[Moon-Net] Green Heron vs Alfa Spid Controller

Bob Atkins ka1gt at hotmail.com
Wed Apr 7 05:55:30 CEST 2021


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 this?  https://bobatkins.com/radio/spid_ras_hr.html and  https://bobatkins.com/radio/spid_electronics_update.html

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.

73
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

Thanks
Les
W2LPL
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