electric steering ..help with electronics

[pistnbroke]

Hi need to build an electric steering system for a small 5 hp outboard ...mechanics no problem ...wiper motor driving threaded rod and nut ..reverseing with two change over relays ...pot on motor and steering wheel for feedback ...but can I get through all the differential amplifier tutorials and stuff on car electric steering on google to come up with a circuit to test ...no

So anyone got one inscribed on the inside of there forehead or a link ?

Update ..found CDKs thread on electric throttle and that combined with my research should produce a workable circuit

[Tim B]

Use the differential amp to compare the requested input (helm position) with the achieved output (OB position). This needs to be converted to a signal that an H-Bridge can use (using some comparators). The H-Bridge then drives the motor forward/backward (OB Left/Right). There is a PDF with a load of OP-AMP circuits, somewhere, but it should be easy enough to find some info. Don't get confused between the difference phase, and driver phase of the design. You won't find an OP-AMP to drive your motor directly.

I would suggest drawing a system flow diagram to help you work it out.

Hope this is of some help,

Tim B.

[pistnbroke]

thanks for that found some good stuf on comparitors at http://home.cogeco.ca/-rpaisley4/circuitindex.html#26 and with that and what I picked up from CDK post I think its time for a trip to the shed.....( should have a squiggle rather than a dash before rpaisley..my computer dont have one )

[CDK]

I'm glad I didn't post that one for nothing.

A wiper motor seems a bit slow for this application. Look at www.firgelliauto.com, they have exactly what you need: sturdy, good looking, potmeter in the gear housing.
If you want to make it yourself, use a 12V fan motor to turn the spindle.

[pistnbroke]

thanks for that link ..excellent and easy to fit ..worried that they move too fast and as you know moving an outbard too fast will rock the boat.. I want it for a canal use so small steering increments are needed. hence a wiper motor on fast driving a threaded rod in a tube would be quite fast enough. They have distributer in Australia but dont seem to do the feedback ones except in the usa...am waiting for a reply to my e mail

[Landlubber]

pistnbroke,

Why not just use one of the el cheapo Raymarine tiller pilots...or are funds really that low that you need to make it yourself.

[pistnbroke]

will check out the tiller pilot .. did that $600 ..all I want is a mini steering wheel without cables or ropes...

The linear actuator CDK recomended is brilliant and cheap( $136) BUT you carnt get it outside the US eg australian or UK distributer and they are ass holes about replying to e mails ....oh yes all out of stock .. but when will they be in stock ??? No answer

[CDK]

This is the guy I did business with directly. I paid by PayPal and he shipped the items the same day: "Troy Newton" <tnewton@firgelliauto.com>.

[pistnbroke]

finally got a nice considered reply quote "end july" so will build the electronics in the meantime...will go for the 8 inch 150 ib as it will be slower having the 20 :1 gearbox

[jonr]

I would just use a microprocessor - it's easier to put in extra functions like variable gain, safety functions, gps interface, etc. Arduino is easy to use and you can get motor control (H bridge) add on boards for it. I'll help program it if you want.

[pistnbroke]

no no mate this is just pushing a 5 hp briggs and stratton outboard up a british canal at 4 mph you might use a microprocessor but I would prefer a simple left right switch unfortunaltly the canals are a bit straight so I need a centre position /proportional control ...KISS like very simple and very stupid
VSVS

[Tim B]

jon,

I appreciate what most people would call overkill in electronics, but I find it more amusing than useful. Create something that performs one task and does it well. Then add the complexity.

Tim B.

PS. If you really want overkill, drive it from OpenPilot.

[jonr]

It may be overkill here, but it is surprising how many times it is cheaper and easier to use these tiny general purpose off-the-shelf microcontroller boards vs doing a custom circuit of any kind. It comes in the mail and it's fully working 10 min later.

[pistnbroke]

give me a website or spec page so I can see how hard its not...

[CDK]

Jonr is right of course, a microcontroller is the fastest way to get things done.

BUT.... if you have a virtually endless stock of linear and digital ICs and discrete components like I do and can make a printed circuit board in your wife's kitchen when she isn't there, making your own circuit can also be very rewarding.
Plus: for most parts I need no books to show me the pin-out, it is sort of engraved in my mind, whereas a new micro means studying first.