Thursday, October 16, 2014

Robot Toy

finished robot

I have been working on a constellation project with my oldest daughter for school. My 6 year old decided she wanted to do a project with me too. She wanted to make a gray robot with eyes that light up when you push a red button on his chest. I asked her to draw the robot so I had an idea of what she was going for.

robot "blueprint"

boxes for the body and head

With blueprint in hand I looked through my collection of junk to find some suitable robot parts.  I found a bunch of small boxes for her to choose from. She selected two gray plastic boxes, a large one for the body and a smaller one for the head. I was going to use two LEDs for the eyes until I found a collection of buttons, lights, and music from an old baby toy I had disassembled. The electronics were powered by three button cell batteries which were just about dead. I can't stand button cells so I pulled a 3 AAA battery pack from a cheap flashlight and wired that in. We then used hot glue to secure the electronics into the body. The button had a flat back and only needed a small hole for the wires to pass through.

electronics in

We tried to drill the 1" holes for the eyes but the box cracked. Luckily I had more. So I used a small tip on my soldering iron and cut out the holes by melting the plastic. That worked pretty well. The eyes were then hot-glued in place. We joined the head to the body with a screw through a short length of 1/2" PVC pipe. The head can swivel left and right.

starting to look like a robot

My daughter adapted the design and decided one antenna was better than two. So we used a length of wire and a bead. For arms we used 3/8" nylon tubing, one piece through the whole body. The fit is tight enough that we didn't need to glue them in. That makes them somewhat poseable as they can rotate around. The boss decided to nix the hands.

arms and antenna

We looked through my junk for some suitable legs. Instead we decided to give her robot wheels. We used two lids from ice cream containers and screwed them to the body. To keep the robot upright, I made a little leg out of a short piece of aluminum tubing with an end cap. I threaded the tube 1/4"-20 and screwed it to the body. Lastly we needed a "smile". It was very important that it was a smile, not your typical robot grille mouth. I found a cable of multi-colored wires that my daughter like so we cut it to length and glued it to the head.


support leg

That left only one thing, the all important button needed to be red. Well she made one more executive decision and decided to go with blue. She colored it with a permanent marker.

robot eyes!

When you push the button, the eyes flash and the robot plays one of about 5 different tunes. She is so proud of her project; she planned a big reveal for the whole family and even brought him into bed with her that night. Can't wait to see what she comes up with next!

Tuesday, October 14, 2014

High Standard Recoil Pad

new recoil pad installed

The original recoil pad on this High Standard Flite King shotgun was dry rotted and rock hard. It made for some pretty uncomfortable shooting. I could not find a High Standard replacement piece, so I ordered a Pachmayr #325 Deluxe Skeet replacement pad. It's not an exact match but the Pachmayr pad resembles the original.

original recoil pad

The details of the installation are the same as in this post. This time however, I remembered to follow the angle of the toe line on the stock. This pad was a little tricky to install because the vertical lines on the pad exaggerate any uneven sanding on the pad. The pad will look off-center unless each side of the pad is shaped exactly the same.

vertical lines require careful shaping

proper toe angle

The fit came out nearly perfect, nice and flush to the stock. The Pachmayr pad is nice and soft, recoil will not be an issue. This shotgun is ready to return to the field.

pad is even with stock

Monday, September 1, 2014

Floating Airsoft Targets - Part II

A few months ago I posted about a floating target system I built for my airsoft pistol. It works well but the balls pop off of the air column and the target balls don't hold up to multiple shots. I finally got around to improving it.

straws packed in

To smooth out the airflow, I used plastic stirring straws. I cut each in half (2.5") and packed 17 into each tube. They hold in with just friction.

new targets

For the target balls, I found these Callaway Soft Flight golf balls. They feel like they are made of a dense foam. They float stably and aren't damaged at all when shot. They will be able to withstand hundreds of shots. With those quick improvements the target system is much more reliable and fun. Happy shooting!

Tuesday, August 12, 2014

Dewalt 18V LiPo Battery Conversion

Many moons ago I purchased a Dewalt 18V drill and trim saw combo. They served me well for a long time but the Ni-Cad batteries crapped out on me. Why not just buy a new battery? Well, a new battery is 89$. And if that wasn't bad enough, a new drill with two batteries and a charger is...$89! New drills with lithium batteries are just so much nicer. They last longer, charge faster, and are much lighter. Let's see if we can't update this old workhorse with an inexpensive lithium polymer battery.

dead DeWalt Ni-Cad battery

The Battery

I started by disassembling the battery and taking some measurements of the inside. I have seen some people put large LiPo packs in by having it stick through the battery case. It may work and give long run times, but it looks like crap. I want my LiPo to be concealed inside the original battery case. After measuring and searching online, I figured I could fit a five cell 2250 mAh 130C pack.  A 5S pack has a nominal voltage of 18.5 volts.  Fully charged it puts out 21 volts.  The drill should be able to handle the extra volts but you could always under charge the battery if you are concerned about it.

disassembled pack

Five torx screws hold the pack together. I removed them and pulled the halves apart. The end with the copper contacts must be pushed down from the top to get the battery bundle completely out. It's just a tight friction fit; no glue.

push down on the contacts with a blunt object

Once the battery bundle is out, desolder one of the battery contacts and carefully pry up the other contact that is spot welded to the battery.

save this piece.

Now we need to solder some silicone wire to the battery contacts. The contact that was soldered is positive. The spot welded contact is negative. Solder your red and black wires to the corresponding contacts. I placed an XT60 connector on the other end of the wires. That way, the LiPo battery can be easily removed.

new LiPo battery

I cut a small slot in the base of the pack so that I could access the balance lead.  Balance charging keeps your cells even and the battery healthy. During reassembly, I noticed the plastic screw holes were starting to crack so I reinforced them with some epoxy.

perfect fit


finished pack

The Charger

With the pack done, we need a way to charge it. The original Ni-Cad charger will not work with LiPo batteries. Doesn't matter anyway because my charger got fried when a pipe burst near it. Rather than jury rig some alligator clips from my LiPo charger to the battery pack, I decided to re-purpose the DeWalt charger. I pulled out the circuit board and cut off all of the components except the battery clips.

Charger circuit board. I don't think this works anymore.

bare circuit board

Next I cut the circuit traces going to the battery clips so that they are electrically isolated from the rest of the board. After that I cleaned the board.

Battery clips are left center. Note the cut traces.

Then I sanded the insulation away with some emery paper and soldered on some 14 ga silicone wire.

I sealed everything back up in the original case and soldered an XT60 connector to the end of the wires.

finished charge adapter

To charge, I just plug the base into my battery charger. Charging takes about 1 hour with a conservative 2.3 amp charge. The battery can handle an 18 amp charge but my charger maxes out at 6 amps. So at 6 amps I can charge the pack in about 23 minutes.

charging the pack

The new battery works great. It has plenty of power, doesn't bog down a bit even under heavy load. It runs at full power until the pack is dead instead of winding down as you use it like with Ni-Cad batteries. And as a bonus, the new pack is much lighter than the original. The old pack made using the drill feel like lifting weights. Extended drilling is now much easier, especially when drilling over your head. Check out the pack in action in the video below. It easily drills the long way through a 2x4 with a 1/2" bit. Looks like I've coaxed a few more years out of this old drill.

Sunday, July 20, 2014

LED Conversion of Magnifier Lamp

converted magnifier light

My Luxo magnifier light stopped working recently. It turned out to be a bad ballast. The light is a very expensive unit and has proved invaluable for lighting and magnifying various tasks in my shop. I needed to fix it, but unfortunately I could not find a replacement ballast. So I decided to convert it to LED lights.

the light

removed the bad ballast unit
removed the light housing

LED strip from Radio Shack

removed the protective silicone covering and
used foam tape to mount strip into light housing

had to make cuts to get it to follow the curve

used solid core wire to bridge the gaps

LED strip mounted in housing.  Not shown: soldered LED
wires to existing wires in magnifier.

LED strip requires 12v @ 1.5A.
Found this old Power Wheels battery charger in my pile of junk

spliced power supply into magnifier power cord

It works! Nice and bright.
Original power switch turns it on/off.

view from above

This light is back in action and I can finally see what I am working on again. 30 bucks to save a $400 magnifier, not bad. The light is just as bright as before, maybe brighter. If I decide to add a PWM controller, I can even adjust the brightness. I even have about 18" of the LED strip left over for a future project.

Monday, April 14, 2014

LCD HD Television Repair

working again

My inlaw's Vizio V037L FHDTV10A stopped working. When you turned it on, the picture would come on for a few seconds, then disappear. You could still hear the audio, but there was no video regardless of input. After some online research, it seemed like the backlight inverter board was to blame.

I found a used but guaranteed replacement on ebay for $16.30 with free shipping. For that price, even if I was wrong about the diagnosis, it was worth the risk.

remove the back cover

backlight inverter is in the lower left corner


remove top cover

remove inner cover

replace board and 4 wires

The entire process was very easy; it took less than 15 minutes total.  Note: if you look closely the boards are not the same. There are about three different part numbers that will work.  They are Phillips 6632L-0490A, 6632L-0504A, and 6632L-0506A. Buy whatever is available or cheapest.