Re: [CAD_CAM_EDM_DRO] Electronics gurus please help

Hi Vajk,

The clock frequencies you are using have no relevence to your problem
and the shapes of any traces. Sound's like you're doing all the right
things but may still be missing a little "boo-boo" on the new pcb's.
The fact that both new boards don't work suggest something they have in
common. Firstly, troubleshooting electronics without a scope is really
hard! Not impossible, but really hard and generally wastes a lot of
time. It's like trying to work on your car outside at night, with
sunglasses on...

Post a question in some of the online electronics groups saying where
you live and asking if anyone with a scope would consider giving you a
couple of hours access - maybe for a case of beer? Let us know here,
too - there just may be someone on this list who lives in your area and
owns a scope and possesses a thirst!

I don't know how you laid out your pcb but regardless of whether you
used a PC based program or red & blue tapes? you must have some artwork
- you'll need a couple of positive images, i.e. same as the final etched
copper. As to tracing a circuit - firstly, make absolutely certain that
the circuit you have drawn up from your first two prototypes is exactly
correct to how you wired your first two prototypes. (You may have made
the pcb to the circuit, but the circuit isn't quite the same as your 1st
prototype.) Next, make a photo-copy of this circuit and buy a red
pencil or pen - not black. As you follow every little line of your
circuit diagram, locate its electrical equivalent on the pcb artwork .
As you locate every single connection, you draw over the associated
part of the circuit diagram with the red pencil. When done, your entire
wiring circuit is covered in red lines and you have verified the circuit
for correctness in one regard.

Now starting with a fresh circuit diagram (copy) you kind of do the
reverse - tracing from the circuit board back to the wiring diagram.
Especially watch for small bridges between tracks and pads etc. If
there is an extra connection, this second check will usually catch it.

I know this is incredibly boring and tedious, but I always do the first
test before I send a board out for prototyping and it always catches
something that I have missed. Also, I then find my prototypes often
work first time - provided I have designed things right. Not always the
case...

Keep us posted.

Cheers, Peter



letting you


life




Vajk Fekete wrote:

>hi,
>
>i am building a stepper driver for my homemade mill, that i am going to use with EMC.
>
>i have salvaged some steppers (60ozin, 6 wire), and also the driver chip from old printers.
>the driver is a sla7026, 3A max chopper, unipolar.
>
>question1: is a chopper unipolar driver much worse than a chopper bipolar drive?
>
>question2: a bit longer, and i badly need advice here:
>
>i have built an axis drive on veroboard, with rather long wires, etc, and it worked ok.
>then i made a rather simple pcb, built a sigle axis on that, and after correcting some errors, it works ok.
>then i made a final design for the pcb, built one axis, and it does not work. built another, and the with same symptoms it is not working.
>
>so experts: at a chopping frequency a couple 10Khz, could the pcb layout have this much influence? i checked all the components, all the connections, spent about 2 days on it, so i am 98% that the
>working and not working circuit only differs in the shape of the traces.
>
>i am no EE, but have some electronics building experience, more from the digital world. and i do not have a scope, so cannot check if the timer is working ok or not.
>
>any ideas are welcome,
>
>thanks,
>
>vajk
>