Lego loving about to be 9 year old having his birthday party at the house and wanting a party with a bunch of other 8/9 year olds (plus his 6 year old sister). Theme is Lego of course. Tore apart the backyard to create a Lego obstacle course which the kids will run in time trials. Other portions of the course will be shown in different instructables. Here, is the part which was the primary source of frustration. I'll spare everyone the stuff that didn't work. The result here is a laser shooting range where the kids get real laser guns (5mW lasers attached to toy light guns) and get to shoot at the henchmen of the main villain in The Lego Movie. They are called Micro-managers.
Step 1: Print Off Images
The first thing I did was go onto the internet and find images of Micro-managers to print off. I then built a 3 foot by 2 foot rectangle out of 2X4 (wood I already had). Purchased some white 1/8 thick poster board. Tacked the board to the wooden rectangle and glued the images onto the board. I then went over them with some laminating paper, but afterwards realized that probably was not necessary.
Step 2: Lights and Motion
The toy guns used came with lasers built in, else I would have had to connect them. They make a lot of noise, so I was not sure connecting sound to the target would work without a speaker system. So, I decided on lights and motion to let the kids know when they hit a micro-manager in the "sweet" spot. I pulled a three foot strand of LEDs and strunk along the top.
Step 3: Wiring the Back
My kids got advent calendars for Christmas. After the holiday was over I pulled the black cartons out of the boxes and now use them for a host of things. I took three of them and glued them to the back of the board with the Micro-managers on the other side. They would hold the photo cells and relays. They are perfect because they are totally dark inside. I cut out three holes on the Micro-managers to let the laser in.
Step 4: Relays
I purchased photo sensors with built in relays. I used the recipe for ooogoo from Mikey77 found here - https://www.instructables.com/id/How-To-Make-Your-Own-Sugru-Substitute/ and made 1/2 inch rubber footers to place under each relay. This lifted them just enough so they were in the middle of the quarter sized hole cut into the Micro-managers.
I did not take pictures of the wiring like I should have. I ended up using two power supplies. One was a 6V supply made up of 4 AA batteries. It was wired to the power of each relay. The second supply was two 9V batteries wired in series to give me 18V. The 18V was necessary to run the 24V motor.
Step 5: Motor (fan)
I needed some motion to occur whenever the laser hit the sensor, so I decided on a less than spectacular, but cheap and effective cooling fan from an old PC. It is 24V, but ran at a decent speed at 18V. I used a gear from an old torn apart printer (was after the stepper motors in it) and the disc from a broken hard drive. I used an old laser pointer aimed at the disc while it rotates to give off a light effect. The 9 year olds thought it was cool enough but it does not take too much to impress them.
Step 6: Wiring
I used a case from out of the old printer I mentioned in order to house the electronics exposed in the back. I wired two circuits. All of the power for the relays (6V) is wired in parallel so all are on. The 18V is wired in parallel going to each relay in turn. The circuit is normally open. So when any of the relays switch over after detecting the laser the circuit closes. The closed circuit parallel circuit is then tied to a separate circuit tied the power supplies of the LEDs and motor together. Once the circuit closes, the lights come on, the fan spins, and the laser goes off.
I had trouble with the Texas spring sun constantly triggering the photo censors outside. So I decided to create small shade visors for the target holes. I took some old styrene strips I had, cut them into a shade shape and hot glue to piece them together and attach to the Micro-managers. I used the lenses from an old pair of kids sunglasses as well to limit the light going in except for directly hitting with the laser. However, alas, the powerful Texas sun was just too much. Even adjusting the potentiometers I was not able to stop the photo sensors from picking up direct sunlight. So, I move the target range inside.
Step 8: Aim and Fire
The kids stood at the end of our long back countertop which measured about 12 feet. After the first one hit the top Micro-manager and the lights and motion went on, a cheer with oohs and aahhs followed. "How did your Dad make that. He must be a scientist" was heard shortly afterwards. But like I said, they are 9 and easily impressed. Anyway, it was a big success.
Step 9: Abandoned Concepts
I know there are a lot of other things I could have done. There is a lot of room for improvements. I originally was going to use an arduino as a counter and a 16X2 display so the kids could see how many hits they got. However, for various reasons that became impractical. Other wonderful thoughts filled my head, but the short answer for most is I ran out of time before the party. We did a lot of stuff for the party and the laser target was only one of them, so it's end result is directly related to the amount of time I had to spend on it. However, the end result satisfied the promise of a Lego target game with real lasers. The kids had a blast.