5 replies to this topic

[Jeff Goldberg]

While our kids and grandkids get stuck writing "What I Did on my Summer Vacation" reports, I chose to write an article on PWM MOSFET driven slot car controllers.

Over my summer vacation, I designed an experimental PWM MOSFET drive board for HO and home set cars. A "must read" article for anyone interested in using or designing their own MOSFET motor drive controller, it covers design issues addressed during board development, circuit protection, test results, and on-track performance with HO, home set, and retro cars.

 MOSFET_Technology_Paper.pdf   332.24KB   954 downloads

[chaparrAL]

Nice work! Thanks, Jeff. Had to print that out for further study.

Are you going to do a run of these modules? I have a nice Difalco for 1/24 but lately I have been running much more HO where I like to do my own thing as much as possible.

Here are some pics of what I been tinkering with the last twelve years or so.



The resistor is 60 ohm Parma in a Turbo frame and a Ruskit handle. NEO on the red sticker means that box is for the stupid fast cars.



I use a Power Bipolar Transistor affixed to a heatsink. it's PT# NTE 331 at Frys or 511-MJE3055T from Mouser. The specs are Max current 10A, Collector-emitter volt max 60V, Emitter-base volt 5V, Max Op Freq 2MHz, Power dissipation 75000mW, DC current gain hfe nin 20@4A@ 4V. They work for me. I have three boxes and one controller to run T-Jets to NEO cars.



Note only two hookups on this box, this is for magnet car racing where I run a crapload of coast and skip the brakes. My third box has a red lead and adjustable brake for T-Jets, at the flip of a switch. The switches are for low and high range speed sensitivity and coast.

My stuff looks crude next to Jeff's but I have it well sorted-out. But I am always looking for a way to up my game. In my quest to find more speed how can a MOSFET controller make me faster?

Best,

[chaparrAL]

Now that I checked your website out, I discovered you are way ahead of me with this stuff.

I guess it's time to think new controller. Will the HO module work with your Linear 100 wiper board assembly?

[Phil Smith]

Very interesting, Jeff! Thanks for sharing that with us. Good luck with your MOSFET controller!

[mazur50]

Very nice article. Your design is very similar to one I have been working on.

Very nice piece.

[Jeff Goldberg]

Al,

I'm not sure whether you really meant to direct your question to the Linear 100 wiper board or the Linear 200 wiper board. The Linear 100's wiper board and handle was hardwired to its transistor and heat sink. It won't work with the Linear 200 transistor modules.

JayGee Racing's first generation Linear 100 controller:



By contrast, the Linear 200 was designed from the ground up as a modular design. The wiper board and handle was designed to derive its functionality from whichever transistor module it is plugged into. For example, when connected to the Pro 40 transistor module, you get a linear throttle response and either the Brake N' Release™ or Extended Range PWM brake profiles.

Linear 200's modular design, shown with Pro 40 transistor module:



Linear 200 experimental PWM MOSFET board with quick-connect USB cable:





When the experimental PWM MOSFET board is plugged in, the throttle response changes to the SOFTouch™ throttle profile. This profile is softer on the bottom end than a linear profile, which testing showed was a requirement for making 1/32 scale and HO cars more drivable.

Depending on which microcontroller is plugged in the PWM MOSFET board's socket, the brake profile can either be extended range PWM, Brake N' Release™ or powered coast. The functionality of the brake pot changes accordingly... adjusting brake strength for extended range PWM and brake duration for Brake N' Release™. In powered coast, the pot provides extended range PWM braking during its first two-thirds of rotation, then adjusts how much power is applied to the motor over the last third of its rotation.