122-28176 Parallax Inc, 122-28176 Datasheet - Page 208

• Manufacturer Part Number: 122-28176
• Description: GUIDE STUDENT PROCESS CONTROL
• Manufacturer: Parallax Inc

Specifications of 122-28176

• Accessory Type: Manual
• Product: Microcontroller Accessories
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• For Use With/related Products: Propeller Education (PE) Kit
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant, Contains lead / RoHS non-compliant

One method of using potentiometers to set these two pins is shown in Figure 6-13.
Instead of using potentiometers, which must be manually adjusted for different ranges,
can you think of a simple way to have the BASIC Stamp set the offset and span voltage
of the ADC directly?
Recall how filtered PWM was used in Chapter 5 to set the voltage of the fan. The same
principle may be applied here as shown in Figure 6-14. Due to the low impedance of the
Vref input, the filtered PWM must be buffered prior to being applied. The ADC0831’s
Vin(-) is higher impedance and does not require buffering.
Additional Parts Required:
(1) LM358 Op-Amp
(2) 0.68 µF Capacitors
(2) 10 kΩ Resistors
√
√
√
√
√
Construct the circuit in Figure 6-14.
In StampPlot, set "ADC Span" to 0.5 and "ADC Offset" to 0.7.
Connect and plot.
Heat the LM34 again.
Click the "Scale Plot 70-120F" button on StampPlot to cover the selected range.
Figure 6-13
Span and Offset of
ADC0831 Using
Potentiometers
DO NOT BUILD