38 lines
1.1 KiB
Python
38 lines
1.1 KiB
Python
#!/usr/bin/env python3
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def calc_output(v_c1, v_c2):
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vref = 3.3 / 2 # [V]
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rref = 1/(1/10e3 + 1/10e3) # [Ohm]
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vpos = vref + (v_c1 - vref) * rref / (rref + 220e3)
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# vneg = vdiff + (v_c2 - vdiff) * 10e3 / (220e3 + 10e3)
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# vneg =!= vpos
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k1 = rref / (rref + 220e3)
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k2 = 10e3 / (220e3 + 10e3)
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# vdiff + (v_c2 - vdiff) * k2 = vref + (v_c1 - vref) * k1
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# vdiff + v_c2*k2 - vdiff*k2 = vref + (v_c1 - vref) * k1
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# vdiff * (1-k2) = vref + (v_c1 - vref)*k1 - v_c2*k2
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vdiff = (vref + (v_c1 - vref)*k1 - v_c2*k2) / (1-k2)
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adc_counts = vdiff / 3.3 * 0xffff
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print(f'{vdiff:.3f} V ^= {round(adc_counts)} counts')
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return adc_counts
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print('Results for 18 V')
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a = calc_output(18, 0)
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b = calc_output(0, 18)
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print(f'middle = {round((b+a)/2)} counts')
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print()
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print('Results for 24 V')
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a = calc_output(24, 0)
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b = calc_output(0, 24)
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print(f'middle = {round((b+a)/2)} counts')
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for v in range(11, 25):
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print()
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print(f'Results for {v} V with 0.7 V diode drop on GND')
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a = calc_output(v-0.7, -0.7)
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b = calc_output(-0.7, v-0.7)
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print(f'middle = {round((b+a)/2)} counts')
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