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Laserboy correction amp - Does it incorporate -12v for full galvo swing?

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A friend of mine says although this style correction amp uses -12v, it does not incorporate -12v (or is it -5v?) into the output, meaning your scanners will only get a positive voltage, limiting your scan angle.

Is he correct?

I can post the schematic but I assume someone will know this off the top of their head. for now here is a link, scroll down to post #13 and #14 Correction Amp

Thanks in advance.
 
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They were probably making mention that with the stock dual rail power supply IC that is lower in voltage, you may not get the +/-5v swing.

With the recommended alternative power IC, you can get the +/-5v just fine. I just built one and scoped it.
 
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Thank you so much for your reply and helping me out.

#1) Which alternative IC? Would the TL082 give the improved voltage or is the TL072 fine?

#2) So there is a positive and negative signal coming from one single connection which is fine BUT the galvo driver connection is as follows:
(+)(G)(-)
And we are doing this:
(+-)(G)
and then leaving its negative connection free, surely it has that separate negative connection for a reason?

Fabian.
 
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1) uCLinux is talking about the DC-DC power supply IC (NKA0512SC), not the opamps (e.g. TL072 or TL082). I believe the original used a +/- 9V IC which limited the scan output. Both op-amps have the same output voltage range for a given input voltage range, so I don't think swapping one for the other would help.

2) The galvo input is differential, so you connect to the + and the -, and can leave the ground floating. For example, if you're using something that doesn't have negative voltages, e.g. 0V is the far left, 5V is the far right, and 2.5V is the middle, you would connect the 2.5V virtual ground to the - input, and the signal to the +. That way the differential voltage would reflect the signaling. If you have an input that swings around 0V, with +/- voltages, just connect the signal's ground to the - pin, and the signal to the +.
 
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Bionic is right. I used the NKA0512SC IC (+/-12v) for mine and I get the full range (+/-5v)

I have the gnd and - pins tied together and the signal line that comes out of the op-amp tied to the + pin. I have to admit, that was the part that confused me the most of everything too... and the ilda docs did not help!
 

Benm

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You can use the dc-dc converter if you want the amp to be powered from USB - good if you want a standalone unit that provides the ilda signal to a connector you can use for any projector you like.

If you are building only one projector however, i'd suggest building the usb sound card and correction amp into the unit. This way, you can easily power the correction amp from the already present power supply. Personally i used 7815 and 7915 voltage regulators to create a clean dual supply for the opamps out of the -24/+24 galvo driver supply.

The correction amp only uses a few mA on either supply line, so the extra load on the existing mains supply is no problem at all.
 
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Hi Ben and thanks for the reply, as to everyone else!

I decided to scrap the laserboy correction amp and use your (ben's) TL082 correction amp which you posted a while back!

Thanks all for your help.
 
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It might be worth noting that if you use a PCI sound card and put the correction amp inside the computer case, you can get +12 & -12 VDC from the PCI slot. Since you need to tack wires onto the sound card to get the direct coupled signals out of the DAC channels, it's no big deal to tap the voltages too. If you tap the PCI card directly instead of tapping into the power supply, the whole thing comes out in one piece when you remove the PCI card. Just look up the PCI slot spec. It works. I made a few like this. It's kinda neat. You can use a motherboard parallel port header ribbon to a slot mounted DB25 and your computer will have an ILDA port!

OMG! Did I just write a whole forum post without using the word....... LaserBoy ????


........... nope! ...........

James. :)
 
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Cool idea James, thanks! What's the story with that avatar? Its my favourite!!!
I feel rather honoured that I received one of your 39 posts here on LPF. :wave: yay Love your software and I have been reading tons on the laserboy forum.
Have come a long way. Long way to go. ANYWAY!

QUESTION: Does anyone know a simple way to switch off power to lasers if the USB cable is mistakenly unplugged during a show? The way the beams shoot out at a strange angle at high-power is seriously concerning. I use a laptop and its very 'iffy'.
Possibilities include a relay connected to soundcard USB power and then connecting it to my laser +12v and the other possibilities... okay that's all I can think of. Will this work? I gather there is no simple driver solution.

Always a work in progress hey :)

cheers from South Africa.
 
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Humphry, you use the 5VDC power (VBUS) provided by the USB cable (assuming this is the USB device, not the host) to switch a transistor or another switch. When the device is disconnected from the computer or USB hub it'll kill the VBUS power input. Here's the connector wiring diagram.
 
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