# Interesting circuit, need help poss. 555 timer?

Discussion in 'The Projects Forum' started by ChevyLT1Camaro94, Jul 9, 2009.

1. ### ChevyLT1Camaro94 Thread Starter Active Member

Jan 9, 2009
32
0
Okay so i need to build a circuit for my car that will once recieving 12v from my accesory power )when i turn the key on) delay about 15 seconds and then pulse 12v once and thats it, its to automatically turn off traction control, i know how to wire it into the switch but i need to know how to make the circuit, anyone? i thought maybe a 555 timer would work somehow? im a radio shack parts guy so yeah haha. thanks anyone who can help! also, could someone build this same circuit but to pulse 5v once, since im not positive if its a 5v or 12v signal.

2. ### jj_alukkas Distinguished Member

Jan 8, 2009
751
5
If u want a 15 second delay ckt, u can build one using 555..

The 1M+100k is the resistance (R)
220uF capacitor is (C)

so time (in seconds) = 1.1 x C x R

C is in Farads and R is in ohms

So for 15 seconds, you need to place a 100uF capacitor and a resistor of abt 140k instead of that 100k+1M

Pin 3 will provide you 12v and a maximum load of 200mA, so replace it with a relay and protection diode..

Last edited: Jul 9, 2009
3. ### jj_alukkas Distinguished Member

Jan 8, 2009
751
5
I didn't understand what u meant by that pulse.. please clarify it.. this circuit changes the output state from high to low after 15 seconds at pin 3..

4. ### ChevyLT1Camaro94 Thread Starter Active Member

Jan 9, 2009
32
0
i just need it to send a 12v signal for maybe .75 sec and thats it, im not qite sure how your diagram applies , and where does the 12v input from the acc power go in and where does the 12v to the switch come out?

5. ### jj_alukkas Distinguished Member

Jan 8, 2009
751
5
We apply 12v to the upper line of the ckt ,i.e, at pins 8 and 4 and ground at pin 1
and the output pulse comes out at pin 3 and Pin 8 but the problem will be that you will need another ckt to create a pulse.. Anyway this ckt gives you the delay of 15 secs.. i hope a schmitt trigger can do it otherwise you will need one more 555 or a single 556 ..Wait for more responses... I have an idea for this concept but it would be a bit complex for you but does the job. .It involves driving a relay which would give the pulse as well as shut down the ckt after the job.. But I guess there are brighter minds here which would help you do the job simpler...

6. ### ChevyLT1Camaro94 Thread Starter Active Member

Jan 9, 2009
32
0
well post that idea, i may be able to do it as long as iu can explain it haha, and i can get a 556 or use 2 555's so let me know wut you think

7. ### jj_alukkas Distinguished Member

Jan 8, 2009
751
5
The relay idea needs some illustration, so leave it as a last resort.. Using 2 555's is an effective idea.. the first ckt I gave gives an output after 15 seconds, we use that to drive another 555 ckt in monostable mode to give a high for a second .. Isn't that what you need?? Could you explain one more thing?, what do you want to control with this?? To switch on or off a device?? If so, what is the switch like and voltage runs in it??

8. ### ChevyLT1Camaro94 Thread Starter Active Member

Jan 9, 2009
32
0
its a traction control button, i want to have it turn off when i start the car, its annoying to hit the button EVERY time i get in the car and by having it just pulse once it will turn it off and then i can turn it back on if i so choose, how do i build the second circuit youre talking about?

9. ### jj_alukkas Distinguished Member

Jan 8, 2009
751
5
Its the same circuit as the first one except that you need to change the resistor and capacitor value for 1 second and use pin 3 and pin 1 as output for the second 555.. I still have a feeling there is an easier way for creating that pulse instead of a second 555.. If you can wait you will get help.. MAybe a single capacitor and transistor instead of the second 555 will do

10. ### ChevyLT1Camaro94 Thread Starter Active Member

Jan 9, 2009
32
0
i only want it to pulse once and turn off, what will the first circuit u posted do exactly, what is its output, and how do i use 2 different pins as the output??

11. ### jj_alukkas Distinguished Member

Jan 8, 2009
751
5
Here's a rough sketch.. I hope this works.. You may get a simpler solution from the geeks over here if you wait... As for the first half, im confident as there is no cheap and precise way to attain this and one circuit I completed yesterday using the same.. For the second half, to generate a simple pulse, there are simpler ways and this is an accurate way.. i added the relay to make it robust as if you give a direct connection from that ic to switch, you'll short the whole circuit..

You may use a 556 if you know how to wire it...

Edit: oooops.. I forgot to add a protection diode across the relay's inputs.. please do not forget it..

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12. ### ChevyLT1Camaro94 Thread Starter Active Member

Jan 9, 2009
32
0
no problem i have one of those already to go lol thanks a lot, ill give this a try if anyone has a better solution any suggestions are more than welcome but thanks man!

13. ### Steve C Active Member

Nov 29, 2008
86
0
if a really really fast pulse is all you need to turn traction control off, then you might be able to use a couple resistors and a capacitor to do it.

http://www.kpsec.freeuk.com/555timer.htm#edgetrigger

in that example (you'll flip yours upside down) the output is pulled high, then the output of the 555 pulls the output low as the cap charges. after the cap charges the line will be high again. But we are talking about a pretty fast pulse. might work.

you might want to change the 555 trigger to the starter wire rather than the acc wire. When you hit the starter the whole car cuts off and you'll be triggering and retriggering acc1 and thus your 555. this might be OK if you always go straight from a dead car to started, but sometimes you might want to have the radio on and the car off (for more than 15 seconds). This can change the desired behavior of your circuit.

using the starter, the 555 will never activate unless the car is imminently starting.