All posts by thetazzbot

Magic Sing Karaoke Microphone Tear Down, Part 2

I’m back!  I have a tendency to pause projects for lengthy periods of time, so here is part 2 of my Magic Sing Karaoke Microphone Tear Down.  This time, we’re actually going to look inside the microphone, which serves as a remote control as well.

On the outside we see a nicely designed case with buttons, and an LCD screen.

Upon power up, the LCD reads “SYNC”.  When you turn on the base station, they connect and the LCD says “Karaoke” which is the default menu option.  The communications is two-way, what happens on the screen is reflected in the LCD.  When you enter a song # or browse for a song and select it, the song # is displayed.

Let’s open it up!  (Carefully)!

We see one lengthy PCB with a silver box on the end.  That silver box indicates RF shielding…So that means the radio is under that hood.

Confirmed!  These chips are a TI CC2400 transceiver (2.4ghz), an undocumented CASUH retaw1-05, and an SST 1Mbit flash chip.  The retaw1-05 is a RF modem chip, but could not find a datasheet on it.

The back of the radio board is boring, but has a couple of connectors.  Moving on…

How the two boards look when separated.  At the left side of the long board is an ATMEGA48.  It is right under the LCD so I’m going to guess it is the button/LCD controller.  I’m pretty sure we can assume that the Atmel also connects to the retaw1-05 radio modem chip.


They made a failed attempt at covering that ATMega48..

Below we can see the codec chip (AIC311). This chip is responsible for converting the audio from the microphone into a digital stream.  It has some other neat capabilities such as pitch changing, base, treble adjustments, etc. By the location, and the traces that run out to the right, I can extrapolate that this chip feeds directly into the bottom black connector going to the radio board.  The Atmega48 surely has some control lines going to this as well.

To Do:

It would be really neat if I could sniff the packets coming out of that CC2400.  I’m also not sure if both the RF Modem and the CC2400 are generating radio frequencies. The datasheet (two page only) that I could find on the Retaw says it is 2.4ghz but it also says it can interface with a CC2400.  There are many products from Korea that use this chip alone for both audio and data (phones, head phones, etc), so I’m a bit confused why they use both chips.

Magic Sing Karaoke Microphone Tear Down, Part 1

I bought this Magic Sing Karaoke microphone system many years ago and my family and friends have enjoyed and some times been annoyed by it quite often!  It truly is a really neat gadget..  I’ve got a plethora of photos of the inside, the outside and the on screen displays.

The microphone base has 2500 songs built in, and has several add on slots for song chips that are available online for about $60 a pop.

The base also has an SD card slot, but it is not for songs.  It is only used for storing user content, photos, backgrounds, movies and songs recorded live.

The system includes two cordless microphones that also each act as a remote control.

The model # I have is the ET19KV.  I originally paid $499 for it!  But that was like eight years ago!

Under the top cover of the base unit we find the slots for expansion chips.  I’m impressed by the number of slots.  Some song chips have 200, 400 songs!  But most have between 60 and 100.  The songs are of the MIDI type.  You can watch the video at the end of the article to hear the actual sound quality.


The rear of the base has the output connections:


The wireless microphone antenna:


Let’s open it up!  Don’t tell my wife!  At least I put it back and no extra screws were left!



Interesting things in here.  The big black parking lot sized chip on the left is an FPGA!  The chip on the right is a flash memory chip, which holds the circuit design for the FPGA.  If you’re not familiar with FPGAs, they are essentially a blank canvas for creating eletronic circuits using logic gates.  They have millions of gates or connections that can be configured into just about any digital circuit imaginable.




I’m very curious about the squigly lines shown above.  These traces, they were intentionally designed that way, I wonder why?

The chip on the bottom left of the below picture is the NTSC/PAL video encoder/decoder.


Another big chip!  This one is a Sunplus DVD/Mpeg1/2 decoder.  I suppose this is for playing movies off the SD card:


You can store Karaoke Movies on an SD Card and play them on the MagicSing.  There is special software called MagicSing Encoder that you need to use to get the best results.  There are lots of sources for Mp3/CDG files that can be converted to the video format usable on the MagicSing.  You can scrounge up CDG discs at yard sales etc and rip them to your hard drive if you have the right CD reader.


Here is the song chip.  This chip holds 200 songs.

The card edge connector is a 40 pin, 2 position, male variety.

The contacts are about 0.050″ (1.27mm) pitch.  Hard to measure!  The card is .031″ thick.

The actual chip inside is a NOR Flash variety.  Some information about NOR vs NAND memory chips:

The connector looks like a Harting 40 pin Motherboard to Daughterboard:

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This is a Spansion S29Gl064N90TF104 64 megabit NOR flash chip, storage space is 8 megabytes.  It is a 48-pin TSOP.  22 Address pins, 15 data pins. It can operate in 8 bit or 16 bit address/data communications.


This is a 40 pin edge card connector.  I’ve got a temptation to hook this up to my mbed enabled STMicro nucleo board and download the data to see whats in it!  The nucleo board is an ARM powered development board that costs $10 and has plenty of IO pins to connect to this chip.  I had thought seriously about trying to decode whats on this chip but in the end it will be fruitless.

Some work has been done by some smart fellas on NAND flash chip bit banging through the FTDI break out board.  I wonder how this could be adapted to the NOR chip?

Now for some screen shots.















Getting better prints – The ultimate first layer

There are a lot of variables involved in 3D printing.  Assuming you have the printer setup correctly and there are no loose parts to worry about, getting great prints depends on many different configuration parameters.

The most common workflow for 3D Printing involves these basic steps:

  • Design and export, or download, an .STL file
  • Load the .STL file in a slicing software (Cura, Repetier Host, Slic3r, Prontrface, etc)
  • Configure your desired quality settings (layer height, shells, infill, etc)
  • Print

However, let’s say for discussion, you’re not getting ideal results..

Getting an optimal first layer is important to your print because it is the foundation.  If it doesn’t stick properly to the bed, you’re print is going to come out awful.

The settings involved can be very confusing.  I’ll go over some very basic settings.

Layer height

This is the overall “print quality” and determines how smooth the walls of your print will appear.  The typical settings range from .1mm to .3mm and higher for really rough draft type stuff.


This determines the amount of “stuffing” your printed part will get.  A general rule is more than 33% is a waste.  Very strong parts can be made with 33% infill.  For basic things like Yoda heads or non-structural parts, you can get away with 15% or even less.

Shells or Perimeters


In the above image, I’ve drawn three red lines that line up with what are called the “shells” or perimeters of the print.  This setting in Cura/Repetier Host specifies this in mm value.  You divide this by the nozzle diameter (mine is .4mm) and you get the number of shells.  This basically is the “wall thickness” of your print.  You normally will not want this less than 3 times your nozzle diameter.


Top/Bottom Thickness

This is related to your layer height, and determines the number of top and bottom solid layers.  I have mine set to 3 (3x .4mm = 1.2mm)

For most printing, you’ll want solid top and bottoms.  For Vase printing, depending on your STL file, you might want to uncheck Solid Top to have a hollow top.  Also for Vase printing, you’ll want zero infill.  Then you just set your shells to your desired wall thickness.



Designing for 3D Printing – Making useful things – Part 1

I’m starting a series of articles and accompanying videos on designing for 3D printing, using 123D Design as a starting point.  As I learn more about other software such as Solidworks, I’ll try to pass that info along.

Disclaimer:  I’m not an expert, I just figure things out and make notes here on my blog.  If those notes help you that’s great!  If I make mistakes or you know of shortcuts that I could benefit from, please leave me a comment!

This first article will discuss how to make a small simple part for a 3D printer project: A nut!  Yep, a simple nut, but this nut is for aluminum extrusion!


A good 3D printer design emphasizes a solid frame as its foundation.  Some good inexpensive material for this is called Aluminum Extrusion.  A really good supplier for this material and many accessories is Another fine distributor is 80/20, Inc.



As you can see in the above image there are slots on all four edges.  Special nuts are made to fit inside these slots.  But sometimes you need a few extra, or just want to do some quick and dirty prototyping.

In this article, I’m going to show you how to make a nut that will fit inside this profile.  Some extrusion profiles are small enough that you can just use a regular metric or SAE nut and slide it in and tighten it.  However, with the larger extrusions, the slot is too big and the nut won’t seat properly or you will have to use a really big bolt.  The nut we’re going to make is called a pre-assembly nut:



On Misumi’s website, they provide a great amount of details and dimensions to help us decide which part to pick.dimensions

It’s difficult to know which way is up with these things and our dimensions can get confusing.  The way the nut fits into the extrusion should help us:


I’m going to call 6.3 the width, 15 the length, and 14 the height, because that is basically how it will load into 123D Design.

In the above image you can see the dimensions for our part.  I will note these here for reference later:

Width:  6.3 mm
Length: 15 mm
Height: 14 mm

You can use the product configuration tool to order parts and download 2D/3D cad drawings of certain parts.  However, for the nuts you can only download the 2D profiles.

Misumi Part Config Tool


Now that I’ve made my choices, I’m going to download the 2D cad file.  Here is the file that I downloaded if you want to follow along. Here is the part profile that I downloaded. It is for the HFS6 30×30 extrusion profile.

Inside the zip file are three .DXF files.  Each has a different profile design and I’m going to use the one that gives me enough room to insert a standard M4 nut into the back of the 3D printed part so that I can tighten the screw appropriately.  The three choices for this part are:






I picked HNTT6 because of the wider bottom (which is pointing right).  This gives me room to create a nut capture hole for the M4 nut.

Opening the .DXF files in Inkscape allows me to edit them and remove all the stuff I do not need, so that I can save it as an SVG file.

Here is what it looks like after I cleaned it up:



I’ve selected all the parts (Control-A Windows). Then we have to click on Path, Stroke to Path then Object, Combine so that when we load it into 123D design we do not get an error message stating it could not find any valid paths.

Save the file as an .SVG on your desktop.

Now we’re ready to import it into 123D design.  Open 123D Design, the click the 123D Menu drop down to open the menu, and select Import SVG, then As Solid.


Here is what it looks like after the import:



Looks great!  However, you need to inspect this closely.  The file I have imported seems to have two faces.  So when I click on the top of the solid body, and move it over, this is what I see:


You can see there is an outer shell.  So I drag the solid to the left to reveal the entire shell, then I select all of it except the solid and hit delete.  This is easier done from the TOP view:




Now we’re going to do some measuring.  We want to measure the length, width, and height, and we’ll need to put these somewhere so we can recall them.  I use Google Docs/Spreadsheets for this so I can do the math there as well.


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Use the measuring tool and measure from one edge to the other being careful to select just the edge and not the face.  Make sure you select furthest parallel edges to get the overall size.

As you can tell, it is wayyy too big.    So we need to scale it.  But as far as I know, 123D is not a “Parametric” design tool like Solid works.  So I haven’t really figured out the easiest way to re-size something to specific dimensions, so I’ll show you “my way”

I measured all the dimensions, and put them into Google Sheets.

I then added a formula column to show me the scale factor.  This is determined by dividing my desired dimension with the measured dimension:



Now, I can go back to 123D Design and select my object, then select Scale, Non-Uniform, then enter the values above.  However, 123D Design only allows 3 digits to the right of the decimal, so we have to round to 3 decimals, so I added that to the sheet:


Now we can scale it properly.  Sometimes it’s hard to know where the X, Y and Z are relating to our dimensions, so just change one and observe how it shrinks, then you’ll know.


After we’ve scaled it, we can re-measure each dimension to see how close we got.


My end results were 6.322, 15.008 and 14.00.  These are totally acceptable!

Now we need to make a hole for our screw and a nut socket.

You should use some inexpensive digital calipers to do your measuring.  Here I am measuring the diameter of the nut.

PLEASE NOTE:  I didn’t have any M4 Nuts!!!  Argh, so I had to use an SAE nut that was approximately the same size.  The dimensions below should work as well for M4.


We’ll need a cylinder about 4.2 mm in diameter for our M4 screw, so we’ll enter 2.1mm for the radius.  Note, we’re making the hole for the screw, not the nut.  Drag the cylinder around until it “snaps” to the center, and enter your dimension of 2.1 for the radius and 20 for the height:


Next we need to position to make the face of our cylinder and the face of our shape to be flush:


Now at this point we could “cut” the cylinder from the shape leaving a hole, but let’s add our polygon first.  Use the Draw Polygon tool:


We want to “snap” the polygon to the center of the cylinder:


The diameter of an M4 nut is 9.45 mm, so we need to divide that by 2 and give it a little extra, so we’ll go with 4.75 which will come out to 9.5mm.  We need 6 sides for our polygon.

Now let’s extrude our polygon into the object and that will create a 6 sided hole:



The nut is 3.2 mm thick so we’ll enter that as our depth:


Now we can delete the sketch that was left behind:


And lastly, we can cut the cylinder from our shape and we’re done!



Now let’s print it, and see how it fits!





In my next post, I’ll show you how to take an STL file, and convert it to a 123D Design object that you can edit!  Stay tuned!



3D Printing Fusible Alloys

I’ve been doing some research on fusible alloys. These are metals that have a very low melting point, around the temperature of boiling water (212 degrees F, maybe 95-100 degrees Celcius).

Care must be taken with many of these alloys because of most of them contain toxic ingredients such as Lead, Mercury and Cadmium.

The mixture I see working that is non-toxic is Bismuth and Tin.

So the steps roughly seem to include the following:

  1. Build an extruder
  2. Buy some Bismuth shot and Tin inguts
  3. Melt them together 62.5% Bismuth, 37.5% Tin
  4. Extrude to 3mm filament
  5. Print metal objects at about 95 degrees celcius

With a dual extruder setup, we could use High Impact Poly Styrene as a support material and dissolve it using Limonene.




Buy Bismuth from




Buy Tin from


Who’s with me!? In case anyone does this, you read it here first ! lol or maybe second…

Finally getting some decent prints

After what seemed like endless hours of fine tuning, I’m finally getting decent prints.  I still have work to do, and learning to learn, but I’m happy with the results so far.

Here is a vase printed at .2mm layer.  That’s like a “medium” setting, and is my standard setting.  The nozzle in my printer is .4 mm.  This red plastic is called High Impact Poly Styrene.  It doesn’t warp like ABS and so far has been a real gem to print with.  It’s also harder than ABS.


Here is a thing that someone tossed out as a challenge for RepRap machine owners.  mine printed it fairly.  I mean, it printed it.  Without failing.  But I wouldn’t call it amazing… yet.



I decided to load up the PET+ that I bought a week ago at MicroCenter here in Dallas.  I had been reserved about printing this in my cheapo Jhead hot end because it has a PTFE liner inside.  If you run that hotend too hot, it will melt that liner.  Well, PET+ needs 250-260 degrees C to work properly.  Well, it printed nicely!  I’m so stoked by the results.  I’m quite amazed that this machine that I built out of random bits, fine tuned over about 150 hours of work is producing these results.  I’m not giving up on fine tuning because I’m sure there is more to do, but for now I’m a happy printer owner!


2 inches tall by 3 inches across the top.

Madesolid Sapphire PET+ 1.75mm diameter

Printed in sprial mode, .2mm layer, 250-260 degrees hotend, 90 bed, probably around 40mm/s

Koch Tealight Vase on Thingiverse

Here is a sample of the layering consistency I’m getting at the moment.


Analysis of the Y Axis (Bed) on a Cartesian style printer

I’ve been observing the dynamics of the print bed on my 3D printer which is a Prusa i3 style Cartesian printer.  The bed has 3 linear bearings that rid along two smooth rods.  The bearings are arranged in a triangular pattern, with the drive belt down the center line.  I have noticed that with some bearings, that have play or are loose, I get wiggle in the bed.  I believe it is due to the following:


I’ve surmised that because the bearings have play, the motor applies a force on the bed which the single bearing receives as force across the horizontal axis in this picture, which is opposite (accros) the belt. This allows a “wobble” or slight rotation of the bed in the center point of the triangle.  Because of the unreliable specs of the bearings, each has a different tolerance and even the smooth bars may not be manufactured to any type of specification.  If the bearings aren’t fitting on the bar with minimal play, then you will get inconsistent layers, and your walls will not be smooth/straight.

For beds arranged like this, the situation is different and maybe non-existent:


Three bearing designs are great for machines that have expensive, tight tolerance components.  For RepRap printers, four bearings are probably better over all.

The following approach would minimize the problem for three bearing designs:


The reason for this is that in three bearing designs, you typically have “leaders” and “followers”.  The Leaders are the drive bearings.  The follower is a supporting bearing.

These are my theories based only few hours of observation and non-scientific brain-storming.  I’m not an engineer, just a mechanically inquisitive person who was raised in a junk yard.

Hardening your Prusa i3 3D printer

I believe the current and original design of the Prusa i3 3D printer has a lot of areas that need improvement.  It seems the printer serves a great purpose of teaching you about Fluid Deposition Modelling (FDM) printers, but as a printer in itself, it leaves a lot to be desired.  They should have called it “The Trial and Error Printer.”

If you make the mistake, as I did, of building your printer out of lexan or acrylic, you’re going to have a lot of problems.  Additionally, if you buy some random set of printed parts off ebay for your printer’s structural members, you’re going to have even more problems.

All in all, it is a wonderful  stepping stone to the next printer project, but in itself, I would not call it a production class machine that you can rely on day in and day out.  No, sadly, those cost a few more bennies.

Here are some pictures of what I have done to harden my machine so it prints more precisely.  Note, I’m not calling it reliable, or precise, but “more precise” than a vanilla kit machine.

My first priority was to stabilize the platform and frame.  I made a bad choice in using the 6mm acrylic frame.  But I’m stuck with it for now.  So I am doing the best I can with it.

I dug out a piece of 18×24 MDF for the base.  I set the printer about in the middle and marked the places where the frame had zip tie holes and drilled through the board.  I ended up using zip ties for the time being, but reality is, a screw and nut will be a more permanent solution.








Next on my list was the X axis carriage.  I reduced the bearing count from four to three, and re-arranged it so the two bearings are oriented on the top where the two belt ends connect to the carriage.  Though not scientific at all, my theory was that this was a better arrangement to control wobble on the X axis carriage.




The next big area of improvement, especially when using printed bushings, is to constrain the bearing sleeves on the X axis.  The combination of ABS and HIPS here causes too much slip.  So I used M3x6 screws as a set screw.  I drilled a hole in the side of the X Motor carriage bearing sleeve using a 2.78 mm (7/64) drill bit.20150530_103421I then followed suit on the right side X Axis Idler.  Additionally, pictured above and below you can see a set screw that holds the Z axis nuts in place.  These are important because these nuts come unseated easily.



Next thing I wanted to do, but didn’t get around to it until now, is to get rid of the silly zip ties on the bed that hold the bearings in place.  I finally got these half printed before something happened and oh well I used them anyway.  These greatly minimize the wobble of the bed that is caused by the zip bearings rotating in their seat.  The zip ties do not constrain it enough.


Lastly, I used dry lube that you can get at a quality bike shop.  This is the lube we use on chains to keep dust from collecting on the chain.  Apply a thin coat with a foam brush to all your rods and move your axis all the way from one end to the other several times.

20150530_105020Now you should have a fairly stable and solid Prusa i3 printer.  There are still yet more tweaks to be done to this project-disguised-as-a-printer.


High resolution closeup of 3D Printer quality

Here are some high res photos of things I’ve printed, or attempted to print.

These were printed at .2mm layer height, green is ABS, red is HIPS.

Some of these are duds.  They either didn’t finish or didn’t make the cut.

This is a set of bushings I was printing.  These are duds because I had the wrong infill setting and you can see the dimples on the middle one’s side…


Some more bushings that didn’t survive.  Not the printer’s fault, I just had to tweak yet another setting…


This dragon was printing very nicely, albeit a few holes that I haven’t quite figured out, but then in the end, this green filament is very blobby and caused the print to fail. I’ve given up on this filament because of this issue.  It was Shaxon from Fry’s Electronics.



Here is a hollow block I printed by accident.  I had left the infill set to zero for a previous print, and this is what I came out with.

The interesting part is the excellent bridging.  Look into the hollow block and you can see the bottom of the top, where it bridged. Also, you can see the layering on the sides and how nice and even they were.  I don’t see any banding either…






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