AVR MEGA8L problem

[sarang1_in]

Hi all.
I have used a MEGA8L to give pulses to ignition coil for generatring sparks. The pulses are generated by a timer 555, and I am only making a pin high or low. for 10 secs. Repeatedly for 3 times. I am igniting the oxi-acetelene flame which I am sensing and making the sparker off. When coil is not connected everything works fine( On and Off the timer pulse generator for 3 times) but as soon as I connect the coil the pin of MEGA8L goes high and coil starts sparking contienously and does not repeat the sequence for 3 times (It remains contineously On instead of On and Off)
The coil is placed 3 to 4 meters apart from the actual circuit. AVR operates on 5V and coil on 12V, but the ground of both is common. Is it EMI which is creating problem?? Please suggest something as I can't isolate the grounds (and sometimes that also doesn't work)

 

[techknow]

can any one give me a circuit diagram of AT90S2313 programmer (serial/parallel) hope for soon

 

[williB]

Hi all.
I have used a MEGA8L to give pulses to ignition coil for generatring sparks. The pulses are generated by a timer 555, and I am only making a pin high or low. for 10 secs. Repeatedly for 3 times. I am igniting the oxi-acetelene flame which I am sensing and making the sparker off. When coil is not connected everything works fine( On and Off the timer pulse generator for 3 times) but as soon as I connect the coil the pin of MEGA8L goes high and coil starts sparking contienously and does not repeat the sequence for 3 times (It remains contineously On instead of On and Off)
The coil is placed 3 to 4 meters apart from the actual circuit. AVR operates on 5V and coil on 12V, but the ground of both is common. Is it EMI which is creating problem?? Please suggest something as I can't isolate the grounds (and sometimes that also doesn't work)

is the output of the mega8 toggling?
a scope would tell you what the output is doing..

 

[sarang1_in]

AVR MEGA8L

No. The output should be 1(HIGH) for six secs and 0(LOW) for 2 secs. This cycle is repeated for 3 times. But after connecting the Sparker coil it(The output) becomes contineous.

 

[Nigel Goodwin]

Perhaps you should post the circuit, so we can see what you are doing?.

 

[williB]

can any one give me a circuit diagram of AT90S2313 programmer (serial/parallel) hope for soon

have ya tried to google the part in question..?

 

[williB]

Re: AVR MEGA8L

No. The output should be 1(HIGH) for six secs and 0(LOW) for 2 secs. This cycle is repeated for 3 times. But after connecting the Sparker coil it(The output) becomes contineous.

i suspect that the output of the controller is incompatable with the sparker circuit you are trying to drive..here is a test you could try..
take a 5V wire ( or whatever the voltage output of your controller is)and a ground ...and touch it to the input of the sparker...

 

[sarang1_in]

Hey thanks to all. I sorted out the problem.It was only noise which was causing the problem. I used a current limit and later changed the coil. Previously the current consumption was 1.5 A now it is 0.5 amps. Also the loop was too big and now I have reduced it.
Thank you.