Laser Harp (Open Source) !

[HIMNL9]

.....
The upside to using a camera is you can use things like the position of your hand up and down the beam to adjust things like pitch.

BTW, this can be done, in a certain range, also with stepper motor configurations, using "line positional" (or the name is "row" ?) sensors, and a shutter "slith".

the reflex on the hand falls on a different point of the "line" sensor for each position of the hand, so this can add some sort of extra control

Also, if "line" sensor is not readily available (or too high cost) , it can be "DYIed" someway using few cheapy photodiodes


EDIT: about diffraction gratings, they have 2 "bad" things to consider, imho ..... first, the beam is divided, so for have the same visibility of a, say, 50mW beam module, for 10 strings you need a 500mW beam ..... and also, you cannot regulate the distance between the beams ..... true that with stepper motors that distance is not freely regulable (opposite than with real galvos), but still can be varied if needed, where with diffraction gratings this cannot be done (ok, ok, you can use a different grating for get different distances, but is a bit impractical, and need a change in the software that track the position of the beam, when you change the grating)

 

[ar1999]

I am well aware of all those facts! Also, you are forgetting the cost of the Arduino, and all the other support components. A $12 stepper will not run all by itself!!!!

However, a $5 webcam, free software (especially using Linux), a cheap diffraction grating that when used with fog, is practically just as visible. Yes, it may be a bit dimmer, but still PLENTY visible. Considering most will be using software synths now days, there should be essentially no issue with using a webcam. Also, it has the potential to do a LOT more considering it is PC/Image based, instead of an Arduino!!!

Ok I see what you mean. A $5 webcam would be great.
Maybe in the future I can make an upgrade for that (use a camera and free software as sensor)
For now I dont have the knowledge about how to do that.
Any tips from forum members would be highly appreciated.

 

[ar1999]

I'd suggest moving away from using laser pointers for things like this and using lab modules instead. With the duty cycle of a laser harp, it wouldn't surprise me at all if the laser overheated rather quickly. Their drivers also aren't too happy with switching on and off at such speeds, as they need a little time to stabilize each time its turned on.

If you use a lab laser with TTL or analog modulation, there is no need to worry about current draw and transistors etc, it can be controlled directly from the Arduino pin ...

Where would you recommend to buy a laser like this at a reasonable price?

 

[HIMNL9]

Just as suggestion:

5V 4-Phase Stepper Motor + ULN2003 Motor Drive Board | eBay

According with this seller description, the motor (that apparently include a gear reduction) is a 5.625/64 degrees for each step, that made 0.08789..... degrees each step (or 4096 steps each turn, if you prefer)

This, apparently, can give more control about beam spacing than a direct-driven 1.8 degrees/step motor ..... and for less than 5$ free shipping, the cost looks really cheap (it also include the ULN chip ..... not that i need it, i think i still have 8 or 10 of them here and there, but is still a bonus )

I ordered one just for the curiosity, but getting packages from HK to here take usually from 4 to 6 weeks ..... there is anyone of you that already use these motors, and know if they are good enough ?

BTW, ar1999, what nema17 motor is your one ? ..... the OSM site include a lot of different models of "nema17" motors, 2, 4, 6 phases and hybrids included ..... all starting with "nema17" :thinking:

 

[Sputnik77]

Just as suggestion:

5V 4-Phase Stepper Motor + ULN2003 Motor Drive Board | eBay

According with this seller description, the motor (that apparently include a gear reduction) is a 5.625/64 degrees for each step, that made 0.08789..... degrees each step (or 4096 steps each turn, if you prefer)

This, apparently, can give more control about beam spacing than a direct-driven 1.8 degrees/step motor ..... and for less than 5$ free shipping, the cost looks really cheap (it also include the ULN chip ..... not that i need it, i think i still have 8 or 10 of them here and there, but is still a bonus )

I ordered one just for the curiosity, but getting packages from HK to here take usually from 4 to 6 weeks ..... there is anyone of you that already use these motors, and know if they are good enough ?

BTW, ar1999, what nema17 motor is your one ? ..... the OSM site include a lot of different models of "nema17" motors, 2, 4, 6 phases and hybrids included ..... all starting with "nema17" :thinking:

Yes, but its also 1/64 of the speed. Considering most steppers top out at around 1000rpm max , with a 64:1 reduction your talking around 15rpm.

I dont think thats going to be fast enough!!!

 

[ar1999]

Just as suggestion:

5V 4-Phase Stepper Motor + ULN2003 Motor Drive Board | eBay

According with this seller description, the motor (that apparently include a gear reduction) is a 5.625/64 degrees for each step, that made 0.08789..... degrees each step (or 4096 steps each turn, if you prefer)

This, apparently, can give more control about beam spacing than a direct-driven 1.8 degrees/step motor ..... and for less than 5$ free shipping, the cost looks really cheap (it also include the ULN chip ..... not that i need it, i think i still have 8 or 10 of them here and there, but is still a bonus )

I ordered one just for the curiosity, but getting packages from HK to here take usually from 4 to 6 weeks ..... there is anyone of you that already use these motors, and know if they are good enough ?

BTW, ar1999, what nema17 motor is your one ? ..... the OSM site include a lot of different models of "nema17" motors, 2, 4, 6 phases and hybrids included ..... all starting with "nema17" :thinking:

I have tryed one of those stepper motors (5V 4-Phase Stepper Motor + ULN2003 Motor Drive Board | eBay) and they are way too slow... like a toy... it will not work for a laser harp.

You need the fastest nema17 you can find. It doesnt need to be strong to lift anything. I used a Wine Cork Stopper glued with a small mirror and that weights near to nothing.

I guess 4 wires or 5 wires stepper may be easier to drive , but since I have not tried them I cant tell if they are fast enough.

I got mine from a local store and they did not give me any specs... go figure!
So I had to find out all by myself how to make it work...

All I know is it is a nema17, it has 8 wires and it is working with a 15 Volt DC power supply (found that by trial and error also).
Dimensions are aprox. 30mm x 30mm x 30mm.

I think it is 1.8 degree each step. And you are right about more control for beam spacing but I found out it is work ok for 9 beams. I can always use more mirrors to control beam spacing to fit what I want.

The stepper moves by applying current to 2 wires at a time. So I have 4 steps (2 wires per step).
The way I figured the wire pairs whas conecting a baterry with 2 wires each time until I found out. Then I connected it to the ULN2003 as shows the drawing below.

Hope that helps.

 

[ar1999]

Here is a nice video guide about how to figure your stepper motor (wires) - link and video below.

Eastern Geek: How To Identify Stepper Motor Lead Wires – The Fool Proof Way




Also a high speed step motor video demo (claims to be at 4000rpm). Link and video below

High speed step motor control - YouTube

 

[HIMNL9]

BTW, you know that, if you need, you can half the angle driving 2 coils at the same time, right ? (it's called half-step driving, and double the number of steps per turn).

Probably the more quick nema17 motor that you can find is the bipolar 17HS08-0504S, with 1.8 degrees per step ..... or the bipolar 17HM08-1204S, with 0.9 degrees per step .....

Your motor looks very strange ..... according with the producer site, all nema17 in catalog are 42x42mm, and none of them is wired with 8 wires ..... afaik, the 2 coils for each phase in unipolar motors are usually connected together, and sometimes also in common, so they have normally 6 or 5 wires ..... and bipolar motors have 2 or 3 separate windings, so 4 or 6 wires ..... it must be a custom product for some company, not a "standard" product from OSM, so probably for this reason is not in their datasheets.

The only serie that they have with dimensions similar to your one is the nema11 serie (28x28mm) ..... also the nema14 serie is 35x35mm (except one model that is a 4-wires round motor 36mm diameter) ..... if there is no part number on the motor, is difficult to find any datasheet (the part "nema17" is only part of the number) ..... and the only other stepper motor with similar number that come in mind was an old Tamagawa that was called "nema17 size" (probably meaning the 42x42mm size) .....

 

[ar1999]

BTW, you know that, if you need, you can half the angle driving 2 coils at the same time, right ? (it's called half-step driving, and double the number of steps per turn).

Yes, I heard about it, but for now I need speed first, and I think this would make it slower...
I would love to do double step, not half step... Is there a way to do that?

Your motor looks very strange ..... according with the producer site, all nema17 in catalog are 42x42mm, and none of them is wired with 8 wires ..... afaik, the 2 coils for each phase in unipolar motors are usually connected together, and sometimes also in common, so they have normally 6 or 5 wires ..... and bipolar motors have 2 or 3 separate windings, so 4 or 6 wires ..... it must be a custom product for some company, not a "standard" product from OSM, so probably for this reason is not in their datasheets.

Yes, it is very strange! It's from a Brazilian company. But I guess I could do this easier with 5 or 6 wire step motors.

The only serie that they have with dimensions similar to your one is the nema11 serie (28x28mm) ..... also the nema14 serie is 35x35mm (except one model that is a 4-wires round motor 36mm diameter) ..... if there is no part number on the motor, is difficult to find any datasheet (the part "nema17" is only part of the number) ..... and the only other stepper motor with similar number that come in mind was an old Tamagawa that was called "nema17 size" (probably meaning the 42x42mm size) .....

The only reason I used this one is because it was the only one at hand at the time...

To buy a 5 or 6 wire step motor from china or US would take me about4-6 weeks more to complete the project...

 

[HIMNL9]

Well, nom, it does not slow down the process, in fact moving half step requires almost half time ..... but i suppose you are using more than one step, between the beams, so this make sense .....

There's no ways for do 2 steps in one time, the motor just "jump around" randomly in this way ..... the only way for increase the speed, is to get smaller stepper motors ..... specifically, smaller diameters ..... or getting ESCAP "disk-magnet steppers", but expect to pay 70 to 90 $ each, so i suppose this is not an option .....

Anyway, your problems about slow movements are probably due to the static inertia of the rotor ..... large rotors have more strenght, but also a lot more inertia ..... compare, as example, the nema8 (20x20mm motors) and the nema17 (42x42mm motors) series ..... also the smallest nema17 existing have 15 g/m^2 of inertia, the "cubic" ones (42x42x39mm) ones are at 54g/m^2 ..... where instead the nema8 size goes from 2 (min) to 4 (max) g/m^2 of inertia ..... ofcourse, they have a lot less strenght, but you need only to rotate a small mirror and no other, so no need to high torque motors, here, and there is a lot of difference in moving them, instead the high-inertia bigger ones

The better way for increase the speed, as first thing to do, is find a small diameter motor .....

And yes, i understand your problems about shipping times, all the times i order something from HK, the package need 4 to 6 weeks for arrive here (when the custom office guys don't simply steal them )

 

[ar1999]

Well, nom, it does not slow down the process, in fact moving half step requires almost half time ..... but i suppose you are using more than one step, between the beams, so this make sense .....

yes, at this time I am using 2 steps per beam(one + one) for a total of 9 beams.

..... the only way for increase the speed, is to get smaller stepper motors .....

Speed is working ok for now but maybe I will try to update the laser harp project with a smaller stepper motor in the future. (if I can dinf them at a reasonable price)