Pulse Generator and timer project.

I'm totally new to Arduino, I'm working through the tutorials and whatnot, but before I go out and start buying stuff, I'd like to know if my project is practical for an Arduino.

What I would like to do, is switch fuel injectors on and off, mimicking their run cycle. In the car application, they are actually powered constant hot, and the ECU pulses the ground to cause them to fire.

So my goal is, push a button, injectors run at 50hz, or a 20ms duty cycle, for 20 seconds, and stop. That's it.

I had this working with a pulse generator, a timer, and a relay. But I couldn't get the relay to cycle fast enough, and then the pulse generator burned out, likely because it couldn't take the load.

So any tips, or critiques, I'd really appreciate.

For the timing part you can use the millis() function. Here is a tutorial that may help.

An Arduino output pin cannot drive an injector so an external circuit is necessary (like your relay). A MOSFET is a good choice. Here is an injector driver circuit. Choose a MOSFET that has a logic level input and can handle the current required by the injector. The diode is necessary to protect the MOSFET from the high reverse voltage when the injector is turned off.

MOSFET INJECTOR DRIVER.jpg

Using a gate driver would be a good idea too. Keep in mind, heatsinking the mosfet might be required.

groundFungus:
For the timing part you can use the millis() function. Here is a tutorial that may help.

An Arduino output pin cannot drive an injector so an external circuit is necessary (like your relay). A MOSFET is a good choice. Here is an injector driver circuit. Choose a MOSFET that has a logic level input and can handle the current required by the injector. The diode is necessary to protect the MOSFET from the high reverse voltage when the injector is turned off.

MOSFET INJECTOR DRIVER.jpg

Thank you for the tips! On the MOSFET, does it matter what type? I keep seeing logic MOSFET referred to, but all I find are the IRF type on breakout boards.

Would something like this be appropriate? https://www.adafruit.com/product/1455

Or would using a IRL540 be preferable? This is my first project, so I’m unsure if these MOSFET’s can be used “loose” or if they want to be fastened to a board.

Some more googling brought me to this board, which I believe satisfies the requirements of the diagram.

Yes, that board by DrAzzy will suit your needs, and allow for 4 circuits. He might even chime in on this since he is a member of the forums.

That board will give you a means to attach it to a board. All you would have to do is connect wires, 12V supply and injectors.

Do not forget the fly back diodes across each injector. The gate (180*) and pull down resistors (10K*) are on the board, though.

  • ref my schematic

tinman13kup:
Yes, that board by DrAzzy will suit your needs, and allow for 4 circuits. He might even chime in on this since he is a member of the forums.

That board will give you a means to attach it to a board. All you would have to do is connect wires, 12V supply and injectors.

Great! I've ordered it and a starter kit so I can work through the lessons and get some misc pieces as well.

groundFungus:
Do not forget the fly back diodes across each injector. The gate (180*) and pull down resistors (10K*) are on the board, though.

  • ref my schematic

Yes sir, I've printed it and it's on my work bench, I will report back, probably next weekend, once everything is here and I give it a whirl.

You guy's have been very helpful!