Friday, 23 March 2018

Wire up gear selector solenoids and gear range status switches - and set up gear parameters. Success!

Sod it. Let's just wire up the solenoids to the 2 spare relays, connect the high and low microswitches to 2 of the remaining 3 inputs and see where that gets us. The Centroid "support" is very terse ie almost nonexistent. I suppose that's to be expected, as we are hobby users and they make their money from the professional users with the proper purses.

I have a 24V PSU of about 20W (I'm not certain which model I bought now and the part number label is buried) but currently it's only driving the soft start relay which must be taking sod all current. I can't be arsed to check back for either the PSU or the relay ratings but I'm pretty certain I have spare capacity. It's independent of the main Acorn system, so the worst case (over)load situation isn't going to damage anything.


So - status microswitches wired up thus (closed when that range selected):

  • Common (ground) - green
  • High range - orange
  • "Medium" range (my low speed) - red
And solenoid connections:
  • O/P 1 - yellow (low speed range)
  • O/P 2 - pink (high speed range)
  • Ground - green
Here's how I configured the IO using the wizard:



And the spindle settings:



I swapped the "Mist" function back and forth between OP1 and OP2 using the wizard, then manually enabled the mist button in the VCP display. There was only one such function button on the VCP that could be quickly configured using the wizard, hence the reeated use of the wizard.

Pressing Alt-I shows the status of the inputs and outputs, so it's easy to check it's all doing what it should.

High range, with O/P 2 and I/P 2 high (1170rpm):



Low range with O/P 1 and I/P 1 active (234rpm):


That works - and the spindle does actually spin in the correct range. 

NB: In the wizard I set the gear ratio in the low range as 0.2 for now, until I look back and calculate the correct ratio. Sure enough though, when I change the ratio it knows and changes the displayed set point accordingly. I guess that if I demand a spindle speed that exceeds the allowable range it will complain. And vise versa. I'll check tomorrow.....

The gear ratio numbers were noted back in January. In summary,

First reduction stage input gear - 23t
First reduction stage output gear (Tufnol) - 64t
Second reduction stage input gear - 22t
Second reduction stage output gear (on spindle) - 48t

Overall ratio: 64/23 x 48/22 = 6.07:1


The Centroid parameter required is the inverse of this, ie 

0.16471354166666666666666666666667

I think we can safely round this down to 4 significant figures, ie

0.1647

Next - try to figure out how to modify the M3 macro (and then copy over into the M4 macro) to automatically switch the solenoids over (with the spindle stopped!!)
then start the spindle. That will be a little more challenging.

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