Topic: Howto: simple Differential Amp + TTL ?

[Fanny Pack]

What about RS-485? 

[James]

What about you go piss up another tree?

James. 

[James]

The nice thing about the breadboard is that you can wire it up all sorts of ways and see for yourself what happens.

James. 

[Fanny Pack]

Fine.  I am deleting my account from this nonsense.  James sent me an email to fuck off so I will.  Alec, go ahead and approve my deleted account.  As moderator I can initiate my own addition but I need you or James to approve it.

Have a nice day.

[James]

Final PM conversation with Gary as follows:

James wrote:

In case you didn't know, Xer0 has already decided to buy a DAC from me. So have a few other people on this forum.

So fuck off.

James.

Gary wrote:

Yea, thanks.  They all come and buy Spaghetti next.

James wrote:

That's fine.

I wouldn't tell anyone not to get it.

I really don't care about that.

Gary wrote:

And you shouldn't.  But you should at least care enough to put out a decent product instead of the what you are selling.  No differential outputs and not even enough voltage to drive the scanners to maximum angle is lame.  Even if you don't agree with it, the ILDA standard specifies it.  But, as usual, you don't care about what the rest of the world does.

And before I could respond with "This works just fine. It is easy to understand." he bailed.

For the record: No. I really don't care what the rest of the world does. I use math and science to figure things out for myself.

James.

[BlinkenLights]

STOP
There is no reasone for this kind of bickering..

gary has a great product that works well

James has a great product that works well

the two (products) compliment each other very well

the dac DOES drive the scanners a t full angle BTW (mine does anyway)

Spaghetti works great with the sound card dac...

qwitcherbitchen!!

[meandean]

 Using a USB audio DAC on a laptop is a great advantage, as a laptop 'floats' vs a desktop PC.
As long as something on the projector end is earth grounded, then the single-ended output of the
audio DAC should be just fine.

 With that said, there are bigger fish to fry... Some people are carrying on like a bunch of
kids, and that's OK for other forums, but not here... Point and counterpoint are a key part
of what makes this Forum unique; it would be a shame if someone left over something stupid.

 Take a freakin' pill and get over it!!!

                                                                        Dean

[James]

Xer0, I have very little to gain by making a sound card DAC for you. If you don't want it, just let me know.

If you want to do it all yourself, that is fine with me. I would encourage you to be very careful. I'm sure you know well enough to stay away from high voltage. But I would also suggest that you get a decent digital multi-meter. The ones that Radio Shack sell here for $25 to $50 are actually quite good. If you have no knowledge of electronics, I would suggest getting a nice book for beginners. If you work with a small 5 volt power supply and one of those DC/DC converters, you can do all kinds of neat things with op-amps without much worry. Make sure you know what you are doing before you hook anything up to your computer's USB port or your laser projector. I would be glad to continue answering your questions.

Doing this modification to a sound card and so on... is not exactly a good first project for beginners. I understand your enthusiasm for getting this done. But this is not something you want to rush through. You have the rest of your life to understand this.

James. 

PS. For an even safer power supply for op-amps, use (2) 9 volt batteries. Tie the negative of one to the positive of the other. That is the GND. The remaining positive and negative are your +/- 9VDC.

[Xer0]

omg, this is gona be some Quote madness... why FF doens't have an Extension for that.

In case you didn't know, Xer0 has already decided to buy a DAC from me. So have a few other people on this forum.

Ehm... ±. Im interessted, but not now-yet-today, rather for my next Projector which gona be Analog modulated and i want to use the 7+8ch for Audio. it just will take too long for getting your build from USA or i have to spend a hell of shipping for express; in this case i would rather add 100 bucks and get a miniLumax or RIYA and just plug&play. And my PF-114 will come next week so i must have the plans ready over this Weekend and put them together on Breadboard.

Gary wrote:
Yea, thanks.  They all come and buy Spaghetti next.

Yes... at least i want. but going to build my new PC in March first, after the CeBIT, when the cool new stuff comes (Core i7 in 32nm with USB3.0 Chipset and SSD *drool*). Gary, you dont have a License Transfer possibility in Spaghetti, so i could start with my old Desktop and later move on to the new Maschine?

But I would also suggest that you get a decent digital multi-meter. The ones that Radio Shack sell here for $25 to $50 are actually quite good.

We dont have RadioShack but we have Reichelt
I've a Voltcraft VC444 DMM. Has the ususal stuff. i would show you the specs, but its from the pre-millennium Era and there istn any PDF of it on the web. But i think it should do the Job.
Plus, i have a friend who has an Oszi and knows nearly everything about Electronics.
Besides, my brother has an simple DX USB Soundcard for DJ'ing (Headphones to prelisten). With a voltage divider i could use it as virtual Osziloscope, or?

PS. For an even safer power supply for op-amps, use (2) 9 volt batteries. Tie the negative of one to the positive of the other. That is the GND. The remaining positive and negative are your +/- 9VDC.

I wonder why this works in Real Life but not in NI Multisim 10 !!!


So guys.
Lets be calm and friends now and i will try to combine both of your worlds:
Differential Amps for XY (weartronics) with adjustable Gain (James)
and simple Single-Stage Ampchans for the TTL colors. (Dean)

*off drawing plans*


TC
just sees the text effect bbcodes
they are crazy

[BlinkenLights]

That DMM should be fine.

[Xer0]

Well...

Im simulating weartronic's Circuti now, but it works "50%" only
The Vref Spurce gives stable 2.25 like it should.
And the first OpAmp really amplifies

But the second one gives not a symmetrical negative signal, instead just an negative offest to the + one!

any clue?


PS: in the real thing i will generate -5V by using an ILC7660 / MAX1044 !

[meandean]

  The connection between V1 and V2 should be tied to GND. Interesting simulator!

[Xer0]

Well... when i tie GND between V1 and V2, nothing hapens to Output A and B, they stuck at 3.4V

When i disconnect GND from U2- and use the signal generators negative pin for it, the output on A changes, is amplified, shows clipping; but B is stuck at some millivolts.

// Yes a neat Tool! just search katz.cd for it

[meandean]

  Not sure why your circuit isn't working, but try this in your simulator: keep the U1 offset reference
circuit as is, but set it to about -2.25v to start and use this drawing.

  Please excuse my sloppy drawing... 

[Xer0]

Jeah, this done it!

It produces clean symmetrical Output now. On first run there was clipping, due to the fact that TL072 are not R2R and thus need more than 5V to swing full, like mixedgas and ElektroFreak said on PL. so i raised the supply to ±12 and now it can swing up to 7V without clip.
You can see the crossing lines (zero-point) at 2,25V DAC input too and a test with 50k resistors.

Still, i wonder why it did'n work out with weartronic's original drawings. He uses this circuit himself assembled without problems. But on the Sim you need GND to both - opv imputs...
//Pic 5 with the full original opa based Vref-Buffer but your modifications. worx like a charm