Add v-regulator resistor calcs

diff --git a/sch-pcb/devboard/vreg.py b/sch-pcb/devboard/vreg.py
new file mode 100644 (file)
index 0000000..ba0692e
--- /dev/null
+++ b/sch-pcb/devboard/vreg.py
@@ -0,0 +1,45 @@
+#!/usr/bin/env python
+
+from pylab import *
+from wag import engstr as es
+
+def rvals(Vrange, Rpot):
+    Vmax = max(Vrange)
+    Vmin = min(Vrange)
+    R2 = Vmin * Rpot / (Vmax - Vmin)
+    R1 = (R2 + Rpot) * (2*Vmin - 1)
+    return [R1, R2]
+
+def vout(n, r1, r2, Rpot=1.0, Vref=0.5):
+    return Vref*(1 + ((1-n)*Rpot+r1)/(n*Rpot+r2))
+
+n = arange(0, 1, 1/256.0)
+
+Rpot = 100e3
+
+Vref = 0.5
+Vmin = 0.5
+Vmax = 1.8
+assert(Vmin >= Vref)
+
+r1, r2 = rvals([Vmin, Vmax], Rpot)
+
+print es(r1), es(r2)
+
+close('all')
+
+subplot(131)
+plot(1-n, vout(n, r1, r2, Rpot, Vref), 'x')
+
+subplot(132)
+r2mod = ((r1+Rpot/2)/1.4-Rpot/2)
+plot(1-n, vout(n, r1, r2mod, Rpot, Vref), 'x')
+ylabel('fixed r1')
+
+subplot(133)
+r1mod = (1.4*(r2+Rpot/2)-Rpot/2)
+plot(1-n, vout(n, r1mod, r2, Rpot, Vref), 'x')
+ylabel('fixed r2')
+
+print 'r1mod:', es(r1mod)
+print 'r2mod:', es(r2mod)