My FB project, Question on MOSFETs

**mx270a** · 05-07-2008, 08:17 AM

H3rk, I built the software from the ground up.

Bes, I have been thinking about getting a couple of those to test. The load is a coil on a hydraulic valve, and it was creating a voltage drop/spike that the FB didn't like. Moved the FB to a different power source, and it has behaved normally ever since. I'm also seeing some odd behavior from my GPS antenna, which I suspect is also being caused from the voltage drops/spikes. I'm going to change where they are powered from to isolate that spike, which means a mosfet won't work for me any more. For right now, I like the sound of the relays to know what they are doing, but ultimately I need something more resilient, and a solid state relay looks to be a good option.

-Lance

**HiJackZX1** · 05-07-2008, 10:24 AM

Originally Posted by bes51659

Fastest way to goal is to buy solid state relays. And maybe safest...

Quick search: http://www.ab.com/industrialcontrols...ate_relay.html

Solid state relays have issues, they can easily send signals back up the wrong way causing more headache of problems. Solid states are good for HDD, but when it comes to solid state switches, i would stay away. If you google the issues Solid State Relays have you would get a whole list of issues.

**sandmanx5** · 05-07-2008, 10:43 AM

Originally Posted by bes51659

Fastest way to goal is to buy solid state relays. And maybe safest...

Quick search: http://www.ab.com/industrialcontrols...ate_relay.html

If you go with solid state - look for ones that are built using opto-isolators or just look at using an opto-isolator directly...

http://en.wikipedia.org/wiki/Opto-isolator
and
http://homepages.which.net/~paul.hil...rol/Optos.html

These are likely the solution I'll be using in my setup.. Absolutely no chance of power leaking across the gate as there is no physical connection for it to happen to.

Brilliant idea for running a tractor BTW.. I should show your idea to my aunt.. Maybe she'll let me pimp out her tractor too!

**jimp** · 05-07-2008, 10:43 PM

Originally Posted by h3rk

What a scary thought.. At least this is way out in the open.

"SCARY" you obviously haven't driven through Houston lately! I think I'd prefer to know a computer was in charge of things than some of the idiots around here!

**dupa2** · 05-08-2008, 09:18 PM

WOW1 Man!
I work for a company that makes all kinds of relays.... I'm going to spread the word how these are used....

Solid state relays will do the job, these can handle up to 125 Amps...

**mx270a** · 10-14-2008, 12:07 AM

Here are a couple videos of the system in action. The first video is what it looks like in the cab, the second video shows the blinky lights on the FB.

http://www.youtube.com/watch?v=YFqfTlqF2NY

http://www.youtube.com/watch?v=YBoFKmAFVfc

Since I originally posted, I have added a yaw sensor to the system, which makes the steering much smoother. The only time I feel it make a steering adjustment is when I go through some rough ground. Even then, it is only a 3-6" steering move. I have gotten the line-holding ability down to staying within 6" of the line, and I'm still working on making the even smaller. My goal is 2-3".

And since you guys brought it up, I am told that there are city buses in Minneapolis that are being driven by GPS. The driver brings the bus to the curb, and puts it back in the traffic lane, but then the computer takes over and steers the bus along the route. The driver still has control of the throttle/brakes, and of course can manually steer to avoid a collision or whatever.

-Lance