Please view this spice file.. (fuel injector driver amp)

ome

se.

aid

the point is that you want it to clamp at a low voltage when you are doing pwm to maintain current (that what the diode is for) and you want it to clamp at a high voltage when closing to dump the current fast (that happens in the FET)

something like this will give a higher current to open the injector and then keep it open at a lower current

Version 4 SHEET 1 2440 680 WIRE 1808 -496 1008 -496 WIRE 1728 -112 1488 -112 WIRE 1808 -112 1808 -496 WIRE 1808 -112 1728 -112 WIRE 1728 -96 1728 -112 WIRE 1808 -32 1808 -112 WIRE 1488 -16 1488 -32 WIRE 1728 -16 1728 -32 WIRE 1728 -16 1488 -16 WIRE 1760 -16 1728 -16 WIRE 1488 16 1488 -16 WIRE 1104 64 992 64 WIRE 1232 64 1184 64 WIRE 1344 64 1296 64 WIRE 992 80 992 64 WIRE 1488 112 1488 96 WIRE 1808 112 1808 64 WIRE 2048 112 1808 112 WIRE 1344 160 1344 64 WIRE 1376 160 1344 160 WIRE 1424 160 1376 160 WIRE 1808 208 1808 112 WIRE 1488 240 1488 208 WIRE 1104 256 992 256 WIRE 1232 256 1184 256 WIRE 1344 256 1344 160 WIRE 1344 256 1296 256 WIRE 992 272 992 256 WIRE 992 368 992 352 WIRE 1808 400 1808 288 WIRE 1456 480 992 480 WIRE 1760 480 1536 480 WIRE 992 512 992 480 WIRE 992 608 992 592 WIRE 1808 608 1808 496 FLAG 1008 -416 0 FLAG 1808 608 0 FLAG 992 608 0 FLAG 2048 176 0 FLAG 1488 240 0 FLAG 992 160 0 FLAG 992 368 0 FLAG 1376 240 0 SYMBOL voltage 1008 -512 R0 WINDOW 123 0 0 Left 0 WINDOW 39 24 44 Left 0 SYMATTR InstName V3 SYMATTR Value 12 SYMBOL voltage 992 496 R0 WINDOW 123 0 0 Left 0 WINDOW 39 24 44 Left 0 WINDOW 3 -438 45 Left 0 SYMATTR InstName V4 SYMATTR Value PULSE(0 12 1m 1u 1u 50m 200m 1) SYMBOL ind2 1792 192 R0 SYMATTR InstName L3 SYMATTR Value 10mh SYMATTR Type ind SYMATTR SpiceLine Rser=3D2 SYMBOL schottky 2064 176 R180 WINDOW 0 24 72 Left 0 WINDOW 3 24 0 Left 0 SYMATTR InstName D1 SYMATTR Value MBRS360 SYMATTR Description Diode SYMATTR Type diode SYMBOL nmos 1760 400 R0 SYMATTR InstName M1 SYMATTR Value irl3915mod SYMBOL res 1552 464 R90 WINDOW 0 0 56 VBottom 0 WINDOW 3 32 56 VTop 0 SYMATTR InstName R1 SYMATTR Value 1k SYMBOL pmos 1760 64 M180 SYMATTR InstName M2 SYMATTR Value IRF7343P SYMBOL res 1472 -128 R0 SYMATTR InstName R2 SYMATTR Value 5k SYMBOL zener 1744 -32 R180 WINDOW 0 24 72 Left 0 WINDOW 3 24 0 Left 0 SYMATTR InstName D2 SYMATTR Value BZX84C12L SYMATTR Description Diode SYMATTR Type diode SYMBOL npn 1424 112 R0 SYMATTR InstName Q1 SYMBOL res 1472 0 R0 SYMATTR InstName R3 SYMATTR Value 1k SYMBOL voltage 992 64 R0 WINDOW 123 0 0 Left 0 WINDOW 39 24 44 Left 0 WINDOW 3 -440 53 Left 0 SYMATTR InstName V1 SYMATTR Value PULSE(0 12 0 1u 1u 60u 400u 5000) SYMBOL voltage 992 256 R0 WINDOW 123 0 0 Left 0 WINDOW 39 24 44 Left 0 WINDOW 3 -430 55 Left 0 SYMATTR InstName V2 SYMATTR Value PULSE(0 12 1m 1u 1u 5m 200m 1) SYMBOL res 1360 144 R0 SYMATTR InstName R4 SYMATTR Value 10k SYMBOL res 1200 48 R90 WINDOW 0 0 56 VBottom 0 WINDOW 3 32 56 VTop 0 SYMATTR InstName R5 SYMATTR Value 10k SYMBOL res 1200 240 R90 WINDOW 0 0 56 VBottom 0 WINDOW 3 32 56 VTop 0 SYMATTR InstName R6 SYMATTR Value 10k SYMBOL diode 1232 272 R270 WINDOW 0 32 32 VTop 0 WINDOW 3 0 32 VBottom 0 SYMATTR InstName D3 SYMATTR Value 1N4148 SYMBOL diode 1232 80 R270 WINDOW 0 32 32 VTop 0 WINDOW 3 0 32 VBottom 0 SYMATTR InstName D4 SYMATTR Value 1N4148 TEXT 1264 -544 Left 0 !.tran 0 .100 0 startup TEXT 1984 504 Left 0 !.model irl3915mod ako: irl3915 bv=3D55 TEXT 952 456 Left 0 ;ON time TEXT 968 40 Left 0 ;PWM TEXT 936 224 Left 0 ;OPEN pulse

Watch out for plastic parts.

-- "For a successful technology, reality must take precedence over public relations, for nature cannot be fooled." (Richard Feynman)

What is that suppose to me ? :)

Please fill me in! I am all ears!

Jamie

Solvency in Xylene?

RL

What the hell does that mean?

mean? I am getting old, my fingers don't move as fast as my mind! :)

Jamie

The valve will not drop out between pulses.

And I don't want it to. When it's done with that cycle, I'll simply turn it off.

The idea is to snap it on hard with a longer pulse and then shorten the duty cycle to ease back on the current.

I came up with the driver amp that will return the energy to the power supply. I now simply need to create a pulse timer that has a long pulse width on first initial start and then start pulsing with a shorter duty cycles. When that request is done from the external trigger source, it will simply turn off the clock source I have for the pulse train.

It's as simple as that.

We will most likely be using a throttle body type TBI and they require a lot of current on the initial pull and then it needs to be eased back to not burn out the coil. This is where the PWM duty variation comes into play.

I will need to also have a one-shot timer to adjust the over all demand on each cycle.

I suppose one could do this with a dual 555 timer. One as the One-shot the other has the PWM signal.

There is a way to set up a 555 timer to have a longer starting pulse, that maybe the easiest thing to do for this.

I was also thinking about using a LM324 type chip and current sense to create a hysteristic pulse where I can simply vary the current as the portion control on the holding current.

Jamie

Xylene softens and even dissolves some plastics. Similar to benzene.

Automotive injectors can incorporate plastics, make sure they're compatible with xylene.

"For a successful technology, reality must take precedence over public relations, for nature cannot be fooled." (Richard Feynman)