Week 4 - Journal

My idea is to make a simple manual sound alarm with light, made of a simple circuit using an on /off switch when the device is on a buzzer emits sound and a red led light goes on. This device can be used to alarm people in case of an emergency by turning on the switch the buzzer starts emitting sound and the led light helps warn people with disabilities in hearing.

2- then i made my schematic diagram for my circuit

3- then i started the simulation for my circuit with tinker cad website and made the simulation for the multimeter readings

Maximum current that the battery can give

Making sure of the voltage required by the led bulb

4- when applying my circuit in real i faced a problem i didn't find the convenient resistor with the resistance need and not near it so i repeated my simulation with a 100k ohm potentiometer and applied my circuit in real with a potentiometer instead of the 360 ohm resistor ( but it is not preferable to do so, a resistor with a resistance value near the required value is the optimum solution not the potentiometer)

5- then i applied my circuit and tested it and toke the readings for resistance of the potentiometer and the current reaching the led and the voltage across the battery

• to connect the circuit i started by connecting the adaptor to the dc jack with the jumpers.

• the i put the jumper from the +ve terminal of the adaptor and the the jumper from the -ve terminal of the adaptor in the power rails of the breadboard in +ve and -ve rails respectively

• the i connected 2 jumpers in the 2 terminals of the on/off switch and put on of them in the +ve power rail of the breadboard

• the second terminal of the switch is connected to one terminal of the buzzer

• the other terminal of the buzzer is connected to the -ve power rail of the breadboard

• at this point by turning on the switch the buzzer starts emitting its tune

• to connect the led in parallel with the buzzer i put 2 jumpers at the 2 end of the buzzer one jumper to be connected to the ground of the potentiometer and the other jumper to be connected with the cathode of the led light while the other leg of the led is connected to one of the 2 terminals of the potentiometer.

• now the swich is controlling both the buzzer and the led light

• to measure current intensity across the led light the multimeter is connected in series with it

• to measure voltage across the buzzer, the voltmeter is connected in parallel to it

• to measure resistance of the potentiometer the 2 terminals of the avometer in connected to the ground and the terminal connected to the other leg of the led

• the probes and the selector was set in each case to measure current in millampere (and also exchanging the probes place ) and dc current voltage less than 20 and the range within 100k ohm to measure thr resistance

Testing the circuit

Measuring the exact resistance for the potentiometer

6- i brought a cartoon box and toke the dimensions for the switch and the bulb and the dc jack and to cut in the cartoon box to fit these components in the box to be easily used by others (users) and exchanged some jumper connections with crocodiles to be easier in fixation and i got my final device ready to use.

I didn't know how to know the exact model for the led light and other components that has no serial number on it in order to know the voltage and the vurrent intensity required for it and I asked my instructor about this issue and now I know that some components are standard and all I had to do was to search with the name of the component I want it's data sheet and found the component similar to mine to get my info without a need to know its model or serial number.

Also One of my peers asked a question related to drawing the schematic diagram of the circuit and I really understood the idea whatever are connected in the diagram in a point will also be connected in appoint in the applied circuit so I had to follow my connections to draw the schematic diagram correctly. Also a question related to getting readings from the avometer really helped me to get my readings: The probes connections and the selector ranges of the multimeter to measure voltage, current intensity and resistance and what helped me the most was the continuity measurement to make sure 2 points are connected in the circuit by hearing the whistle from the multimeter.

I faced a problem that nothing happens in my circuit, t thought there is no current. so i recorded a video with a question to find out if i had made a wrong connection and share it on flipgrid and i got an answer from my instructor that really helped me. he adviced to me to use the multimeter to detect the problem,to connect voltmeter in parallel with the bulb to measure the voltage across the circuit and if the voltage equals 0 then i have a faulty adaptor but that was not my case. and to measure the current by connecting the ameter in series with the bulb and if the current is zero then i have a faulty bulb or jumpers and that was my case since when i made the series connection the lamp was powered on and then i knew the problem was in my connections and the problem was in one of the crocodiles i was using and i replaced it.