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Topic: Mega 2560 for project (Read 2 times) previous topic - next topic

rjshust

Hello,

My son and I are doing a project that will require close to 50 inut / outputs, so the Mega 2560 looks like what we need.

If this works, we want to make more copies of this project.  I know if a project is based on the uno, you can put just the chip on the PCB.  Can we do this with the chip from a Mega, or would we be better off just buying more Megas?

If this is possible, could someone point me in the right direction on how to do this?

Thanks,
Rob

PaulS

Quote
Can we do this with the chip from a Mega, or would we be better off just buying more Megas?

You will have a much harder time removing the chip from the Mega that from the Duemilanove or UNO. Depending of your skills with a soldering iron, it might be easier to just buy more Megas.

SirNickity

Megas are surface-mount chips.  Tiny, tiny pins to be soldering by hand.  There are options available to have them fabricated by a production house, if you're ordering in quantity.  Or, you can learn how to do SMD PCBs yourself.  It's not trivial, but not impossible.

You might think about IO expansion on through-hole chips instead.  Look into shift registers, for starters.

Graynomad

#3
Mar 29, 2012, 08:58 am Last Edit: Mar 29, 2012, 08:59 am by Graynomad Reason: 1
It may depend on how many you intend to make, Megas are expensive so if this is to be a commercial product you really should build your own board, soldering those chips is not rocket science but you certainly have to hold your mouth right.

I have a mate who just had a few (8 I think) boards loaded with the hard bits (including a 2560) for his invention, it wasn't real cheap but OK. See here

http://arduino.cc/forum/index.php/topic,69358.0.html

So I think it depends on whether this is 100s for sale or 5 for the local sports club.

______
Rob
Rob Gray aka the GRAYnomad www.robgray.com

Coding Badly

Quote
require close to 50 inut / outputs


How close?

rjshust

Thanks for the responses.  Confirms what I suspected.

The project is for our own version of a guitar effects pedal controller.  Originally inspired by this: http://www.geofex.com/article_folders/rmtswtch/rmtsw.htm, but after all of the changes / features we keep addining, it only has a slight resemblence to the original.

Right now we are at 44 input / outputs (LCD, LEDs, Stomp buttons, relays, etc...).

He is talking about some more features that could add up to 12 more IOs, so we are filling up the mega pretty fast.

We have tested all of our needed programming and electrical proofs individually, and did a small scale test of all our programming concepts combined on the uno (used all the digital IOs).

We now have a mega, and have ordered all of our parts, so hopefully in the next few months we will have our prototype up and running.

We also made our first PCB (acid etched a copper clad board).  So that is one more thing to check off our list of things we need to be able to do.

There are a few friends who say they want one if it works like we think it should (plus my son has dreams of selling some - we will see about that way down the road).

Thanks again for the help,
Rob

CrossRoads

If you are doing any quantity, then order ten 100mm x 100mm boards (max) for $24.90 from iteadstudio.cop, much more reliable way to go.
Solder masked, labeled, the works.
Designing & building electrical circuits for over 25 years. Check out the ATMega1284P based Bobuino and other '328P & '1284P creations & offerings at  www.crossroadsfencing.com/BobuinoRev17.
Arduino for Teens available at Amazon.com.

fkeel

you may also want to consider using multiplexers...

SirNickity

Yeah, dude...  You could easily do this with through-hole parts if you use a couple shift registers.  There's really no need to use a Mega unless you must have the UARTs or memory that you just can't get on the lower end chips.

I mean, if really want to, knock yourself out -- but absolutely consider the easier route first.

rjshust

I have been programming for years, but I am weak on the electronics side.

Could someone supply me with any good info on multiplexing?

SirNickity

Look at the ShiftIn and ShiftOut tutorials on arduino.cc.  The 4021 and 595 chips are cheap and easy.

Graynomad

Also look at the 4051 and 4067 to get extra analogue inputs.

______
Rob
Rob Gray aka the GRAYnomad www.robgray.com

winner10920

If you buy atmega2560 you will have to learn about bootloading and isp, I've soldered one tqfp chip before and its not so bad with the hot air method and solder paste, definetly needs a custom pcb tho,

CrossRoads

Could also try a '2560 on a Schmartboard, get access to all the IO pins.
Designing & building electrical circuits for over 25 years. Check out the ATMega1284P based Bobuino and other '328P & '1284P creations & offerings at  www.crossroadsfencing.com/BobuinoRev17.
Arduino for Teens available at Amazon.com.

rjshust

Am I correct that with multiplexing, I can only have power to one output at a time? 

This project will have around a dozen relays, plus LEDs as indicators where many could be on at that same time.

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