magnet control through PIC

[SterlingY]

Okay, so I'm not sure where to put this thread.

I need to control multiple electromagnets from a PIC18F4550. The strength of the magnets needs to be varied over time, and each magnet individually controlled. To make this more difficult, I need to control more magnets than the PIC has outputs.

Thoughts?

-Sterling

[Russ Kincaid]

Implement a 4 bit binary counter and use '154 one of 16 decoder. With a 2 port PIC you could control 128 magnets easily.

Russ

[SterlingY]

I understand the 1 of 16 decoder, but I'm lost, those decoders have 4 inputs. Two '154 ICs would require 8 pins from the PIC I'm guessing the 4bit counter resolves this, but I'm not clear how.

Can you be a bit more specific to my untrained brain?

Thanks,

Sterling

[SterlingY]

What about using a 1-wire network to address each magnet seperately? Maybe that's much more costly. I have no experience with 1 wire networks.

[mackrackit]

Depending on the wattage of the magnets, there are several ways to control them. Use PWM or maybe even FREQOUT. Connect the mag circuit to you chip with an opto-isolator or drive the mags with a MOSFET or IGBT. There are pros and cons to each though.

How many more mags than pins? How many mags need to be on at a time? Look at some of the recent post about LEDs, add driver hardware and...

[BobK]

Hi SterlingY,

Don't know your level of expertise, but if it would help, there's a book out for Basic Stamps (these are PIC's) called "The Microcontroller Application Cookbook" that has a chapter on expanding I/O using only a few port pins and it has some code examples. Volume 2 also has some interesting I/O examples. These books are available from www.parallax.com and www.nutsvolts.com and probably from Amazon.com.

HTH,

BobK