31st : Embedded Systems - Day 3

Lots of activity today with varied results. Checked all the components purchased. Thermistors, Light Dependant Resistor and ADC.

The thermistor obtained , NTC 10D-11 , was unsuitable for my application. It is mainly used to control the Inrush current in circuits thereby preventing damage to the equipment. Such components though not suitable at present , will provide increased knowledge that can be valuable in future situations. So, no effort goes waste ! We will get LM45 : Precision Centigrade Temperature Sensor tomorrow and hopefully work on it.

The next component was LDR (big) type which usually has a very high resistance in dark and a low resistance in light. Using a thumb to close the LDR from light and using a digital meter, I checked that the resistance was > 1Mohm in dark and about 700K when there was moderate light. I have to check in bright light tomorrow. So, LDR is OK.

Then I got the ADC connected on the breadboard. We got to the pin level understanding of the operation of the circuit. The timing diagrams were understood. The ouput from the ADC will be given to a 7 segment display through a BCD-to-Seven Segment decoder (SN7447). This is for tomorrow. 7 segment displays come in two types (common anode and comon cathode).

Finally, I could locate a suitable multiplexer (there are both analog and digital multiplexers). We need an analog mux to interface the sensor world to the ADC. That could be AD7501/7502/7503 from Analog Devices. Wait and C.

So, honestly, we touched everything but came out with more to be done tomorrow. You might be wondering how the I has become we ! Yes, I a joined by a few more enthusiastic staff in this activity.

Finally, we need to brush up our C , shouldnt we ?

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Supposing that each integer occupies 4 bytes and each character 1 byte, what is the output of the following program ?

#include "stdio.h"
main()
{
int a[] = { 1,2,3,4,5,6,7 };
char c[] = { 'a', 'x', 'h', 'o', 'k' };
printf ("%d\t %d ", (&a[3] - &a[0]),(&c[3] - &c[0]));
}
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The day actually started with a different practical ! I got the ticker tape (below the header) to the right size with the help of CSE faculty. Thanks to them.

The first student to post the right answer to the C-code question above will get a small complement :)

Have a nice day