Archive for the ‘TECHNOLOGY’ Category

November 1st, 2017

Halloween Zombie Apocalypse

Here is my yard haunt for 2017. I have done a miscellaneous display for the past couple of years but this year I finally came up with a theme. The house was turned into a zombie containment lab with the zombies trying to get out.

My display was somewhat abstract with lighting and sound creating most of the effects. I started putting out props several days leading up to Halloween to tell the story that the house was being transformed/taken over by the zombie containment activities.

The elements:
1. Lighting – Green flood lights in all the windows and 4 DMX controlled LED PARs slowly alternating from yellow to green with the occasional strobe. Leading up to Halloween the green lights in the windows faded on and off slowly to indicate something was building up.

2. Driveway – Lighted signs warning of zombies inside along with a motion activated scoreboard buzzer combined with blinking stage light with radiation symbol gobo.

3. Sidewalk – Motion activated store bought hanging zombie prop and atmosfearfx zombie apocalypse dvd projected in the front window. Also a homemade control panel that appeared to be ripped off the wall was made to flicker via a florescent starter.

4. Front door – An industrial control panel made from plywood and electrical parts (indicator lights, meters, knobs, etc.). When the door bell was rang the store bought electrical box prop mounted on the side of the control panel was triggered along with a strobe light inside the front door.

5. Miscellaneous – Mr. Cool fog machine, a few random severed limbs, ‘caution’ tape, a 50 gallon blue drum, and some other random warning signs.

January 18th, 2017

Customized JAMMA switcher for 2-in-1 light gun arcade

So here is the dilemma… You buy a video game cabinet and then decide that just having only one game in it does not satisfy your inherent need to make it contain more than one game. And what if you cabinet was a ‘gun’ game for which that type of arcade machine is at a distinct disadvantage for using with MAME type emulation? Well there ought to be a way to switch between multiple game PCBs right? Well yes there is, you can get a switcher for just this purpose… But, after implementing such a setup, I don’t recommend it. Read on for more details….


Here is my Lethal Enforcers II arcade machine that I purchased many years ago. Some point after I acquired it, I decided to purchase the PCB for the original Lethal Enforcers arcade machine for which I remember playing so much in the college dorm laundromat. For years I got by just having the 2nd PCB mounted to a tray inside the cabinet and swapping the JAMMA and gun connectors when I wanted to switch games. This was fine if just a little kludgy.

But it just so happens that there are products intended to solve the problem of switching all of the wires in the JAMMA harness between PCBs that sort of work. Here is the one that I purchased:


It seems like it should be a straight forward task to switch between two game PCBs, but it is not. To make wiring a video game cabinet a standard practice so that a different game board could be swapped into a cabinet without changing the wires, the JAMMA (Japan Amusement Machine and Marketing Association) connector was invented. It standardized the pin-out on game PCBs and the associated wiring to components in the arcade cabinet. There any many different types of signals in play on a JAMMA harness. Including:

  1. Power: +5v, +12, -5v (not used by most PCBs) & Ground
  2. Sound: Mono “+” and “-” speaker output
  3. Video: Red, Green, Blue, Sync and Video Ground lines.
  4. Contol Inputs: Joystick (Up, Dn, L, R), Buttons (Shoot, Start), Coin Trigger, etc. [for two players]

In addition to the standard JAMMA harness, this cabinet also has extra connectors for the two optical guns and stereo speakers. So how will this switcher handle that? Not very easily it turns out.

Let’s look at the switcher as it arrived:



The basic theory of operation for this switcher involves using relays and diodes to switch back and forth between the two games when the button on the wireless remote is pressed. The relay on the right of center alternates routing the +12v and +5v power feed between the PCBs. Note that this switcher does not switch the -5v signal between PCBs, instead it leaves those pins unconnected. This is not an issue since most PCBs do not use the -5v power feed. The second relay alternates routing the speaker connection between the PCBs. The remainder of the connections (video and control signals) are tied together from both PCBs to the cabinet JAMMA harness. The two rows of diodes prevent signals from one PCB from from entering the opposing PCB. Since only one game is powered up at a time, the arrangement works. But there is a problem, if you look closely at the spots between the pin connectors, there are spaces for eight diodes that are not installed. Unfortunately these missing diodes were intended to separate the video signals (Red, Green, Blue & Sync). As a consequence, it can be said that this JAMMA switcher fails to work as advertised. Strike one against the idea of easily switching between PCBs in the same cabinet.

On to the modifications! Hint: Lots of relays.


Six DPDT relays to be exact. By using relays, the signals for Video (Red, Green, Blue, Sync), Stereo speakers (L+, L-, R+, R-), and both of the optical guns (trigger and optical sensor) are able to be switched cleanly across both PCBs. The +12v pin going to the PCB #2 JAMMA connector is connected to the coil of all of the relays. So when game #2 is active, all six relays are switched on and the above connections are switched over to PCB #2.

Also note that the +5v and ground wires that power the optical sensors for both guns are not switched through the relays, instead they are connected directly to constant +5v and ground. This arrangement powers the guns’ optical sensors directly from the power supply and not through the switcher. Lastly of note, the video ground pin for both JAMMA PCB connectors were separated from the power supply ground and tied together. So the video ground pins of both PCBs are jointly connected to the monitor and nothing else. After soldering all of the various connections to the original switcher and creating jumper cables for the guns and speaker connections, this monstrosity is now complete. Final score: power, start buttons, service switch and coin triggers are routed through the switcher’s relays and diodes and everything else including video signals, optical gun signals and the stereo speakers are routed through the add on relay board.

Here is the finished product:

Here it is connected to PCB #2 (Original Lethal Enforcers). The two gun connectors are on the left side and the stereo speaker connector is on the right side.

Here is the switcher and relay board installed in the cabinet:


The PCB original to the cabinet (Lethal Enforcers II – The Western) is in the background. The second PCB (Lethal Enforcers I) is in the foreground. The game select button was installed in the front of the cabinet next to the coin door.

Video of the switcher in action:

Final thoughts:

While this was quite a bit of work, the final product does work pretty well in my case. Switching between the two games in my cabinet is seamless. However given the low quality of JAMMA switchers that are still available for sale, I would not recommend purchasing one unless you are prepared to solder on it.

The only small issue that I have with the final product is the monitor. Monitors in these older game cabinets have manual analog controls that need to be adjusted to produce the best picture for the game that was installed in the cabinet. Since only one game was installed at a time, the picture could be properly centered and the brightness and contrast controls set just right (very important on an optical gun game). When switching between two games, the picture settings need to be a compromise between the two. In my case, the brightness setting needed to get reliable gun hits in LE II caused the picture to be somewhat washed out in LE I. But I can live with that. If you are thinking about doing a 6-in-1 light gun cabinet like in the link below, note that it could be very difficult to get a good picture on all six games without having to adjust the monitor every time the game is switched.


Further reading on JAMMA switchers & Light gun games:

November 20th, 2016

DIY LED Christmas tree

Here are two of my DIY Electronic Christmas trees. The first one was made two years ago for an office Christmas decorating contest. I decided to update it this year with a little more modern technology.


First tree:
This is a fiber optic tree with a halogen light and color wheel in the base. I decided on a technology theme using electronic parts that I had on hand by making my own blinking light strands out of red and green LEDs soldered onto cut up ribbon cables. The LEDs are driven by a 555 + 4017 + 2803 IC combo circuit assembled on a breadboard. For those who are not sure what that means… The 555 is a general purpose timer IC that supplies the clock pulses. The speed is adjustable by the potentiometer knob. The 4017 IC acts as a sequencer/chaser. It has ten output pins that switch on in sequence per each clock pulse. The next chip is a ULN2803 that acts as a amplifier for the output of the 4017 to drive multiple LEDs. In this case, I am using 7 channels of outputs with two LEDs on each strand. Here is a schematic if you want to make this circuit:



The ornaments on this tree are old ICs that were spray painted white and red. I am happy to report that I did win the decorating contest with this effort. I was going for an ‘electronic steampunk’ theme, which I think this captured. Charles even said that it looked ‘old school’, high praise indeed!

Updated Tree:


This year, I updated the original tree with a Bluetooth LED controller instead of the discreet ICs of the original version. I decided since now that it is 2016 and all of the box stores sell LED light strands and power strips with embedded Bluetooth controllers and their own ‘app for that’, my entry should reflect that technology. I thought about using a Raspberry PI and writing some PWM code in python to blink and dim the LEDs (and send tweets too!), but I decided that was a bit overkill.


I settled instead on a standalone Bluetooth LED controller (BL 370) that I bought for $25 on A-Maze-On. The device is made to control RGB LED strips, but I thought it would do fine driving 6 each red, green, and blue LEDs for my Christmas tree (Note that there is a 470 ohm resistor inline with each LED; I re-wired them after taking the pictures). The device has its own app called ‘Magic Light BLE’ for Android and IOS. The app works pretty well with lots of options to blink the lights. The only downside is that it seems like a fairly dodgy app since now on Android it requires location permission to start. So I borrowed my Mom’s old iPhone to load the app instead. While sitting next to the tree, the phone actually complements this years theme of ‘App for that Christmas tree’. Any suggestions on what to use for ornaments?  Maybe of bunch of cut off USB connectors if I can find a ready supply?

March 31st, 2014

Guitar Amp

I got a guitar a while back, but no amp to go with it. So I decided to make my own practice amp mostly using electronics parts that I had lying around. The amp cabinet is based on a vintage Fender Champ (5F1) practice amp that was introduced in the 1950’s. For my version, the cabinet is constructed from a single select pine board and joined together with finger joints. The speaker panel is 1/2″ plywood and holds a single 6″ speaker. The back panel cover pieces are 1/2″ birch plywood with edge banding on the tops. The cabinet is finished with Minwax golden pecan stain and two coats of tung oil.

The amplifier section is my implementation of the Noisy Cricket Mark II schematic from Beavis Audio. The Noisy Cricket amp is designed around an LM386 1-watt audio amplifier chip that is intended for clock radios, boom boxes, etc. The amp circuit is constructed on a small project board with only a few resistors & capacitors as support components. The three knobs control volume, gain, and tone. The switches control power and grit (distortion). The amp is powered from a 9v battery.

Here is a video demonstrating the Noisy Cricket amp:








Click this link for the picture of the plans that I found and used for this project.

Edit: It looks like the Beavis Audio site has gone away. I have put the plans for the amp circuit here.



February 9th, 2014

Nexus 5 Oak Wireless Charger Stand

I recently bought a wireless charger to go with my Nexus 5. I liked the concept of wireless charging, but I didn’t like the mechanics of laying the phone down flat on a desk and having to slide it around to find the sweet spot where it would attach to the magnets in the charger. I decided to make a stand to house the charger that resembled the charging cradles that used to come with older cell phones.


The Nexus wireless charger is a small, square shaped device that charges compatible phones and tablets. It is powered by a plug-in USB power adapter. When the phone or tablet is placed over the charger in the right spot, magnets in the charger will hold the two together. The phone or tablet will make a special sound indicating that charging has begun.


I started making my charger stand by tracing an outline of the phone on a piece of paper. I then cut out the template and taped the sides to the phone. Next I took the charger and placed it over the paper on the back of the phone and positioned it in the right spot for charging. I then traced the outline of the charger on the template.


The back of the stand is a piece of 1/2″ red oak with a cutout that holds the charger in the proper position to make contact with the back of the phone. The bottom is cut at a 30 degree angle. The height of the back piece is approximately 3/4″ shorter than the overall height of the phone to allow a place to grab the phone when removing it from the charger. The arc of the top matches the arc of the phone itself. The overall width of the back is about 1/16″ wider than the phone to allow a slight gap when placing the phone into the charger. The two side pieces are glued in place to provide a cradle to position the phone in the charger.



The reverse side of the back has a grove chiseled into it to allow space for the micro USB connector and wire that powers the charger.


The charger assembly is glued on to an oval shaped base of 1/2″ red oak.


The completed charger base before finishing.


The back side of the charger has a cover plate installed to hold the charger in place.


The completed charger finished with Minwax #210B Golden Oak stain and two coats of polyurethane.


March 20th, 2011

LED Shed Lights

I put in a plastic storage shed last summer and have been trying to customize it to my tastes. One thing that I thought would be cool was to add some lighting. I eventually came up with the idea of using LEDs and a SLA battery to power them. But how to make them look nice? That would soon come to me…

In early January, the orange depot was clearing out all of their Christmas stocking stuffer gift crap. I ran across their LED flashlights that were marked down to $1 each and I knew I had found my light source. I bought 8 Aluminum LED flashlights [6 LEDs in each flashlight – batteries included!]. I also got a 12v 2.3AH SLA battery and a 12v solar car battery maintainer (meant to sit on the dash and plug into the cig lighter to keep a car battery charged when it sits for long periods).

I started by cutting 2 strips of 5/8″ MDF and then drilling 4x 1″ holes equally spaced into each of them. I also made a shallow 1/4″ dado cut centered along the length of the back of the strip.

I then cut all the flashlights right behind the LED assembly and began wiring them to the board. I experimented with 7805 5v regulators to lower the 12v battery down to 4.5v for the flashlight head. I used 2 regulators (4 lights per regulator). They got really hot even with a heat-sink, so I figured that this heat was wasting lots of battery power.

In the end, I settled on using 2x16ohm (32 ohm total) 5 watt resistors running two light heads in series. So each of the 4 pairs of light heads has its own resistors lowering the battery voltage down to the proper level. I used a small relay controlled by a regular house light switch to turn the lights on and off (to try and avoid some line loss of power between the switch and the battery).

P1000443 P1000444 P1000446 P1000461 P1000463 P1000464 P1000466 P1000467P1000469 P1000480

To install the light bars in the shed, I used hanger bolts (wood thread on one side, machine thread on the other) to bolt the light bars to the metal rafters in the shed. The rafters are ‘U’ shaped, so they made a nice place to tuck the battery away in. The solar panel is held up to the shed sky-light with some safety wire. A length of phone wire connects the relay module to the light switch that is installed in a shallow plastic work box screwed to the shed wall. As you can see, the lights provide more than adequate illumination for finding things in the shed at night.

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Thanks to the folks at the orange depot for ordering too many flashlights at Christmas. Without their $1 flashlights, this project may have never materialized!