Since my hand injury is keeping me from doing any real manual work, I've started back on my long, long on going project, an electrical discharge machine. So my question is how do you make a CD4013 flip flop always be in the same configuration on power up? I know you chose either the set or reset pin, depending on how the circuit starts but how do you make sure the right one is used at every circuit start up?

 

hi sb,
This is one option, Vcc is the power rail.
E

 

This is one option,

You could add a 10kΩ resistor in series with the CLR input in place of D1 to limit the IC input reverse current (data sheet states 10mA max.).


I would also increase the R1C1 value in case the power supply comes up slowly.

 

You can check the real application -- The sound active control circuit.

 

Thank you all for your answers.

I'm very dumb about circuit design. When I posted my first iteration of this circuit way back in the day, there were so many mistakes and I got very discouraged, and went back to things I know how to do machine work and fabricating things. But this project is always on the back burner.

My original design was way too involved and just plain bad. What this is going to be is similar to a R-C oscillator but digital. I know what it's supposed to be doing just not how to make a schematic. I can usually find things but it helps when you know the right question to ask. Again thank you guys for the help.

 

BTW, this is called a Power-On Reset (POR) circuit.

ak

 

I generally use a Schmitt trigger rather than a D-type. You can build one with two or three transistors or an op-amp which works from 5V.

 

I generally use a Schmitt trigger rather than a D-type.

I'm confused.
A Schmitt trigger circuit and a D Flip-Flop perform entirely different functions.

 

BTW, this is called a Power-On Reset (POR) circuit.

ak

I found that out after I started the thread. Not being trained or schooled in this stuff is hard on a 75 year old guy. By the way, will this power on reset work on both the set and reset? I am assuming it will.

 

I generally use a Schmitt trigger rather than a D-type. You can build one with two or three transistors or an op-amp which works from 5V.

I'm not smart enough for doing that. What I half way know is using simple logic gates.

 

Hi guys, new question on the same thing. I'm using both flip flops on a single CD4013, can I use only a single cap and resistor for the two of them, or do they each get their own POR circuit?

 

Hi guys, new question on the same thing. I'm using both flip flops on a single CD4013, can I use only a single cap and resistor for the two of them, or do they each get their own POR circuit?

A single circuit should do the job since the inputs are high impedance for all CD4000 series parts.

 

can I use only a single cap and resistor for the two of them, or do they each get their own POR circuit?

You can use one POR circuit for as many CMOS chips as you have that need the function.

 

@Papabravo @crutschow Thank you again for the help. This kind of thing isn't shown in any of the flip flop information I've been able to find.

 

@Papabravo @crutschow Thank you again for the help. This kind of thing isn't shown in any of the flip flop information I've been able to find.

In designs with a microprocessor there are often little circuits called "microprocessor supervisory circuits" which provide a power up reset signal that lasts long enough for the processor oscillator to start beating up and down and stabilize before releasing the RESET or RESET* pin. The MAX809 and MAX810 are parts that I have used. This feature is also quite useful in other types of applications for a small cost in $ and board space.

https://www.onsemi.com/pdf/datasheet/max809s-d.pdf

 

The MAX809 and MAX810 are parts that I have used

Thanks for that, but I'm trying to use the things I have already bought, for my old design. Every thing is using 12VDC and through hole. I'm a dinosaur that doesn't know enough to just die.

 

Thanks for that, but I'm trying to use the things I have already bought, for my old design. Every thing is using 12VDC and through hole. I'm a dinosaur that doesn't know enough to just die.

Sure, no problem. Still, more information is better than less information.

 

Back with another dumb question. Will the POR circuit also work to debounce a push button switch? The switch is NO and will send 12V to start the circuit. All of the switch debounce circuits I found seem to be for a switch going to ground not going "high".

 

Will the POR circuit also work to debounce a push button switch?

Yes if the the input is not sensitive to the signal rise-time.
For example, some clock inputs require a minimum rise-time for proper operation.

 

Yes if the the input is not sensitive to the signal rise-time.
For example, some clock inputs require a minimum rise-time for proper operation.

I've generally seen maximum rise and fall time requirements. The only time I've seen minimums is when the part requires a minimum clock frequency.