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The Design Process Getting Output From Your System

Learn about the design process to create a system that receives input, performs processing, and produces an output display. Explore LED displays and how to select suitable components.

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The Design Process Getting Output From Your System

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  1. The Design ProcessGetting Output From Your System by Prof. Michalson

  2. Design Problem • We’ve been working on a system that receives input, performs some kind of processing, and produces an output display. • The display should must provide a 3 digit number indicating, for example, water (fluid) temperature.

  3. A System Block Diagram Micro controller Analog Input Processing Display Power Supply

  4. A Really Simple Display • Lots of displays are: • 1) LEDs • 2) Based on collections of LEDs • 3) Have similarities to displays made with LEDs • So, let’s see what’s involved with using just an LED. • It won’t meet our requirements, but we need to gain expertise first, then apply that new knowledge to achieve what we want.

  5. Turning On an LED • To light an LED generally requires: • Forward biasing the LED • Controlling the current through the LED • How can we know: • What’s important? • What “typical” means? • What the details of lighting an LED are? • Course textbooks • Other (Google “Using LEDs”)

  6. We Quickly Find Direction! • A little searching and we find lots of information about LEDs • Including a circuit! Source: Using LEDs – It’s Easy, Jaycar Electronics

  7. Refining Our System Design • Based on our searching, we’ve learned some things that are important to look for when selecting an LED. • Specifically, we need to consider: • LED color • Forward Current (IF) • Forward voltage (VLED) • In our system we also need to consider: • Supply voltage/current

  8. Datasheets?!?!? • Our research also helps us select components. • For example, go to digikey.com • There are many, many options! • Sorting options may require more research! • Let’s try: • Green • 50 mcd (typical indicator light) • Maximum viewing angle

  9. HSME-C265-ND Datasheet • The first thing I notice on the datasheet is a picture of the device! • It’s not very convenient for our project! • However, it’s not totally useless, since it at least lets us see the typical information that’s provided.

  10. Back to the Drawing Board! • We now know that package styles are important! • Let’s focus our search a little more: • Package style • Color • Brightness • Etc. • We finally find a (potentially) suitable component!

  11. But We Need a 3-Digit Display! • We basically know how to drive an LED. • A multi-digit display is really a bunch of LEDs in a single package. • We can repeat the process we just used to try to find a suitable 3-digit display. • Consider the following Digi-Key parts: • 67-1424-ND • 754-1656-5-ND

  12. But Wait, There’s More… • Now we have some ideas how to: • Drive an LED • Interpret a datasheet • Find (potentially) suitable components • Next, we need to see how the options we find for actual output devices impact the circuitry that actually drives the display.

  13. Ramifications… • Hardware-related considerations: • Processor drive capabilities • Voltage • Current • Pin counts • Drive each pin separately or multiplex lines? • Software-related considerations: • Encoding of data to drive display • Scan rate of display • Etc.

  14. Design = Iteration? • Every decision you make at one point in a design will impact decisions made at another point in the design. • Thus, every decision may require revisiting previous decisions. • Sometimes you’ll find that things won’t work together the way you planned. • It’s better to find out before you start building! • Iterate through design options until all your requirements are satisfied.

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