Combined CNC Engraving Technologies. Spindle + Laser

Hi,
some help here please. I am not very good with electronics.

I am looking at the pdf and i see some difference between the 2 drawings

some questions:

-the caps on the 1st /hand/ drawing go to ground and on the second not? I started soldering like the first, then saw the difference, so which one is correct?

-there are 2 more caps on the second drawing /DIR , STEP/ ??

-i will use +-12v from PC ATX instead of 7-9v do i need to change something? UA741CN

http://www.mycncuk.com/attachment.ph...id=14735&stc=1
http://www.mycncuk.com/attachment.ph...id=14736&stc=1

It's difficult to answer the question about capacitors as it's so difficult to follow the second diagram, but it looks to me as if they are doing a different job. However, I think that they should all have one end to ground. You can probably use the capacitors in both diagrams - in the first, they are power supply decoupling caps which are a good idea, and in the second probably to reduce noise and small random fluctuations on the output which you often get when a variable resistor is involved.

As for power supply - the original diagram shows +7V and -7V. You could replace these with +12V and -12V from an ATX supply. That should work fine and is well within the 741 ratings. You can't use just +12V and ground; the 741 would be happy but the output would not go right down to zero.

Thanks Neale,
Meanwhile I have soldered everything as per second diagram.

Now i wonder how to test and adjust everything without burning my BOB or the laser driver. I still dont have the diodes. It seems i have to install the program and start from there.

I still don't understand what these pots do. The one at the output seems to adjust the max voltage output, right? I mean its still not clear how to adjust them.

I am frustrated at the point of freelancing sb to make PCB drawing and even revising all and making me a PCB where double laser driver and this is integrated in one so its very simple to connect and operate. Not sure if there would be enough public for this but i am ready to jump and sale it slowly later or some kickstarter campain.

Quote:

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Originally Posted by silyavski

I still don't understand what these pots do. The one at the output seems to adjust the max voltage output, right? I mean its still not clear how to adjust them.

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The pot connected to the input of the 741 is to adjust the output to zero, and the pot at the output is (as you say) to reduce the nominal 0-5V output range to 0-something less, that is, reduce the output swing. I assume that the "digital pot" device has an output range of 0-5V and the output of the 741 will follow this.