update lesson changes

docs/lessons/seismograph.md

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+# Seismograph Lesson 
+
+Build a seismograph with household materials
+
+## Topic 
+
+Acceleration & Analog Read Pin
+
+## Quick Links
+
+* [activity](/lessons/seismograph/activity)
+* [challenge](/lessons/seismograph/challenges)
+
+## Prior learning/place of lesson in scheme of work 
+
+Learn how to **show LEDs** to turn on a LED light pattern on the LED screen. We will be learning basic comments such as show LEDs and pause.
+
+## Documentation
+
+```cards
+basic.forever(() => {
+});
+led.plotBarGraph(input.acceleration(Dimension.Strength) - 1023, 0);
+led.plotBarGraph(pins.analogReadPin(AnalogPin.P0), 0);
+
+```
+
+## Objectives
+
+* learn how to repeat code forever in the background
+* learn how to display a vertical bar graph based on the value. 
+* learn how to return the sum of the two numbers
+* learn how to get acceleration value in milli-gravitys 
+* learn how to read the connector value as analog as a value comprised between 0 and 1023