Améliorations de l'AFFICHAGE et VARIATION de la vitesse 

pour les rotors du type KR400 et  600 

Dave Robinson WW2R, G4FRE

 

Introduction

For the past 6 years in Texas, I have been using a Kenpro KR600 rotator to rotate my antenna arrays for up to 7 bands. With the addition recently of a 10 and 24GHz dish it was realised that better pointing accuracy and the facility to slow the speed of rotation was needed. Discussions with Dave Powis G4HUP pointed me to a design in DUBUS which I had previously missed, mainly because it was written in German and has never been translated. It was entitled “Einfach Drehzahlsteueurung fur rotoren”, by Michael Kuhne, DB6NT and was published in DUBUS 2/99 pages 77-80. The DB6NT design is intended to be incorporated into the existing rotator controller box. Upon review, it was seen that few of the controllers components remained in use; transformer, left and right switches and the 100uF non polarised capacitor. It was decided to build a stand alone unit, leaving the original controller untouched for future resale.

 Design

 The circuit is shown in Figure 1. It is shown wired for 110V AC; however the components were chosen to easily accommodate changing the supply voltage to 240V AC.  

A 5 volt regulated supply is fed across the feedback potentiometer in the rotator. The voltage produced by the wiper of the potentiometer is used, suitably scaled to give 0 to 360 readout on a 200mV Full scale LCD meter unit.

To control the speed of rotation of the rotator, the AC supply voltage to the primary of the transformer, which drives the rotator motor is pulsed using a solid state AC relay (RL1). The frequency (VR1) and width (VR2) of the pulses are adjustable and can be used to set the speed to suit particular needs. Two independent supplies, one 9V, one 5V are needed due to the operational requirements of the LCD; the LCD cannot share its ground with the circuit it is measuring. The push button switches chosen have integral lamp/LED holders. The illumination method employed is derived from the one employed in the KR600 controller. The LEDs in the “left”/”right” switches (SW2, SW3) are normally illuminated, but when the rotator is activated their corresponding LED is extinguished. The LED in the full speed/slow speed switch (SW4) is illuminated in the “full speed” position and flashes when the unit is in the slower speed position, as do the left and right switches.

Construction  

The original board  obtained from DB6NT needed physical modification to use components readily available in the USA. Therefore a “USA” PCB was devised, the track layout is shown in Figure 2 and the component overlay in Figure 3. This PCB suits the components given in Table 1. If an equivalent has to be used for the solid state relay, RL1, It must be one with low drive requirements. The specified one requires under 2mA of drive current which IC3 can supply. Other, non buffered solid state relays can require up to 30mA of drive and will not work. All the components were mounted in a 8x6x3.5” Bud box. The rotator is connected to the controller through a 6 pole waterproof connector on the back panel, a type which I standardised on for all my rotators 20 years ago. Numerous RF decoupling capacitors and RFC were added to stop the adverse effects of RF, especially when operating on 50MHz

 Calibration

Firstly determine accurately the direction of true North. Make sure SW1 is in the “full speed” position.  With the Left (anticlockwise) switch turn the rotator until it points true North. Using VR3 set the LCD to read 000. With the Right (clockwise) switch turn the rotator 360 degrees until it points again exactly true North. Set VR4 to read 360 on the LCD display. These settings are interactive so this process will need to be repeated a couple of times to get exactly the correct LCD readings. VR1 and VR2 are adjusted to give the required slow rotation speed with SW1 depressed

Conclusions

The unit was finished just in time for the ARRL 2002 September VHF contest (OK to be exact it was calibrated the morning OF the contest).  The number of times that the beam heading was calculated, the antenna pointed at that direction and peaking the antenna on a signal resulted in no improvement in signal strength, even on 10GHz was amazing. Having the ability to point the antenna in exactly the same direction 12 hours apart, to have a second attempt to work the same station was also a revelation. It was well worth the effort in constructing the unit.

 Table 1 Composants :

R1                    68R
R2                    27k
R3                    680k
R4, R5, R6       2k2 1W
R7                     for 240V operation 4R7 5W
VR1                 200k preset Bourns type 3329H (DK 3329H-204)
VR2                 10k preset Bourns type 3329H (DK 3329H-103)
VR3                 10k 10Turn Bourns type 3299Y (DK  3299Y-103)
VR4                 100R 10Turn Bourns type 3299Y (DK 3299Y-100)
C1, C2             470uF 25V electrolytic
C3, C4             10uF 25V Tantalum
C5, C6             1uf 25V Tantalum
C7                   100uf 60V NON POLARISED
C8                   3u3 ceramic
IC1                  7809
IC2                  7805
IC3                  74HC00
D1                   1N4518 (Shottky)
D2, D3             100PIV 1A minature bridge rectifier (DK DB102DI)
D4, D5, D6      IN4001
V1                   120V Varistor
LCD                3.5 digit200mV FSD 5V supply 
TR1                 Toroidal transformer. Primary 2 x 120V Secondary 2 x 12V 1.1A (DK TE62072)
TR2                 PCB Transformer. Primary 2 x 120V Secondary 2 x 10V 0.3A (DK MT2111)
SW1                DPDT latching, integral LED holder (NKK LB26SKW01), Red Lens (NKK AT419C)
SW2, 3            DPDT momentary, integral LED holder (NKK LB25SKW01) Green Lens (NKK AT419F)
SW4                DPDT Mains rated.
LED1, 2           Minature Green LED
LED 3              Minature Red LED
RL1                 Solid state relay CMOS drive (MP120D4, Newark 91F5736) (see text)
(DK = Digikey; www.digikey.com)

Figure 1:Circuit Diagram

Figure 2:PCB layout

Figure 3: Component Layout

 

 

derniére modif 18 January 2006