<p> ECE 323L Basic Electronic Circuits Laboratory Lab 10</p><p>Names:</p><p>Do the following exercises. Report your results by editing this Word document and submitting it in WebCT.</p><p>This laboratory is the third in a series of experiences using digital electronic components. You will use a 7805 voltage regulator chip to convert your 9-volt battery supply to a 5- volt supply from the last two weeks and the seven-segment display from last week.</p><p>1. Interface a counter based on a 74LS90 chip to your seven-segment display. Use a 555 timer circuit (see lab 5) to trigger the counter (pin 14). Demonstrate the circuit to the lab assistant.</p><p>INPUT B 1 14 INPUT A R0(1) 2 13 NC R0(2) 3 12 QA NC 4 7490 11 QD VCC 5 10 GND R9(1) 6 9 QB R9(2) 7 8 QC</p><p>Figure 1. Pin diagram of LS7490 chip</p><p>11 1 D B 8 C 7490 9 14 B I A 12 N A</p><p>2 3 6 7</p><p>Figure 2. Circuit for simple decimal counter 2. Measure the period of your 555 timer using the oscilloscope. Measure the period of the counter by using a watch to time a fixed number of counts (ten or more). Note that noise may cause the counter to update more frequently than the timer, at least it did on my breadboard.</p><p>Measured Period Timer Counter</p><p>3. (Optional) Try to trigger the counter manually by connecting and disconnecting pin 14 to ground. Chances are you will observe contact “bounce”, the counter will make several steps instead of one.</p><p>4. (Optional) Connect your counter to the output of your SR-flip-flop. By first setting and then resetting the flip-flop you should be able to make the counter increment cleanly. maintained by John Loomis, updated 24 March 2008</p>