Topic: UK Newbie wants to build a correction Amp

[harani]

Hi All


I'm new to the forums.


I have a red/green(yellow)  DJ laser that I have been running off DMX to show it's inbuilt patterns. Now i want hook up the ILDA port on it and see what it is really capable of.


It has proper galvos not steppers, though i am unsure of their speed (any easy way to check this ?) and the lasers seem to be TTL controlled.


As it says in the above title I want to build a correction amp.
All the links to components i've seen in the forums so far seem to be US sites. I wondered if there was anyone here could recommend some UK suppliers for the components, especially  for the DC-DC converter.


Also some recommendations for a suitable USB sound card please ?


Many thanks in advance.

[James]

You should contact staroflaw and llawlander on this forum. They just completed a very nice home made system with a sound card and correction amp; plus they made their own analog diode drivers so they have full RGV analog!

They are from the UK.

James. 

[harani]

Thanks,

I'm just putting a parts list together based on the info you gave in this post

http://laserboy.org/forum/index.php?topic=277.msg3263#msg3263

In your parts list you have 6 x  10uF capacitors
but in the accompanying diagrams i can only see 3 being used for the DC-DC converter circuit.
Please can you advise  where are the other three are used  ?


 

[James]

The others are used on the negative voltage regulator that gives you the -Vref to mix with all of DAC output signals.

Do you Skype?

I'd be glad to talk to you about all of this!

I'm james_laserboy

James. 

[harani]

Hi James,
 
 
Sorry my previous posting was incorrect i meant to say I can see 3 caps being used in the -Vref circuit diagram. So where do the other three come into play ?
 
I have the -Vref Diagram and the Op-amp diagram. am i missing something else. is there a diagram ffor the DC-DC converter ?
 
and also do these diagrams supercede this circuit i found on your site ?
http://laserboy.org/p_laserboy_95.html
this circuit uses Zeners which aren't on your parts list as well as different value caps and pots
 
Would this be a suitable soundcard ?
http://cgi.ebay.co.uk/USB-7-1-channel-Sound-Card-Box-SPDIF-Hardware-8Channel-/280547481708?pt=UK_Computing_ComputerComponents_SoundCards
 I notice a lot of 7.1ch chards are actually only 6channel anolog and the full 8 channles are only accessble from the SPDIF signal. This one however seems to have full 8 channel analog out

 
I don't use Skype but I can easy install it if need be. I'll get my parts together first and i might give you a shout. Good to know there's someone at the end of the line if i get stuck.
 
 

[James]

Hello harani and welcome to the LaserBoy Forum!

Looks like you found a winner! You are absolutely correct about the whole 6 / 8 channel thing.

Yes. the other three tantalum caps are for the DC/DC converter.

The schemo drawn in pencil is the very first design by Dean Hammonds.

I've made so many prototypes of this thing, I've tweaked it up a bit and made it more precise.

The schemo for the DC/DC is very simple. It takes GND and +5VDC from the USB line as input. There is a 10uF tantalum cap across the input pins. And it produces its own GND, +9VDC and -9VDC. There are tantalum caps across each of the + & - 9V to GND. NOTE: Tantalum caps are polarized, so put the negative lead on the most negative side of the voltage.

Since the newer version of the circuit uses a negative voltage regulator, you can adjust it for just about any reasonable DC offset you might find on any sound card. When the original circuit was designed, it was assumed that all sound cards had a DC offset of about +2.25 to +2.5 VDC. Later, we found that to be not true. Some of the USB sound cards out there are powered by 3.3VDC and therefore have a DC offset of only about +1.25VDC.

Tell us a little bit about yourself! How did you get into lasers? What kind of equipment do you have? What do you expenct to accomplish? Also, please post a lot of pictures! We love pictures!

James. 

[meandean]

Since the newer version of the circuit uses a negative voltage regulator, you can adjust it for just about any reasonable DC offset you might find on any sound card. When the original circuit was designed, it was assumed that all sound cards had a DC offset of about +2.25 to +2.5 VDC. Later, we found that to be not true. Some of the USB sound cards out there are powered by 3.3VDC and therefore have a DC offset of only about +1.25VDC.

  Just a footnote: There are a number of 6ch correction amp kits that were offered by drlava and 300Evil that used
the same resistor values as in my original print. If you have one of these boards and want to use it with a soundcard
that has the lower 1.25v offset, you can replace the 10K resistors leading from each channel of the soundcard to the
correction amp (R6 on original print) with a value of 5.7k and everything should fall into place. Many newer soundcards
are full 8ch; 7 & 8 are a bonus pair commonly used for stereo sound, so they can be piped right into powered speakers
without a correction amp.

                                                Dean

[harani]

Tell us a little bit about yourself! How did you get into lasers? What kind of equipment do you have? What do you expenct to accomplish? Also, please post a lot of pictures! We love pictures!
James. 

I guess I got into lasers in a big way after seeing my first Tangerine Dream concert.

My first personal laser was a simple pen pointer I bought on vacation in New York probably about 14 years ago  I remember being blown away I could "spot" water cooler towers half a mile away with something that I could hold in my hand and the first thing I did when I got home was build a "spirograph" to project it through.
My next purchase was a proper laser crab and I soon had the puny 1mw diode out of it a replaced with the guts of my laser pointer. ,  Although it produced nice patterns they only projected onto a single place so my next build was a slow moving pan and tilt mirror to clip in front of it and sweep the pattern around the room. This was operated by serial driven servos and controlled from a laptop running a BASIC program I wrote to define the sweep patterns. It later got further upgraded with a nice green diode


My next purchase was a 40mw green DMX laser. It only used stepper motors and the built in patterns left a lot to be desired but looked good on simple stuff like fans, time tunnels and liquids skies. And if I pulled the pattern down into a spot I could X-Y control the beam using fast computer controlled DMX. I still use this at parties but in conjuntion with Diffration gratings to get lots of nice beams because as I say the patterns aren't that great.


My lastest is a CR-TEC "Super-3" laser this is  a 150mW 635nm Red + 120mW 532nm Green with "high speed gavlo scanners" whatever that means, I haven't been able to determine exactly what speed they are yet and have so far only been running it on DMX with the built in patterns. The built in patterns are only 8bit so I'm expecting much better out of it when I get it working through the ILDA port


In conjunction with my other hobby,  old Arcade games http://www.arcade-museum.com/members/member_detail.php?member_id=356481 what I would love to get working once my correction board/soundcard is built, is a large asteroids or Battlezone projection :-)

[James]

Fantastic!

It sounds like you have a very good grasp of electronics and some computer programming skills!

You'll get all this stuff; no problems!

You know there is a game called Laseroids that will run with the modified sound card DAC!

James. 

[harani]

most of the components arrived today, however my supplier was out of stock of the DC-DC converter. It's on back order but could take a couple of weeks. i guess i can use batteries for now.

So, just waiting for the soundcard to arrive and I can crack on.

is there any way to interface a soundcard/amp to MAME ?

[James]

If you are using a regular PC with a typical ATX power supply, you can also get +12 / -12 VDC from that.

MAME? That's a good question!

I think so.....

rMuD was one of the guys who wrote the original LaserMAME.

James. 

[harani]

I'm just using a laptop for portability but I do have an arcade cabinet PSU that will give me +/-5v

I could use that until my DC-DC converter turns up. I  guess it will work but give me less deflection ?

[James]

If you are using TLO72 op-amps, you will also not be able to get to the full +5VDC on the color signals.

Some op-amps can go full swing rail-to-rail before clipping, but not the TLO72.

I think your idea of using batteries is a good one. Just two 9V batteries should be fine.

James.