1490 Digital compass signal to H bridge circuit

[barnsie]

I am very new to electronics. My project involves connecting two outputs from a digital compass to a 12 volt DC geared motor. I have the compass working properly. My problem is the motor needs to rotate clockwise and anti clockwise in response to the two different compass signals and do nothing when there is no signal. I do not need to control the speed of the motor or how far it rotates. It seems simple but I don't know how to do this.

The compass outputs are equivalent to an open collector of an NPN transistor and capable of sinking 20mA continuously or 25mA intermittently.

The motor is rated 140 mA no load, 800mA at rated load and stalls at 3000mA.

I am using a motor twice as big as needed so should be drawing around 400mA.

I think a L298 or LMD18200 motor driver chip may be suitable but my compass does not generate a PMW signal. Will this matter? Do I need an oscillator to generate a signal. Is there an easier way that will use the compass output. I will need to make, or get made 500 of these circuits a year so ease of assembly is important. Any help would be appreciated.

 

[FvM]

Your claiming that you don't need to control the motor speed. Why you are asking for a PWM?

I guess your intending to build a very basic autopilot. I fear, you'll need to control the motor speed respectively implement some kind of proportional controller action, otherwise you'll drive a funny zigzag course. The 1490 device, that can only distinguish 8 different headings may reveal unsuitable for an autopilot design.

 

[barnsie]

Thanks for taking an interest. I thought I needed a PWM to get an off position with these components. I am using two compasses and setting them slightly offset to give a target window for the course.

I intend to use both compasses north for signals, if the compass bases are rotated away from each other slightly the angle in the middle is the target area (OFF no signal). One compass signal needs to signal to turn right and the other left when the vessel veers outside the target window. To set or change the course the compasses are rotated by the operator. The compasses are on gimbals inside a small tube.

The device currently works marginally well without ANY steering, slow zig zagging is fine and expected, Rudder angle changes by 6 degrees per sec. Limit switches will prevent over angle steering but will seldom be reached. If you need more info I could PM you as it is commercially sensitive beyond what I have told you.

If the thing winds up within fifteen degrees of where I want it after 7 minutes at 5 knots I would be really pleased. The existing non steering ones are difficult to get within 60 degrees of where you want them.

 

[FvM]

I think, an analog compass sensor with a 8-pin microprocessor would be a suitable minimal hardware solution, more flexible than combining two "digital" sensors. It could also perform proportional control (e.g. utilizing PWM) and limit alarm action. I hope, someone located in your region can support the development.