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LED Display

LED Display. Prof. Betty Lise Anderson. Here ’ s what you ’ re going to build. Need to learn some things. How to read an electrical schematic What parts we ’ re using How design the display How to build the display. Reading Schematics:. Battery. What ’ s this?. How about this?.

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LED Display

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  1. LED Display Prof. Betty Lise Anderson

  2. Here’s what you’re going to build

  3. Need to learn some things • How to read an electrical schematic • What parts we’re using • How design the display • How to build the display

  4. Reading Schematics: • Battery What’s this?

  5. How about this? • Resistor

  6. What’s this? • Diode • Lets current flow one direction but not the other YES X NO

  7. Will current flow?

  8. How about here?

  9. And here?

  10. Let’s take a look at the components • 16-segment alphanumeric display • Green, yellow, or red • 18-pin package • There is one LED inside for each segment

  11. How to read the data sheet • This page is general propaganda

  12. Next is dimensinos

  13. Ah hah! What’s inside

  14. This is called the pinout

  15. Absolute maximum ratings

  16. Electro-optical characterisitics

  17. Additional information

  18. What value of resistor? • What is voltage across the diode? • Hint: look at electro-optical characteristics • How much is left to go across the resistor? + 2V - + 7V -

  19. V=IR • I= current • R=resistance • Don’t exceed 25 mA through diode • (see absolute maximum ratings) • What are tradeoffs in choosing current? + 2V - + 7V -

  20. So, what will you choose? • R=V/I • Example: • V=7V • Choose I=20 mA • 0.020 Amps • R=7/0.02=350 Ohms • We don’t have that • But we have something close + 2V - + 7V -

  21. So here’s what you’ll build

  22. Figure out what to write

  23. The breadboard

  24. The buses Every hole along this green line is electrically connected

  25. There are four buses you can use

  26. All rows connected too

  27. To connect to your devices • Recommend putting displays across center channel

  28. To make connections • One end of wire is connected to the bus • And anything else connected there • Other end is connected to one pin

  29. Now, look at circuit diagram • Need to make these connections

  30. Negative bus and safety resistor BLACK

  31. Connect positive RED RED BLACK BLACK

  32. Now, look at circuit diagram • Need to make this connection What pin is this on the display? All anodes connected to a common point at this pin Which pin is the common anode? Connect pin 18 to the positive bus

  33. Connect common anode to positive bus

  34. Another negative bus will come in handy

  35. Next, connect cathodes • One resistor for every segment you want to light? • Where do you connect them?

  36. Connect resistor for every cathode you need to ground

  37. OK, once it’s working • Repeat for every other segment • Once done, remove safety resistor

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