# (A+B)(A+C)=A+BC circuit doest not work (protoboard)

• Engineering
• Noob of the Maths
In summary: Also, 74LS is not very strong at driving a "high" output. It is better at driving a "low" output, so you may want to add an inverter (or a transistor) at your circuit's output so it can pull the cathode of the LED Low (rather than trying to drive the anode high). Check the datasheet for values of Voh, Vol, Ioh, Iol, etc. It may also help to use a high-efficiency Red LED, which can generally be driven with less current.
Noob of the Maths
Homework Statement
Reproduce the boolean expresion: (A+B)(A+C)=A+BC (in protoboard)
Relevant Equations
Nothing
Hi guys :)!
I have a little problem with my homework protoboard circuit:

First, i try to connect the simplification (A+BC), the LED it doest not turn off and not response when i push the buttons.

All the components its ok, all its works. If the simplification works, the complete expression become easy to continue.

Last edited:
Please post your schematic. Also, you should be grounding all unused gate inputs (not outputs though, obviously).

berkeman said:
Please post your schematic. Also, you should be grounding all unused gate inputs (not outputs though, obviously).

I make the schematic in proteus and its works fine.

If A is high (set) or if both B and C are high, the light should come on.

Your schematic doesn't match either one of your equations in your first post, IMO. Also, where are the switches? What logic family are you using? What are the Vcc connections and ground connections? If you are using CMOS logic, the unused inputs of the other gates need to be grounded.

Mark44 said:
If A is high (set) or if both B and C are high, the light should come on.
Yes, but in my case the LED is always turn ON and not responding to the buttons to take off ;(

berkeman said:
Your schematic doesn't match either one of your equations in your first post, IMO. Also, where are the switches? What logic family are you using? What are the Vcc connections and ground connections? If you are using CMOS logic, the unused inputs of the other gates need to be grounded.
The schematic corresponds to A+BC. I use logic probe like switches in the schematic, Vcc and ground are the blue connections in the first image.

What logic family? 74HC? 74VHC? Vcc=5V or 3.3V? The switches are single pole double throw, break before make?

berkeman said:
What logic family? 74HC? 74VHC? Vcc=5V or 3.3V? The switches are single pole double throw, break before make?
74LS, Vcc= 5V. The switch are pushbuttons in the protoboard

Noob of the Maths said:
The switch are pushbuttons in the protoboard
What value of your resistor pullups or pulldowns (depending on which way the switches pull)?

Do you have a DVM where you can monitor the voltage at each gate input and output? That may help you figure out what is going on.

Also, 74LS is not very strong at driving a "high" output. It is better at driving a "low" output, so you may want to add an inverter (or a transistor) at your circuit's output so it can pull the cathode of the LED Low (rather than trying to drive the anode high). Check the datasheet for values of Voh, Vol, Ioh, Iol, etc. It may also help to use a high-efficiency Red LED, which can generally be driven with less current.

Noob of the Maths

## 1. Why is my (A+B)(A+C)=A+BC circuit not working on the protoboard?

There could be several reasons why your circuit is not working on the protoboard. Some common issues include loose connections, incorrect wiring, faulty components, or a short circuit. Make sure to check all of your connections and double check your circuit design before troubleshooting further.

## 2. How can I troubleshoot my (A+B)(A+C)=A+BC circuit on the protoboard?

To troubleshoot your circuit, start by checking all of your connections and making sure they are secure. Next, use a multimeter to test each component and make sure they are functioning properly. You can also try replacing components one at a time to see if that solves the issue. If all else fails, try rebuilding the circuit on a new protoboard.

## 3. Do I need to use specific components for my (A+B)(A+C)=A+BC circuit on the protoboard?

Yes, it is important to use the correct components for your circuit to work properly. Make sure to use the appropriate resistors, capacitors, and other components as specified in your circuit design. Using incorrect components can cause the circuit to not work or even damage the components.

## 4. Can the placement of components affect the functionality of my (A+B)(A+C)=A+BC circuit on the protoboard?

Yes, the placement of components can have an impact on the functionality of your circuit. Make sure to follow the correct circuit design and place components in the designated locations. Incorrect placement can result in a circuit not working or even causing damage to the components.

## 5. How can I prevent my (A+B)(A+C)=A+BC circuit from not working on the protoboard in the future?

To prevent issues with your circuit on the protoboard, it is important to double check your connections and circuit design before powering it on. Make sure to use the correct components and place them in the designated locations. It is also helpful to use a breadboard or simulation software to test your circuit before building it on a protoboard.

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