Hi Jarda,
Thank you for your note and sharing your thoughts.
Your assumptions are correct. Even though the circuit of the controller of the G-450XL (which rather different than the G450(A) and the G5500 btw) makes it less suitable to control it with a LVB type tracker, it is rather clever in that it compensates for an aging potentiometer inside the rotor. Indeed it uses a DC motor to display the direction.
I did look at those manuals before and that's how I noticed the differences. Actually, the board inside the G-450XL controller identifies it as a KP-650XL.
The potentiometer in the rotator and the one in the controller are part of a bridge circuit. When the rotator moves and the value of the pot meter in the rotator changes, the bridge gets unbalanced and a voltage gets generated that will drive the motor in the controllor until the pot meter in the controller balances the bridge again. So it's a synchronous system.
I did add an opamp circuit between where I pick off the indicator voltage from the pot meter inside the controller and the tracker. That did not make things linear. I think it's the two transistors near the bridge that start to play a role once the rotator passes 180 degrees that make things non-linear. I'm not even sure why they are there.
The condition you mentioned is indeed occuring. The voltage varies from 1.54-4.44 for 0-360 degrees. I have a PIC programmer and a few extra PIC's on order. I think if I can manage to add calibration points for every 30 degrees it will work OK.
73,
--Alex KR1ST
On 2021-03-20 08:59, ok2gz wrote:
Hi Alex,
I guess that Your trouble with LVB tracker is made by the circuity of G450 azimuth sensor and connection between G450 and LVB.
LVB tracker was developed for G5500 rotator, which (as I guess) has different internal circuity.
I Guess also, that g450 Azimuth rotaror uses DC motor in the control box to show position in the scale 0-360 degrees and internal circuity serves for liear driving DC motor inside (as position indicator).
Manual for GS232 says, that Yaesu tracker GS232 (similar to LVB) works with :
G800,G1000,G2800
G400,G500,G550
G5400,G5500, G5600 rotators..
Please look for three manuals (pdf files on the web):
1. Your G450
2. G5500
3. GS232 Yeaesu satellite tracker, where is lot of importatn informations
G5500 has sensor constructed with 500 ohm potentiometer feeded by 6V source and regulated by OZ amplifier into the 0-5V limit. For good linearity is very important, that potentiometer - sensor cannot be loaded with low impedance - reason for use the OZ amplifier ( high input impedance for potentiometer, low output impedance for AD converter input!). Otherwise the linearity will go down.
LVB tracker expect, that input voltage from sensor is in interval 0 - 5V for azimuth 0 to 360 degrees (or 450 degrees with G5500).
LVB uses 8bit PIC microcontroller with 10 bit AD converter - 1024 positions for 0-5V (with 5V AD reference voltage used in LVB).
When occur condition:
AZ = 0 degrees : 1.5V signal
AZ = 360 degrees : 4.0 V signal
then You get smaller resolution (half against 0-5V)
And yet - without calibration it is quite wrong.
LVB also expect to make the calibration, which is very well described by G6LVB and also in GS232 manual.
During power-up You must press the button, the LVB internal code of PIC16F876 skip into the calibration procedure. Then You get on LCD display exact hints what to do - as described by G6LVB.
Yet exist commands for calibration via the serial port terminal. They were developed by G6LVB and does not fit description in GS232 manual..
I hope it can help You with Your rotator.
73
Jarda ok2gz
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