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.

Wednesday, March 19, 2014

Astro Invaders Arcade Restoration - Control Panel

Part I - Intro
Part II - Lights & Locks
Part III - Marquee Paint
Part IV - Power Supply Rebuild
Part V - Circuit Board Cleaning

Now it's time to get the control panel in shape. It works perfectly. But the buttons are dirty and scratched, and the paint is scratched in a few spots. Let's clean everything up and protect that cool artwork. The panel was removed easily by unhooking two latches inside the cabinet.

leaf switches

The panel is made up of leaf switches. These are pretty cool, much less noisy than the typical microswitch buttons found in most arcades today. They are durable as well as there isn't much to go wrong with them. The wiring is straightforward. One common ground and a separate wire for each button. All I did below the control panel was straighten one leaf and clean the contacts on the leaf switches with fine emery paper.

buttons removed and disassembled
these things are filthy

While the buttons were working fine, they were a little beat up. I started by disassembling them and cleaning with some Fantastik. That didn't help much. So I put them in my ultrasonic cleaner for two 8 minute cycles with heated simple green. That got them much cleaner, but the plastic was still stained yellow. I tried Goo Gone; no help. I tried a buffing wheel on my Dremel. That just turned the plastic red from the buffing rouge. 320 grit sandpaper worked OK but took forever. The plastic is soft and does not sand well.

new (L) and old (R) buttons

After too much time and several attempts, I gave up on restoring the old buttons. I found replacements for only $2.65 apiece. For under $20.00 delivered I could get new buttons in less time than I spent trying to restore these eye sores. Lesson learned. The new buttons are a slightly different design below but function exactly the same.

The monitor glass is easy to remove once the control panel is removed. So I decided to clean the glass and monitor. With the glass removed I could see the monitor bezel was severely faded. I removed it, cleaned it, and sprayed it with satin black spray paint. The bezel was then stapled back in place. It's a small detail but it makes a difference in the look of the cabinet.

bezel before

bezel after


Next I cleaned up the control panel with some Fantastik. To finish things off, I touched up some of the scratches with a paint marker. Finally, I reinstalled the monitor glass and control panel. Next time I'll work on touching up the cabinet.

back together

Sunday, March 2, 2014

Hexacopter Power Distribution Board

New PDB. It ain't pretty but it should work.

Recently my hexacopter crashed. Luckily I had a GoPro strapped to it and I saw one of the motors stop in flight. You can also hear a"pop" just before the failure.

After the crash I plugged the suspect motor into a good speed controller (ESC) and it worked fine.  So I plugged a good motor into the suspect ESC and it did not spin. Therefore, I concluded that the ESC had failed. I took the ESC apart to see which component failed but I couldn't find anything out of the ordinary.
But when I installed a new ESC, it didn't work either! After a little checking with my multimeter, I discovered that the positive terminal on the power distribution board (PDB) for that ESC was not getting power from the battery. Upon closer inspection, I could see that the circuit traces had burned out. This was a bit surprising considering that the board is rated for 90 amps and my motors should only be pulling around 45 amps max.

Note the 3 burned copper points around the lower right solder pad.

I had a few choices to fix it. Purchase the same thing again, purchase a different one, or make my own. I couldn't put the fate of my several thousand dollar hexacopter in the hands of the same component that failed once already. Other brands were an unknown and probably would not fit as well. I really liked the form factor of the original so I decided to make my own based on that design. I could etch my own PCB but I was concerned that it couldn't handle the power. So I decided to make a new PDB out of a piece of 0.025" copper plate. That's five times thicker than the original copper traces. It should have no problem handling the current.

I choose a piece of 0.093" polycarbonate to insulate the positive and negative sides. I marked and cut the plastic the same size as the original PCB. Then I cut out two pieces of copper plate larger than the plastic.

I glued the copper pieces to the plastic with 5 minute epoxy then trimmed the copper even with the plastic.

Each copper plate is almost as thick as the old PDB!

With that finished I drilled the mounting holes with a 1/8" drill.  I'll use nylon mounting screws to avoid any shorts. I followed by drilling a hole for the negative battery lead. The negative lead was passed through the bottom of the board and soldered to the top. I soldered a set of 3x6 header pins to the negative side of the board for the ESC receiver wires. All of the negative leads are wired together. The positive leads are separate. One positive lead is wired to the power supply wire for the flight control system. And the wiring harness from the old PDB was soldered to the signal wires.

Ready for ESC's
Finally, the six ESC's were soldered to the board. I covered the entire board in several coats of liquid electrical tape. Once it was dry, I screwed the new PDB to the center plate and attached the receiver leads. It fits the hexacopter exactly like the original. It is a little heavier, but this one can handle much more power. Now I just have to slap it back together and get her back in the air.

Ready for reassembly.

Tip: If you've never soldered to copper plate before, you need lots of flux and lots of heat. Coat the area to be soldered with flux. Heat it thoroughly with your soldering iron. Keep touching solder to the area until it melts. When it does, run your soldering iron in circles around the area to tin it with solder. Once you have a small layer of solder on, it will be much easier to solder your leads. Don't try to solder leads directly to bare copper plate.