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I have a circuit which needs to turn on the buzzer and flashing lights when both my switches (switch 1 and 2 left side of the circuit) are on. I was trying to do this with a AND gate but couldn't get it to work (needs to output 9 volts). Does anyone have any suggestions?

Help would be much appreciated as this circuit goes towards my test grade and I'm currently stressing out about it.

screenshot of schematic

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  • \$\begingroup\$ Welcome to EE.SE. As we can see, there's a lot more circuitry than what you describe. What's the purpose of R5 and R6? And why don't you just put the two switches in serial and connect the battery and the rest of the circuit over the two switches? \$\endgroup\$
    – Ariser
    Feb 9, 2020 at 19:47
  • \$\begingroup\$ Are there any connections between the two circuits in the schematic you posted? \$\endgroup\$ Feb 9, 2020 at 19:49
  • \$\begingroup\$ you may be interested in scanning search results electronics.stackexchange.com/search?q=buzzer+led It is easier if you know the impedance of the buzzer V/I because piezo types are much higher than magnetic types. \$\endgroup\$ Feb 9, 2020 at 20:04
  • \$\begingroup\$ your two circuits are similar to you holding a battery in one hand and a lighbulb in the other hand and you expecting the lightbulb to magically light up \$\endgroup\$
    – jsotola
    Feb 9, 2020 at 22:11

2 Answers 2

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If you want the transistor to power the 555 oscillator circuit then the transistor should be an emitter-follower. Then one switch can be between the emitter and the positive supply of the 555 circuit and the other switch can be between the base of the transistor and +9V. Connect the collector of the transistor to +9V.

What is the photoresistor for? So that the circuit works in darkness or in sunlight?

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  • \$\begingroup\$ the photoresistor is so the circuit only works in sunlight \$\endgroup\$ Feb 9, 2020 at 20:39
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Hee, hee. Of course two switches in series make an AND gate.

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  • \$\begingroup\$ I understand, you could not resist posting this, and it is a correct answer, but it's not a good answer in terms of this Q&A site. So I give you a +1 and vote for deletion :) \$\endgroup\$
    – Ariser
    Feb 9, 2020 at 21:38

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