[Moon-Net] Green Heron vs Alfa Spid Controller

Edward R Cole kl7uw at acsalaska.net
Wed Apr 7 08:56:02 CEST 2021


My RAK is the azimuth half of a RAS, essentially.  I'd guess the same 
reed switch system is used.  It lost sync one time counting about 
half the pulses rotated 45 degrees when MD02 indicator showed 90 
degrees movement.  But hasn't seemed to to that all the time. I 
installed a separate digital angle encoder to ensure good tracking.

In my olden days I put up C-band satellite TV dishes that used linear 
actuators, most of which used reed switch system for indication.  One 
thing I recall is the satellite cable had four conductors inside a 
foil shield with a bare drain wire, two of which carried the pulse 
signal.  Never saw any tracking issue due missed pulses.

So maybe running shielded cable would be advisable with the Alfa-Spid rotators.

73, Ed - KL7UW

At 07:55 PM 4/6/2021, Bob Atkins via Moon-net wrote:
>Content-Language: en-US
>Content-Type: multipart/alternative;
>Hi Les
>My SPID RAS HR and MD-02 controller really doesn't lose pulses. I 
>recalibrate from time to time (maybe once month), but it's rarely 
>for than 0.2 degrees off.  I would think the regular RAS pulses 
>would be even easier to count because they are less frequent and 
>they are simple pulses (magnet and reed switch), not requiring 
>quadrature decoding.
>Have you read 
>Pulse counting depends on a couple of things. One is noise. If 
>there's noise on the lines that bring the signal in from the sensor, 
>then you can get bad counts. That leads to the benefit of line 
>drivers at the sensor and good filtering at the controller end of things.
>Never used a Green Heron, don't know what's in the box. The SPID 
>hardware is also something of a mystery as they don't publish 
>controller schematics as far as I know. Their software (PASCAL) is 
>open source I think.
>I'd stick a fast scope on the sensor line and take a see what the 
>pulses look like. Maybe you will see noise which requires filtering. 
>Maybe the shape of the pulses will be distorted, in which case you 
>might want some signal conditioning (Schmitt trigger, buffer, level 
>shifter etc.).  I don't know how fussy the SPID controller is, but 
>it can't object to clean square waves (can it?).
>Any pulse counting system can (and probably will) eventually glitch 
>and lose proper count, but it shouldn't happen often.
>Bob, KA1GT
>From: Moon-net <moon-net-bounces at mailman.pe1itr.com> on behalf of 
>Leslie L via Moon-net <moon-net at mailman.pe1itr.com>
>Sent: Monday, April 5, 2021 9:10 AM
>To: moon-net at mailman.pe1itr.com <moon-net at mailman.pe1itr.com>
>Subject: [Moon-Net] Green Heron vs Alfa Spid Controller
>Hi all,
>Many of  you swear by the Green Heron RT-21AZ controller over the 
>standard Alfa Spid Controller when using  the SPID RAS rotors in its 
>ability not to lose pulses and maintain its accuracy.   I am 
>wondering if someone can explain why the  Green Heron  is more 
>accurate.   Do they condition the pulses?  They are both dealing 
>with the inherent limitations of using a simple reed switch and 
>magnet as the encoder on the rotor itself.   What is the secret 
>sauce that makes  the Green Heron a better controller in this application
>Moon-Net posting and subscription instructions are at 

73, Ed - KL7UW
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   dubususa at gmail.com 
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