The MegaSquirt Project has experienced explosive growth other the years, with hundreds of new MS installations occurring every week - a phenomenal success! MegaSquirt has been successfully used in all aspects of Internal Combustion engine applications including R&D, Industry, Race, and Research. The MS project has transformed itself from a simple R&D project into a full-featured mature engine control system. To reflect this the support structure has also changed to meet the needs of MegaSquirt Users.
Moving forward, the R&D forums for MegaSquirt project are in a read-only mode - no new forum posts are accepted.
However the forums will remain available for view, they still contain a wealth of information on how MegaSquirt works, how it is installed and used. Feel free to search the forums for information, facts, and overview.While the R&D forum traffic has slowed in recent years, this is not at all a reflection of Megasquirt users, which continue to grow year after year. What has changed is that the method of MegaSquirt support today has rapidly moved to Facebook, this is where the vast majority of interaction is happening now. For those not on Facebook the msextra forums is another place for product support. Finally, for product selection assistance, all of the MegaSquirt vendors are there to help you select a system, along with all of the required pieces to make it complete.
A forum for discussing applications and implementations of the MegaShift transmission controller code for the GPIO from B&G. This can control up to 8-speeds and 6 shift solenoids (plus a 16x9 table for controlling a PWM line pressure valve). It has manual and fully automatic modes (16x9 load x speed table), with under and over rev-limit protection, and full data logging of all inputs and outputs (among many other abilities). A TransStim to test your completed board is also available.
I am intending to use PWM3 for a shift solenoid. Can I use a transistor the same as the other PWM circuits or should I stick with the mosfet? If I do stick with the mosfet do I still need the 10W resistor? Any help would be great. I am on a pretty tight deadline!
If the output doesn't change state quickly (like a PWM output), there won't be much heat generated so a resistor isn't needed. I assume that because it's for a shift solenoid that it won't be changing state rapidly. There will be a fly back pulse whenever the solenoid is deactivated so you'll need a diode connected from the MOSFETs drain to +12Volts. If you don't, the MOSFET will almost certainly fail the first time it tries to turn off.
amishmafia00 wrote:I am intending to use PWM3 for a shift solenoid. Can I use a transistor the same as the other PWM circuits or should I stick with the mosfet? If I do stick with the mosfet do I still need the 10W resistor? Any help would be great. I am on a pretty tight deadline!
Use a device called a "low side switch" its packaged like a MOSFET (3 leads Gate, Source and Drain) but it has a built in flyback limiter that works closely like the low impedance injector drivers that are available on the MS2 & MS3. The difference is that it is integrated into one package. In my opinion, I think that by using one of these with a 60 Volt self limit, you can omit the diode and big resistor. Make sure that you mount it to the heat sink. There will a 2-4 Watts dissipated but it controls a PWM solenoid much better than using the flywheel diode. The higher you can allow the fly back pulse to go, the faster the solenoids response. With a 60 Volt switch, the flyback pulse is 48 Volts (60-12). This slows the solenoid current significantly faster than if we let it flywheel. Because it flywheels, the current is (on average) much higher and hence the need for the big resistor. What I'm getting at is that you want PWM solenoids to be fed similarly to a low impedance injector. The big automakers don't use big resistors anywhere!
Just a brief note: the Low side switch dissipates powe (in the form of heat) only during the "off" time while the resistor and flywheel diode dissipates during the "on" time.