1Q after, progress? zero.

After first quarter of the year I though about summarizing some stuff and making some plans for the near future. So, my main thoughts:

1. I did almost nothing in the field of the reenactment  Apart from buying early medieval shoes and a some padded garment for fighting no stuff here worth mentioning. I guess that this stuff will be on hold for some more time.
2. Almost finished with my stuff for airsoft. The rifle is complete and working with 420 feet per second on a 0.25 g BBs and the gear is also complete (apart from med-kit 'stuffing'). Maybe I should post some photos soon...
3. VME crate
1. The crate itself is almost finished
1. Only thing lacking are several nuts and screws and double checking everything if it's ok.
2. The CPU card is running fine
1. But in order to attach an drive to it I need to prepare an breakout box for the P2 VME connector.
2. If it will work I will be able to put an SCSI drive there and install an Linux OS.
3. Together with VME Universe drivers.
3. As soon as the above is done I start working on my own VME card. For now I have CPLDs (xilinx) for the addres decoder and data latch. 
4. Apart from VME CPU card I have an STEBus card that needs to be tested. It has CGA or similar graphics, so it will also need some work to run.
4. At work I'm into several projects that I try to describe here:
1. USB 24 bit 80 sps ADC
1. Need to master the USB connectivity of the AVR used there.
2. After that - write a protocol to work with an LabView developed software easily.
3. Write some code to use the ADC that is on the board, but this should be relatively simple.
2. Short pulse generator
1. Build the pulse generator, as this part is already fully designed.
2. Test some ways of producing high voltage, high current short pulses. I have several routes for that in my head, so after testing them I hope to achieve the parameters that I need.
5. I have acquired some nice machines recently, some of them even running. I guess that this place, apart from the Inventory, is a good place to sum it up.
1. Tulip 8088:
1. Needs cleaning of a leaked battery.
2. And installing a new one.
3. Display - has an CGA card, I do not have an CGA monitor, although I have an CGAtoVGA converter (that needs 12 V to work). It should do the trick.
4. Keyboard - this is an XT, so I need to have an XT keyboard or an XT-AT converter.
5. I intend to use the 8088 with an Xircom Pocket Ethernet do I need to install drivers for this. 
2. IBM 286 is fine and working. 
1. I need only to install Xircom PE3 drivers.
2. And maybe some additional software.
3. 386 is dead at the moment (RAM error I guess)
1. Investigate the RAM error (first 64k). I hope that this isn't a dead motherboard case...
4. 486 is working but without any OS
1. The main problem is in forcing it to boot from a FDD. The FDD is controlled by SCSI card, and this seems to be a bit problematic.
2. If this will work, and the SCSI HDD is alive (it should be) only thing left to do is to install some OS, preferably Windows 95.
5. PICMG Pentium
1. Put it together maybe?
2. Definitely put it together and make it run.
3. Install an OS.
6. PowerMac 7200
1. Need to buy a keyboard; 
2. And mouse (both with ADB interface).
3. Install new Mac OS (9.1?) - english! current is in german.
7. Amiga 500
1. I don't event know is it working still and if I do have all the parts ;-). j/k, but still have to put it together.

I guess that this is all that I have on my mind now. I hope that I will be able to cross out some of this things in the next 3 months.

Short pulse generator, part 1.

Some time ago I have started designing an short pulse generator for time-resolved spectroscopy of electroluminescence. At first the design requirements were high, but after a market query, in search for devices capable of meeting these requirements they were lowered down significantly.

The sample for which this device is planned is a thin sheet of material suspended on an alumina frame, that acts as electrodes. We have measured DC I/V curve for the sample to assess the working parameters:

Therefore what we need is voltage of at least 35 V with current of at least 250 mA. In order to have an reserve in the parameters I assume that we need at least 40 V and 400 mA. For sake of simplicity I assume that the load of the device is almost purely resistive. Assesing the time parameters was a harder thing to do, so I assumes that the lower the better (the pulse time). Where is the limitation? In the power stage.

Using a simple generator, shown below, we are capable of generating a ~1 ns wide 5 V pulse with ease, using standard, from-the-shelf components. This could be even improved with faster ICs (comparators and AND gate.

From this Linear application note.

But this circuit generates only 5 V pulses (or close to that, this is the power supply voltage of the output AND gate). Also, the current is very limited - to 10 mA, offered by a TTL gate. In order to improve these parameters we have to add an output power stage, that will have output current and maximal voltage on the level of the planned device and could be controlled by an TTL pulse. To meet these requirements I have chosen several routes to achieve that:

• A set of parallel bipolar transistor put in the common base topology. This should allow to achieve high rise and fall time of the pulse, but a current of a single fast transistor is low (tens of mA) so I need to put lots of them in parallel and I am not convinced that this is totally safe and will not affect the working of the device.
• A (most probably single) FET/MOSFET device. An easy scheme for achieving high currents, even of hundreds of amps, but the pulse time will be significantly longer. With a dedicated driver and chip-to-pcb mount some people achieved 25 ns pulse width, although with a current of 100 A (as soon as I find the paper I'll post a link here). A stand-alone mosfet usually will have a rise time of several ns and fall time of 100 ns or more.
• A dedicted IC. A RF power amplifier or a MOSFET driver. The first type of ICs seems to be a good idea as it offers tens of GHz in bandwidth, although when I have looked closer in this matter it seems that such IC will only work good in a typical circuit, for example an WiFi amplifier or so. On the other hand, some MOSFET drivers, are capable of almost meeting my requirements. EL7158 from Intersil is capable of producing 12 A pulses with rise and fall time of 12 ns (with 2000 pF load). This gives a chance to produce a 25 or shorter ns pulse, although the voltage is limited up to 18 V. Although this is not the only such driver on the market...

So currently I'm on the stage of parts requirements stage. As soon as I get something new I will post it here for sure.

VMEBus crate - why not.

Recently I have acquired an VME CPU-Card and thought about testing it somehow. As after powering it up the card seemed to be alive I have decided to give it a shot and try to put together an VME crate.

For that I have used an old Eurorack that I have got from some phone central (or some similar telecommunications equipment). After checking that the size of the crate is standard I bought an backplane from e-bay for... 1 Euro (plus 12 for shipping, but that's not the case). Unfortunately only this backplanes are so cheap, regular VME equipment is pricey as hell.

So i have started from taking apart the old backplane:

And putting the new one:

Sorry for the mess. You can see that here the backplane is already in position, and connected to a power supply (it takes 5 V and +/- 12 V). The PSU is also taken from the same equipment that the crate is.

This (above) is the CPU card (on the left) with the display controller removed, and the display controller itself (on the right). The CPU Card is an Pentium 120 MHz with 64 MB RAM equipped with Universe Tundra VMEBus controller. Fortunately there are plenty of drivers for this PCItoVME bridge. The cards equipment covers a wide range of peripherals - starting from two serial and one parallel port, going through VGA, Ethernet and finishing with SCSI-II. The card has two PCI-compatible slots, one of which is occupied by the display controller. It also has an PC/104, ISA compatible socket. The SCSI, together with the FDD connector are on the P2 connector of the VMEBus, so I will have to make a special connector going from the P2 on the backside of the backplane  to the SCSI harddrive. As far as I have tested the CPU-card is fully functional so after I get some free time I will try to connect an SCSI HDD to this setup and install some Linux maybe. After that I plan to go back to few years ago when I was studying and try to re-learn VHDL in order to make some VME cards for this setup