Differing analogue outputs in forward and reverse spindle ??

Having sorted My back/ front tool problems  and spindle reversing issues ,  both now seem to be working well,   but I have a spindle speed discrepancy between spindle Fwd and spindle Rev  ( Machine is  a Boxford TCL125 with original DCmotor and Sprint  DC driver )

1) I select  spindle fwd , indicates  S 300 rpm and I get a speed of  372rpm    at  2.38 v analogue giving an armature voltage of 34.3v
2) If I select Reverse it shows S -300 rpm but I only get  312 rpm  and an analogue input of 2.08  giving  AV of 29.3. (so a significant difference)
3) I have to increase the selected reverse revs to S -345  to get the same speed output of 372  with -34.3v  from 2.4v analog input .. 
From readings 1 and 3 it seems to me that my motor is responding correctly to the driver voltages  but the analog signal is not the same in fwd and rev despite the same  spindle speed being called for.

Now I know that i can change the scale number in hal to bring actual speed into line with selected speed,  but cant see a how I can choose a different scale factor for forward and reverse,   so I really need the analogue outputs  to be the same in both modes .
It is puzzling that they are not .

Is there any way to adjust the analogue outputs for  each respective mode ?

I think you could use a mux2 component followed by a mult2 component.
use the spindle direction pin as the mux select signal
setp the mux inputs to be 1.0 and your scaling factor, say its 1.25
connect the mux output to  a mult2 input
connect the spindle speed  to the other input.

So in forward you will get the actual signal. but if you select reverse, the signal will be 125% of the forward signal (in our example)
Happy coding! You'll be an expert with hal by the end.


 

Will look into that Rodw although the process is not coming over to me quite clearly yet . Maybe it will become apparent when I research mux and mult in the manual.

Initially though it seems like a bit of a fudge . Is there no way to ensure equal pwm outputs in fwd and reverse , and indeed why do they differ in the two modes .

Why not to use a scale component and set the offset and Gain values?
By the way, this issue is not gmoccapy related, as well as it was not the back/front tool part.
It might be better to post you threads in better topics.

Scale component


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