This page describes how to drive low impedance injectors with GenBoard/VerThree

There are different ways to drive low impedance (peak and hold) injectors:

With series resistor, 30V unidir transient diode (high-voltage) flyback is mostly used.

With 30V unidir transient diode (high-voltage) flyback, the PWM parameters MUST BE:

This page is about PWM-ing. PWM-ing is not popular at all, because


GenBoard/Manual/DDFlyback is very important for any injector setup.

When PWMing is configured, the low voltage flyback is the only option. The high voltage flyback will fry (itself and the FETs at least). (while the 20V flyback will always fry, for some injectors or with appropriate series resistor there can be a narrow operational range for the 6V8 flyback: it takes expertise to configure it, simply don't risk it. If set up bad it will fail at the worst possible time, at max power.).

PWM-ing is done as:

GenBoard/VerThree was designed so all 8 injection banks can be PWM-ed. It is achieved by PWM-ing OC0 with the given duty, and turning the PORTA pins IN/OUT-low/OUT-hi.

Without PWM-ing (for highZ injectors, or with series resistors) the common setup is to drive the insulated logiclevel FETs (see PowerSwitcher?) from the AVR's pin, with 1k gate resistor (the FETdriver is replaced by simple bypass wire).

good to know for v3.0 v3.1 v3.2

PWM-ing requires

HW notes

We use MC33151D or MC34151D (inverting) and R154 OC0 pullup under AtMega.

The IXDN404SI (noninverting) and R153 OC0 pulldown under AtMega

should work, but not supported.

2x R-network SIL5 (4+1 pin 2k2..10k) throughole (usually yellow)

Jason's debug session:

C20, C24 0.1 .. 1uF. The FET is about <1nF, so 100 nF will drop 1/100 of the voltage when the gate is suddenly switched on. 220nF is installed by our standards