Hello

I stripped an ignition coil of a car and have it on the bench. The primary coil has the terminals p1 and p2, the secondary coil terminals being s1 and s2. I believe it is a toroidal core transformer setup.

When I briefly touch p1 & p2 to the terminals of a 3v battery, arcing occurs between s1 & s2 which is what it suppose to do, notice it happened with out using a capacitor between p1 & p2 as it is not the case with automotive ignition systems.

Now I made up a 555 circuit to do the “briefly touch” action of fast on/off of the primary coil current but I can not get the arcing between s1 & s2 regardless of a capacitor presence or not.
The circuit blinks a LED so it should work fine. please notice the circuit attached, the LED and the p1&p2 get connected between the Output "pin 3" and V0 off the 555 chip, the capacitor gets connected between these points as well.

R1 and R2 are LDR
C1 = 47μF
the is a capacitor between pin 5 and V0 of the 555.


Please help me understand why I am not able to obtain spark using the 555 circuit regardless of using 12v or 3v battery.


Thank you

 

Hello,

Did you try fixed resistors for R1 and R2 ?
See this page for more details:
http://www.uoguelph.ca/~antoon/gadgets/555/555.html
Did you use a transistor and protection diode for the coil?
See this page for more details:
http://www.uoguelph.ca/~antoon/circ/hv/hvpulse/hvpulse.html

Greetings,
Bertus

 

One major problem you face is that it takes more current than the 555 can handle to make the spark. The spark coils I am familiar with require a current of about 7 amps to build a field sufficient to deliver an effective spark at the sparkplug.

Yours may be different in that it requires less current, but it is almost certainly beyond the capability of a 555 timer's output.

The 555 can control the conduction of a power FET that can handle the current requirement of the spark coil.