Anyone played around with Arduinos?

[berry120]

Last time I looked at them they were ok, but there still seemed to be a few teething issues (this was a good few years back though.)

Now they seem to be brilliant - low cost, easy to program, reliable, customisable with shields and the like as well as being open source in design.

I'm planning on using an uno (perhaps two) for a project I'm hoping to look at over the summer - has anyone got any experience, nuggets of non-obvious information or the like when working with them? They seem quite popular so I figured someone might well have done. If not then I might order a couple in due course and start playing around!

 

[Hex]

I looked at a video on youtube.
I still have NO IDEA what they are
What do you use them for and what do they do?

 

[berry120]

Arduino - HomePage

They're basically little computers you can program to react to a number of different inputs / outputs - old school style. The uno (most popular) has a 16Mhz processor with 32Kb of RAM, so we're talking very low power, low capacity embedded devices. You connect them to the PC, program them, then disconnect them and let them run!

 

[root]

I'm still using pic16f (628 or 877) with a home made programmer.

To be honest I've always thought that the chip is a bit expensive for what it does, to the point where leaving it in a project becomes a problem, I get the chips I use as free samples from microchip, so I don't even think twice over how and where I use them.

 

[berry120]

I'm still using pic16f (628 or 877) with a home made programmer.

To be honest I've always thought that the chip is a bit expensive for what it does, to the point where leaving it in a project becomes a problem, I get the chips I use as free samples from microchip, so I don't even think twice over how and where I use them.

I thought about going down the home-brew PIC route but then decided by the time I'd got the programmer and all the required bits it'd probably work out more expensive - especially if I broke something screwing it up (not impossible on the arduino, but far less likely.)

Interesting point about the free samples though - I've just signed up for it in the hope of playing around a bit in the future but both the 628/877 haven't got any entries in the sample column - am I missing something or are there no samples available in the uk or something like that?

 

[root]

ummm, I'm in the UK.
I might go and look at the site now. I went a bit made getting samples ages ago so I still had loads left...

even if the don't have any free samples of that particular chip on ebay they are only about a pound, (and I'll send you a tube with a few in for free)...

the programmer I use is the JDM programmer.

it works on the serial port of a desktop PC (it won't work with laptops, they don't produce enough voltage).

I'd hazard a guess that you could build a JDM programmer on a breadboard for less that the price of a single Arduino chip. (mines on a bit of vero board).

or a programmer is available on ebay for £10 -I know this because I've finially decided that I want a new programmer that will work on a laptop so that I don't have to keep hold of a desktop.


as for the other bits, the 16f877 does require a crystal and a capacitor for the clock circuit.

but the 16f628 has an internal oscillator, you don't actually need any external components at all. it's a bit limited in so far as you only have 2 ports (port A and port b) to play with, but either port can be set to either input of output, there is no analogue in (there is on the 877), but you can do serial transmission on both...

I program using C, but suppose I could use assembler, there is a free compiler available called HiTech C (though I use a paid for cone called PicC). then I use ICProg to load the program onto the chip... though if I get myself a Pickit programmer (the USB one) then I'll be able to program directly from Mplab without having to use a separate program to get the compiled code onto the chips...


what is your project going to do?

free samples

go to Microchip Technology Inc. is a Leading Provider of Microcontroller and Analog Semiconductors, providing low-risk product development, lower total system cost and faster time to market for thousands of diverse customer applications worldwide.

hover over the buy sample menu and click sample
log in
on search for samples select 8-bit pic controllers for the producet line
and 16f628a for the chip type (i think that the 16f628 isn't made any more which is why there are no samples)

or click 16f877a for the other chip.

(i stick to these two chips for the simple reason that I happened to have them when I built the programmer, and to program these you have to pull a specific pin low... I didn't have a switch at the time so my programmer is stuck on configured only for these two chips).

but there are plenty of chips that you can program either with the Pickit or the JDM programmer.
(pic kit is £10 on ebay, jdm can be built for around £5)...

 

[berry120]

Hmm, you're seriously persuading me to go down the home brew route I must say! My electronics knowledge is rusty and not hugely advanced (I got full marks in my AS level for it but other subjects prevented me taking it further) but it's always something I've wanted to be better at so perhaps this might be the way forward!

The project is a bit of a different one, I'm intending to use it as the brains controlling the drive system / sensor system for an underwater ROV. The other advantage with the arduino in this sense is I can just plug in an ethernet shield and then run some CAT5 for everything, essentially writing a little web server to sit on board the arduino and respond to requests for sensor data or to drive the motors. Any idea how I'd go about putting an ethernet port on a home brew version? That's something I've never really looked into before.

Oh and thanks for the offer of sending a few chips on - I think I'll leave it for now because I'm probably not going to get a chance to start this project for a while but it's much appreciated!

EDIT: Ah yeah thanks for that, I was looking at the out of date ones without the "a" at the end. I'll see if this works Is it just me or is the site being really slow at the moment?

 

[root]

the did seem to be rather slow when trying to change between product types in the catalogue.

to be honest, you can get chips with a network stack pre-programmed, (then you can just configure and use the port in standard read/write functions), I'd go as far as to say it's impossible to program your own tcp/IP stack into a 8 bit pic controller, there isn't enough program space or memory.

but the good news is that servo control is actually really easy. (just uses PWM).
motor speed control can also be done with PWM,

and you can either get a chip with a built in tcpip stack, or communicate via the serial port.

How many sensors do you have? are the analogue or digital?

 

[berry120]

to be honest, you can get chips with a network stack pre-programmed, (then you can just configure and use the port in standard read/write functions), I'd go as far as to say it's impossible to program your own tcp/IP stack into a 8 bit pic controller, there isn't enough program space or memory.

Cool, I thought this might be the case (or if not possible, very complicated.) Any recommendations for such chips or does it not really matter?

but the good news is that servo control is actually really easy. (just uses PWM).
motor speed control can also be done with PWM,

Yup, I figured that motor control can be done with PWM (via relays?)

and you can either get a chip with a built in tcpip stack, or communicate via the serial port.

TCP/IP stack sounds good to me, if nothing else I'm used to working with it.

How many sensors do you have? are the analogue or digital?

Combination of both, but mainly analogue. I'll be looking to basically have all the sensors I can sensibly get on there - I'd like a 3-axis accelerometer, pressure sensor, light sensor etc. which would all be analogue obviously. But there will probably be some digital ones - if nothing else I'll want a water detection circuit in the bottom of the waterproof electronics housing to sound alarm bells (perhaps physically!) if a breach is there and any water does get in.

 

[root]

Yup, I figured that motor control can be done with PWM (via relays?)

relays won't switch fast enough.

you'll need transistors, either BJT or mosfet transistors to deal with the current that you want to power the motors