Andrew Kilpatrick

Andrew Kilpatrick has done a really cool framed laser harp on PIC microcontroller basis. After building, he did a great documentation on his website http://www.andrewkilpatrick.org.

In the following interview we talk about selfmade laser harps – motivations, approaches and Andrew even gives some hints for people who want to start such a challenging project. Here we go…


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1. What was your inspiration and why did you decide to build your own laser harp?
I had never seen a laser harp, or even seen any videos of Jarre but I was already a Jarre fan by the time I started to work on my harp. There was only one picture of Jarre that I could find on the net. In my last year of highschool (1996/97), I helped my friend Jonathan Fuerth build a prototype harp for a school music project. We came up with the basic concepts that my harp uses. There were many problems that I wanted to try and fix in my own version.

2. When did you start and how long did it take to build it?
I started in the summer/fall of 1998 as I was entering my 2nd year of university. The idea was jump-started because I had done some wiring for my mom, and was left with some extra lengths of 1/2″ steel conduit. I realized that these could be part of a laser harp, so I bought a bunch more and started to design my harp. My friend Michael Kolos helped considerably with the mechanical parts. We made many many trips to Home Depot to look for materials. The main parts of the harp were finished in a month or two, but it wasn’t until the winter that I had a chance to finish the electronics and microcontroller code. This was my first microcontroller project, so it took a very long time for me to get the code working.

3. Tell me something about the process of designing and building. Why did you choose the framed concept? What kind of problems did you face during the build? How did you design the electronics? Did you run into situations that required re-disigning one or several sections?
When I started working on the project, I didn’t know anything about microcontrollers. The first task was to make the frame and beam splitters. I designed a nice harp shape and then Michael and I worked to make it out of the tubing. To increase the strength of the pipes where they would bolt together, I pounded dowels into the ends of them. The hardest part were the beam splitters. At first we tried to use a large piece of plastic drain pipe, with the beam splitters mounted inside. This didn’t work very well, and it was too hard to calibrate. The next idea (and the final one) involved a box made of pine to hold all the parts. The beam splitters are 1/8″ plexiglas, six per laser. The tilt action is from hinges that have been tightened, and the swivel action is with a single bolt through each hinge into the wooden box. This seemed to work very well, and it was easy to calibrate because the box was mounted on the base of the harp. The electronics started off as just the comparator circuits that I had designed for Jonathan. I connected them to a PC with a 24 I/O ISA interface card. Then I wrote software in DOS using DJGPP and the Allegro game library to interface with a Sound Blaster MIDI interface. This was connected to a synth to make sounds. This allowed me to work out a lot of the details about the lasers and analog stuff before working on the PIC programming. The PIC programming was the most challenging part of the electronics because I had never made a project with a PIC before. Also, I had a PIC with no UART, so I generated all the MIDI timings in software with delay loops. Once I had MIDI sending, I interfaced it with my comparators with a 74150 multiplexer. This made it so I could have 12 beams plus 3 mode buttons. All of the hardware and coding was a very big learning experience.

4. You really did fantastic documentation. What was your intention to write so detailled information about your harp?
At first I didn’t want to write up all the details because it’s a pain. But I did have a small site devoted to my harp and I got a lot of email, so in the summer of 2000 I took apart my harp and figured out how it worked. As it was a prototype, I didn’t have a finished version of the schematic.

5. Did you build your harp all on your own? Or did you do it with other people together?
As I mentioned above, there were a few people that were very important to the harp’s construction. The electronics and code were done by me alone, but it wouldn’t have happened if not for Jonathan Fuerth and Michael Kolos. Also, Alex Johnson, who I hung out with in highschool introduced me to Jarre in the first place.

6. You are using 2 <1mW laser ponters. I guess the beams are nearly invisible… How is it goin with these low power lasers?
Higher power lasers would be great. Also, 12 small lasers and no beam splitters would be excellent. If I were to do it again I would not use beam splitters. With fog you can see the beams, but in regular performance they are not visible.

7. How did you solve the problem of random notes?
It is important to keep the room dark while playing. My comparator board has a single pot that sets the threshold for all 12 beams. This needs to be adjusted carefully.

8. Are you planning to update your harp with a more powerful laser?
I would like to build a new harp sometime, but right now I have limited space and also some for-profit projects on the go. I anticipate it will be many years before I will do any laser harp projects again. I have too many other things to try first. 🙂

9. Did you ever use the laser harp live? How was the performace and your personal experience when performing? How was the reaction of the audience?
I did do one concert with the laser harp in 1999. The audience was impressed by it, although I did have some trouble with too much ambient light. Also, I’m not very good at playing it, so I had to put tape marks on the frame so that I could remember which beams to play.

10. Could you imagine building a frameless harp one day?
Obviously getting emails about laser harps gets me thinking about harps from time to time. I’ve thought of lots of new ideas, many of which involve the idea of a frameless harp. Since building my harp I have seen the Jarre in Moscow DVD, which shows his frameless harp very well. Had I seen that before making mine, I probably would have done things a lot differently.

11. Once in a while, people offer me money for a laser harp… Do you get these offers as well? And if so, do you build laser harps for money?
I have had some people ask me to build harps, but I have found that they are either not very serious, or don’t understand that custom electronics is a very expensive and time-consuming task. I would probably only consider making laser harps if someone else did the marketing and I just did the technology. I already run my own company making lighting control products, and it is hard enough by itself.

12. I think that it is not the way simply buying a laser harp off the shelf! A laser harp has to be built! It is a great challenge and an experience. Owning and playing a laser harp means to me that you went through the process of designing and implementing, facing these milions of problems and so on. what do you think?
I believe this about a lot of things. People should have to write software to understand to appreciate how complicated it is. It is very easy to take things for granted, and we all do it all the time. Each time I work on a new project, I feel as though I am better for it. Not just more experienced, but also a better person for understanding some new thing that I used to take for granted. But you need the right attitude… something that I find not many people have. I get a lot of email from people that just don’t want to spend the time learning, and want everything handed to them. That is not the way to enjoy an interesting and fulfilling life, and those people will soon realize that beer tastes better at the end of the day if you have earned it by kicking some ass and figuring stuff out for yourself.

13. Are you in touch with other hobby laser harp constructors?
Not in touch, persay. I do try to answer all the email that I get about various topics.

14. If someone is starting building a laser harp what tip/advice would you give?
Well, now that there is your site, I would say that one should do a lot of reading and examine other harps. Come up with a plan, and go to the hardware store a lot, but don’t buy anything at first. Going to a place like Home Depot and just look at a lot of stuff to see how things are built, what materials are available and how much stuff costs. But the biggest thing I can say is that if you are not willing to learn to design your own circuits and code, don’t start building a harp. Many people email me asking questions that makes me realize that they are totally lost and not willing to learn enough background information to make the electronics work properly.

15. What about feedback? Are you getting much mail, suggestions, questions, etc.?
I get email once in a while. I have probably received email from maybe a half-dozen people that say they are attempting or have built laser harps. It would be great to hear from more people. As much as my time is limited, I always make time for brainstorming and helping people with ideas. That’s the part that I like the most.

Thanks for the interview, Andrew!

{ 1 comment… read it below or add one }

Mark January 31, 2013 at 4:57 pm

I saw my first harp on britains got talent and thought id love to have a go. I sat and thought how I would design the circuitry for it and am pleased that it is very similar to your diagrams above! I would like to know if it is necessary to multiplex the separate lasers or can they be left on permanently?but I wondering if they turn into cutters doing this? Also I would like to know what frequency to multiplex at if needed. Is it best to go for green lasers as they seem brighter in pictures I’ve seen? Do you convert beam breaks to short pulses to play short and fast notes? Best regards mark. Hnd electronics and PC technician.

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