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Egis control and other things ... 3 týdnů 1 den zpět #10

  • jeff
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Hello friend and moderator,

First , sorry for my approximative english.
Second, i'm here in Belgium
Third, humbly i will try to add somes pieces of this brilliant idea you have.
I don' say it's the best solution with a tv set in the living room or in the day to day life.
Simply it's a way to bypass the controler via ethernet.

So,
One day one of my bestss friends gave to me an old Egis with the controller and the wire harness ( crane câble)
After cleaning and greasing the bearings and regarding the quality of the mechanic and the quadratic sensors,
My objective was : minimum:0.5 ° resolution on a 1..8M offset with ethernet control.

Solution: take out the obsolete controller. ( by the way, i have two EGIS controler for sale ...) and replace it by a cheap alternative.
Question:
Cheap , easy for a non programmer like me , ethernet controlable motor with quadratic encoder interface ?

Yes possible.

Look at : github.com/k3ng/k3ng_rotator_controller

Yeah, flashing a arduino mega with a ethernet card is easy... But, when you try with the Egis on your table you say :
Hoooo the Arduino Mega is too slow to handle the interrups created by the encoders ( 400Hz each à motor speed max.)
A Arduino is not able to handle this level of interrupts with ethernet.
Solution applied :
Trash the arduino and put a Teensy 3.6 ( it's arduino IDE/ CODE compatible).
Now, my EGIS is functionnal in Azimuth and elevation with the resolution of 0..1°
The motors encoders permit a resolution of 0.01° (readed and validated in test by software reading)
Actualy, I command the antenna via a telnet server or via a software ( i run it on Win7) :
www.qsl.net/yo3dmu/index_Page346.html
For info : Yes you have geosyncronious sattelites and position memories in this soft .



To the moderator :
The idea to port the EGIS on rasperry is a brilliant thinking.
Your project is excellent because you will give to the hardware a new live.
You have developped a interface to the encoders and to the motors, i will give here somes of my " hardware improvments" ;

For my hardware interface, we are similar, i use two BTS7960 bridge for each motor and fast opto isolators.
The encoders cables are separated and shielded apart the motors cables ( 2mm schielded section for motors)
Main power supply is a 10A @ 24V for the main system.
Protections : motors pwm filtered, all interfaces ( in /out) opto isolated by high speed ( 10 MHz bw) optos.
Protection of overcurrent of the motor : MOV (Metal Oxide Varistor, count 30V@ 4A)

May be theses infos can help you, I dont' know...
But continue in your projetct: the principe is evidfent !

Bests Regards,
JF.

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Egis control and other things ... 3 týdnů 20 hodin zpět #11

  • Hugocz
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Hi Jeff, thanks for the compliment. It made me happy.

I never used the Arduino because the Raspberry Pi was much more powerful from the first versions. That's why I chose him and I don't regret it.

Thank you for the link to the K3NG Rotator Controller project. I'll see what he can do.

BTS7960 is an interesting alternative. The finished module for Arduino would definitely go to use. I will think about it.

I have a question about PWM control of EGIS motors. What should be the optimal frequency? 50Hz, 100Hz, ... Can motors withstand higher PWM frequencies? Can you comment on that? Thank you.
Poděkovali: jeff

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Egis control and other things ... 3 týdnů 11 hodin zpět #12

  • jeff
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Hello Hugocz,

About PWM,

yes on a big strucure like a dish it's really interesting to have this functionnality
The PWM main advantage for DC motors is a better torque at low speeds
With smooth starting and stopping motors,
you eliminate the oscillations of the entire strucure
you eliminate possible postion overshoot
you preserve the mechanic of the EGIS gears
The frequency is 500 Hz, PWM is simply a variation of the duty cycle of the rectangular signal generated.
Increasing behind 500 Hz is not usefull for the two motors inside the EGIS.

In principe, you should have this behaviour:
set target position, slow start, increase the speed and near target (5° for exemple ) decrease the speed and stop.

Pay attention to the balance of the antenna: in somes positions, the elevation motor need more power.
Simple solution:counterweight at the rear.

Some notes :
TBS7960B: Cheap (6 euros on Epay ...) can wistand 43A, isolated and are compatible with 3.3V commands logic level.

The hardest thing to adapt for the Egis is not the Azimuth axis but the elevation axis:
Mine is not linear because the elevation plate can do 0 to 90° in elevation
Two solutions : a correction table in the soft or a external inclinometer connecteud to the controler.

There are a lot of things to dicuss on the subject, it's fun and really intersting.

Bests Regards,
JF.

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Egis control and other things ... 3 týdnů 9 hodin zpět #13

  • Hugocz
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I don't have much experience with PWM, but 500 Hz for EGIS motors seems a lot to me. I would try a maximum of 200 Hz. But rather only 100 Hz.
I think that for PWM 500 Hz, the motor construction should already be made of modern materials. My EGIS positioner is 40 years old. Original production Japan.

Do you really run EGIS motors with PWM control with a frequency of 500 Hz?
Poděkovali: jeff

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Egis control and other things ... 3 týdnů 7 hodin zpět #14

  • jeff
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Hugocz,
Look at :
circuitdigest.com/tutorial/what-is-pwm-pulse-width-modulation
The page explain a basic PWM waveform
Duty cycle = (Ton/(Ton+Toff))*100... simply.

So, yes sure, i use my EGIS at 500 Hz No problem at all :)

Bests Regards,
JF.

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Egis control and other things ... 2 týdnů 6 dní zpět #15

  • Hugocz
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I know the principle of PWM and I can run it on a Raspberry Pi. I just didn't know which frequency to choose for specific motors in the EGIS positioner. Information on using 500 Hz is important to me. I will definitely perform tests in the range of 50 Hz to 500 Hz.

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