Do you mean 0.1uF for C1?
Do the cross near ignition switch means anything?
The battery current wont spoilt the circuit rite?

 

No, C1 is 0.01uF. The X means that the dashed line, that was the original connection between the switch and the ignition, circuits is cut.

The battery current wont spoilt the circuit rite?

?????

Ken

 

Ok,i just bought the components from a nearby shop.
2N4402 is not available and the shop guy ask me to use 2N4403 as replacement,can be used rite?
LM555 and NE555 is same rite?
What i meant was,car battery has high current,I just worried if it could spoilt the circuit bcoz my past project components already blown.
Ken,has u tried the circuit?

 

The 2N4403 should be OK.

The LM555 and NE555 are the same. But, the IC I used was an LM555C, which is not the same. It is a CMOS version, that has a lower current draw, and is better for longer timing periods.

It's not the high current (for the most part) that causes problems with electronics in an automobile, it's the high voltage spikes, and electrical noise. Like I said earlier, I have made no provisions for this.

I have tested the circuit on my work bench. I have not tested it in a automobile.

Ken

 

I see,i bought NE555.Cannot test the circuit with NE555?
Has to buy LM555C on monday.
Thanks for ur effort Ken.I really appreciate ur effort.
Can you explain me the operation of the circuit specifically?
How to modify it if i want 3 LED connected to the circuit,one to show that the power is ON,one to show that the timer had started and one to show that the time has finish?(schematic plz)

 

Yes, you can test it with a NE555.

I added 3 LED indicators to the circuit. Each is an LED and a 1K resistor, in a rectangle for clarity.

LED1 ON=ignition switch ON, OFF=Ignition switch OFF
LED2 ON=timer ON, OFF=timer OFF
LED3 ON=engine ON, OFF=engine OFF

All OFF: ignition switch OFF and engine stopped
LED1 and LED3 ON, LED2 OFF: ignition switch ON and engine running
LED1 OFF, LED2 and LED3 ON: ignition switch OFF and engine running
All OFF: ignition switch OFF and engine stopped

I'll have to get back to you on an elaborate explanation of the circuit...my wife wants to go out for breakfast.

Ken

 

I'll have to get back to you on an elaborate explanation of the circuit...my wife wants to go out for breakfast.

U mean Relay 1 and 2 works opposite(when relay 1 is energised,relay 2 deenergised)?
Well,its night here.Enjoy ur breakfast

 

In the circuit with two relays, the 555 cannot provide enough power to activate the 12v/30A relay, so the 555 turns on the small relay and it turns on the big relay. The circuit with one relay uses the two transistors to amplify the output of the 555 to turn on the big relay.

Ken

 

Well ok.
I understand now.
The circuit should work like this.
When the handbrake is pulled up and the ignition key turned off,the timer should start work and turn OFF the engine after the time desired.Which switch should i connect to handbrake and which switch to ignition key?

When the ignition switch is turned OFF it triggers the timer.

How this works?

 

I guess I missed the part about the handbrake. Is there an existing switch associated with it. If so, how is it wired in the vehicle, and is it open or closed when the brake is set?

Have to go help my daughter hang some things ona wall in her house. Back later.

Ken

 

I guess I missed the part about the handbrake. Is there an existing switch associated with it. If so, how is it wired in the vehicle, and is it open or closed when the brake is set?

There will be a switch at the handbrake to light up the bulb at the indicator in the dashboard.See the picture above.
Im sure u can recognise the indicator from the picture.
Actually its a NO switch,i mistakenly typed NC.
When we pull the handbrake,it will light up the indicator(circuit is closed).
Well,we can use that switch to tell the circuit that the car is in parking mode(which usually people do b4 turn OFF the engine).
I think the switch will give +12V to the light.
I will tap a wire from the meter panel.
So,this timer must be work only if the handbrake is pulled.
And if can,we must avoid the relay from getting heat.

 

OK, here is a "possibility". I have not bench tested this...I can't until Monday. My concern is how the timer circuit will react with the ignition switch ON and the hand brake OFF...the normal driving condition. This supplies some power to the timer circuit through R1.

Ken

 

When the ignition switch is ON and the hand brake is OFF,it should be like normal driving(without timer=engine stop immediately).
If the ignition switched OFF while the hand brake is ON,then the timer must function.

This supplies some power to the timer circuit through R1

Can we use relay to avoid this?

 

It should work as you stated, and it may not be a problem, but I would need to bench test it before I would recommend this circuit.

Ken

 

Damn!,LM555C is not available at my area.
What a dissapointment.

Ken,can a 7seg display added so that i can see the time?
Or with a few LED's to indicate the timing?
Im sorry if asking too much,just want to improve my knowledge.

 

If you can't get a CMOS 555 (best option) then go with the one you have.

I suppose you could, but at that point I would switch to a digital timer solution...like a presettable count-down timer.

Ken

 

If you can't get a CMOS 555 (best option) then go with the one you have.

Is it ok if i use NE555?

I suppose you could, but at that point I would switch to a digital timer solution...like a presettable count-down timer.

I couldnt find the digital circuit in the net,thats why i turn to use 555 timer.
I want to use switchable fixed resistor for variable timing,how to calculate it?

 

Is it ok if i use NE555?

I don't have an NE55 to try, but it should be OK.

I want to use switchable fixed resistor for variable timing,how to calculate it?

http://home.cogeco.ca/~rpaisley4/LM555.html#2 Use 330 for C1 and put in various values for R1 to find the time.

A question for you: Since the brake indicator lamp is part of the instrument cluster, and I assume that the instrument panel goes dark when the ignition is shut off normally, do you still have +12V on the brake switch with the ignition switch off?

ken

 

Thanks for the link.
Ken,do u have any idea to add LED to indicate the timing on the circuit.
Like this,lets say 5 LED,this should be working like running light but based on the timing we choose through VR.
First LED indicate the timing had started and last LED to indicate timing finish.
The time taken from 1st LED to last LED is the time taken to switch off the relay.
Any idea?

 

One way might be to use an LM339 quad comparator, All comparators' (+) inputs would be connected to the timing capacitor's (+) on the 555. Each comparator's (-) input would have a pot set to a voltage that corresponds to a 20% multiple of the time period. Each output drives an LED. LED1 in my schematic would represent the 0-20% segment.

Ken