Fan controller +bells+whistles+diy(?)

[ecat]

If I were you, I would start a little smaller and work my way up first. 30 probes is vary overkill, IIRC, Martinm210 had 32 probe hookups on his testing rig and only used like 18. . .the standard user isn't going to need even that many, maybe 6. . .tops. 2A per channel would be a vast improvement but 1.5 would probably be a better starting point. I've got a few more things to add to this list but unfortunately, work beckons me to show up. I'll add them in a new post later.

Some good points...

I picked 30 as an example figure. The devices communicate over a single wire and this single wire can connect to a virtually unlimited number of devices, if you write the code to access 2 devices on a single wire the same code will access 100 devices. In reality I think splitting the devices over, say 4, separate channels will simplify both the timing requirements of the code and the cable runs.

I was thinking of people like Martin when putting the design of this together. This unit will sit on a desk, log n channels of data to better than 0.1C resolution, display the data that has been logged and at the end of the day upload the data to a pc.

This thread is directed at the 'standard user', at least the standard XtremeSystems user. I'll do things one way if I build this exclusively for myself, I'll do things a different way if I build this so others can follow the instructions. One of the reasons for this thread is to find out how many, if any, are willing to drop $200 on a box of bits and soldering iron.

25Watt, 2 Amps per channel just happens to be the rating of the ready built modules I'll be using. The same company makes a 10w unit with the same form factor that costs about £5 less, I think the 25w unit is the correct choice. For reference, my original do it all yourself design was rated for around 5 Amps per channel but this would have required a custom circuit board and some very tricky soldering. The off the shelf module comes with a guarantee and can tested in isolation before making a small modification, again I think this the right choice.

As an aside, if you're happy setting the speed with a small screwdriver or you get inventive with a plastic rod and some glue the 25w module makes a lovely manual speed controller. I have one set up here just now, stripped naked of all plastic and aluminium, running six Nexus fans at 9v the unit is not even warm.

I reckon you could do most of this with a PIC and a PIC programmer.

<chuckle> The controller is a PIC, a PIC32MX460F512L in fact, built into a ready assembled module. It is quite a powerful beast to be honest, the main reasons for choosing it are:

1) The pre-assembled module saves messing around trying to solder the tiny surface mount PIC.

2) This particular module has a number of nice features including: inbuilt voltage regulation, inbuilt USB port, some switches and LEDs and comes pre-programmed with some useful software. It can be tested straight out of the box with nothing for then a USB cable.

3) The pre-programmed software allows the module to be programmed with nothing more than a small windows/linux application and a USB cable. No special programmer is required.

4) I needed more than 16 control lines and this was the cheapest option I could find .

N.B. You'll find the phrase 'tested out of the box' or 'tested before modification' appears several times in my replies. I'm trying very hard to ensure that each individual module used in this project can be tested with the absolute minimum amount of work. You buy the module from wherever you like, you test the module with the minimum amount of fuss, you send it back if it doesn't work. Once a module has been modified you are on your own, well, I'll help diagnose where I can.

Edit:

ecat

awesome list

addin some huge heatsinks and fan mounts for the heatsink

Thank you Huge heatsinks and fans eh? At 90% efficiency and 25w the power modules may need a small heatsink to help with the 2.5w dissipation, to be honest they are better than 90% and designed so the whole pcb acts as a heatsink. As for fans, the last thing I need is another one

ecat
PIC microcontroller...they're good stuff i used them in my robotics class

I don't like PICs all that much, at least I don't like the MicroChip complier and some of the library functions always feel somewhat broken. Still, the software is my problem, once you get these PICs working they work well.