The Analog Of Things - Part 1



The study of electronics, which for me started in high school, started with the analog side of the textbook. The curriculum continued until in college we get to what is known as NQF4 and now we are studying Digital Electronics. You know that change of state where the input is read in terms of being on and off, rather than a varying voltage. A varying voltage in digital electronics is undesirable as it confuses the input, and instantaneous (or near to it) change is preferred.

Long before digital electronics took the world by storm, there were such things as analog computers which to some extent we learned about with summing amplifiers and so on. No, this is not intended as a nostalgic trip down the analog lane, however, what cannot be ignored in embedded electronics is the constant run-in with the analog value that needs to be interpreted as a digital quantity.

When considering the differences in complexity when working with both, I am going to compare the LM35 with the TL074.

The LM35 is a three-pin device, runs on 5 volts, and needs one pin on your microcontroller to work.

The TL074 is a 5 PIN device, you have the choice of 3v3 and 5v0, however, you would also need to understand how to use and implement the I2C protocol as that is the means of data delivery.

The LM35 could potentially be used on very low-count PIN devices whereas the TL074 would need a device with the I2C interface as a peripheral or a software implementation which could be tricky if you get the timing or the protocol wrong.

The LM35 would not need a microcontroller to be useful, and you could use it with a simple op-amp in comparator mode. However, this is perhaps where the TL074 has the advantage. The device would only ever take up two pins because of the I2C interface, and many devices could be daisy chained forming a network of devices.

The LM35s would require a pin for each device and potentially require buffering circuitry to ensure signal integrity. The need for signal source isolation may need to be considered, and

Supporting a collection of LM35s would require a much higher BOM when considering the need to ensure signal integrity and no interference.

Although you could potentially position an LM35 “further” from the embedded PCB, the limitations of the I2C interface would curtail the length or distance – unless you included buffering circuitry.

If you are wondering at this point which is the better option, over the next few releases we are going to be looking at this question with various options when it comes to using sensors and how best to use them. We will be contrasting, where possible, an analog sensor or method versus a digital one.

Next >> The Analog of Things Part 2