Azimuth and Elevation Controll Project - Need an Expert Eye!

Projects General Guidance
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Hi!

I've got a project I am working on which I could do with a little help and support on if anyone can help?

First of all, I will say have some electronics and programming knowledge and some formal training in both but most of it was a few years ago and I never got the opportunity to complete the course so I'm really sketchy at some things. Some things I get and understand really well, some things I'm just like.. ERM, WHAT? So please bare with me!

I've made a start on my project and have a few designs for what I want to do which is, in a nutshell, this...

I am a Radio Ham and I'm wanting to build my own Azimuth and Elevation system for steering a bunch of Yagi type antennas into space to receive satellite signals of various kinds on various frequencies and bands.

What I want to do is this: I want to use Orbitron, a sat tracking program which should output the AZ/EL data via Serial to my arduino. The arduino in turn takes the position data and translates that into movements to my motors.

I am a bit of an eccentric worker which doesn't help so I tend to pick away at the things that need doing in the order I feel capable of doing them so my work is a bit all over the place but I've made a start designing one side of the control circuits but I'd like someone just to take a look at what I've got this far just to see if everything looks okay. I'm not an electronics engineer, I've just been piecing together parts of common circuit layouts to make what I want so it's probably a very noobish circuit. I'm also not familiar with any circtuit deisgn software yet so I pretty much drew my circuits in a simple way that I could follow using VISIO LOL so some of the symbols may not be entirely accurate so I used ones close to what I need just to emphasize what the parts were.

It took me 18 hours straight at the computer to get this far LOL

E2A: Okay, so I thought the image wasn't showing - it's just slow to load....

This side of the circuit is purely for the elevation motor which is a 36V DC Horizon to Horizon dish motor which will be mounted on it's side and on top of a regular antenna rotator to provide elevation to the system.
The rotator or azimuth motor is going to be pretty much the same design except IT runs at 24VDC and not 36VDC so I'll replace them for 24VDC relays there.

As far as I can tell, that circuit looks done and ready but I'm no expert so could do with someone a bit more knowledgeable just to check it for me if they wouldn't mind please to see if they can see any obvious mistakes?
A friend of mine (who isn't always available to assist me) tells me there are better general purpose transistors out there than the TIP 120 for this application but failed to disclose any particular one so the TIP 120 may get swapped out when and if I find suitable replacement. Trying to get my head around the facts and figures for transistors has been a job in itself LMFAO.

I know I could probably go out and buy a shield or three to do half of the stuff I am wanting but I get no pleasure from assembling kits when I want to learn and for me, I get great satisfaction when I've done most of the work and built something from the ground up.

Any help, advice, support with my current design would be appreciated!

E2A: Just wanted to point out, in case it wasn't clear, the motor or elevator unit depicted in my circuit diagram is a phased motor. One common 0V with two +VCC cables; one to drive the motor forwards, one to reverse it and there are also 3 more wires which go to a 500 Ohm position keeper POT. I have not included the line of communication back from the POT to the arduino in this diagram but thought I should point out it does exist.

Thank you kindly!

Mike.

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Image doesn't load...

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Thanks for letting me know!
Sorry about that, how about now?

My website, where the image is hosted decided to throw a major wobbly shortly after I uploaded and linked to it (typical)

It was giving me some grief while editing my original post - one minute the pic was there and then it wasn't I just thought it was initially being slow to load :confused:

I've cleared my cache and it seems to be loading okay now...

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Image still doesn't load.

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Okay, have uploaded to TinyPic. 8)

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How can the microcontroller switch on Relay #1 ?
The output of the transistor is connected to both ends of the relay if I understood your drawing...

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robtillaart:
How can the microcontroller switch on Relay #1 ?
The output of the transistor is connected to both ends of the relay if I understood your drawing...

Relay 2 appears to be connected in a similar way...

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The circuit looked broadly credible to me but looked as if it had a few typos in it which resulted in things being grounded that shouldn't have been. Was it copied from somewhere else and not properly checked?

I would have thought you would have a much easier time of it if you simply bought a motor or relay driver - you can even get inexpensive Arduino clones with some integral low current H-bridge drivers which would be enough to operate a small relay. Alternatively get a higher current H-bridge driver capable of controlling the motor directly. Once you have direct electronic control you can get much better control over the motor speed and acceleration which would be kinder on the mechanical parts and give you much better positional accuracy. True you can make a simple electronic circuit yourself for less money, but we're not talking about a lot of money either way and making your very first electronic circuit can be a lot of work and no guaranty that you'll get it right at the first attempt. I get the impression that your priority is to get the finished article and not throw yourself into the deep end of electronic design and construction for its own sake, so DIY from scratch does not seem like the best approach.

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PeterH:
The circuit looked broadly credible to me but looked as if it had a few typos in it which resulted in things being grounded that shouldn't have been. Was it copied from somewhere else and not properly checked?

I would have thought you would have a much easier time of it if you simply bought a motor or relay driver - you can even get inexpensive Arduino clones with some integral low current H-bridge drivers which would be enough to operate a small relay. Alternatively get a higher current H-bridge driver capable of controlling the motor directly. Once you have direct electronic control you can get much better control over the motor speed and acceleration which would be kinder on the mechanical parts and give you much better positional accuracy. True you can make a simple electronic circuit yourself for less money, but we're not talking about a lot of money either way and making your very first electronic circuit can be a lot of work and no guaranty that you'll get it right at the first attempt. I get the impression that your priority is to get the finished article and not throw yourself into the deep end of electronic design and construction for its own sake, so DIY from scratch does not seem like the best approach.

Hi Peter,

Thanks for replying!

No my friend, there are no time constraints, I was just a little frustrated yesterday at my friend for letting me down to be honest. He's supposed to be giving me guidance but getting an answer out of him, especially anything useful when I need it is proving nigh on impossible of late.

Anyway, back to the subject at hand... The motors being used in this project are dedicated antenna rotators which are already geared etc.
Here is the circuit diagram of one of the rotators (it's at the end of the document) http://www.radiomanual.info/schemi/ACC_rotator/Daiwa_DR-7500_DR-7600_user.pdf
This motor / rotator is the 24V rotator that will be used to rotate about the azimuth axis while another motorised 36V dish mount will elevate the antennas.

On the right of that circuit diagram is the wiring for the motor / rotator itself while on the left is diagram for the controller unit which would have been used to manually switch the motor forwards or backwards.
I aim to replace the controller with my own circuit driven by micro-controller. Looking at that diagram suggests to me that the motor just wants switching.

The driver circuit I've been working on is all my own design, to a point, based on common circuit designs for common purposes found on the internet. I've just taken the simple circuits for switching relays etc and have adapted them to suit my design for my needs and the circuit I originally posted in my first post is what I had come up with. For me, this is not only about getting the project done so I can use it, but so I can learn about components and building simple circuits and this is where my friend was supposed to be giving me guidance since this is his area of expertise.

I do have relay shields and H bridges BUT I'd rather learn something while building my own :slight_smile: I've always been that way though.. In at the deep end, hands on monkey see, monkey do style.
I'm not one for books.. I do read tutorials and guides etc when I need to but I find I learn far more efficiently when I'm shown how to do something once and I repeat it. I don't know what it is about reading books but I just can't concentrate on them or visualise what's being written about when I don't understand what it is I'm reading.. I've got heaps of books all half read and forgotten about where I've opted to seek out my answers in guides with pictures or in videos LOL. When I was at College I had to physically force myself to read books but I really didn't enjoy it and it made the learning I wanted to enjoy a chore.

Anyway, I've been back in VISIO and have corrected some mistakes to my circuit based on how I think the components should be wired and have corrected some design layout errors and this is how my circuit looks now:

If I've followed it through logically, the only real design floor I can really see now is that it's possible for both relays to be on at the same time. There is no switching / checking logic at the hardware level to only allow one relay to be energised at a time. I know I can stop this from happening with the program in the micro-controller however, I'd far prefer some hardware safety in there in case I manage to make a mistake with the coding and enable both PWM pins at the same time.

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Hi Mike,

This is the project I'm doing for my radio station

and...

73
Clay, IZ1DNJ