Tracking work-eqs.el

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diff --git a/work-eqs.el b/work-eqs.el
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+;; WORK (NON-EDITING) RELATED DEFUNS
+(defun square (x)
+  "Calculate the square of a value."
+  (expt x 2))
+
+(defun cube (x)
+  "Calculate the cube of a value."
+  (expt x 3))
+
+(defun scaleval (pmax pmin emax emin &optional ai)
+  "Calculate the slope and offset given PLC Max/Min and Eng. Max/Min.
+With optional argument 'ai', also calculate a final scaled value from an input."
+  (let ((div (/ (- pmax pmin) (- emax emin))))
+    (let ((ofst (- emin (/ pmin div))))
+      (if (not (eq nil ai))
+         (let ((final (+ ofst (/ ai div))))
+           (list div ofst final))
+       (list div ofst)))))
+
+(defun cfm-circ (fpm radius)
+  "Calculate the CFM of a circular duct given fpm and radius (in)."
+  (list (* pi fpm (square (/ radius 12)))))
+
+(defun cfm-rect (fpm width height)
+  "Calculate the CFM of a rectangular duct given fpm, width (in) and height (in)."
+  (list (* fpm (/ width 12) (/ height 12))))
+
+(defun pid-tune (Ku Tu p-type)
+  "Use the Ziegler-Nichols method to tune a P, PI or PID loop.
+Takes Ku, Tu and p-type (P, PI, or PID) as arguments, and returns appropriate kp, ki, and kd."
+  (cond ((or (equal 'p p-type)
+            (equal 'P p-type))
+        (list (* 0.5 Ku)))
+       ((or (equal 'pi p-type)
+            (equal 'PI p-type))
+        (list (* 0.45 Ku) (/ (* 0.54 Ku) Tu)))
+       ((or (equal 'pid p-type)
+            (equal 'PID p-type))
+        (list (* 0.6 Ku) (/ (* 1.2 Ku) Tu) (/ (* 3.0 Ku Tu) 40)))))
+
+(defun gn-water-per-lb (temp humidity)
+  "Calculate the grains of water per lb of air, given temperature (F) and humidity (%).
+Returns a list of Sat. Water Press., Hum. Ratio, and Gns water/lb air."
+  (let ((sat-water-press (+ .0182795
+                           (* temp .001029904)
+                           (* (square temp) 0.00002579408)
+                           (* (cube temp) (* 2.400493 (expt 10 -7)))
+                           (* (expt temp 4) (* 8.100939 (expt 10 -10)))
+                           (* (expt temp 5) (* 3.256805 (expt 10 -11)))
+                           (* (expt temp 6) (* -1.001922 (expt 10 -13)))
+                           (* (expt temp 7) (* 2.44161 (expt 10 -16))))))
+    (let ((hum-press (* (/ humidity 100.0) sat-water-press)))
+      (let ((hum-ratio (/ (* hum-press 0.62198) (- 14.7 hum-press))))
+       (let ((gns-water-lb-air (* hum-ratio 7000)))
+         (list sat-water-press hum-ratio gns-water-lb-air))))))
+
+(defun k-to-c (tempk)
+  "Convert degrees Kelvin to degrees Celsius."
+  (- tempk 273.15))
+
+(defun c-to-k (tempc)
+  "Convert degrees Celsius to degrees Kelvin."
+  (+ tempc 273.15))
+
+(defun c-to-f (tempc)
+  "Convert degrees Celsius to degrees Fahrenheit."
+  (+ (* tempc 1.8) 32.0))
+
+(defun f-to-c (tempf)
+  "Convert degrees Fahrenheit to degrees Celsius."
+  (/ (- tempf 32.0) 1.8))
+
+(defun k-to-f (tempk)
+  "Convert degrees Kelvin to degrees Fahrenheit.
+Applies `c-to-f' to `k-to-c'."
+  (c-to-f (k-to-c tempk)))
+
+(defun f-to-k (tempf)
+  "Convert degrees Fahrenheit to degrees Kelvin.
+Applies `c-to-k' to `f-to-c'."
+  (c-to-k (f-to-c tempf)))
+
+(defun max-counts (resolution)
+  "Calculate the max count for a PLC analog, given card's bit-resolution.
+Formula is 1 - 2^(resolution)"
+  (- (expt 2 resolution) 1.0))
+
+(defun volts-to-counts (vin vmax resolution)
+  "Convert a voltage signal to a PLC count.
+Calculates a ratio of vin/vmax, then scales by `max-counts'."
+  (* (/ vin vmax) (max-counts resolution)))