Wednesday, August 6, 2014

A Photoduino variation

Well, I'm sure someone has heard of the Photoduino. A DIY controller for cameras and flash units based around the Arduino.

The Photoduino has a bunch of sensors such as audio, light, pressure and can control various devices such a camera, flash units, laser, LED, solenoid and whatever you can plug in to it.
I  built mine based on the photoduino website and made a few changes, mostly software. The biggest difference is the screen, wich originaly is a small LCD with a parallel interface. I had this lovely VFD display lying around and it ended up in the project.

Now the VFD is a serial device so that meant changing the code and making the software play nice with it. While doing so I decide to do some modifications with the buttons, menus, configurations, multiple languadge support, volume control, extra control ports and provably other minor changes.
The software is based on version 9 and hence the ALT meaning alternative version.

A small mishap (or rather, a string of bad luck) meant burning:
2 Atmega328
1 Atmega8u2
1 USB to serial adapter
1 Disconfigured VFD
If you include the eBay shenanigans, other things breaking, burnt fingers, having to travel 200km for parts and forget something then you could say it was a pretty depressing week!

I never really figured out what killed the Arduinos. The VFD used to share the serial TX from the Arduino so when I programmed the sketch I had to remember to turn the display off or garbage would be displayed on the device. But worse than garbage is changing the configuration parameters of the VFD and it's subsequent lack of functionality, hence the 200km trip to pick up the original VFD wires, install a virtual windows XP (the software only works on XP or previous), setting the configuration and getting everything back up and running.
During this proces the USB adapter and Arduinos died. All 5V TTL signals, current limiting resistor on the serial lines, working in a ESD safe area, verifying the dead microcontrollers with AVRDude, all grounds connected... No idea of what happened.

The photoduino now runs on a damaged arduino with a dead Atmega8u2 programmed via ICSP and the VFD runs on a sofware serial pin with an apropiate current limiting resistor (even the atmega8u2 had resistors on the serial lines and died)

I finally got around to labelling the conectors, a great improvement in functionality! Well... more like less wasting time guessing which conector does what.
Another change is an extra IO used exclusively for IR remote control of the camera.

The cheapest enclosure I found is a storage box from a hardware store. Such a waste of space...

Actually it doubles as a container for the sensors, cables and power supply!

Did I mention L.A.S.E.R.? Everything is better with mighty lasers!

Oh, yeah! And a sample shot that left me with a very oily kitchen and popcorn everywhere!

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Tuesday, July 1, 2014

Mini flash with optical slave

Normally each year around christmas I will be involved in a couple of Secret Santas and one of them is a "all hand made" type where buying the gift is not allowed. Some very creative gifts have showed up!

Turns out I had to come up with something for a photographer... being one myself I know there are many usefull things to make but many are expensive or take a decent amount of time to build.
In comes a mini slave flash with an optical trigger!

Like many projects things don't tend to run to well on schedules so I deadbuged the circuit of a disposable camera flash so it would fit inside the case and have room for the battery (nope, didn't happen!). Here is the circuit diagram for the flash from Sam's repair faq.

In order to squeeze the battery inside of the case everything needed to be small and well laid out. Unfortunatly the transformer is what ultimately stop my from my goal. I had to come up with a small and simple trigger for the flash unit. Provably too simple if used in broad daylight, but i works reliably in bright artificial lighting.

Three components make up the trigger. This conects directly to the trigger pins of the flash circuit.

Here is a side view of the little flash unit.

And another from the back. The beam pattern is maybe a bit too wide but it'll do!

And a size comparison to a comercial flash unit.

So what could it be used for? Small spaces, highlights, inside objects... lots of uses!

The person I gave it too seemed to enjoy it quite a bit. I hope he can find a use for it.

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Monday, June 30, 2014

Allegro 2917 Dual stepper shield

One day a came across a great find, a HeNe laser scanner/projector , a 2000W stroboscope with a color wheel, a Gobo/disco scanner,  a buch of HP printers and other various electronics.

I recently had aquired an Arduino UNO from cooking hacks and with the abundance of obtained stepper motors I wanted a small platform to easily control them. While disassembling the HP printers I noticed that they had a small IC to controll the motor. After a quick search of the part number I found out that they were dual H-bridge IC (45V 1.5A) with current controllable current limiting.
The project began! I found a template for the Arduino headers and got to work in Eagle. This was my first time using Eagle, and provably my third home made board, please forgive the horrible layout!

Not to mention that I placed many vias under the IC's... I had to make sure that they all made good contact and that they were flush with the board before placing the IC on top.
Solder, check, repeat. The same for the other IC.

 Things were going well, wrote some code in the Arduino IDE. Enable OK, phase OK, PWM... not ok. Motors would spin well with low supply voltages but would stutter with a higher supply voltage.
Re-check everything and find out that the stuttering only happened on one of each phase of each IC so I decided to sapw the chips over. The same behaviour on each phase of each IC. So basically the chips were damaged from the begining :(
For some reason I choose to take the board apart so I could stick it the oven pull the IC's off (pretty hard to do with a 25W soldering iron when 22 pins are part of the heatsink/ground plane).
Turns out the cheap boards I purchased were not FR4 material... well thats the end of that project!

For those that want the files they can find them here in Eagle's format.

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Wednesday, June 25, 2014

Tesla Coil

Any one who does electronics should know about Tesla and if you are into high voltage stuff then there is no escaping the Tesla Coil!
On Christmas break 2010 I was tidying up my room when I stumbled upon my second Tesla coil (my first being a micro coil on a Smarties tube) made from a giant Smarties tube. Suffice to say they were both pretty much a failure...

Misaka is not impressed...

So I decided to build a real Tesla coil! Well, actually it was on my mind for a while, I even managed to pick up a used Hameg HM203-6 20Mhz scope for 125€ (Yes, that is cheap. The lowest price I had found for a second hand scope...) to really help to tune the tank circuit.
After doing much research to properly understand the theory of opperation and minimum design requirements I chose to use JavaTC to do most of the calculations and ended up with a flat primary design to keep things simple. The coil has:
-A 901 turn secondary wound with 0.05mm wire and a lenght of 50cm and a diameter of 9cm.
-A 12 turn primary wound with 6mm wire and an inner diameter of 15cm and outer diameter of 32cm.
-A spherical topload with a diameter of 28cm.
-A 20nF 15kV MMC bank.
-A ballasted quad microwave oven transformer stack (aprox 5400W).
-A static spark gap with 5 18mm diameter pipes with a 4mm spacing in between and another adjustable gap.

The tesla coil is still not finished due to lack of time and funds but here is the proces so far!
From the start I was in a rush, xmas break is only for about 2 weeks and I had plenty of other commitments apart from tinkering with copper! There was no way I would be winding the secondary by hand so I used some wood and some skate wheels in much need of being changed to build a winding jig. I added a DC motor from an HP printer and a model train set power supply. I was crude and build in about 30 minutes. Suprinsingly it's still in one piece somewhere.

The PVC pipe used as the form for the coil got a good cleaning followed by lots of sanding to remove all traces of ink, dirt and other unwanted grime followed again by more washing and drying.
I needed a way to keep track of how many turns I had done so I resorted to the calculator method of "1+1="... on a computer.

The calculators I had either were too simple for this method, were not mine or good quality devices that I would rather not modify. So I cracked open a USB keyboard and traced the Intro key and wired up a magnetic reed switch:

The reed switches are the little black components on the PCB on the winding jig and come from a nice big DMX 2000W color strobe. Just add magnets!

The magnet (fragment) is from a hard drive and works very well with the reed switch. After a while and a few interruptions the coil started to take shape. It's important to do the coil properly and "save" your work with a bit of tape so that it doesn't completly unwind!

After much winding the secondary coil is finished. The coil is designed to be modular so the secondary can be simply droped into the primary so it is easier to transport. A stip of metal tape forms the ground contatc under the primary.

To make the secondary look even better and to stop humidity getting into it I painted it with some varnish. It also stops the coil from unwinding. To stop the varnish from sagging while it dried I applied the coats on the jig. I followed the instructions for the varnish but... It didn't dry properly!! ARRGGGH!!!

Here is a mockup of how the Tesla coil should look, notice how the top load is made from two Ikea bowls placed on the secondary.

The first low power tests were nothing impressive, but hey, no tuning at all!

The coil was being powered by a F.A.R.T neon sign transformer (Yes, they are a company named fart) that I got for free, sadly it was not fully functional but hey, it was free!

After much tweaking I found out that the topload was to big for my home made capacitor (the white box poking out the side of the cabinet) and that my capacitor was too small. Notice the color of the primary coil, it's not copper but steel cable witch is not very good for high frequency and high power jobs. Basically my coil was severly underpowered, the transformer, the capacitor, the tunning, the spark gap, the primary... nothing was perfect! I built an MMC with 10 1500V 100nF capacitors and got a slight improvement.

I needed more power. I wanted more power. More power is always better!!

In comes the 5400W MOT stack. It has a tendency to BURST INTO FLAMES when least expected. I need to get it under oil and improve the wiring. It is ballasted with a giant 2200W MOT with a shorted secondary. 16A breakers don't play nice with a 5400W Tesla coil, I need to find a way to soft start this beast and remove the ballast...

Next up is a better sparkgap with a more uniform separation of the electrodes plus an adjustable sparkgap (I can adjust it with a 3m wooden stick with a screwdriver on the end). It also has a hair drier blowind air over it.

A better MMC was also built, now it has a total capacitance of 20nF. I am still really pushing the 15kV rating... The plan was to build 4 strings of 15 capacitors for 26.5nF and 22kV but... money.

The primary coil got a major upgrade from steel cable to copper cable that was donated from a local workshop. The primary runs a bit cooler and that translates to less power loss!
The supports for the primary (and for the MMC) are made from 5mm acrylic sheets. I got these from a truckload of Point Of Sale units, they are the backlight difuser screen. Easy to work with and very strong.

The top load was also improved with a proper mounting method so I can take it apart easily. Made with more acrylic. Maybe the top load is too high now...

And that is my Tesla Coil so far. I hope to tune it better and get some decent wiring in place (flimsy alligator leads don't work well, they like to melt).

I also purchased a small AC motor from a scrap yard to try and convert it to a synchronous motor for use in a rotating spark gap.

This meant grinding two flats on the rotor. Grind too little and it's not synchronous, grind too much and it will overheat...

I managed to get it to rotate synchronously but the motor just got too hot to use. So that is another thing to improve!

So, how did these improvements affect the Tesla Coil? Quite well actually!! I believe there is plenty of room for improvement, I am getting 70cm long streamers and I am sure that could be improved to up to 90cm with some care.

The top load is provably too high and causes discharges from the secondary, these could be disastrous for the Tesla Coil and are also a safety hazard to the user if it strikes the primary coil. Another addition should be a ground ring just above the primary coil to help prevent secondary to primary strikes.
I honestly have no idea what it was striking... It never striked the grounded rod near the coil nor the step ladders on the wall but liked to strike the wall. Radio frequency high voltage is very hard to predict, so take speciall care around Tesla Coils!

In my case I don't just discharge the MMC bank, but also the top load (holds a decent charge) and the secondary coil (OUCH!). The varnish coating strores a tremendous amount of static charge wich I found out the hard way. Trust nothing, short everything!

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About a PS3

So my mother bought a PS3 in 2006 or 2007 because it was the cheapest Blu-Ray player on the market. Of course if there is a way to run code on it I'm in!

The chosen path was a PSGroove based around the PIC18F2550 (My first microcontroller with native USB!) and here you can see how simple is is (and what a waste of a PIC!).

So why even post about a 2007 PS3 hack? Well, I only have 3 games for it and only one of them gets played (Trinity Universe). Now, I really dislike loading times, so I have a copy and play it from the internal hard drive. All is great up until now as the PS3 was upgraded from 3.41 to 3.70 (most likely a Blu-ray movie) so the solution is invasive surgery (direct NAND manipulation)!!

After poking around the net I found it is possible to reflash the internal memory of the PS3 so that is something I would like to do (plus it's an exscuse to delve into the console) but I do not want to buy a special flash tool.

It can be done with a cheap Teensy++ 2.0 so that got me thinking a bit. After looking around on many forums there don't seem to be many options for DIY tools. Either the Teensy++ 2.0 or Progskeet or other more expensive tools or kits. Of course I could buy a teensy but I don't like the idea of spending money on a relativly low end and slow board. I already have an Arduino Uno and various PIC boards.

I am assuming that the lack of other DIY tools is due to the programming involved with the microcontroller. Therefore after looking into some of the code used and chip timmings I believe it would be a great experience to "port" or write new code for a developing board that interest me.

Something nice and fast with plenty of I/O and a host of features yet cheap and easy to use in projects. 30€, 48IO, USB host, 70Mhz and up... Well... thats for another time. I have other projects to get done first and learning how to properly handle flash memory, USB connections and data managment.

In the meantime I'll just have to deal with the loading times and search for a nice development board!

Here is a photo of my previous P16PRO programmer before getting a wonderful pickit2 :)

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