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[SOLVED] Help needed: a simple circuit for car Ignition control

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Manu, C3 is paper or electrolytic? I've 1uF both paper and electrolithic capacitor. going to test the circuit in breadboard now
Edit: Sorry, I got only Electrolytic type. 1uF 63V
 
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Manu, The circuit is perfect, thank you, but the input from fingerprint module is not detected as trigger for 555. As I said before the finger print module outputs short pulse of 5V(multimetwr readings). When I use the 12V from supply as trigger it is working perfectly. Which resisitance value has to be changed? Also the time gap between pulses from fingerprint module is 8 seconds to be exact. So i've used 47K and 22K in series for R1. Waiting for a reply
 

hmm.. you might need to remove the capacitor C3 , resistor R4 and connect it directly to the 2 nd pin i.e the Trigger pin. if that proves no use, then increase the capacitor C4 to much larger one.
its better to use a >8 sec delay. so add another 10k in series with the 47 k and the 22k
cheers!
 

Magvitron said:
hmm.. you might need to remove the capacitor C3 , resistor R4 and connect it directly to the 2 nd pin i.e the Trigger pin. if that proves no use, then increase the capacitor C4 to much larger one.
its better to use a >8 sec delay. so add another 10k in series with the 47 k and the 22k
cheers!
Click to expand...

Sorry, My mistake, Emitter of that transistor was not grounded. Now it is sensing the trigger from Fingerprint module.

Yes, the delay of monostable mutivibrator is not enough. I need to add a 10K resistor to the present 47K+22K. Thanks. Let me try and let you know

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YAY!!!:smile: It's working perfectly now. Thanks a lot Manu. Now I need to make it into PCB, make a housing and find a good place in my car to install this. I'll be buying this push button switch from dealextreame. http://www.dealextreme.com/p/blue-light-push-start-ignition-switch-for-racing-sport-dc-12v-22347

Here is an image of the setup in breadboard. Will surely post the final results when it is completed.
26_1345053886_thumb.jpg
 

I made the circuit. Everything is working as it should be other than one small problem. When I power on the circuit, the 555 is triggered sometimes. so sometimes the relay is activated when 12v is connected to the circuit, which is undesired as we need the ignition ON only after sensing the fingerprint. Can you find a solution for this? I didn't notice this when I tested it in breadboard.

I'm using 1uF 63v Capacitor just before trigger for 555
 
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Update:button relay.JPGcircuit.JPG
Yesterday I recieved the push button and 80A Relay from Dealextreme. Took almost a month for shipping.

Today I managed to dismantle the key barrel of Matiz and studied the OFF, ACC, IGN ON and Engine start characteristics. Really took some time to understand the functioning. Eventough it don't have immobiliser, it is still complex.

I need one more automobile grade realy to complete the circuit(for starting motor). It is strike here due to Diesel price hike, so none of the shops are open. So have to wait until Monday:cry:

Manu, I got one problem. I thought the hand brake signal will be a positive +12V, but it is not. Actually the switch is getting grounded when Hand brake is engaged. So how should we tweek the circuit to work in this scenario?
Attached are the push button and the circuit I made
EDIT: Hand break diagram from service manual attachedbrake.JPG
 
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