digilite update october 2013 · technomate tm-2600m3 digitwist dual diseqc controller . catapult...
TRANSCRIPT
DigiTwist
An Experimental, Simpler,
Lower Cost Satellite Tracker
Presented at BATC CAT17 by
G4EWJ
Some Current Options
• Yaesu G5500 AZ-EL rotator around £650
requires PC interface
• SPID RAS AZ-EL rotator around £900
includes PC interface
• Several homebrew systems with
stepper motors and feedback pots
E.g. G4KLB system using VK5DJ controller
Total system cost around £300
G4KLB System
The dish has 240v motors with gearboxes and position sensors
Photo:
G4KLB
A Possible Solution
Technomate
TM-2600M3
DigiTwist dual
Diseqc controller
Catapult Dish at Goonhilly
UPPER = arcsin (sin (AZ) * cos (EL)) LOWER = arccos (sin (EL) / cos (UPPER))
Photo:
G8GTZ
View from front Partial view from right side
Satellite
dish with
both
motors
centralised
Round tubing
Shaft angle of rotation = plus or minus 80 degrees.
Possible Configuration
Alsat Dark
Superior motor
TM-2600M3 motor
38mm square bar
Possible Configuration
TOP VIEW
Extension and
counterbalance
Possible Configuration
SIDE VIEW
TM-2600M3 motor
Joining Bar
Photo and CNC milling: M0DTS
Mounting Arrangement
Looking to the North
Orbitron Satellite Tracking Software
PC Interface Software
Visual
Basic
6
ISS Track
Orbitron
tracking software
Max ISS latitude
is 51.6 degrees
Advanced Torque Test Facility
Torque:
Alsat: 1.4 kgm
TM2600M3: 2.1 kgm
DigiTwist Advantages
• Rather cheaper than a G5500 (£650 vs £130)
• Uses the ‘Goto Angle’ Diseqc command
• 12/18v operation - no mains voltages
• No feedback pots or turns counters (see disadvantages)
• Rotate over elevate configuration like the Goonhilly Catapult dish
• 2 horizontal rotors at right-angles - no drama when the satellite goes
overhead
• Arduino Nano based positioner controller
• PC interface program accepts DDE position data from Orbitron
(other interfaces should be possible)
• Unknown if the positioners will last with loads and orientations they
weren’t designed for
• End mounted antennas only
• Antenna cannot be counterbalanced – it may be possible to
counterbalance at the rotor
• Only 2-3 degrees / second rotation speed - but this is usually fast
enough to track the ISS
• Low torque - about 2.1kgm - but this may be enough
• Basic rotor range is only +/- 80 degrees - operation near the horizon is
restricted (possible workarounds)
• No feedback – you don’t know where it is - only where you’ve told it to go
• Stops and starts when receiving a command, even if it was going the
correct way
DigiTwist Disadvantages
DiSEqC
• Digital Satellite Equipment Control - invented by Eutelsat
• Used to send data between satellite receivers and equipment such as
LNBs, switches and positioners
• Uses bursts of 22kHz tone superimposed on the 13/18v on the rx cable
• 22kHz tone was originally used to switch the local oscillator on LNBs
• Diseqc 2.x is bi-directional
• Diseqc 1.x is outgoing only
• Diseqc 1.2 allows positioner control with memory storage
• Diseqc 1.3 (also known as GotoX) allows angular control of the rotor
• USALS, invented by STAB, is used with GotoX and knowledge of your
LAT / LONG to position to any satellite using its longitude
Diseqc Protocol
18v 650mv
pk-pk
E0 31 6E Ex xx CLOCKWISE
E0 31 6E Dx xx ANTI-CW
22kHz
RT5047A
LNB Voltage Regulator:
Surface mount 1.27mm pin
spacing with underside
ground pad
Finding Local South
• Compass
• Google Earth
• Shadow of mounting pole
• Shadow of a southerly rope attached to the pole
Local noon time varies from day to day
At the Greenwich Meridian (zero degrees longitude):
9 September 2017 11:57:17 UTC
31 July 2017 12:06:23
1 September 2017 11:59:57
2 November 2017 11:43:31
https://www.esrl.noaa.gov/gmd/grad/solcalc/
Lightweight Dishes
Construction
and photo:
GM8OTI
Based on a
design from
the RSGB
International
Microwave
Handbook
http://www.marwynandjohn.org.uk/GM8OTI/proj2mdishantenna/proj2mDishAntenna.html
Lightweight Dishes
Construction
and photo:
GM8OTI
Based on a
design from
the RSGB
International
Microwave
Handbook
http://www.marwynandjohn.org.uk/GM8OTI/proj2mdishantenna/proj2mDishAntenna.html
DigiTwist
Presented at CAT17 by G4EWJ