Hey everyone,
I have perused through the textbook you guys offer, and it's really helped me a lot. I have been trying to build a "bang bang" style controller with little success. I recently built the circuit in the attached jpeg.
To describe the circuit, both opamps are LM741's. Both voltage sources are 9V batteries. The resistors connected to V2 are actually just a potentiometer, to allow me to emulate the changing sensor voltage (from a temperature sensor, the LM35) that was supposed to be the trigger voltage.
The circuit with V1 attached is supposed to provide voltage boundaries for the bang bang controller (like a temperature sensor IC, piezoelectric, ion selective electrode, etc). The top op amp is supposed to provide the high voltage where the circuit turns off. The bottom op amp is supposed to provide the lower voltage where the circuit turns on. This is meant for a system where the environment naturally causes voltage to decrease unless the circuit is on (it is a heater, and the temperature sensor IC's voltage increases linearly with temperature).
The inductor pictured was supposed to be a toggle relay, which I don't have the symbol for. At Vhigh, the toggle relay would be opened (GND at bottom op amp, V+ at the top op amp, toggle oriented so that it would switch open). At Vlow, toggle relay would be closed (V+ at bottom op amp, GND at top op amp, so reverse voltage as V high, pushing toggle switch the other way).
This circuit does not work however. I set everything up as is. The last thing I add is V1. Upon connecting both terminals of V1 to the circuit, V1 begins to discharge as if there is a short circuit. The battery quickly loses voltage, which slowley returns upon rest. As a chemical engineering major, this represents the battery limiting its discharge due to likely a chemical gradient inside of the half cells, limiting the reaction. Also worth mentioning, a potential does form at the outputs of the op amps, regardless of the value of R4/R5, and these potentials compared to GND of V1 are +3.6V at the top Op amp output, and +1.7V at the bottom op amp output. These voltages slowly decline by about 0.01V/s.
Perhaps you guys could point me in the right direction, offer me some tips or a schematic to a working bang bang controller, that I can understand? The few I have found online are generally based heavily on IC's and offer little to no explanation. Thank you!
Also: The values of the resistors R1: 100kohm, R2: 250ohm, R3: 3800ohm. Both voltage sources are between 9 and 9.2V, and R4 and R5 are provided by a 5k linear potentiometer (correctly wired, checked with multimeter).
I have perused through the textbook you guys offer, and it's really helped me a lot. I have been trying to build a "bang bang" style controller with little success. I recently built the circuit in the attached jpeg.
To describe the circuit, both opamps are LM741's. Both voltage sources are 9V batteries. The resistors connected to V2 are actually just a potentiometer, to allow me to emulate the changing sensor voltage (from a temperature sensor, the LM35) that was supposed to be the trigger voltage.
The circuit with V1 attached is supposed to provide voltage boundaries for the bang bang controller (like a temperature sensor IC, piezoelectric, ion selective electrode, etc). The top op amp is supposed to provide the high voltage where the circuit turns off. The bottom op amp is supposed to provide the lower voltage where the circuit turns on. This is meant for a system where the environment naturally causes voltage to decrease unless the circuit is on (it is a heater, and the temperature sensor IC's voltage increases linearly with temperature).
The inductor pictured was supposed to be a toggle relay, which I don't have the symbol for. At Vhigh, the toggle relay would be opened (GND at bottom op amp, V+ at the top op amp, toggle oriented so that it would switch open). At Vlow, toggle relay would be closed (V+ at bottom op amp, GND at top op amp, so reverse voltage as V high, pushing toggle switch the other way).
This circuit does not work however. I set everything up as is. The last thing I add is V1. Upon connecting both terminals of V1 to the circuit, V1 begins to discharge as if there is a short circuit. The battery quickly loses voltage, which slowley returns upon rest. As a chemical engineering major, this represents the battery limiting its discharge due to likely a chemical gradient inside of the half cells, limiting the reaction. Also worth mentioning, a potential does form at the outputs of the op amps, regardless of the value of R4/R5, and these potentials compared to GND of V1 are +3.6V at the top Op amp output, and +1.7V at the bottom op amp output. These voltages slowly decline by about 0.01V/s.
Perhaps you guys could point me in the right direction, offer me some tips or a schematic to a working bang bang controller, that I can understand? The few I have found online are generally based heavily on IC's and offer little to no explanation. Thank you!
Also: The values of the resistors R1: 100kohm, R2: 250ohm, R3: 3800ohm. Both voltage sources are between 9 and 9.2V, and R4 and R5 are provided by a 5k linear potentiometer (correctly wired, checked with multimeter).
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