Fuel injector pulse detector - Electronic Circuits Projects Diagrams Free

brjones · 30th August 2004, 09:18 PM

I am trying to come up with a circuit that will do the following:

1. Monitor an input pulse signal, a fuel injector pulse in this case.
2. When a pulse in recieved on the input, trigger to output signal for 1 sec.

That is the easy part, I am guessing that a simple 555 set up in monostable mode with the appropriate R and C for a 1 second delay. This will give me a one second pulse when the input triggers.

This is the part I cannot figure out:
3. When another pulse arrives on the input after the 555 has already been triggered, I want the 1 second count reset so that the output of the 555 remains high as long as there is at least one pulse per second.

If there is a better approach to this please let me know. At the end of the day I need a circuit that will monitor an digital input, as long as that input has pulse activity at least once per second then single output of this circuit will remain high. After activity on the input has ceased for one second the output goes low.

Any comments would be appreciated, thanks.

Just a though, what would be the effect of tying the trigger and reset pins together?

hotwaterwizard · 31st August 2004, 12:20 AM

I know I have shown this circuit many times on this Website but it is a wonderful circuit. When you push the button it resets the timing circuit. If you don't push the button before the timing cycle times out the circuit turns off the load. Kinda sounds like the circuit you are looking for doesn't it? You have to play with the values to get the Timing Cycle you need but the Simpli little circuit works like a charm. Jost change the capacitor to a smaller size and use a 50k pot instead of the 33k resistor and you are in business. You could use a transistor relay driver circuit to short out the Capacitor instead of a normal switch.

Eclipsed · 31st August 2004, 01:42 AM

Injectors can produce some nasty kickback/flyback voltages, make sure you use a shunt or something similar to protect the rest of the circuit.

ante · 31st August 2004, 08:07 PM

brjones,

If the injectors are the plastic encapsulated type you can pickup the pulse with a coil on the outside. This way you have galvanic separation and won’t disturb the EFI circuit.

Ante :roll:

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30th August 2004, 09:18 PM	(permalink)
brjones	Fuel injector pulse detector I am trying to come up with a circuit that will do the following: 1. Monitor an input pulse signal, a fuel injector pulse in this case. 2. When a pulse in recieved on the input, trigger to output signal for 1 sec. That is the easy part, I am guessing that a simple 555 set up in monostable mode with the appropriate R and C for a 1 second delay. This will give me a one second pulse when the input triggers. This is the part I cannot figure out: 3. When another pulse arrives on the input after the 555 has already been triggered, I want the 1 second count reset so that the output of the 555 remains high as long as there is at least one pulse per second. If there is a better approach to this please let me know. At the end of the day I need a circuit that will monitor an digital input, as long as that input has pulse activity at least once per second then single output of this circuit will remain high. After activity on the input has ceased for one second the output goes low. Any comments would be appreciated, thanks. Just a though, what would be the effect of tying the trigger and reset pins together?

31st August 2004, 01:42 AM	(permalink)
Eclipsed	Injectors can produce some nasty kickback/flyback voltages, make sure you use a shunt or something similar to protect the rest of the circuit. __________________ Eric.

31st August 2004, 08:07 PM	(permalink)
ante	brjones, If the injectors are the plastic encapsulated type you can pickup the pulse with a coil on the outside. This way you have galvanic separation and won’t disturb the EFI circuit. Ante :roll: