Circuit to drive a fuel injectors with NE555

[milkoni]

Hi all,
I have a question about my circuit. Which position is better to switch On/Off the injector?
Or to build a driving circuit with NE555 for each injector?
I'm attaching an image to illustrate.
Thanks in advance!

P.S.
I've decided to use the signal after two transistors gate to MOSFET's gate, to switch injector On and Off. I've tested this on experimental board - it works fine I think.

 

[alec_t]

I've decided to use the signal after two transistors gate to MOSFET's gate, to switch injector On and Off.

That could leave Q1 drawing excessive current. Why not simply disconnect the 12V supply, so as to eliminate any standby current?

 

[milkoni]

That could leave Q1 drawing excessive current. Why not simply disconnect the 12V supply, so as to eliminate any standby current?

I agree Alec. I've changed the circuit.
Thank you!

 

[shokjok]

The circuit may burn the injectors open when you apply twelve volts this way. The internal MOSFET resistance can be supplemented with a resistor to reduce the injector feed voltage.

 

[shokjok]

spec, capacitor C3 ( 220n) should be connected across 555 pins 1 and 8, not to pin 7 as shown, referencing your comment #4 in thread #4.

 

[shokjok]

I realize that this thread is ancient by now.
My question to milkoni is: why is the Q5 collector in your circuit connected to MOSFET U3 only and not the other MOSFETs?