W2 Lab - Lab Electronics

I used the ToolSmart Digital Multimeter, a bluetooth enabled auto-range multimeter.

Measuring continuity

I followed the instruction on the user manual and set up the meter. When I touched the tips of two probes, there was a continuous beep, however the readings on the screen kept fluctuating as I changed the contacting point of the leads or as my fingers touched the leads. For example the two readings I got was 0.2Ω and 1.0Ω as opposed to the <0.1 value in the lab guide. I double checked the connection of the jacks, probes were both plugged in properly. I am certain there was connection as there WAS the beep, but I'm not sure whether the frequent fluctuation in reading is normal during continuity check, and what are the factors that could influence the reading?

--update from class 3: different meters react differently to continuity. The reading shows the resistance in the circuit, eventually the readings should go down and close to 0, but depending on the environment(temperature, humidity, etc), the readings would sometimes fluctuate.

A switched LED circuit

V is read 0 when button is either released or pressed. As there is no voltage going through the button when the button is released; When button is pressed, as there is almost no resistance across the button, R=0, V=R*I=0*I=0;

Voltage of resistor+Voltage of LED=2.75+2.13=4.88V is less but close to the voltage input 5V

Components in series

The voltage across resistor and two LEDs read as: 1.13, 1.95, 1.92 adding up =5V

when a 3rd LED is added in series none of the LEDs lit up, as each LED needs about 2V to light up, adding a 3rd one split the voltage going through each LED even smaller.

Components in Parallel

when I measure current across three LEDs, I disconnect one LED from the circuit and complete the circuit with my meter in series with the LED. My readings for each LED was around 40mA.

Generating a Variable Voltage with a Potentiometer

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A simple application for switches and LED circuits:

I created a system with red, yellow and blue LEDs parallel to each other. With a pushbutton controlling on and off of the red and yellow LEDs, and the yellow LED has a dimmer made from a potentiometer.