Hello folks, first time posting so go easy on me.
I'm an amateur that knows just enough to get into trouble.

I'm designing a vehicle pushbutton start using a 4013 flip flop circuit for the vehicle power and a 555 with a 1 second delay for the start function.

In planning ahead, I think I might need a debounce for the input to the 4013 so I don't flop when I want to flip.
(Sorry about the bad joke)
The input to the 4013 is a +12V input controlled by a relay activated by a momentary switch.

Could someone point me to a debounce that's on the + side of the input instead of the usual - side that I find?
Thanks for the help.
Dan

 

Have you considered just using simple a RC input to the FF?

 

Have you considered just using simple a RC input to the FF?

Do you have an idea on what values I should use for the components?
Most of the RC circuits I find are negative trigger. Is it a matter of reversing the cap in the circuit?
Please forgive my ignorance of stupid questions.

 

Do you have an idea on what values I should use for the components?
Most of the RC circuits I find are negative trigger. Is it a matter of reversing the cap in the circuit?
Please forgive my ignorance of stupid questions.

I would think a 1K resistor on the switched side of the push button and a 0.01uF to 0.1uF to gnd should do.

 

Thank you I appreciate the help.

 

Thank you I appreciate the help.

I just re-read your first post and I made a boo boo! If the FF is being triggered by the contacts of a relay then the RC filter should be connected to the switched side of the relay contacts, not the switch . Sorry....!

 

Please see attachment. Is this how you're wired?

 

Please see attachment. Is this how you're wired?

Yes. I knew you meant to connect the RC components on the relay side.
I am using the 4013 circuit here--> Click Link but with a relay instead of the switch.
So if I'm reading it and your suggestions correctly, it already has the 'debounce' built in?
Thanks again for the help.

 

Yes. I knew you meant to connect the RC components on the relay side.
I am using the 4013 circuit here--> Click Link but with a relay instead of the switch.
So if I'm reading it and your suggestions correctly, it already has the 'debounce' built in?
Thanks again for the help.

Yeah, that circuit already has a 100K and a 1uF cap in there. That should give ample immunity from contact bounce.

 

Sweet.
Thanks again for the information and the reassurance.
Dan

 

Sweet.
Thanks again for the information and the reassurance.
Dan

Dan-O I forgot something else too!!!

To say..
WELCOME TO THE FORUM!!

 

Well, I finally had a few minutes to tinker.
I'm having some issues.
The 4013 is really sensitive to noise/contact bouncing.
I think I might need a more aggressive way to debounce the + switch input to the 4013.
I misspoke in an earlier post, I do have a switch input not a relay input to the 4013.
I am using the 4013 circuit here--> Click Link

The way my circuit works is by holding a shared pushbutton + input (both the 555 and 4013 share the same + input)
A relay engages and the engine cranks through the 555 after 1 second. That end works perfectly. But, as soon as I release the switch, the 4013 shuts off the vehicle power relay.
Suggestions?

Also, should I have a diode or a resistor from 11 to my transistor? I'm using a 3904 with the base connected to pin 11 of the 4013.

Thanks for the input.
Dan

 

Dan, could you please post your complete schematic? It will make diagnosis much easier. As they say "A picture is worth a thous..... "

 

I found a schematic of what I'm doing with the 3014 and modified it with the transistor I have to control the relay coil. Not pictured is the usual clamping diode across the coil for spikes.
I appreciate the help.
Dan

 

There should be a 1K resistor between the base of the NPN and the chip.

 

Thanks, I added it.
Do you think that was angering the 3014 and causing my issue?
I added the 555 and updated my schematic.

 

You have a few things wrong here.
(1) The base resistor should be ~ 1.0K not 100K. 100K will not provide enough base current.
(2) The 555's vcc (pin8) should be connected to the 12V supply.
(3) You may also need a driver transistor for the 555 relay coil. What's the current draw for that relay.

There may be more but I have to get some sleep.

 

Current draw is low, it's not a typical Bosch relay. I have to look it up, but I believe the coil resistance is up there, like 720 ohms or so.
I made some revisions to my schematic.
Thanks for the help.
Dan

 

Try this configuration.

EDIT: For bystanders reading this thread, please read subsequent posts.

 

Hmm, there's a few things I don't understand: What are the TP notations in the schematic?

Actually, I don't have an issue with the 555 doing it's job; the 1 second starter delay is working great.
The issue I have is with the 4013 not changing state.