to be retractable landing gear. The spectator "Wows" you hear when the gear goes up is a big reward. But it just doesn't look right to see the wheels fling closed at lightning speed instead of slowly retracting.

The solution is to use a "servo-slow," which is an add-on device that {like its name implies} can slow down a R/C servo. But instead of using a commercially made solution, we rolled up our sleeves and designed our own. The result is much more than a retract controller and you will soon see that it is simply fantastic. Or in this case, it is Landtastic!

Landtastic is a little microcontroller based device that allows you to slow any proportional R/C servo. With it installed between your R/C receiver and servo, your landing gear will move at realistic scale speeds. Servo transit times can range from one to ten seconds.

In addition to the servo-slow feature, it can optionally add remotely activated landing lights and anti-collision strobe lights. This project is ideal for scale model aircraft since attention to these little details will usually earn additional contest points. And more crowd pleasing "Wows".

Please note: It can also be used to slow down a camera panning servo. This will allow you to obtain smooth camera movement from a switch or stick controlled R/C servo.

And for those that need extra protection, Landtastic even includes a Lost Model Alert feature. By installing a miniature (but loud) piezo buzzer, your model will emit a high pitched alarm noise whenever the Tx is turned off. This is perfect for locating models lost in the brush.

Your R/C equipment is not modified in any way. Landtastic connects between your servo and the receiver's Gear or Aux channel. For proper operation, your R/C transmitter should use a toggle switch control; spring-centered sticks are not supported.

Landtastic Feature Summary:

  • World's first fully featured, user programmable, R/C parkflyer landing system controller.
  • Slows down any proportional R/C servo, allowing up to ten seconds of retract time. Servo torque is not affected.
  • End-of-travel inertia brake gently parks the retract system.
  • Sophisticated navigation lighting; Remote activated Landing Lights and anti-collision Tail Strobe.
  • Lost Model Finder alarm for those unexpected landings in the brush.
  • Compatible with AM/FM/PCM systems. Note: The Lost Model Alarm is not available when used with failsafe (PCM or DSP) receivers.
  • Works with stock proportional servos, analog or digital.
  • No modification required to the R/C system. Plug-in installation.


What's Tiny, Black, and Has Eight Legs?

The project is based on a tiny black 8-legged chip (no, its not a spider). Our 8-legged host is a MicroChip Technologies PIC12F629/675 MCU. Also known as a PIC microcontroller. It requires software (called firmware in this situation) that is available in the file download section.

The PIC decodes the R/C servo signal and adds a time integration factor to the servo pulse in order to slow down the servo. It also handles the landing light's on/off control and blinks the strobe light. Furthermore, it carefully checks the servo pulse for suspicious signals and will discard any that are corrupt. If the R/C signal is missing it will sound a very loud alarm (hey, just turn off the R/C Transmitter to find your lost model).

Even though a microcontroller is used, cost is minimal. You can build the basic system for under $10. Total parts count is very low (two parts!) and the assembled prototype weighs under 5 grams. It can be as small as you care to make it (typically about 3/4" square).

Landtastic's PIC12F629/675 PinoutThe eight pins on the PIC chip exist as one of three kinds of signals: Power, Digital Input, or Digital Output. The digital inputs are level sensitive and are said to be logic high when the voltage is greater than 2.0VDC and logic low when they are less than 0.5V. Output voltages are similarly defined. Logic high output voltage is equal to VCC and a logic low output is 0VDC.

If you are ready, let's take a quick tour of the various signals on the PIC chip:

PIN

FUNCTION

DESCRIPTION

1

VCC
(Power)

Allowed voltage is 3.9 VDC to 5.5 VDC @ 2mA current draw. Landtastic works well on a four cell R/C pack (4.8V) or the 5VDC BEC output of most electronic speed controls (ESC). Do not exceed the maximum voltage.

2

RC-OUT
(Output)

R/C servo pulse Output. This output connects to your proportional servo. Can directly drive up to five servos.

3

LMA
(Output)

Lost Model Alert. This optional output connects to a piezo buzzer. Logic high active, must be buffered by a transistor.

4

RC-IN
(Input)

R/C servo pulse Input. This input connects to R/C receiver.

5

STROBE
(Output)

Anti-collision Strobe light. This optional output connects to the Strobe light. Logic high active, must be buffered by a transistor.

6

LANDING
(Output)

Landing Lights. This optional output connects to the Landing Lights. Logic high active, must be buffered by a transistor.

7

CONFIG
(Input)

Configuration mode enable. This pin is used to configure the Landtastic for operation with your R/C system. Logic low active (e.g., connect to ground).

8

GND
(Power return)

0 VDC. Ground.

Your exact PIC choices have some flexibility. You can use a PIC12F629 or PIC12F675 (your choice). The PIC is a "Flash" part, so it can be re-programmed hundreds of times. This allows for cheap software upgrades since the same part can be used.

Be sure to properly select the PIC's configuration fuses before chip flashing. They should be automatically set by the hex file, but it is always a good idea to verify them. These fuses are managed by special settings within your chip programmer's menus.

Example of hobby type flash programmer screenshot. Click to see larger view For example, the screen shot on the right (click for larger view) shows how they may appear in your hobby grade flash tool. The required fuse settings are summarized below:
Oscillator (OSC): IntOSC GP4
Watch Dog (WDT): Disabled
Power Timer (PWRT): Enabled
MCLR (Master Clear): Disabled
Brown Out (BODEN): Enabled
Code Protect (CP): Disabled
Code Protect Data (CPD): Disabled

Warning: If your chip programmer asks if you wish to use the OSC CAL value from the hex file, then be sure to click the response that leaves the value alone. If you use the data from the file it will over-write the factory stored CAL data and the PIC will be rendered useless! You should also read this: OSC cal data corruption work-around.

The required firmware (hex file) that is needed to flash-program the PIC is provided at no charge for personal/hobby use. This means that a R/C hobbyist can install the firmware into their PIC, license-free. You are not allowed to do this for others and you cannot sell the project. In other words, anyone that wishes to offer a pre-programmed part (or a finished product), must first contact the RC-CAM site for written permission. Sorry, but the text based source code is NOT available.


Construction: It's Tool Time!

There are two sets of schematics for you to choose from. One shows the basic Landtastic design that offers just the servo-slow feature. Only two components are needed; the PIC and a capacitor. The second schematic shows the deluxe version, which includes the optional Navigation Lighting and Lost Model Alert. This version requires very few additional parts and is highly recommended. By the way, you can pick and choose your options as you see fit -- you do not need to install them all. The board's components are from www.digikey.com and the navigation lighting LED's are from www.superbrightleds.com.

Perfboard construction works wellThe circuitry can be built using nearly any technique you wish. Ours was built on phenolic perfboard and point-to-point wired using 30 gauge insulated Kynar wire (Radio Shack #278-502 white or #278-503 blue). I recommend a temperature controlled 40 watt or less soldering iron (700° tip).

On the left you can see the basic Landtastic circuit (no options). The cable connects to the R/C receiver and the 3-pin header under it connects to the servo. The 2-pin header on the right is used for configuring the Landtastic. Not shown is a little jumper block that temporarily plugs into it to make feature setup an easy task.

Perfboard layout is not critical except that the C1 cap should be close to the PIC, which is seen as the little yellow blob at the top end of the IC. If possible, use a socket for the PIC chip (machine pine type is recommended). If size and weight are issues, you can skip the perfboard altogether. Instead, just solder the parts directly to the IC socket. If weight is really an issue, skip the socket too. Landtastic shown with LED drivers

If you wish to use any of the optional features, then perfboard or a custom PCB will be needed. For example, the board on the right has the Tail Strobe and Landing Light options on it. It only took two transistors and three resistors to complete the job. The two SIP sockets at the lower right are used to connect the navigational lights (high-lumen LED's), but you can hardwire yours if you wish.

Adding the Lost Model Alert requires just one more transistor and a tiny piezo buzzer. By the way, the buzzer serves double duty. During system configuration, it will beep special codes to indicate the setup/config status. This is very convenient and highly recommended, but adding the buzzer is not mandatory.


Click image to visit the LED Calculator PageThe R1, R2, and R3 LED current limiting resistors show values for the LED lamps that are specified. However, you may wish to use alternate colors or intensities, so be prepared to optimize the resistors for your chosen LED's. We created a handy online resistor calculator to make this a painless effort. Please visit the RC-CAM LED Calculator web page and follow the instructions. Valuable LED information can be found there too.

The LED's are connected to the board using appropriate lengths of small gauge wire. I highly recommend using 30AWG Kynar (wrapping wire). Do not worry about the wire's small size -- it will carry enough current for any LED that you may use.

Be careful how you run the tail strobe LED wiring near your receiver's antenna. Some R/C installations have antennas that run down the length of the fuselage or inside the wings. This might be the same path that your LED wires need to travel. The two will not get along unless you separate them by at least a couple of inches. And to further reduce the chance of R/C receiver interference, each LED's wire pair must be twisted along their entire length, about three twists per inch. The schematic shows this as criss-crossed lines, so use that as a reminder.

Noise Suppression Ferrite CoreIn the rare case where servo glitching occurs at the strobe's blink interval, you should try installing the optional C2 cap. Also helpful is a tiny ferrite toroid core installed on the tail strobe's LED cable. The core must be installed within one inch of Landtastic's circuitry. At least five wraps (more is better) tightly threaded around the toroid core is all that is needed. Two likely candidates are the the (Electronic Goldmine #G4357, 0.31" OD x 0.15" ID x 0.14"H) or the Digi-Key #P11364. The photo on the right shows an example of the Goldmine core with five wrapped wires. It was not needed on our model.

For more information on Navigational Lighting projects you might want to read the RC-CAM Nav-Lights page. Perhaps you'll pick up a tip or two from that project.


Let's Test Basic Operation:

It's time to check out your newly built board. Let's assume you built the deluxe version with all the options. If your circuit is not using the extra features (Lighting and/or Alert) then just skip the text that mentions them.

Please double check your work, especially the wiring to the J1/P1 connectors and U1 pins 1 and 8. Simple mistakes can destroy electronic parts, servos, and may generally ruin your day. If any step fails, immediately remove power and check you work.

  1. Plug J1 into your receiver's gear channel and connect the servo to P1. Verify that the jumper at P2 is NOT installed. If possible, remove the pushrod from the servo if it is connected to your retract mechanics.
  2. With the R/C Tx (transmitter) turned off, turn on the Rx (receiver). After a short delay, you should see the tail strobe slowing blink (20 to 30 beats/min) and the piezo alert should beep at the same rate. This demonstrates the Lost Model Alert feature.
    Note: The Lost Model Alarm is not available when used with PCM Rx's or those that have failsafe-like features (as seen on some of the new "DSP" designs).
  3. Turn on the R/C transmitter. After a moment, the beep should stop and the tail strobe should go out. The servo may slightly jump, at full speed, as it initializes to its home position.
  4. Flip the Tx gear switch to the other position. The servo should move, but at a speed that is much slower than usual. If you watch closely you may notice that the servo's speed slows even more at the end of the travel; the final little stepping is the inertia brake. If the strobe light is not winking (double blink at about 50 beats/min), then flip the gear switch again. The landing lights should turn on and off, depending on the switch position. Do not worry if the servo direction or light control is reversed. We will take care of that in a moment.


But First, a Word About Our Sponsor:

With Landtastic, your R/C transmitter's mix features are unaffected. Only the servo speed is changed. So it is often more convenient to set up the retract mechanic's travel before you install Landtastic. Once installed, you will need to configure it for your desired travel speed, servo direction, and Tx switch's gear-down position. We will fully explain how to do that in the next section.

The nice thing about Landtastic is that it includes a servo reversing feature. This is handy to have if your Tx does not include that on its Gear/Aux channel.

When you use the optional landing lights and tail strobe options, a special Arming Feature is employed. The lights will not be enabled until the Gear/Aux channel is put through a simple initialization sequence (similar to motor ESC arming). So, when you first turn on the system ALL the lights will be off. This helps conserve battery power while working in the pits.

Here is the proper way to use the system when the lights are used (you can ignore this section if they are not installed):

  • Set your Gear/Aux switch to the "Gear Down" position. Turn on the R/C Tx, then turn on the R/C Rx.
  • When you are nearly ready to launch the model, hold the model off the ground (to protect the retracts) and cycle the Gear/Aux switch at least one time.
  • The strobe light and landing lights will now be operational.
  • Once airborne, flip the retract switch to the "Gear Up" position. The landing lights will go out as the landing gear retract. The anti-collision strobe will remain on.


System Configuration: Have it Your Way

At this point your newly assembled board is ready to use. If you like the default five-second retract time then no further action is required -- just install it and head on out to the flying field. However, if you want to personalize the system for your special needs, then we've got you covered!

The various operating parameters are user-configureable. All it takes is your R/C transmitter and a little jumper that is installed on Landtastic's P2 connector. The configuration is stored in the PIC's EEPROM memory. It is retained even if the battery is disconnected. A one time setup is all that is necessary, but you can change it as often as you would like.

You will need a servo channel controlled by a variable stick or knob in order to enter the configuration data. Sorry, but the simple on/off toggle switched channels cannot be used for this. I suggest you borrow the elevator channel for the task. Let's assume that is what you will use.

Before you get started, you need to identify the native stick direction for both the Gear/Aux and Elevator channels. With the Landtastic board removed, connect the retract servo to the Rx. Set the Gear/Aux switch to the "Gear Down" position. Make a mental note of the servo's position.

Now connect the same servo to the Rx's elevator channel. Move the stick around to determine which stick direction moves the servo {in the same direction} that represents the Gear Down position. During the programming steps, when asked to move the stick to the Gear Down (or Gear Up) positions, please use what was observed here. To configure Landtastic, please follow these simple steps:

  1. Connect Landtastic to your R/C Rx's elevator channel and to the servo. Verify that the Tx's elevator trim lever is centered and that dual rates, if present, are disabled. If your Tx has adjustable travel volumes (EPA, T-ADJ, ATV) then ensure they are at least at 100% (125% is best).
  2. Install the jumper on P2. With the Rx off, turn on the Tx and hold the stick in the extreme "Gear Down" position.
  3. With the Tx stick held in position, turn on the Rx. If the piezo buzzer option is installed, you will hear one or two beeps, depending on the stick's position (one beep for normal stick direction, two beeps for inverted stick direction).
  4. You have just told Landtastic the Gear Down stick position. So far, so good.
  5. You will now notice that the servo is slowly moving back and forth. It is waiting for you to enter in the servo travel speed. Just move the stick until you see the retract speed that you like best. There are ten available speeds, from about one second to a little over ten seconds.
  6. Once the best speed is found, hold the stick steady while you remove the jumper. A long beep will be heard to indicate that the configuration data has been stored. You can now move the stick around to watch the servo cheerfully use its new speed. If you ever wish to change the speed and/or stick direction, then go back to step 1.

When fast servo speeds are used (under five seconds of travel time) an end-of-travel braking feature is available. When enabled, it will slowly step the servo whenever it is close to stopping. If you wish to change this (enable or disable it), then follow these steps:

  1. Continue with the setup described above in step 1.
  2. Turn off the Rx. Re-install the jumper on P2.
  3. Turn on the Tx. Hold the Tx stick exactly at center position (a spring loaded stick's hands-off position).
  4. Turn on the Rx. You will hear three or four beeps. Three beeps indicates that you are requesting to turn the inertia brake on, four beeps means you want to turn the inertia brake off.
  5. If a piezo buzzer is used, and an undesirable beep count is heard, then turn off the Rx's power NOW and go to step 12 (this conveniently aborts the brake mode change). Otherwise, continue with the update by leaving Rx power on.
  6. Remove the jumper -- the brake programming is complete. Please note that this configuration feature is a toggle function. Each time you fully complete steps 7-12 you will toggle the inertia brake on and off. Please keep this in mind if you do not have the piezo beeper installed.

Once you have re-installed Landtastic on your Rx's Gear/Aux channel and connected the servo to the retract mechanics, you need to verify proper servo direction. If you discover that the servo direction is reversed, do NOT fix it by using the reversing function found on your R/C Tx. Instead, you must configure the servo direction from Landtastic. Please follow these steps:

  1. Ensure the jumper is removed from P2. Turn on the Tx and Rx.
  2. Re-install the jumper on P2. This will toggle the servo direction. You will hear five beeps or six beeps, followed by silence. The servo will not move.
  3. To enter the new servo direction please go to step 16. To abort the change just turn off Rx power and continue to the next step.
  4. Remove the jumper and confirm servo direction is correct.


File Downloads: It's All in the Details

The technical details are available as file downloads. There is no charge for the information when used in a personal (hobby) project. Commercial users must obtain written approval before use.

Please be aware that the information is copyright protected, so you are not authorized to republish it, distribute it, or sell it, in any form. If you wish to share it, please do so only by providing a link to the RC-CAM site. You are granted permission to post links to the web site's main page (http://www.rc-cam.com/). Please respect this simple request.

Schematic Files Schematic Files: CAD files for the circuitry. PDF Format.
Revision: A. Released Jan-19-2004.
Jan-24-2004 Update: Added drawing of 2N7000 pinout.
PIC Object Code Files PIC Object Code: Firmware (HEX file) for flash-programming the PIC chip. You should occasionally check for updates.
Revision: V1.1. Released June-01-2005.
PCB Art Files Instructions: PDF file of the configuration instructions.
Released Jan-19-2004.



The Small Print:

If you need a part then please consult the sources shown in the project (see schematics download). I do not work for, nor represent, ANY supplier of the parts used in this project. Any reference to a vendor is for your convenience and I do not endorse or profit from any purchase that you make. You are free to use any parts source that you wish.

All information is provided as-is. I do not offer any warranty on its suitability. That means that if you build and use this device, you will do so at your own risk. If you find software bugs then please report them to me. I can only make corrections if I can replicate the bugs, so please give me enough details to allow me to witness the trouble.


FeedBack:

I would enjoy hearing from anyone that uses the Landtastic model landing system. Please send me an email if you build it.




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