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  1. #1
    Moderator Expert
    Join Date
    Jan 1970

    Default Yaesu G-400 Antenna Rotator Controller


    Antenna Rotator Controller
    ( only for the inexpensive type with pot feedback )

    A very simple controller circuit, with fairly smart performance! Can't afford a fully automatic computer controlled rotator, but would like more capability from your basic rotator? Would you like a simple to use "point and shoot" computer controlled antenna? You've come to the right place!

    What it does -

    • Sends the rotator to a specific heading without you needing to hold a switch down
    • Allows your digital mode or logging software to control the rotator heading
    • With PC software supplied, you can send the rotator to favourite headings, or a specific country
    • The controller lives inside the rotator control box, and operates from its supplies

    What it doesn't do -
    • Control every rotator under the sun (only the inexpensive type with pot feedback)
    • Operate with elevation rotors or azimuth/elevation rotors
    • Provide sufficient accuracy for VHF/UHF satellite tracking
    • Control more than one rotator

    The ZL1BPU Rotator Controller has been designed as an add-on unit for the popular Kenpro KR-400 and Yaesu G-400 rotators. The controller consists of a small circuit board which fits inside the rotator control box (see picture). With this unit the rotator gains automatic heading seeking, computer control, and even heading control by clicking on a map or selecting a country prefix! The ZL1BPU Rotator Controller should work with any rotator with AC motor drive and a 500 Ohm feedback pot, such as the CDR CD-44 and the HY-GAIN HAM IV. It will also operate with both North-centred and South-centred rotators, as only the PC software setting changes.
    Computer rotator controllers tend to be expensive - however you can build this one for under $50! The firmware supplied supports a rich specialized command set and also responds to SARTEC, ORION and YAESU commands, making it compatable with most popular multi-function logging and digital mode programs that feature rotor control.
    The controller could also form the basis of a self-contained replacement controller, for rotators with faulty or missing controllers. Just add the power supply circuitry shown in the G-400/KR-400 Rotator Schematic - all you really need is a 24V AC supply, a 6V DC supply, and a 70 - 100 uF AC motor capacitor.
    The small circuit board can be fitted inside the rotator control box, and operates from the controller's power supply. No holes need be made in the box, and all modifications are internal and reversible if the need arises. There are only five wires between the unit and the existing rotator box. The serial (PC) control cable can sneak out the back panel through an existing hole.
    The suggested circuit board is single sided, 60mm x 60mm (without the relays), and can be etched or engraved. See the picture to the right, which is larger than life-sized. The board contains an inexpensive micro controller, a 5V voltage regulator, a simple transistor RS232 interface, and two relay drive transistors to activate the rotator. The relays are interlocked with the existing LEFT and RIGHT switches, so there is no possibility of motor or controller damage.
    The unit is given heading commands via the PC serial port, from a special program, a digital modes or logging program with rotator control, or a simple terminal program. The commands are in the form of hexadecimal or decimal numbers, depending on the protocol, and the controller in effect "pushes the buttons" on the associated rotator control box until the requested heading is reached. This means that it will go to the correct heading without the need for a button to be held down to keep the rotator moving. It also allows for sophisticated computer applications to control the rotator.
    How it Works
    Positioning Accuracy

    Accuracy is limited mostly by the host rotator and control unit. Typically 2° to 3° heading resolution and about ±5° positioning accuracy. The smallest command that will cause movement is about 5°. A heading approached from clockwise may differ from the same heading approached from anticlockwise by ±5°. Hardly a problem with HF beamwidths of 30° or more, but not appropriate for some VHF and UHF terrestrial and satellite systems. The Rotator Controller uses hysteresis through the use of a window comparator technique, to prevent hunting and poor stability, which results in the heading uncertainty specified. The hysteresis could be reduced to improve positioning accuracy, but diminishing returns result due to poor positioning pot supply regulation and overshoot in the motor, since these simple rotators generally lack effective brakes. No braking control is provided.

    The Rotator Controller operates from the host controller's power supply. It requires +12V (9 to 15V) at 10mA for the micro controller, and an additional 60mA while active (rotating). Operation from higher supplies would be possible if the relays were changed. The Rotator Controller includes its own +5V regulator. No heatsink is required. The computer interface is a simple RS232 type. Idle is about -9V (derived from the PC TXD line), and active is about +4.5V. Passive pull-down allows future multi-drop capability. A DB9 female connector is used, and configured for DCE, allowing direct PC connection with a modem (pin-for-pin or "mouse") cable. Communications are full duplex, 9600-N-8-1. Only three connections are used (TXD, RXD, GND), with no handshake; thus the handshake lines on the PC port are available for other purposes such as PTT, if the application software permits it.

    The unit is assembled on a 60 x 60 mm single sided PCB. The relays can be added, requiring an extra 20 - 25mm in one dimension, depending on the relays used. (The KR-400 controller has 94 mm width inside, and conveniently fits a 60 x 90 mm PCB slung from the top rails). No extra holes need be drilled in the outside of the controller, and no non-reversible modifications need be made. Command Protocol Control Software Embedded Firmware Construction


    Rotator Controller - Construction

    The controller is built on a small single-sided copper laminate board, and can be etched or routed/milled/engraved. The basic board is 60mm x 60mm. NO CIRCUIT BOARDS ARE AVAILABLE FROM THE DESIGNER.
    No CAD files for manufacture are available, but the design is otherwise well documented. The table below lists the schematic, top and bottom PCB views, component placement guide and a suggested routing or milling guide for a hand made PCB. The board does not include the relays. They can be hand wired and mounted on the bottom of the controller box with double-sided tape, or as the author did, assembled on an extension to the basic board (at the bottom of the drawings in each case). The relays were omitted since just about every possible relay has a different footprint!
    Ro_schematic.gif Design Schematic. Print in landscape format. PCBtop.gif Drilling Guide, top (component) side. Includes components. Holes are black. Should be scaled while printing so border is 60x60mm. PCBcomponent.gif PCB component placement guide. Note - resistors and diodes are placed vertically (saves space). PCBcopper.gif PCB positive etch pattern, bottom (copper) side of board, viewed from the bottom. Should be scaled while printing so border is 60x60mm. PCBengraved.gif PCB positive hand routed/engraved/milled pattern, bottom (copper) side of board, viewed from the bottom. Should be scaled while printing so border is 60x60mm. Yellow lines are the engraving marks. G-400/KR-400 Schematic Original schematic of one model of the 400 family rotators. Most are similar. G-400/KR-400 Annotated Schematic Annotated schematic showing connections to micro board and relays.
    Parts List

    CCT REF PART DESCRIPTION C1 1u0 25V Mylar film capacitor C2 C3 27p 50V Ceramic plate capacitor, NPO C4 C5 C8 10u 25V Al electrolytic, radial lead C6 C7 100n 50V Ceramic monolythic - 10n 50V Ceramic (fit across R2 in case of RF instability) D1 LED RED High brightness 3mm LED (optional) D2 D3 D5 D6 1N4148 Diode, silicon signal D4 1N4002 Diode 1A 200V power D7 BZX85C5V1 Zener diode 5.1V 400mW J1 2x5 HDR Two row 2.54mm pitch header, 2 x 5 pins J2 DB9F RS232 connector, female, with cover (not shown on schematic) K1 K2 12V CO 12V 1W 1PCO relay 10A 120V AC contacts (not shown on schematic) R1 1k0 - 4k7 5% 0.25W Select on test to give about reading of 0xB4 when rotator fully clockwise The best answer is to use a 1k resistor and a 10k trim pot (not on the PCB) R2 R3 R5 R6 10k 5% 0.25W R4 1k5 5% 0.25W R7 R10 4k7 5% 0.25W R8 R9 R12 R13 10k 5% 0.25W R11 100R 5% 0.25W S1 DIL20 0.3 in Socket, DIL IC TR1 BC547B Bipolar NPN transistor TR2 BC557B Bipolar PNP transistor TR3 TR4 BC337B Bipolar NPN transistor, 100mA U1 78L05 Regulator, 5V 100mA U2 AT90S2313-10PC Micro controller, ATMEL 10 MHz DIL X1 4.0 MHz HC-23U Microprocessor crystal
    Mechanical parts are not shown. Other miscellaneous wires, insulated links and mounting hardware will be required to suit the installation. A 1m 3-core screened cable is suggested for the RS232 connection. The microcontroller U2 should be socketed. Four insulated mounting pillars with 3mm nylon nuts and bolts are used to hold the board into the enclosure.
    Make the PCB. (If milling or routing the board, drill the holes first to aid location). Use a scale print of the PCBtop.gif as the drilling guide, taping it to the top of the board in order to drill through it. Be as precise as possible with the IC drill holes, as this will make the socket easier to fit, and make the engraving much easier. Drill mounting holes in appropriate places to suit - the best place is likely to be upside down between the top front-to-back metal rails inside the controller case. Place all the passive components, and the IC socket. Using good anti-static techniques, place the active components and insert U2 in its socket. Using a temporary 12V supply, fire up the unit without the micro installed, and check that the chip voltages are correct - +5V on pin 20, 0V on pin 10, and no other pin with anything less than zero or greater than +5V. Then remove power, insert the micro, connect the programming cable, reapply power and program the controller.
    Wire up the board to the rotator box as described, and shown in the following diagrams. Points marked "A", "B" and "C" are shown in RED on the Annotated Schematic. These provide power, ground, and rotator position respectively.
    The relays are wired to provide interlocking, to prevent motor and power transformer damage in case of a switch or relay fault. Pay close attention to the wiring diagram below. You will need to lift point D from the front panel switches. The wire becomes D, while the switch contact becomes D'. This technique allows for manual operation (accidental or during test) and controller operation at the same time without fear of damage due to short circuits.

    Relay and direction switch wiring Note that the relays are wired before the original KR-400 switches. This is because the crucial final NC (Normally Closed) interlock contact is usually missing from the KR-400 "LEFT" switch. If your controller has this contact, you could wire the relays from this point, and the connection D - D' will not need to be cut.
    Don't be tempted by the possibilities of other wiring configurations. It is possible to wire the relays to provide braking (shorts the motor ends together when power is removed), however not only is there then no interlocking, but the relays have a bad habit of welding closed!
    The relay coils are wired one from the "UP" connection on the PCB to the adjacent "+12V" connection, and the other from the "DOWN" connection on the PCB to the adjacent "+12V" connection. For now it does not matter which relay is which, although the one connected to "UP" should be the relay with contacts connected to point F.
    If you think you will need to use the controller manually, you must provide a way to disable the micro controller. The easiest way to do this is to fit a switch between the "+12V" point and the two relays. Mount the switch on the back panel, perhaps by relocating the trim pot bracket to another back panel screw, and using the trim pot's hole. Wired this way, and with the switch off, the controller will continue to report antenna heading even though it cannot correct any "errors" introduced via the switches, or carry out commands from the PC.
    Checkout and Setup
    It is important that the rotator be set up to operate correctly before the controller is added. Check that the meter goes LEFT when the LEFT switch is pressed, and check the calibration of the meter so that the meter indication and physical azimuth of the antenna coincide. Apply power (switch on the AC power switch to the rotator unit). Check that everything is OK, nothing gets hot, and that there is +5V DC on the output of U1. Connect a PC serial port up to the RS232 connector, and check that numbers are coming out by running a terminal program such as Windows Terminal (or failing anything better, Hyperterm) set to 9600-N-8-1. The controller should be stable with no relays clicking. The current heading "$ nn" will be displayed three times soon after power up.
    The next thing to do is check that the relays are wired the correct way round. This test relies on having the switches and relays correctly interlocked, so if the panel light goes really dim during this test, switch off the power quickly and investigate. After the power has been on for at least 10 seconds, (and the serial comms message "$ nn" has been sent) press one of the front panel switches in order to manually change the heading. After it has moved a few degrees, a relay will pull in and should return the rotator heading to where it started (the switch you hold down will be ignored). If instead the heading continues to change in the same direction until the meter hits the end of its travel, you have the relays reversed. Simply swap over the leads to the points "UP" and "DOWN" on the PCB.
    Hardware Setup
    Check the range of the A-D converter. Disable the relays (switch off or disconnect the "+12V" connection to both relays). Press the LEFT front panel switch so the antenna turns anticlockwise. Stop at the left extreme (pointing exactly South on a North-centred rotator). Jot down the heading reported by the micro on the computer screen. This is the OFFSET value. It should be between "00" and "10". The default value in the firmware is "08", so if your value is widely different, consider recompiling the code with a different value. The value is set at the bottom of the file. Before you go to the trouble, complete the calibration procedure in order to be sure what the correct OFFSET value should be. Repeat using the RIGHT switch to take the meter exactly to the right extreme (South again). The procedure from here depends on the commands you intend to use. The ORION/YAESU setup is recommended as it is the most versatile:

    • To use only the ZL1BPU commands, just ensure that the clockwise value is between "80" and "F0". Jot down the reading. A suitable value for R1 will probably be about 4k7.
    • To use the SARTEK command, the full scale reading MUST be 0x80 + the anticlockwise value. (The default is 0x08, so set the clockwise value to 0x8. Use a 1k resistor for R1. Fit a 10k pot between point C and the rotator pot, and this pot to give the correct value.
    • To use the ORION or YAESU commands, the full scale reading MUST be 0xB4 + the anticlockwise value. (The default is 0x08, so set the clockwise value to 0xBC). Temporarily fit a 10k pot on wires in place of R1, and adjust to suit. Once the reading is correct, measure the pot and later replace it with a fixed resistor (or two) as close as possible to this value.

    Recheck the anticlockwise value again (it may have changed slightly) and them retrim the pot for the correct clockwise value. Enable (or switch on) the controller again, and from the PC, issue a few "GO" commands to check that the rotator turns to the requested heading, and stops reliably when it reaches the heading. Try several values between the two limits jotted down. The rotator position should approach the heading command given, and slow down to stop close to the correct value. It may overshoot slightly, and the other relay will pull in to correct it. (It is not easy to test some of the commercial commands by hand, but the YAESU "Mxxx<CR>" is easy to check). The heading should be repeatable within 5°. For example, send "G99", wait for the rotator to stop, then "G80", and note the heading on the meter when it stops. Then send "G66", and when it stops send "G80" again, and see if the heading is different approaching from the LEFT and the RIGHT. You will note that the value reported on the PC screen is not exactly the same as the command, for example when it stops after the command "G80", it may report anywhere between "7E" and "82". Using the YAESU command, check that "M000<CR>" sends the rotator exactly fully anticlockwise, and "M359<CR>" sends it exactly clockwise. "M180<CR>" should cause it to move to the centre.
    Software Setup
    If you plan to use application software that will operate a rotator using the ORION, SARTEK or YAESU command format, you will need to configure the software. Run the software and select the COM port you plan to use. Set the COM port to 9600 bps, no parity, eight data bits, one stop bit (9600-N-8-1). Connect the Rotator Controller to the com port. Select the relevant protocol (ORION, SARTEK or YAESU) in the application software, and then set the heading offset. For a South-centred rotator this will be "0"; for the more common North-centred rotator, set the offset to "180". Check that the rotator responds correctly by trying a few headings. The Rotator Controller will only respond to the commands listed in the specifications table - it is not intended for use with Azimuth/Elevation type controllers used for satellite work.
    The final check should be done with the PCB connected in place and all the wiring tidy. Fit the cover to the control box, and operate full power on all available bands. If the rotator control is stable with no clicking relays, then all is well. If there is any tendency to misbehave, it will likely be caused by RF on the pot feedback signal. A 10 nF capacitor across R2 should fix this. If the problem happens on VHF, try fitting ferrite beads to leads "A", "B" and "C". A bead on "C" may suffice. Don't be tempted to omit D7. This diode clamps transients coming down the cable that can easily damage the micro. The Zener diode does a much better job that signal diodes to the supply rails, since it has much greater energy absorbtion, and will not result in pumping of the supply.
    If an accident occurs which shorts the motor or switches and relays, a possible outcome is welding of the contacts. The effect will be that the rotator continues to turn one way or the other without being told to, or won't turn when expected. Relays can generally be "unstuck" by giving them a sharp tap on the top, but there is no solution for the switches other than dismantling them to free the parts. Better to ensure that the wiring is correct first time!
    If you like, you could fit a GREEN LED and a RED LED across the RIGHT and LEFT relay coils (using 1k series resistors), and embed the LEDs in the front panel, or in the top of the meter. It looks really cool to see the LEDs go on and off as the rotator is controlled. You might also mount the LED D1 on the panel - it glows steadily while the rotator is in motion either way, and flashes slowly if there is an error. If you use all three LEDs, use a yellow LED in this position.
    DO NOT LEAVE THE ROTATOR CONTROLLER UNATTENDED. It is probably not a good idea to leave the shack with the rotator controller powered up, just in case the micro locks up, or a relay jams. While all care has been taken by the designer to make the system safe and foolproof, in order to protect the expensive rotator and power transformer, you will rest more easily if you at least switch the front-panel power switch OFF when you leave. It is not a good idea to leave your equipment all fired up unattended anyway. The responsibility is yours - not that of the designer.


  2. #2

  3. #3
    Junior Member Junior
    RDI - Board Default Avatar

    Join Date
    Jul 2013


    It is a really great information about G-400. You are giving out circuit diagrams, PCB schematics, Gerber pictures, etc. Can I use these information and modify the unit? Is it a proprietary product or an open-source?

  4. #4
    Moderator Expert
    Join Date
    Jan 1970


    See the LINK

    You can build it for yourself but not for commercial purpose I guess.



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