555 on/off AND resetable

Thread Starter

stillgrowingup

Joined Jul 15, 2015
210
Hi all

I have a circuit that I can not seem to configure to do as I would like ... I would like a GND pulse from a N/O push button to toggle on the 555. The 555 will trigger a 12V relay, sending power ONLY to my vechicles dash/gauges. (Please note the dash power and the vehicles 12v Ignition is separate.) When I move the ignition key forward, turning on the vehicles Ignition circuit. The 555 chip turns off. Allowing the vehicles ignition circuit to supply the Dash its power. The 1st circuit I attached to this post accomplishes this task I mentioned above. ... BUT .... I would like the GND pulse from the push of the N/O Power button to activate AND another push to deactivate the 555 circuit. PLUS, have the vehicles 12V ignition also deactivate the 555 circuit.

I did try to use a PNP BD140 to shunt across the SET and RESET triggers of the 555 circuit. (See drawing 2)

In my SIM the BD140 works, but not on my bread board. :(

I am asking for guidance to accomplish what I am looking for.

Thank you,
TONY
 

Attachments

Thread Starter

stillgrowingup

Joined Jul 15, 2015
210
what is the 555 used in your circuit?


I am using the 555 to convert the ground momentary pulse, into toggled latched ouput. I want this 555 ouput will control a relay, and illuminate an led, indefinitely til one of 2 things happen that will deactivate it.

1 .... the button that started the 555 can also deactivate it with a ground pulse.

Or

2 .... the 555 sees 12v and deactivates.

Tony
 

shortbus

Joined Sep 30, 2009
10,045
I have a circuit that I can not seem to configure to do as I would like ... I would like a GND pulse from a N/O push button to toggle on the 555. The 555 will trigger a 12V relay, sending power ONLY to my vechicles dash/gauges. (Please note the dash power and the vehicles 12v Ignition is separate.) When I move the ignition key forward, turning on the vehicles Ignition circuit. The 555 chip turns off. Allowing the vehicles ignition circuit to supply the Dash its power. The 1st circuit I attached to this post accomplishes this task I mentioned above. ... BUT .... I would like the GND pulse from the push of the N/O Power button to activate AND another push to deactivate the 555 circuit. PLUS, have the vehicles 12V ignition also deactivate the 555 circuit.
Most ignition key switches do what your asking. Don't know about the new push button switches though.
 

Thread Starter

stillgrowingup

Joined Jul 15, 2015
210
I wonder if I can look at this another way. I have attached another circuit that I have bread board and confirmed that it works on my breadboard. So this circuit will turn on and off from the same push button.

The question is how to get the 12 Ignition to kill this circuit. I am thinking of having the 555 power source go through a mosfet or transistor. That way the when 12v Ign is brought to the base of either the mosfet or transistor. It would kill the 555 chip, shutting down the circuit. Is this a option?

TONY
 

Attachments

eetech00

Joined Jun 8, 2013
3,859
Hi

You can try this alternate circuit if you like.
It uses a CD4013B and couple of 2N3906 BJT's.
When the button is pressed, Q1 inverts the input to provide a positive trigger pulse to U1A. U1A send a short clock pulse to U1B that toggles its output and energizes the relay. If the button is pressed again, U1B's output is toggled again, de-energizing the relay. All this only happens if the key is in the "on" position. If the key is switched to the "off" position, power is removed from the circuit, so if the relay is energized, it will de-energize.

edit: oops...sorry ak...guess you posted as I was replying.
 

Attachments

AlbertHall

Joined Jun 4, 2014
12,345
You could add this to your '555 circuit. Disconnect the '555 RST pin from the +12V and connect it to the collector of the transistor. When the ignition is switched on, it will hold the '555 reset.
upload_2016-11-11_21-34-13.png
 

Thread Starter

stillgrowingup

Joined Jul 15, 2015
210
It uses a CD4013B and couple of 2N3906 BJT's.
Thank you for your suggestion. I tried something like 4013 before.

http://forum.allaboutcircuits.com/t...ed-latching-circuit-using-transistors.120668/

The circuit in the link DOES work. But the 4013 gets hot and the debouching is awful. The circuit still latches, but sometimes I have to press the Trigger button a few times before it stays latched. That is why I was looking to do the 555. It seems pretty stable in comparison and doesn't get hot. :)

You could add this to your '555 circuit.
Thank you. I will give this a try.

TONY
 

eetech00

Joined Jun 8, 2013
3,859
Thank you for your suggestion. I tried something like 4013 before.

http://forum.allaboutcircuits.com/t...ed-latching-circuit-using-transistors.120668/

The circuit in the link DOES work. But the 4013 gets hot and the debouching is awful. The circuit still latches, but sometimes I have to press the Trigger button a few times before it stays latched. That is why I was looking to do the 555. It seems pretty stable in comparison and doesn't get hot. :)

Thank you. I will give this a try.

TONY
Hi

If the 4013's are getting hot then something else is wrong. They hardly draw any current...less that 6mA. Sounds like a design issue.
 

Thread Starter

stillgrowingup

Joined Jul 15, 2015
210
Hi All

I have a bit of a problem. First, the 555 circuit works great. I use this 555 circuit to engage a mechanical relay. This Relay powers up a electronic device with a 600mA draw, indicate in drawing with 'J1'.

The problem is ... once the relay is energized. The time duration of the relay switching from N.C to N.O , my device shuts off. Brownout I think its called.

I am wanting to placed a electro capacitor as indicated in the drawing to solve this problem. I first tried a 1uF 50V capacitor, that didn't work. I then tried a 470uF 50V and the charge lasted to long to discharge. Next I tried to 22uf 50V and that just popped ... LOL.

I am wondering what size capacitor should I use? ... Do I need anything else with the capacitor? Like a Diode, Resistor in series with the cap? I am just wanting to maintain voltage above 10.2V during the 500mS it take for the relay to switch over.

Thanks
TONY
 

Attachments

AlbertHall

Joined Jun 4, 2014
12,345
So it sounds like a value between 1uF and 470uF will do the job. Extra components won't help. The 22uF popped either because it was faulty or it was connected the wrong way round.
 

Thread Starter

stillgrowingup

Joined Jul 15, 2015
210
So it sounds like a value between 1uF and 470uF will do the job. Extra components won't help. The 22uF popped either because it was faulty or it was connected the wrong way round.
So just placing a capacitor across the 12v out and common ground should do it? .. Great, I was hoping it was that simple. I looked at my other post about this and I was not certain if diodes and resistors would be needed in conjunction with the electro cap.

TONY
 
Top