Need suggestions for creating blanking from 5V ttl with non-ttl laser module

[michelrietveld]

so will a red laser ttl driver than also work for a green pen?

[michelrietveld]

so for the blanking part 1 i will try to use the blank/fading mirror approach
this is to be done by connecting a galvo amplifier to the 0-5v ttl 0(blank) 5v(laser) output of the pt-itrust controller.
As suggested i will use a 10K potentionmeter for tuning.

But, when i look at the amplifier schematic i am not sure where to present the signal to.

I have attached the schematic as a tiff file for the people who would like to take a look and share some advice. the galvo is a g120dt.

[mixedgas]

connect ground to Jp1 ground and JP1 -in, connect signal to JP1 +in.

Steve

[JasonB]

See there are a few kinds of TTL used in the laser world. The real TTL switches at 1.6 and 2.4 volts. Fake TTL is high speed CMOS logic and switches from about 100 mv to 4.90 volts.

If you have "fake" TTL you will need a potentiometer to reduce the signal to your blanking galvo amp, and then you will be ready to go.

If you have real TTL, you may need a simple "LEVEL SHIFTER" circuit to develop enough swing

IF, and it is not likely, but IF you need a level shifter, here is a simple one:

* AHA! * Steve, this post just made me realize something I've been thinking about and trying to get working for over a year
I've been struggling with getting my blue laser to blank correctly for over a YEAR; the red and green work perfect. All lasers are different and chinese as well.
The red runs on 5VDC and shares my common +/- 5VDC power supply for my opamps, comparators, etc. , green runs on 120VAC and accepts the common 5VDC blanking just fine..
But that Blue....I have not been able to sort it out.... It requires a 12VDC supply and I've breadboarded comparators, inverters (as current sinking buffers), tried sinking/sourcing it's TTL input and only can get 'flakey' blanking response at best.. It drifts over time.

Maybe just sharing the 0VDC reference for the multiple power supplies is not sufficient, perhaps I should try that level shifter circuit and reference the blue laser's 12VDC supply to the transistors collector, set the pot, and see what happens.
I wonder if its possible this laser requires 'its own' power source to complete it's TTL input circuit ? Its hard to say without being able to look at a schematic of the laser.

Does it make we weired that I want to leave work right now, drive home, and breadboard this circuit ? ** This could be the final tweak to my homebuilt RGB to make it work correctly! **
Steve you are THE MAN!

Steve this post is right along the lines of a previous post you made:

thread 13712

Chinese low cost blanking wants to see a current sink instead of a current source. Since most laser systems output a source, you need to add a simple NPN transistor to ground to "invert" the blanking signal, or use a TTL buffer chip between the laser software and the laser.

For some lasers, a 2n2222 with a 470 ohm base resistor is all you need. Emitter to ground, collector to the laser, base to the laser software via the 470 ohm. In some cases you may need a pullup resistor, perhaps about 1K on the collector to +5. Most lasers have the pull up, and the opamp in the FB3 is not good at fighting them. The FB3 meets the TTL specs, but the Chinese lasers can need more then 20 mA of sink to turn on, which is outside the limits of most opamps.

The Chinese lasers really want to be driven by a TTL totem pole output stage, but only in sink, they do not need the source side, so you need to fake one. Open collector TTL inverters are good for this, as are AC, ACT, HC or HCT series CMOS.

Steve

-Jason