NE555 Ignition Driver Issues

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Suraj143

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Guys I made this ignition driver & it worked very nicely.I got 2cm arcs very nicely.

I loaded an oil type coil.

The problem is after 2 minutes the frequency increased automatically (I don't know how) & burned out the NE555.

I think when the load changes the frequency varies.!!

What will be the problem?How to prevent this?
 
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The FET is rated at 500V. Perhaps (I'm just guessing) the coil voltage spike exceeds this, the FET breaks down and enough current gets dumped through the 555 to affect its timing and, ultimately, to destroy it. If that is indeed what happened then a cure would be to use a different coil and/or higher-rated FET.
 
Back when I was experimenting with those things, I tried the same circuit and similar things happened. The protection circuitry is absolutely crucial to protect the 555, and you need a very high-value FET. What were you using for a power source?
 
Hi guys thanks for considering.

I use a 15V/5A transformer.The FET is working nicely.

Just a hint.I couldn't find out any 2.2uF capacitors in my junk box.So I used a 1uF capacitor & changed the R2 resistor.

As per the diagram those are the timings.

Pulse ON time = 15.4mS
Pulse OFF time = 329mS

As you can see the pulse ON time is 15mS which is not enough to energize the coil since it needs minimum 30mS ON time.

Can this cause to burn my 555?
 
The FET is working nicely
Click to expand...
Unless you have a scope to monitor voltage and current during FET turn on and turn off can you be sure? What peak voltage do you have at the FET drain at turn-off?
 
Suraj143 said:
Hi chemelec whats the purpose of 1N4005 which is coming from coil to the drain pin?
Click to expand...

Just helps preventing some spikes into the mosfet.
Many Hundreds of this circuit have been built all over the world without any problems.
But as with ANY Electrical circuit, a inline fuse is a good idea. (1/2 or 1 amp)
 
hi,
This is the one I use, works fine.

I used a relay because the area where its used, gets a lot of lightening, the semiconductor drivers used to pop.!
 

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Hi Eric thanks for your circuit.

I found another scenario after reading an old reply from audioguru & same used in your circuit too.That is most of used CMOS7555 not NE555.

Because NE555 produces a 400mA supply current spikes when the output switches.May be this will vary my frequency.

But how did it burn?

I must replace the chip with ICM7555 & see.
 
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This is the circuit I usually use:

View attachment 62989

It is from RMCybernetics.com. It's a pulse width modulation circuit, so you can adjust the frequency and duty cycle independently of each other. It will operate a wide range of coils, and you can "tune" it to the signal you want.
 
Guys this is what happened.

I have burned my L7809 voltage regulator from inductive kick back.

I have protected the transistor side so that is working perfectly but I burned 7809 regulator because less considering to that part.

I need to protect it,please help me.
 
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This is the correct setup for the 7809 voltage regulator. Mind the capacitor values carefully:

View attachment 63009

Also, don't forget a heat sink. What is your input voltage? (Sorry if you already told us that. )

Also, I would recommend a full-bridge rectifier, rather than just a half-bridge like you have. It will probably be easier on the regulator.

Regards
 
Hi I use a 15V transformer.

Input side of the regulator I have only 3300uF large capacitor & on the output side I have a 1uF capacitor.That's it.

I don't think adding a 0.33uF capacitor on the input will protect the regulator.
 
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Suraj143 said:
Hi I use a 15V transformer.

Input side of the regulator I have only 3300uF large capacitor & on the output side I have a 1uF capacitor.That's it.

I don't think adding a 0.33uF capacitor on the input will protect the regulator.
Click to expand...

Adding the capacitors stabilize the operation of the regulator and helps reduce stress on it. Also, at 15 volts, you will definitely need a heat sink. Another thing is that I think 7809s can only supply a maximum of 1 amp. Oil-filled ignition coils generally require around 5-6 amps to operate correctly, and to produce a decent output. Trying to draw too much current from it could cause damage, as well. I would either get a higher-current 9-volt regulator, or eliminate it altogether, and just use a lower-voltage transformer.
 
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