750-00004 Parallax Inc, 750-00004 Datasheet - Page 9

• Manufacturer Part Number: 750-00004
• Description: POWER SUPPLY 24VDC 600MA
• Manufacturer: Parallax Inc

Specifications of 750-00004

• Form: Wall Mount (2 Prong)
• Voltage - Output Per Connector: 24VDC
• Current - Output: 600mA
• Polarization: Positive Center
• Cord Plug: 2.1mm I.D. x 5.5mm O.D. x 12mm Female
• Voltage - Input: 120VAC
• Power - Output: 14W
• Transformer Type: Linear, Unregulated
• Product: Microcontroller Accessories
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Efficiency: -
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant, Contains lead / RoHS non-compliant

Main:
Please note the conditional expression within the IF statement; it is true when the value of the inputs is
0. This is because the idle state of the optically isolated inputs is high. Therefore, when NO voltage is
present at the input terminal, 5 VDC will be present on the Stamp input pin. The converse is also true: if
the signal voltage (typically 12-36 VDC) is present on the input terminal, 0 VDC will be preset on the
Stamp input. All digital inputs reference the ground at the terminal Din GND. The diagram to the right
shows how a typical input could be connected.
Analog Inputs
Analog inputs aren't needed for every PLC application. When they are required, the necessity for a high-
quality, low-noise, full-featured Analog to Digital Converter becomes paramount. Since good ADCs aren't
cheap, we designed it to be optional. That way, the core cost of the Stamp PLC is as low as possible.
Maxim's 12-bit, multi-range, 8-channel MAX1270 A/D Converter is the ADC of choice. This ADC can
accept the following inputs: 0-5, 0-10, ±5, ±10 volts DC. The range of the input is selected by writing a
configuration byte to the ADC. BASIC Stamps have built-in commands that configure and read ADCs with
ease. In addition to the aforementioned ranges, the user may install a shunt (jumper) within the Stamp
PLC, thereby configuring that channel to receive 4-20mA current loop signal.
Reading Analog Inputs
Configuring and reading the analog inputs is straightforward. The Stamp's built-in commands, SHIFTIN
and SHIFTOUT, make the whole process quite easy and shrinks the code down to a manageable size.
The first step is to connect the necessary circuitry while the Stamp PLC and your sensor (in our example
a potentiometer) are de-energized. The connection diagram to the right demonstrates one way you can
connect a potentiometer to an analog input. Note that the "Out 5VDC" terminal is supplying 5 Vdc to the
circuit. This output comes from the Stamp's regulator. Do not draw more than 40mA from this terminal.
This 5VDC output is referenced to the Stamp's ground.
Parallax, Inc. • Stamp PLC (#30064) • Version 1.8 • 12/29/2003
DO
LOOP
IF IN6 = 0 THEN DEBUG "Input
IF IN7 = 0 THEN DEBUG "Input 10 Pressed!",CR
PAUSE 250
Figure 9: Stamp PLC to Potentiometer
S
S
ATN
GND
D 1
D 2
D 3
D 4
D 5
D 6
D 7
D 8
D 9
D 10
D GND
+24 VDC
GND
OUT
IN
IN
IN
IN
IN
IN
IN
IN
IN
IN
IN
IN
' Wait for 1/4 second
' then repeat
www.parallax.com
#30064
9 Pressed!",CR
OUT 5VDC
D
OUT
A GND
A GND
D
IN
IN
OUT
D
D
D
D
D
D
D
D
OUT
OUT
OUT
OUT
OUT
OUT
OUT
OUT
A 1
A 2
A 3
A 4
GND
IN
IN
IN
IN
V+
1
2
3
4
5
6
7
8
24 k
Pot
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