Construction and testing
A single side PCB of the transmitter unit is shown in Fig. 4 and its component layout in Fig. 5. One can use this PCB as Arduino shield with Arduino Mega ADK board using 12V power supply at CON2. Otherwise, Arduino Mega ADK board can be interfaced with the PCB using cable connectors and power supply from 12V/1-amp adaptor.
As shown in block diagram (Fig. 2), the MCU is interfaced through an LCD, a keypad and an IC ZIF socket. The flow chart corresponding to the basic working process is shown in Fig. 6. As shown in the flow chart, this prototype is equipped with two methods for checking a particular IC. Both of these are elaborated below.
As different ICs come with their own specifications, checking process for each may vary. Here, we take an example of a common NAND gate IC 4011, whose truth table is shown in Table IV.
In this process, the number of pins of the IC to be checked is entered first. The device then starts manifesting all possible input signals to the IC and takes back its response for each possible input. If a response matches the output of a particular IC in its database, then it declares that IC as good (Figs 7 and 8).
In this method, the IC number is entered first (for example, 4011 as shown in Fig. 9). On continuation, basic detail of that IC is displayed (Fig. 10). At the start of the checking process, an option for truth table is provided for the user (Fig. 11). For viewing the truth tables, this option must be selected. At the next stage, the MCU initialises the signal-processing task.
In case of this specific NAND gate IC 4011, the MCU provides 5V supply to pin 14 and 0V to pin 7. As this IC has four NAND gates, each of these is checked one by one. The MCU provides the necessary combination of inputs to each gate as per the truth table (Table IV) and takes back outputs from the IC (4011) as its input.
Then, by comparing these observed results with expected results as per IC specifications, the MCU yields its conclusion on that particular gate (Fig. 12 shows the result for the first gate along with the corresponding truth table). Finally, the number of good and bad gates is displayed, in addition to the overall condition of the IC (Fig. 13).
Download PDFs and component layout PDFs: click here
Download source code: click here