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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Monday, August 13, 2012

Studio strobe power hack.

Hello again everyone. Today I shall share a usefull hack for cheap photographers like me. Story time; I bought a couple of monoblocks on eBay a couple of years ago, and after lots of thinking I settled with the Godox Mini Pioneer 300DI. Why? Because two of them cost me 270€. With shipping. So, what is the catch? They are pretty close to 300W/s. They do work. But the power control is miserable. 1/3 to full power... not what is advertised!

Last year I added a switch and some diodes but that didn't work too well, especially when I accidentaly flipped the switch with one bank of capacitors fully charged and the other bank pretty empty... result? A very strong weld inside the switch. Lets begin!

Here is the circuit diagram, pretty simple. Two 3A diodes are responsible for the capacitor charging and blocking revers current flow. A larger 60A diode with a surge rating of 950A is used for blocking the charge from one bank to the other and allows the bank to discharge into the flash tube. The strobe has a 10A/300A diode in series with the flash tube but I think that it might be pushing it so I used what I had on hand.

Please be carefull as there are high voltages and juicy capacitors inside. If you don't know the dangers then I suggest you don't do this.br />

Please ignore the yellow wiring and the power resistor. That is my old hack.

This is the flash end of the strobe, to take it apart we need to desolder the four wires and disconect the trigger coil.

The boar can then slide out the back, here are the conectors for tha back panel and their names.

The front end desoldered.

The hollow case.

The top control board. From left to right and top to bottom;
Sync terminal. "Isolated" with an optocoupler but the negative part of the IRLED is conected to mains with a resistor. So much for bein isolated... I do not recomend using these strobes with a PC cable.
Discharge diode. Used to double the tube voltage when firing. Page 5 of this document.
BTA16 Triac. Used for the modeling lamp tracking.
PIC12C508A. Sole purpose is for pre-flash control.
12v Zener diode to power stuff.
Buzzer and buzzer switch terminal, I cut the link to remove the anoying beep.
TL7805 voltage regulator.
BTA20 Triac. Provably to control the charging circuit.

Capacitor bank and provably a voltage doubling circuit. 7 800uF caps rated at 360V.
A total of 5600uF charged to 330V gives 304Joules.

Underside of control board. A small SH69P86 micro controller is provably responsible for all of the functions. Wich aren't many.

Underside of the capacitor bank. Again, please ignore my awefull hack.

As you can see, the track width is very small on this trace. Especially when it's the discharge path for the flash... Scrape away and apply some solder to help things a bit!

Onto the hack! First I removed my hideos hack and bridged it. Then I cut the track as to separet the bank into two banks of 2 and 5 caps (do as you wish here). And finally at the rightmost part I cut the trace from the charge circuit.

Here I placed the charging diode for the small bank.
Important note! You must place a resistor to the same place as the diode because the diode blocks the reverse voltage and the charge control will not know if it is charged or not! Mine simply didn't charge above 150v, some might continue.

I used a 4.7k resistor as it only draws 300uA. Values up to 100k work but the charge voltage goes up to 350V wich for cheap 360V caps is provably not the best idea. But hey if you want more power now you know!

Edit; Here is a picture from my other strobe of the resistor in place.

Here I have placed the switch, the second 3A diode, the powerful 950A surge diode and I have conected the main board again.

Important detail! The ground wire is conected to one of the scews, don't forget it.

Reconecting the flash head.

Back into the housing. This is where I soldered the 4.7k resistor, on top of the diode. I had to be carefull not to melt the wires. Yeah, I'm lazy.

New switch, uppside down but that can be fixed.

It lives!!

Now for some numbers with my trusty L-358!
The difference between low power and high power with the small capacitor bank is 2.2 f stops.
The difference between low power and high power with all the capacitors is 2.4 f stops.
The difference between 7 and 2 capacitors on low power is 1.5 f stops.
The difference between 7 and 2 capacitors on high power is 1.5 f stops.
The difference between low power with 2 caps and hig power with 7 caps is 3.7 f stops.

When I get hold of some more 3A diodes I will modify my other light!

Happy hacking!

Oh, and if you got this far, check out my photos as many studio shots are taken with these.

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