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| Wimberleytech:
--- Quote from: nForce on January 26, 2019, 08:10:58 pm ---Yes, I understand you. I am just using the knowledge from known values: First-term the numerator has delta which is 3.3 V so the same reason for the motor the numerator would have 3000 which is delta. Delta is the difference between min and max. --- End quote --- No, the first expression converts bits to volts. The second expression converts volts to volts. The third expression converts volts to RPM. In term of units: (Volts/bit) (Volts/Volts) (RPM/Volts) = RPM/bit <--K If your DAC input changed from 2000 to 2001, a delta of 1 bit, then using the equation, RPM would change by a delta of: 1 * (3.3/4095) * (10/1.65) * (1500/10) = 0.732 RPM |
| nForce:
OK, now I understand in terms of units. Can you just say why is then 1500 rpm? Or maybe another person can write it. Let's be consistent: The first term: delta = 3.3 V - 0 V = 3.3 V Last term: delta = 1500 rpm - -1500rpm = 3000 rpm. |
| Wimberleytech:
--- Quote from: nForce on January 26, 2019, 10:14:49 pm ---OK, now I understand in terms of units. Can you just say why is then 1500 rpm? Or maybe another person can write it. Let's be consistent: The first term: delta = 3.3 V - 0 V = 3.3 V Last term: delta = 1500 rpm - -1500rpm = 3000 rpm. --- End quote --- No, you misunderstand "delta" In the first term 3.3/4095 just the transfer function from the D input to the output of the first amplifier. As far as 1500rpm. That is just the designer's choice based on motor used. No magic. |
| nForce:
Why the first term the range 0-3.3 V is not delta? It seems to me that all the data on the schematic is consistent. Omg, this is going to take forever. :( |
| Wimberleytech:
--- Quote from: nForce on January 26, 2019, 10:42:39 pm ---Why the first term the range 0-3.3 V is not delta? It seems to me that all the data on the schematic is consistent. Omg, this is going to take forever. :( --- End quote --- 3.3V - 0V is indeed a "delta" BUT, that is not the first term. The first term is a transfer function as I said. How long this takes depends on you. I understand the circuit and the equations. You should install LTSPice if you have not already done so. I will upload the LTSPice file and you can play with it. Maybe it will help you get a feel for what is going on. |
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