Combined CNC Engraving Technologies. Spindle + Laser

**JJWMACHINECO** · 22-12-2014

We only drive each Nichia at 1.7a each. That is the max the Data sheet recommends. We never tried wiring 2 diodes in series to one driver, so I can not answer that question. LD's are expensive to replace, so experiment at your own risk. We only have used a dual driver or two single drivers for driving the two Nichia's.

We have Lasorbs on all of our Laser Diode engravers.

Here is our new updated PDF if it will help you any. It has a schematic for the DAC and where to buy the Digital Potentiometer.

http://www.picengrave.com/Pic%20Prog...r%20Setups.pdf

Search here for Laser Diode driver schematics. There is allot of information in the Sam's Laser FAQ.

http://lmgtfy.com/?q=analog+modulati...iver+schematic

The DAC is 8bit (256) resolution for modulation voltage change between the 0-5v. The encoder is 10bit (1024) That's four times finer incremental voltage changes. It must be one of these US Digital MA3 absolute magnetic shaft encoders. We are not familiar with the Galil board, but if it has step and direction pins/ports, a DAC can be wired to it or another stepper/servo motor and controller to drive a MA3 encoder.

**Boyan Silyavski** · 05-01-2015

Hi,
thanks for the info. I bought almost all of the necessary parts. I will go by the digital pot way.

Edited:
ok i have it clear now why the step up converter. To provide +- and ground to the opamp. Just figured that if using PC ATX power supply to power everything it has +-12V so the step up converter is not needed.
I think of powering the diode and the DAC from the same ATX PSU. Will see how it works. Will use Lasorb of course.

**Boyan Silyavski** · 26-02-2015

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

**Neale** · 27-02-2015

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.

**Boyan Silyavski** · 27-02-2015

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.

**Neale** · 28-02-2015

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.

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.