Questions and comments about Stepper and Extruder boards

Over the weekend I put the final touches on my UCBs and tonight I started the job of differentiating them into Stepper and Extruder boards (version 1.2.1 of the UCB ).

First I had to get myself a PIC programmer. I looked around and found a Velleman P8048 KIT for sale on TradeMe (New Zealand version of EBay) by a guy in town so I got it. Normally this is a kitset that you put together yourself but this was already put together and up for around 60% of the price of buying the kit new. It has lots of LEDs to show output and switches to simulate input and separate sockets for 8, 14, 18, and 24 pin chips. Basically way more than I'd need but who know, I may get into PIC programming one day and this is a great tool to let you experiment. The software is Windows only though.

I had issues with getting the chip seated when I was doing my PowerComms board which resulted in the pins being bent a in such a way as it is now a permanent fixture so I decided to learn from that mistake and try a different approach this time. Particularly as the chip involved was going to be programmed in the PIC programmer and then re-inserting in each of my boards in 3 or 4 times by the time I'd finished testing.

The problem was that the 2 lines of pins/legs on the chip are very close but not quite right for dropping straight into the chip holder. To start with (as I'm new at this) I thought that was the way it was supposed to be and there was some simple technique for inserting the chips I just wasn't getting. But then I decided to be a bit smarter... the legs were just a little too wide so why not bend them in a bit? Of course this needs more technique and less force so heres my solution:

I took a small pair of needle nose pliers and clamped them to half a row of pins at a time and just twisted them slightly inwards. It made my day really. After that everything went smoothly, including all the testing. I don't have stepper motors to plug in to the boards yet but the lights on the Stepper test boards turned on and off in a consistent manner. I have no idea what they meant but it did the same thing for all the boards so I guess that means they're either all good or all bad ;-) Does someone who knows about it want to write a little tutorial on how to interpret the LEDs?

My only problem was what I finally decided was an intermittent fault in one of my Tx/Rx wire pairs. Of course, by the time I decided thats what it must have been, I'd lost track of which set it was. Oh well, they're simple enough to replace when I do find them again.

Tonight though I had a couple more issues (probably made more annoying by the fact that I'm quite tired. Firstly, I found I don't have any silicon stuff to put on the heat sinks. No big deal, I've got some at work but its a little frustrating.

Then I found that because R10 and R1 are side by side on the UCB (and the stepper calls for R10 and R11 resistors to be inserted) I'd misread R1 as R11 and put the R11 resistor in there for all 3 of my stepper boards and I didn't realize until after everything was soldered and the legs trimmed. My soldering technique isn't up to unsoldering without the cool solder-sucker thing so I'll have to get that tomorrow as well.

Then the things that just finished me off tonight were when I was trying to put together the last bits of the extruder controller boards. I was trying to find C2 to insert a capacitor for the extruder controller board. I finally found that C2 was already filled as per the instructions for the UCB. Either the instructions are outdated or that is supposed to be C3 (the only other capacitor on the board that isn't used for anything). Which is it?

Also, I was going to put in Q1 (the Darlington) but I wasn't sure which way round it goes. I thought it probably didn't matter but on the silkscreen one hole is square and the others round so maybe it did. Anyone care to enlighten me?

All in all, more frustrating than rewarding tonight but maybe thats just in comparison to the weekend when most things actually went smoothly.

>
> I had issues with getting the chip seated when I
> was doing my PowerComms board which resulted in
> the pins being bent a in such a way as it is now a
> permanent fixture so I decided to learn from that
> mistake and try a different approach this time.
> Particularly as the chip involved was going to be
> programmed in the PIC programmer and then
> re-inserting in each of my boards in 3 or 4 times
> by the time I'd finished testing.

yeah, inserting chips can be a real pain. one technique i use, is to insert all the legs on one side, push/bend them until the other pins line up, then insert those pins.

of course, if you find needle nose pliers to work better, then by all means use that.

this is definitely something we're fixing with v1.3.0... we're adding an ICSP header which will allow you to program the chip while its in the board, simply by plugging a cable from your programmer to the board.

>
> I don't have stepper
> motors to plug in to the boards yet but the lights
> on the Stepper test boards turned on and off in a
> consistent manner. I have no idea what they meant
> but it did the same thing for all the boards so I
> guess that means they're either all good or all
> bad ;-) Does someone who knows about it want to
> write a little tutorial on how to interpret the
> LEDs?

check out this video, it shows how they are supposed to look.

[vimeo.com]


> Then the things that just finished me off tonight
> were when I was trying to put together the last
> bits of the extruder controller boards. I was
> trying to find C2 to insert a capacitor for the
> extruder controller board. I finally found that C2
> was already filled as per the instructions for the
> UCB. Either the instructions are outdated or that
> is supposed to be C3 (the only other capacitor on
> the board that isn't used for anything). Which is
> it?

yes, this is not quite clear. its supposed to be C3. i changed it in the docs.

> Also, I was going to put in Q1 (the Darlington)
> but I wasn't sure which way round it goes. I
> thought it probably didn't matter but on the
> silkscreen one hole is square and the others round
> so maybe it did. Anyone care to enlighten me?

if you're using the standard TIP110, then the heatsink tab is towards the inside of the board. its hard to see with the heatsink attached, but this picture shows it decently well:

[picasaweb.google.co.uk]

Zach just told you the best way to insert new IC's in DIP sockets.

To get them out again You can buy a proper IC extraction tool, but that costs about $15-20. I've used just about everything from a bamboo skewer to a narrow bladed screwdriver to pry them back out. I'd think that needle nose pliers would be a bit awkward.

I'm working with 40 pin PIC's these days and have found by far that the easiest way to get them our is to use a cheap set of compression tweezers like the sort you can get in any chemists to get splinters out of your fingers.

There is also a proper tool for straightening the legs of ICs. They are supplied splayed so that they stay in the board when inserted by a machine until they are soldered.

The production tool for straightening them for manual insertion is just a metal bar, the correct width, mounted on a plate with a pair of ball bearing rollers either side of it. You just slide the chip along the bar through the rollers. I expect they cost a fortune but would be very easy to make.

I just hold the chip by its ends with thumb and forefinger and press it down against the bench to bend all the pins on one side at the same time.

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[www.hydraraptor.blogspot.com]