My FB project, Question on MOSFETs
Well guys, today was the maiden voyage for the project I've been working on - steering a tractor via GPS. I'm using a fusion brain to read steering angle position, and triggering two outputs that control relays that drive an electro-hydraulic valve that steers the tractor. I was letting the software drive the tractor, which stayed within a range of about one foot of the line.
Can I use a MOSFET instead of a relay? Would the FB outputs be alright with that? The clicky clicky of the relays was a bit louder than I prefer. I could move them somewhere else for testing, but just checking out other options? The solenoids I'm driving are 12vDC at ~3.5 amps.
More info (added by greenman100)
Here's a new video:
The machine is a Case IH 2588 combine (~300HP) that is harvesting soybeans at 4 MPH. I'm using the FB to read a steering angle position sensor, a yaw sensor, and a tilt sensor. That is added to a GPS position to drive the machine in a straight line, with each pass parallel and at a consistent distance from the last pass. The fusion brain outputs steering commands, which go to a couple relays, which send power to solenoids on a hydraulic valve that is connected in parallel to the steering wheel orbital.
The header (thing on the front) is 25 feet wide. As you can see in the video, the yaw sensor makes the vehicle control very smooth. It still likes to drift off the line, then slowly come back to it (it can get up to about 8" away from the line.) I'm still working on revising the yaw sensor calibration algorithm, and the method used to calculate what angle the steer axle should be at. Yaw sensors are a royal pain due to their "zero" position changing as they warm up. As slow as the machine is moving, with subtle steering inputs, getting an accurate and precise yaw reading is a challenge.