Affordable XY scanner - where to buy?

[ElektroFreak]

I think you'll be pleasantly surprised by just how accurate they will be if they're anything like my other cheap 20k scanners. I can't see any reason to buy a $1500-2000 Cambridge galvo set when I could buy 3-4 DT40 40k sets for the same money. DT makes the best Chinese galvos..

Regarding shipping, as Things said they will probably try to keep the shipping as it is for the extra security it provides to both you and Spacelas. Even with $45 shipping, they are still the cheapest 20k galvo set around.

 

[noesc]

I have a set of these.. and SAM at spacelas is great at communication..


I would not order the DMX board the one I got puts out 14V+ over the modulation lines... and has fried a few diodes of mine... However a few zeiner diodes inline 1 for each color.. fixed it..


I have videos on here some where of these running with my 405 and green...

 

[Benm]

I think you'll be pleasantly surprised by just how accurate they will be if they're anything like my other cheap 20k scanners. I can't see any reason to buy a $1500-2000 Cambridge galvo set when I could buy 3-4 DT40 40k sets for the same money. DT makes the best Chinese galvos..

Regarding shipping, as Things said they will probably try to keep the shipping as it is for the extra security it provides to both you and Spacelas. Even with $45 shipping, they are still the cheapest 20k galvo set around.

True, i could just consider it "$133 shipped", but perhaps some money can be saved there. Also, if they use EMS, chances are customs will slap on 19% VAT on the whole thing including shipping, so its going to get more pricey.

As for control: It seems to take 5 volt input signals, but does this mean that 0 to 5 volt controls the entire deflection range? Or does it require -5 to +5 volt to go from one end of the scanning range to the other?

 

[carmangary]

I do not know for certain but I am pretty sure that it would be +-5v and not 0-5v. If they were 0-5v then they wouldn't work with any DACs that are available and no one would ever recommend them.

 

[Things]

If they were 0-5V they would really only work with the FB3 and soundcard DAC, as they aren't differential.

 

[Benm]

Good to know.. i'm fairly new to this, so any info is welcome. It wont be a problem to design a compensation amp that translates the souncard output to a -5v to +5v signal... i hope i can source power for that from the included psu.

Btw, are the brightness signals normally also -5 to +5, or just 0 to 5v?


Also, i mailed with the supplier, the $45 is for DHL shipment. Still inquired about other options for that, not sure how DHL is with customs here.

 

[Things]

Analog signals are 0-5V.

You could use a little 5V to +/-9V converter module, that way you can power the whole DAC from the USB bus. Thats what drlava's correction boards use.

 

[carmangary]

That isn't true. Sound card DAC output is +-5V. Differential output is +-10V. Only thing that uses 0-5V is laser modulation.

 

[Benm]

Well, the scanner specs say "Input: Analog +/-5V" - so it sounds like that will be -5 to +5 volts for the full range, doesnt it? The inputs look like they have 3 wires though, so they can still be differential (one line for ground, one for signal, one for signal inverted).

I've got a total quote of $138 incl dhl shipping and paypal charges. I'll ask for a more detailed datasheet first, perhaps that will state exactly what input signals are required.

You could use a little 5V to +/-9V converter module, that way you can power the whole DAC from the USB bus. Thats what drlava's correction boards use.

I could rig one, but since the unit seems to come with a +/- 24V/1A power supply, i figured that supply could easily miss a couple of mA for the opamps in the correction amp.

 

[carmangary]

There is some confusion.

Single ended inputs have 2 pins: input and GND. The GND pin is tied to ground, the input pin takes a +-5V signal. The difference from the GND to Input pin will therefore vary between -5V and +5V.

Differential ended inputs have 3 pins: (-)input, (+)input, and GND. Each input (-) and (+) takes a +-5V signal. But, because of the way the inputs are inverted from the source, the difference between the two inputs (+ and -) ranges from -10V to +10V.

So, technically, both scanners take +-5V inputs.

Bottom line is that it doesn't really matter too much. If the galvos are single ended, you connect between the + input on the ILDA cable and gnd. If the galvos are differential, you connect them between the + input and the - input on the ILDA cable.

The only time it really matters is when you try to use a single ended DAC with a scanner wired for differential because the DAC will not put out enough voltage to get full deflection. In that case you need to either amplify the input or adjust the scanner gain.

Bottom line is don't worry about it too much because no matter what you get you can make it work by either adjusting your wiring or tweaking a potentiometer.

Hope that helps.

 

[carmangary]

PS There is ONE case that I know of that goes against what I have said and that is with Norm's old parallel port DAC (and maybe singled ended FSX). If I am correct, that DAC put out +-10V singled ended which is very wrong. It is fine if you connect it to a differential galvo set across the +- inputs. But if you connect it to a single ended galvo set you are going to overdrive the input. What was Norm thinking?!?!? But, as long as you know what your DAC puts out and wire accordingly, you are safe. I think the sound cards can also overdrive a bit so be careful with those, too.

 

[Benm]

In the last case: I figured the designer had only one supply rail, and made a 0 to 10v signal to cover the entire range. This would work as long as there is no connection between DAC and galvo grounds, AND the dac only considers the differential input.

As i am planning things this would be useless. The correction amp is likely to be inverting anyways, and provide adjustable gain and offset. This would translate, for example, a 0 - 2 volt signal from a soundcard to a -5 to +5 volt signal at the output (offset 1v, gain 5x). Another opamp would be used to invert that again (no amplification or offset) to get the signal in proper polarity.

With that construction it gives the inverted output from the first opamp, so that should be just fine.

As I see it, this could be built with one dual opamp, 2 pots and a couple of resistors per channel - or a quad opamp to do both X and Y if desired. Something like a TL082/TL084 would provide ample gain/bandwidth product to do this at any speed you could move a mirror.

 

[Benm]

I've just ordered the scanner set

I'll try to document my work with it so i can post something informative for scanner starters here on LPF. The current plan is to get the scanners running from a soundcard dac and compensation amp, but i hope to show some preliminary results using a signal generator (or two) even before that.

 

[carmangary]

You can use the DMX board to play with at first. It will let you see patterns and stuff without having any software or need for a DAC.

 

[Benm]

I could, but since those scanners take analog input voltage, i'm sure it wouldnt be a problem to draw some figures using function generators. Using sines those would be spiro like, but using square and triangle waves in the mix, its well possible to cough up some more difficult test patterns.

 

[carmangary]

Be careful. You can easily damage them that way.