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Could I use pots for adjusting the X and Y sizes when using a sound card dac playing converted ADAT shows?
I was thinking of putting a pot in the Y+ and Y- and I should be able to use those to adjust my height correct? Same for adjusting the left / right with the X+ and X-?
Any suggestions on what pots to use?
Gene
The cmrr of the input amps is very dependent on both x- and x+ being exact opposites.
It will be hard to achieve this with two pots.
Not really a problem if you run short cables.
If you value hum suppression and run long cables, high cmrr is preferred.
Sure you can. You just need to use a duel gang pot for each -+ on x and y.
Like this:
Attachment 24365
chad
For once (and perhaps the only time, in your life) the Shack is your friend. These work good. So you need to chuck the matching knob in a drill press and drill it out .010 more, no big deal.
http://www.radioshack.com/product/in...ductId=2062359
100K dual, and even the new metric ones are very good.
Need short cables, to a certain extent, or buffers at the sending end for long runs, but still not bad.
Steve
2 questions:Quote:
Originally Posted by mixedgas
1. Do I need to use the grounds on the pots or can I just leave those with no ground connected to them? If yes I need to ground, to pin 25?
2. I use a 50' cable. Too long?
Thanks!
1. Best use 0vdc rather than ground on the pots.Quote:
Originally Posted by Phredy1
Wiper = output, input signal one end, 0vdc other end.
If you want to use ground for something try grounding one end only of shielded cable.
2. Depends so much on surrounding em noise that this would be difficult to answer correctly. Best try it and see! Worse case scenario you would need to buffer the sending end as Steve suggested. If you do this you would not necessarily need double pots since you would attenuate the single sided input signal to a buffer/inverter.
This also has the advantage of giving you the possibility of increasing the output signal for any insensitive scan amps and also gives exactly inverted outputs instead of approximately inverted outputs. (Double linear pots are never "exact" twins.)
Trouble is that a laser bounced off a scanner is one of the most sensitive galvos you're ever likely to meet.
PS.
1) Do NOT use logarithmic sound pots.
2) If you are installing pots might as well install inverter switches for back to front and upside down.
3) You might want to consider offset pots as well if you go down the "buffering" route.
4) Buffering only involves quad op amp chips (and sockets) and a few resistors but does require a +&- psu.
Best of luck
Cheers:)
I had all ready thought of putting a DPDT switch in to invert X, but never gave much thought to invert Y. I guess if the projector was ever hung upside down that would be the need to invert Y. The invert X came into the plan when I was thinking of projecting onto scrim.
This started out in my mind being a fairly simple idea, but like normal my ideas get more complicated when I try to put them into a build. I think I will just try Steve's suggestion for the double gang pot and see what happens. What is the worst that could happen? Or should I even go down that road.....LOL
Thanks for all the advice!
The worse that happens is you waste a gallon of gas, a hour of your time, and less then 10$ on a radio shack potentiometer and two db25 connectors. call ahead and make sure they have it in stock.
Steve
I complicate mine even further by hanging multi turn trim pots on the main pots so as to be able to choose the "range of the main adjust. (sometimes get "glitches" in the track just in the wrong place, and thats an itch you can't scratch in real time. *vigil
Good luck *DZ
Cheers :)
PS Isn't " a gallon of gas," worth more than a laser these days ?? >:)
I spent a few hours driving around looking for pots and nothing. A ton of singles and some duals, but no dual linear pots anywhere that I could find.
Would this work?
Attachment 24370
$1 each from Futurlec!
Gene
Quote:
Originally Posted by Phredy1
Looks OK to me..... go for it! :cool:
Much cheaper than "driving around" I suspect.
Cheers :)
"Looks OK to me..... go for it! :cool:
Much cheaper than "driving around" I suspect."
I totally agree those will be just fine. It might be a little harder to find a knob but should be no big deal.
chad
Finally got it built and working.
Question: When I turn down (add more resistance) either the x or y, the image gets distorted some. A little wrinkled up is how best to explain it. Before I built it I measured each side of the dual gang pots and found there to be up to 1k difference. Would single 1k pots work to fine tune each side? I'm thinking the distortion is coming from the difference in resistance between x+ and x- in each dual gang pot and 2 single pots would even it out.
Check your connections. DZ built me a splitter box with similar pots that had something of the same problem and I found a bad solder joint after awhile. I re soldered the connection and the issue cleared.
You would be better off using a differential amplifier to convert to single ended, then thru the pot,and driving the scanners single ended..
Quote:
Originally Posted by Phredy1
I find the (add more resistance) comment a bit worrying here! *vigilQuote:
Originally Posted by Phredy1
Each pot should be wired with input at one end and 0vdc at other end so you are never "adding resistance" you are effectively "choosing" the size of the signal which is progressively smaller as it travels through the pot resistance from max at one end to zilch at the other. :cool:
Are you sure you have them wired correctly ? :confused:
As for adding a trim pot... you can do this but if the problem is linearity not overall resistance you would have to readjust your secondary trim pot for every new position of the primary pot which is a bit of a hassle to say the least and rather defeats the idea of using double gang pots in the first place.:p
You can check the linearity by using a couple of batteries (less than max signal voltage obviously) where the centre 0VDC would be where the +of one battery connects to the - of the other. When outputted to the scanners if the laser waves around when you "attenuate", then the pots are NOT linear, if beam stays in same place then they are linear. If the beam slowly moves to one side it just means that the batteries are not identical voltage so if you swap them you should get the reverse movement meaning that the pots are linear. >:)
Hope this helps!
Cheers :)
Attachment 24968Quote:
Originally Posted by catalanjo
The wiring diagram I found online showed pin 2 and 5 as input, so I have X+ at pin 2 and X- at pin 5. Then measuring each output I found that pin 3 & 6 is normal size at full turn on the pot knob to the right (all the way up) and smaller as I turned the knob to the left (down). Using pins 1 & 4 as output was the opposite.
So, I wired it:
X+ input pin 2
X+ output pin 3
X- input pin 5
X- output pin 6
and the same for Y.
My first attempt at wiring had grounding issues, so it ended up taking the 2 pin 25 wires tied together and then attached to one of the nuts holding the DB25 connector to the metal case and that seemed to solve the problem. The pots are only grounded by the nuts holding them to the case now and that is working best I can tell.
I'm guessing my wiring is messed up with a capital F?
Well sort of :poop:........:embarrassed: .. or to be honest YES !*retardoQuote:
Originally Posted by Phredy1
This may be just a terminology problem here! *vigil
The numbers are almost invisible on your post but blowing the pic up a bit I could see that pins 2 & 5 are both wiper (middle) pins. >:)
These should be the OUTPUTS of the pot (but they are also equally the INPUTS to the scan amps).:confused2:
Unfortunately this causes confusion :confused:,since just about any wire is an OUTPUT from one thing but an INPUT for something else, which in turn causes the capital F occasionally when someone takes the name as gospel without thinking much about the circuit. :rolleyes:
The end pins 3 & 6 should be the X+ and X- coming from the DAC so that the wiper (going to the scan amps), when fully clockwise, connects to these pins (= full on).
Pins 1 & 4 should be 0(zero) VDC (not ground) so that the wiper connects to them when pot is full anticlockwise (= full off) or just a point (a bit dangerous this, so perhaps your extra trim pots would serve as a preset "minimum" size limit. :doctor: The zero volts should connect through them to the main pot (wired as variable resistor = just one end and the wiper). :glasses-cool:
I think you should go a bit bigger than 1k for this however (eg.10k) since otherwise min size would be less than 1% normal size) which could be dodgy for an eyeball.:cyclops:
That wiring you used would neatly explain the "wrinkled up deal" :excruciating: as you moved the wiper toward the zero volt end you were inadvertently shorting out the output from your DAC (not nice for the DAC's output op amps!:beat-up:). They will be much happier :kissing: when they have a full 100k between them and zero volts so they don't have to bust their balls trying to maintain their output voltage with an ever increasing current drain as you turn the size down.:bulgy-eyes:
The idea here:glasses-cool: is not to modify the DAC signal :thinking: just to choose how much of it you want to use. :good:
I hope this explanation helps! :fingers-crossed:
Cheers :)
Ok, where do I find a 0v wire in the 25 wires? I don't remember seeing anything like that on Pangolin's ILDA pinout for DB25 on their web site. I'm on my phone now so I can't double check now.
If I wire it correct, what adjustment will I get - X & Y size or position? If its one or the other, is there a way to be able to adjust both size and position on X & Y?
I went back to Pangolin's QM2000 pinout page and the only thing I can see that could be 0v would be either the cyan, deep blue or yellow laser 0 - 5v control wires. Just guessing that any of those would be 0v if they are not being used. Everything else seems to be used or grounded to pin 25.
My incorrect attempt at wiring was thinking reostat (variable resistor) instead of wiring it as a voltage divider (I'm guessing this is the goal).
FYI, I know just enough about electronics to be dangerous....
Hi PM sent :D
Hope it helps, it's a bit tricky to describe circuits with words and I don't know how to post drawings as yet!
Yeah you can get both size and position but not without PSU and opamps.
So best just go for size for now ! *retardo
Cheers :)
I'll take a picture of the pots on my splitter box here in a minute; it should help you out.
Quote:
Originally Posted by allthatwhichis
What's a splitter box ? :confused:
Cheers :)
http://www.photonlexicon.com/forums/...color-palettesQuote:
Originally Posted by catalanjo
This is not a normal splitter box; it is something I requested custom from DZ.
Quote:
Originally Posted by allthatwhichis
OK...LOL ... so what is a "normal" splitter box"? :confused:
Cheers :)
Something that splits your DAC signal to 2 or more projectors. Here is a PIMP splitter from, again, DZ...Quote:
Originally Posted by catalanjo
http://www.photonlexicon.com/forums/...=Ilda+splitter
Just from a quick look at that page, what you achieved is not what I'm trying to make work. And of course it is normal for what I think is a fairly simple project, turns out to be rocket science. Fairly simple I can do. Rocket science is WAY out of my league.Quote:
Originally Posted by allthatwhichis
catalanjo: you have a pm but I'm going to send you another and see if you are interested in something.
Quote:
Originally Posted by Phredy1
Hi Gene sorry to have confused all this with extra complications. >:)
Just connect pins 1 & 4 together on each double pot ! *DZ
Pins 3 and 6 should come from the DAC (and also go to a second set of pots if "splitting") :cool:
Pins 2 and 5 go to the scanners. *warn
Do not connect pins 1 & 4 of the separate pots all together ! *vigil
Do not turn the sizes down too far cos you will get a single point as a result. *vigil
The rest is all extra cosmetics and not "absolutely" necessary just "nice". :cool:
Cheers :)
Quote:
Originally Posted by Phredy1
The box does much more than you want, but it has a set of pots to change the x and y size to one of the scanners recieveing output fromt he box so I can set the main size in Pangolin and then match the one scanner size to the other so they are the exact same size.
The pots are:
http://www.photonlexicon.com/forums/...0&d=1305083044
The connections are:
http://www.photonlexicon.com/forums/...2&d=1305083046
Works like a champ. *retardo
Connecting pin25 (ground) to the signals like that will only work well if you have only ONE earth/grounding point in the entire setup, otherwise you will end up getting noise into your signals !*vigil
Cheers :)
Quote:
Originally Posted by catalanjo
I promise... :cool: but I didn't build it; I just use it.Quote:
Originally Posted by allthatwhichis
Ok, your box does do what I am trying to achieve. As a matter of fact your wiring diagram is exactly the same as what I am wiring mine - except you are using pin25. I am going to try a virtual 0v instead of ground first. If that don't work, plan W is going to be pin 25. Thanks for everyones time sorting my wiring out for me!Quote:
Originally Posted by allthatwhichis