Laserharps Pre-order!

[colouredmirrorball]

Yes but it doesn't use a differential input apparently. Should I just connect + to either X or Y? Would that work?

[Things]

You could try that.

The voltage differential between + and - is +/-6V, if you went between + and say, GND, I think you'd loose 1/2 the beams. I haven't actually tried this, so not exactly ure.

If the inputs can handle say, a 12V differential input, then you should be able to go between + and -.

[Carl B]

@ Colouredmirrorball
To me it sound like you are using single ended 12k scanners with both X and Y amps on one board, correct?
If so you just want to use the Galvos + and G on the harp PCB and wire them to the X and G of the scanner amp. You won't be making any use of the Y input.

Hope that helps you a bit more.

Carl

[colouredmirrorball]

@ Colouredmirrorball
To me it sound like you are using single ended 12k scanners with both X and Y amps on one board, correct?
If so you just want to use the Galvos + and G on the harp PCB and wire them to the X and G of the scanner amp. You won't be making any use of the Y input.

Hope that helps you a bit more.

Carl

That's correct. I hope that works!

[Carl B]

Well I've got my harp working now, well sort of.
I'm having a few issues with it at the moment.
1. My scan pro 20's don't cope to well with scan speed and the blanking speed is to fast for the laser as well. Can the scan speed be lowered?
2. I lose one beam and almost a second one at one side. I have yet to try changing R4 but don't have any 5k resistors.
3. One of the FX notes is not stopping when the harp has finished opening and dose not stop even when I shut the harp.
4. Also having sensor issues with pulsed notes instead of continuous ones when I leave my hand in a beam but I think this could be due to me not having a 100k res to fit to the sensitivaty Pot.
Apart from the above the harp works as expected. Buttons working fine, LCD working fine, RGB LED working.

@ Dan
Can you give us more details about the two blue pots that are used to fine tune the sensor and can you point out pin 6 of the DAC IC.

Carl

[Things]

1. I'll have to have a think about that one, I've never had a problem with that myself, so I didn't really see the need to adjust it. I'll have a think about it.
2. Try adjusting R2 a bit, and you should get the missing beam back. This is the DAC reference voltage, and if this pot is set too high, it exceeds the supply rail on the board. R5 should also seperate the beams if 2 are too close together. I've found this varies with galvos, so if it does move it apart, but not far enough, you may need to put the 5K resistor in.
3. I have a feeling this may have something to do with software. When the harp turns a note off, it simply sets it's velocity to 0. I'm not 100% up to date on MIDI protocols, and whether this is what most software expects.
4. Try using something like a white business card and see if it works better. 99% of the time this is due to the reflection off your hand _just_ sitting on the sensor threshold, so even slight movements are enough to vary the intensity around the threshold. The bigger the room (Or black ceiling etc), the higher you can set the sensitivity.

This is the typical pin numbering for DIP packages:


EDIT: R13 is probably the only potentiometer that'll make any noticeable difference. It is used to set the threshold when the transistor is turned on and off, sort of like a 2nd sensitivity. R10 is kind of pointless and will probably be replaced in future versions. You should be good just setting that at 1/2.

Good to see the rest of it is working though

EDIT: Unfortunately, it seems that changing the scan speed is going to require an update on the main code. I'm talking to csshih about a possible resolution to this, so I'll let you know what we work out.

Really sorry about that, as I only had 30K galvo's on hand, I completely overlooked that factor. However, I'll be doing everything I can to resolve this

Cheers,
Dan

[Carl B]

Hey Dan, it's good to see you are trying to help with bugs and problems we may be having.

Some good news is that I have now got 10 well defined beams. I had to adjust R2 a bit and a bit of retuning of the scanner amp.
I still have 2 beams at one end still a bit to close together but I'm hoping changing R4 to a lower value will resolve this. At the moment the outer of these two beams looks to hit a wall as it gets to the end of the opening cycle.

With regards to the scan speed of the harp. When the harp is in the process of opening or closing the scan speed is considerably slower than when it is in the fully open play position. I know you where looking to avoid the harp from looking flickery but if the play position speed was left the same as when its opening this would greatly reduce the dimming affect of the laser and would be less stressful for the lower speed scanners that I and other people are using.

I will keep you updated with any more progress.

Carl

[Things]

Carl, yes, I've noticed that scan speed change too. I'm not 100% sure why it does that, and I'll be looking into it for sure.

Regarding the squished beam issue, replacing R4 with a lower value is 99% guaranteed to fix that issue

If enough people have the same problem, I'll supply a lower value as default in the next run, so let me know.

Cheers,
Dan

[Carl B]

@ Dan.
Here is a web page that may be of use to you about MIDI protocol.
http://www.gweep.net/~prefect/eng/re.../midispec.html

According to this page there is a definite Note Off command that should be used to stop a note playing. This may explain the reason why I am getting a stuck note when the harp is opening.
Just changing the velocity to 0 technical dose not stop the note.

Edit : Just reread the web page above and it says that a note with 0 velocity is concidered as Note Off. Sorry for doubting you.

Carl

[Things]

I have a theory as to why this might be happening, I'll do a bit of mucking around with the code and see what I can do.

Cheers,
Dan