EEs in our midst: Can you advise me? (1 Viewer)

[Ryan Wright]

Any Electrical Engineers here?

I'd like to build a device with the following features:

1. Serial I/O controlled
2. Switches relays on/off (for fluorescent lighting & other 120V loads)
3. Switches dimming circuits on/off & adjusts dim levels (for incandescent lighting)
4. Ideally, allows queries & reports status of all relays & dimming circuits.

My experience:

1. I can program in any language with a little documentation.
2. I can solder.
3. I can sometimes make sense of _very_basic_ schematics.
4. That's about it.

My questions:

1. What do I need to learn?
2. Where can I learn it, or otherwise get a "crash course" in IC design, programming & construction?

Taking a course at my local college is not out of the question, assuming I can find one that will get me some hands-on experience (I'm not very hopeful).

Thank you!!

 

[Adam B]

There are many resources online to help you with this.
You can try www.parallaxinc.com for starters. They make VERY easy to use microcontrollers and have a lot of documentation and tutorials that will familiarize you with the basics of interfacing ICs to the real world.
The BS2 was the first microcontroller I used. At $50 its quite expensive but it doesn't need any support circuitry. With most microcontrollers, you would need to construct a circuit board with RAM, ROM, clock and power supply regulation to support the processor.
As far as what you want to do:
1. Any of the microcontrollers by the company above will do this.
2. You will need power transistors to be able to drive relays. Microcontrollers are VERY weak. Most can only output 1-5 milliamps not to mention when the relay shuts off the back emf can damage some chips. There are transistor array chips that are designed specifically to allow ICs to drive high current loads.
3. My friend did this in his dorm using an R/C servo and a mechanical dimmer. Not the most elegant, but this is how I would do it.
4. If you use a microcontroller this would be automatic. You would just query the output pins and report back to the PC across the serial connection.
Adam

 

[Ryan Wright]

At $50 its quite expensive but it doesn't need any support circuitry.

$50 is cheap as far as I'm concerned. I want to build this device so I can interface my AMX master controller (home automation stuff) to my lights and get rid of X-10 once and for all. The other option is to buy $4k+ worth of AMX equipment. So, even if I spend $500 building this thing, I'm way ahead.

Thank you for the link & your comments.

 

[John Miles]

Agree with Adam, for your first experience with microcontroller work you can't go wrong with the Basic Stamp II. You may outgrow it quickly, though -- it's one slow mofo.

 

[Ryan Wright]

John: I don't need to do a lot with it. I'll just be saying, "OK, turn this relay on now." An hour later: "OK, these two can be turned off." Pretty basic, slow stuff.

Although, I'd like to know: When/if I do outgrow it, what should I move on to?

Also, are there any good Internet retailers for parts? I'm familiar with DigiKey... what are your favorites?

Also, I don't suppose anyone can recommend any books or other places to learn? I've been researching the stuff at Parallax and will likely make my first few purchases there, but I'm not confident this will show me how to go about building the circuit I want to build. It will get me started, though, which is good.

Thanks,

 

[John Miles]

I'm about to do a lot of work with the Atmel AVR microcontroller family (AtMEGA128, specifically), using it to control a wideband receiver project. This is a pretty cool chip -- 16 MHz RISC with most instructions taking one or two cycles, lots of integrated I/O features. The Atmel chips seem like a good migration path once you've outgrown the Basic Stamp. They are a lot more complex to use, though, so I wouldn't start with them.
DigiKey rules. I use them for 90% of everything I order. I probably order a couple thousand dollars' worth of stuff from them per year. Newark is OK for certain things that DigiKey doesn't carry, but I usually rely on DigiKey.
There is a TON of stuff on the 'net about using Basic Stamps. So much that it can be overwhelming. This seems like a good index site.

 

[John Miles]

Oh, and to help come up to speed on basic electronic stuff (as well as give you a very usable prototyping platform and a good assortment of ancillary parts to play with), pick up one of these. They're awesome -- a co-worker just bought one of these kits to help him use a digital voice recorder chip, and I was very impressed.

 

[Grant B]

Just a couple words.
Building it is one thing, getting it to work is another.
I have a pretty good knack of getting things to work, but rarely do get it to work right off the bat
How are you at troubleshooting?

 

[Ryan Wright]

Grant,

How are you at troubleshooting?

I'm a computer & network tech. I spend most of my days troubleshooting one problem or another, so I'm quite good at it. At least, I assume I must be, because I still have a job.
John: Thank you for the extra info! It is much appreciated! I think I'll start with some learning kits to bring me up to speed. I'm going to involve my 5 year old in them, they look like something she might enjoy as well.

 

[John Miles]

No prob, Ryan. That particular kit isn't something I'd consider a toy for younger kids; it's a pretty serious educational aid. A lot more advanced than the ones they were sellling back in the Seventies when I was 8-9 years old.
I really like it because it doesn't rely on fixed components -- whenever you want to try out a new chip you can just plug it into the solderless breadboard, and the kit gives you most or all the support components you need to experiment with it. That particular kit and a Basic Stamp 2 chip should keep you busy for a long, long time, for around $100.00 total.

 

[Seth Paxton]

Speaking of taking courses, it might be possible for you to learn quite a bit of basic circuit design just by reading the right 1 or 2 books.
I would advise my basic circuits book (forget details right now) and perhaps a solid digital logic design book (mine was pretty good, but you might get advice on others).
When the books are good like those are, you can often learn the course without the prof at all (and sometimes need to with the not so great profs ).
Spending $150 on a couple of nice books is better than $650 on courses and books (and that's a cheap local state school as it is).

 

[Ryan Wright]

Spending $150 on a couple of nice books is better than $650 on courses and books (and that's a cheap local state school as it is).

With this, I agree 100%. However, I'm currently taking classes online to finish a degree, and my employer is paying for it. They'd pay for these courses, too, and I could count them as electives.

 

[Seth Paxton]

Anytime you can get college credit on someone else's dime, you should do it.
Even if it's 3 hours of Advanced Pottery. You never know when it might further your career.