Shop Stuff: November 2009 Archives

Simple DIY Laser Light show

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Ok, I read this interesting article in my latest copy of Make about how to make your own simple laser light show. My particular test device is acoustic based. In short it is real simple, just aim a laser pointer at 2 mirrors attached to the cones of speakers that are wired to your stereo. In my case to keep it real simple, I wired the speakers in parallel - they are both receiving the same signal. Other configurations could have the two speakers wired separately to the Left and Right signals. In practice I doubt this will make much of a difference.

Here's the basic block diagram layout:


I started by mounting my laser pointer. Since I'm just playing around with what it might produce I didn't take time to build a nice box or anything. I just used a vice grip (pliers) to hold the pointer's switch on and then stuck them in a bench vice.


This is shot across my shop to a pair of PC speakers being held in place temporarily by a helping-hand tool. The mirrors are front side coated. They are cut from a bar mirror that came out of a laser printer. I attached them to the speakers with 2 sided tape.


The end result is a neat laser pattern that changes and dances to the music. Bass beats cause the most dramatic effect, although simple voice (radio DJ) generates the most interesting patterns.


I made a couple of videos of the unit in action. As you can tell, the little speakers sound awful. A better setup would be mount the mirrors to the voice coil and remove the cones - this would make the system quieter. Than place in an insulated box with an opening just large enough for the light to escape.

The patterns are dimmer, but more impressive when shot 30 feet across my basement onto the far wall.


Change of plans - getting to the root of the problem

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So, I'm at work trying to plan out my day and my wife calls. Our sewer has backed up. Well, now at least I know what I'm doing for the rest of the day... sigh.

Long story short, after a few valiant attempts at determining the problem (for starters the backflow valve was missing the valve part - apparently they come unscrewed and get washed away), I acknowledged this was beyond me. I did however, buy a new backflow valve and a plumbing snake - these are great for cleaning out drains in the house (they are not much good once the problem is further down the line). They do have one major drawback - after boring through whatever is clogging your drain, you have to pull all that wet messy line out and then put it away somewhere - YUCK. So I came up with a clever and simple storage facility. An ice cream pail.

Snake in a bucket

Cut a hole in the lid, feed the snake in and coil it up inside.

Snake in a bucket

By the way - the professional arrived a couple hours later with a much larger, powered snake and blade. After an hour or so of feeding it back and forth through the sewer to the street, he had amassed quite the pile of tree roots.


I have an ugly poplar tree on our front yard. See, 30+ years ago the city developers figured these fast growing trees were the perfect thing to quickly provide foliage to new neighbourhoods. Unfortunately, these trees are notorious for converting their anchor roots into a fine mesh of feeding roots when they encounter leaking sewer pipes. In the past 40 years, Winnipeg has gone from 2 or 3 companies that clean roots out of sewers, to over a dozen. The guy who did my house says they respond to 20-25 calls per day!

So the logical answer is get rid of the tree right? Not so fast. Even though it is on the grass between my house and the street, it is not mine. It is the cities. And they won't cut them down. Instead they will graciously reimburse me for 50% of my bill up to a $50 maximum and only once per year. Not bad, except these bills tend to be $140-170 plus taxes. So in the end the city barely covers 25% of the cost for a problem they created.

Another alternative is to replace the sewer line from the house to the city line - that is if I don't plan on sending my kids to collage and wish to live in debt forever. Thanks a lot.

Any way, that was how I spent the day. At least I ended up with a small hack.