(we're not kidding - we get a lot of e-mails with questions that are already addressed in the Frequently Asked Questions web page)
Standard construction techniques may be used for this circuit and a printed circuit board is available if desired. The prototype was point-to-point wired on a Radio Shack prototype PCB (part # 276-168B).
If building the TEMP05 from the PCB, refer to Figure 3 for component placement. Begin by inserting IC sockets (highly recommended). Follow this with the insertion of all passive components. I like to proceed by inserting all resistors, then all capacitors. Watch the polarity of the electrolytic capacitors. The positive lead of the electrolytics is the square pad for that component.
There are only 3 types of resistors; 10K, 1.5K and 10M. The color codes for these are shown in Table 1. Insert the resistors where shown in Figure 3.
Table 1. Resistor Color Codes
Figure 3 Parts Placement
Next, insert voltage regulator U3 and full-wave bridge D1. At this time, you should also insert terminal strip J1. Once that is done, put down the soldering iron and get out a suitable power supply (most any 12 volt "wall-wart" will do). Connect the power supply to the terminals of J1 (polarity is not important, even if the power supply is DC instead of AC; the full-wave bridge will take care of the polarity). Power up and then measure voltages between pins 40 and 20 of IC U1. Pin 40 should be +5 volts while pin 20 is ground. If you are wiring this circuit on your own board, then check polarity on the other IC sockets as well. Table 2 shows the voltages required on each IC.
Table 2. Power and Ground Table
Turn off the power and get back your soldering iron. To finish up, insert the crystal, the LED and the remaining connectors. The flat side of the LED should be lined up with the square pad for it.
An optional DS18S20 can be installed at this time in the location provided.
You are now ready to prove in the circuit.
Last Updated January 1, 2020
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