Timed switch

[b1mmuo27]

I have breadboarded your circuit twice with no results. I have a couple of questions. The 12V in your diagram, is it constant? this is +12V? The input you have marked is that my pulsed +12vdc input? What is suppose to be at A? B? May be Im doing something wrong>

 

[Hero999]

The +12V is constant, the input is the trigger it's the 12V pulse.

A and B are the outputs, A is the five second and B is the one second output.

Whoops, I have made a mistake, but it shouldn't have made any difference to the second output, connect LEDs with a series resistor to them to test them.

Sorry, I've forgotton to ask some important questions and I've probably assumed you know more than you do.

By the way what current do these pulses need to be?

Is the load inductive?

If it's greater than 200mA you need a buffer to amplify the output as the 555 can't switch anymore than this, and if the loads inductive you need a diode un reverse parallel with it to absorb the high voltage pulse when it's turned off.

 

[b1mmuo27]

The output current only pulses the coil on the latching relay which in turn opens the contacts in the relay. So current is really low. The load is not inductive. I think we are still not talking the same thing. I don't need a 5 second output. What I HAVE is a one second input to start this timer. Kinda like dominoes. The input pulse of 1 second which I supply starts the internal clock counting to 5 seconds. After the 5 seconds the timer spits out a +12vdc pulse of 1 second. That's it. Job over. It waits until it gets another +12vdc 1 second pulse & then it starts over again. Kinda like tag. I touch you, you count to 5 & touch someone else. The one second pulse I supply to start the counter would go directly to the relay coil. All I am trying to do is delay that pulse for 5 seconds & then apply it to the coil.
Now I have checked this circuit over & over & I have voltage at both A & B without the 12 volt pulse inputting the transistor. So I have no delay or timer. The 0 line actually has the same voltage as the 12 volt line. I have checked the transistor & it's switching ok. I hope this clears up acouple of things.

 

[Hero999]

The output current only pulses the coil on the latching relay which in turn opens the contacts in the relay. So current is really low. The load is not inductive.

Relays are inductive, and big relays can draw up to a amp, how big is the relay?

I think you may've destroyed the 555 with the inductive kick back from the relay coil, replace it, then use a diode in reverse parallel with the relay.

I think we are still not talking the same thing. I don't need a 5 second output.

Well don't use it then.

What I HAVE is a one second input to start this timer. Kinda like dominoes. The input pulse of 1 second which I supply starts the internal clock counting to 5 seconds. After the 5 seconds the timer spits out a +12vdc pulse of 1 second. That's it. Job over. It waits until it gets another +12vdc 1 second pulse & then it starts over again. Kinda like tag. I touch you, you count to 5 & touch someone else. The one second pulse I supply to start the counter would go directly to the relay coil. All I am trying to do is delay that pulse for 5 seconds & then apply it to the coil.
Now I have checked this circuit over & over & I have voltage at both A & B without the 12 volt pulse inputting the transistor. So I have no delay or timer. The 0 line actually has the same voltage as the 12 volt line. I have checked the transistor & it's switching ok. I hope this clears up acouple of things.

The circuit is pretty simple, the transistor acts as an inverter so the positive trigger pulse gets converted to the negitive pulse required by the 555, the first 555 circuit lasts for five seconds, when it finishes it triggers the second which lasts for one second.

Seriously you really need to understand the circuit before you built it, building circuits without fully understanding them is a waste of time in my book and they probably won't work either.

 

[b1mmuo27]

It's a miniture latching relay, pcb mount. Very tiny. Draw is next to zero. I have had in the truck without the time delay for months. I have not connected the realy to this circuit. I check for voltage with an led & a dvm. As for the circuit if I understand it correctly is this not an monostable oscillator circuit?, with an off/on/off time? After the 12v pulses the tranisistor I need the circuit timer to count 5 seconds before it does anything. After five seconds I need it give me a 1 second pulse of 12 v. That's it. Understanding seems to be the problem. Your talking apples still & I want an orange. I'm not proficient in electronics but understanding the problem seems to be the problem. You gave me a 5 second 12 volt ouput. Thanks but that's not want I wanted. I did want the 12 volt 1 secondput though. I want a 5 second delayed ouput.

 

[Hero999]

I've realised I've made a mistake, this should work now.

As for the circuit if I understand it correctly is this not an monostable oscillator circuit?,

No, it isn't an oscillator, it's a monostable, an oscillator is astable, there's no such thing as a monostable oscillator!

with an off/on/off time? After the 12v pulses the tranisistor I need the circuit timer to count 5 seconds before it does anything. After five seconds I need it give me a 1 second pulse of 12 v. That's it.

That's exactly what is does!

It does provide a 5 second output but you don't have to use it!

You can always use the one second output which occurs after the 5 second output.

Understanding seems to be the problem.

No, your understanding of the circuit seems to be the problem. I understand you perfectly, on a 12V trigger pulse you want it to wait for 5 seconds then provide a 12V pulse for 1 second, it alreadey does this, would you like to see a simulation?

Your talking apples still & I want an orange. I'm not proficient in electronics but understanding the problem seems to be the problem.

Your understanding in electronics is alright though you can always learn more, the fact that you've confused monostable and astable shows you lack the knowledge to understand this circuit.

You gave me a 5 second 12 volt ouput. Thanks but that's not want I wanted. I did want the 12 volt 1 secondput though. I want a 5 second delayed ouput.

I've given you both, you don't have to use the 5 second delay if you don't need it, just use the one second output, just connect the relay to output B.

EDIT:
Below is the corrected schematic, I've tested it and it works and I've added the relay to avoid confusion/

 

[b1mmuo27]

Thank you Hero999. I'll give this a try. Hey I'm not blaming you in any way. Me personnelly, make a couple of boo boo's a day. That's the only way I learn anything, by trial & error.

 

[mona_farahmand_mf]

i need to one circuit for parking sensor

 

[b1mmuo27]

Two more questions Hero999. As I can't seem to wrap my head back on electronics & keep thinking electrical is your 0 volt line the same as battery ground? If not how would the coil pull in? I also picked up a 556 & wondered what thie drawing would look like using it. Thanks.

 

[Hero999]

Two more questions Hero999. As I can't seem to wrap my head back on electronics & keep thinking electrical is your 0 volt line the same as battery ground?

Connect the to the negitive (-) terminal of the battery, 0V is just a referance from where all voltages are measured from.

I also picked up a 556 & wondered what thie drawing would look like using it. Thanks.

The 556 is simply two 555s in one package, because of this the pin numbers are slightly different and they share common Vcc and 0V pins, look at the pinouts for the 555 and 556 you should be able to figure it out for yourself.

 

[b1mmuo27]

Thanks, Hero999 I'll take a look.