130-28176 Parallax Inc, 130-28176 Datasheet - Page 299

• Manufacturer Part Number: 130-28176
• Description: KIT PARTS PROCESS CONTROL
• Manufacturer: Parallax Inc

Specifications of 130-28176

• Accessory Type: Education Kit
• Product: Microcontroller Accessories
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• For Use With/related Products: Board of Education Full Kit
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant, Contains lead / RoHS non-compliant

closer the actual temperature got to the setpoint, the less drive that proportional supplied.
If the temperature actually reached the setpoint, the total drive would be 50 %, all due to
bias. However, from previous activities, we found that 50% drive would result in a
temperature of 98 °F.
In order for proportional drive to have control, there must be error. With a K
amount of error allowed a stable temperature around 100 °F. This error is called "Steady-
State Error."
When K
resulting in a temperature even closer to the setpoint. At 1.0, the steady-state temperature
was even closer, but oscillations are beginning. Finally, with a K
closer but had heavy oscillations, and as can be seen, the midpoint of the oscillations are
still below the setpoint.
If bias drive is not correct for the setpoint, proportional drive alone cannot maintain
temperature at the setpoint. Proportional drive is good for driving the system back
towards the setpoint, but there needs to exist error for proportional drive to have effect.
Of course, the logical thing to do would be to adjust the bias to meet the conditions. In
this case changing bias to 70% may provide sufficient energy. But what happens when
the conditions change again? We are back to manual control at the setpoint.
Challenge 8-4
An oil flow system is designed and it is found that 80% drive is needed to drive the pump
for the required flow rate.
1. If bias were set to 50%, would the flow stabilize above or below the setpoint?
2. How would increasing the proportional gain affect the steady state flow rate?
3. How would decreasing the proportional gain affect the steady state flow rate?
P
was increased to 0.5, this increased the proportional drive for the same error
P
of 2.0, it drove even
P
of 0.1, the