Will the LED be ON or OFF in this circuit?

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In summary, the conversation discusses a D flip flop circuit with two inputs, SET and RESET, which are not part of the typical D flip flop design. The purpose of these inputs is unclear, but it is assumed that RESET resets the Q output to 0. The circuit also includes a clock input and a D input, and after reset is applied, the LED will be turned on. The conversation also mentions the use of D flip flops in shift registers and the advantage of capturing the signal at the moment the clock goes high. The conversation ends with the confirmation that the circuit is the switch debouncer.
  • #1
physixchic
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Here is the ciruit. It's a D flip flop
http://i45.tinypic.com/jtpjfc.jpg

After reset is applied, will the LED be ON or OFF. Explain your answer.

The answer is ON but I don't know why.
 
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  • #2
Hi physixchic,

What are those two inputs on the D flip flop that aren't D, Q, Q' or clk? They both have negated inputs.
 
  • #3
cepheid said:
Hi physixchic,

What are those two inputs on the D flip flop that aren't D, Q, Q' or clk? They both have negated inputs.

i assume SET and RESET.
 
  • #4
Is it because RESET makes everything a 0 which makes Q a 0 and Q' a 1?
 
  • #5
physixchic said:
Is it because RESET makes everything a 0 which makes Q a 0 and Q' a 1?

That's plausible, but I don't know for sure, because the D flip flops I'm familiar with don't have those additional inputs:

http://hyperphysics.phy-astr.gsu.edu/Hbase/Electronic/Dflipflop.html

The only thing that I can tell you for sure is that pushing the button pulls the D input low which (after the next rising clock edge) causes the Q output to go low, which causes its complement to go high, which lights up the LED. I have no idea what role the RESET line plays in this circuit.

By the way, I'm assuming that this is the switch debouncer that you posted in another thread about?
 
  • #6
Actually...

These flip-flops are very useful, as they form the basis for shift registers, which are an essential part of many electronic devices. The advantage of the D flip-flop over the D-type latch is that it "captures" the signal at the moment the clock goes high, and subsequent changes of the data line do not influence Q until the next rising clock edge. An exception is that some flip-flops have a "reset" signal input, which will reset Q (to zero), and may be either asynchronous or synchronous with the clock.

Quoted from here:

http://en.wikipedia.org/wiki/Flip-flop_(electronics)#D_flip-flop
 
  • #7
cepheid said:
That's plausible, but I don't know for sure, because the D flip flops I'm familiar with don't have those additional inputs:

http://hyperphysics.phy-astr.gsu.edu/Hbase/Electronic/Dflipflop.html

The only thing that I can tell you for sure is that pushing the button pulls the D input low which (after the next rising clock edge) causes the Q output to go low, which causes its complement to go high, which lights up the LED. I have no idea what role the RESET line plays in this circuit.

By the way, I'm assuming that this is the switch debouncer that you posted in another thread about?

yes it is. thanks for the help I think i got it now
 

FAQ: Will the LED be ON or OFF in this circuit?

Will the LED be ON or OFF in this circuit if I connect it to a battery?

The LED will be ON if the battery is connected with the correct polarity. This means that the positive terminal of the battery should be connected to the positive terminal of the LED, and the negative terminal of the battery should be connected to the negative terminal of the LED.

Can I use any type of battery to power the LED in this circuit?

The type of battery you can use will depend on the specifications of the LED. Most LEDs require a specific voltage and current to function properly. It is important to choose a battery that can provide the correct voltage and current for the LED.

Will the LED be ON or OFF if I reverse the polarity of the battery?

If the polarity of the battery is reversed, the LED will not light up. This is because the LED only allows current to flow in one direction, from the positive to the negative terminal. If the polarity is reversed, the current cannot flow through the LED, and it will not light up.

Can I use multiple LEDs in this circuit?

Yes, you can use multiple LEDs in a circuit as long as you have enough power from the battery to supply all of them. However, it is important to make sure that the LEDs are connected in parallel, with each LED having its own resistor in series, to ensure that they all receive the correct amount of voltage and current.

How do I know if the LED is working in this circuit?

If the LED is properly connected to the battery with the correct polarity, it should light up when the circuit is closed. If the LED does not light up, it could indicate that there is a problem with the circuit, such as a loose connection or a dead battery. You can also use a multimeter to test the voltage and current across the LED to determine if it is functioning properly.

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