Vacuum chamber for optical spectroscopy part 2

I've got some input from my friends and, what's more important, bosses approval of this project. Here it is how the chamber project looks like now (nice render isn't it?)

Now I'm making technical drawings from this to have it turned and milled at the workshop. This will be made from aluminum (unfortunately, as this is vacuum equipment and should be made from stainless steel), with quartz window and fluor-rubber o-rings for sealing.

Precise ammeter - the begginig.

I've started recently designing an ammeter that would be suitable for measurement of very very very low currents. Probably at the level of 1..100 nanoamperes. I need such device for measuring photo-current at work. Currently the project looks like that:

First IC is LMC6081. This is an precision CMOS Operational Amplifier, the main advantage of this op-amp is its very high input impedance (it needs only 10fA for biasing, geez, how do they measure it?!?) and low offset voltage. In this application it works as an I-to-V converter. Bandwidth of this op-amp is limited by C1.
Second op-amp is an low noise precision op-amp that will be used for amplifying the output voltage to measurable level (with 1Mohm measuring resistor R1 the output of the I/V converter is 100mV for 100nA). Second part of the OPA2227 is just an buffer to provide stable output.
PCB design is a real pain in the neck, at the current moment it look like so:

I don't have any idea how to optimize it more, especially to lower any leakage current that might change the measurement. I'm counting for some creative input of several people that I've asked to help me design this module. I hope to post some more info soon.

Vacuum chamber for optical spectroscopy

I started designing an vacuum chamber for our spectroscopy setup at work to measure fluorescence at low pressure. I would like to share with you some early plans of it. This is an image that I made using Autodesk Inventor to show how it may look finished.

The body will be made of aluminum, the windows (far on the left) probably quarz. The NW25 flange on top is for connecting a vacuum valve and pump.

I hope my boss will like it :).

Fried Amiga PSU

I have recently fried my Amiga powersupply, so until I don't manage to get a new one or repair this I will not be showing any Amiga goodnes. The good thing is that my Amiga is still alive (I've tested in on a AT PSU).

Okay, so from now the plans look like that:

• Repair the PSU for Amiga.
• Get some internet on the Linux Box to apt-get needed software (eg. setserial) and download the .adf's for Amiga.
• Install AmigaOS 2.x on the Amiga (as now I have Kickstart 2.05 and probably will not change it for 3.1 now).
• Run AmiTCP. Internet on A500 !!!oneone
• Finish the plans for PAK68/3. I'm planning to make this accelerator for my Amiga, and now I'm at the beginning putting all the schematics into Eagle.

In the mean time:

• Try to write some software for the AT90USB162 on the Intersil evaluation board. I've checked that it can be done. One can download the whole .hex file from the uC and program it with something else.
• Have some fun with a rack. And Eurocard. More info soon.
• I have some loudspeakers to repair. As this is part of a pending project the priority is high :).

Linux Box, some serial buisness.

Yesterday I managed to get sme spare time to get a new computer up and running. This one is planned to be a Linux Box with various uses (for now it has one). The computer itself looks rather harmfull and compact: 

Inside there is a industrial motherboard in PICMG 1.3 standard with an backplane for 6 PCI-X cards. On the card - double Xeon 2,8 GHz and 1GB of ECC DDRAM. Sounds like enough for most of the things that I could be capable of imagining to do on such machine. Also I crammed an SCSI controller that will be mostly used to interface to 50pin disks that I use for the Amiga (as far as I know Linux is capable of mounting FFS and/or OFS file systems). As for software I went with Ubuntu Linux - probably out of laziness (as I had it on some Live CD). I've downloaded the newest distribution of the Ubuntu Server and just installed it on this machine. As the ethernet connection is not running on this machine (dunno' why, have to check it) I haven't installed anything more.

So, let's try to interface with the Amiga. I have connected both computers with a Nullmodem (a standard one, not some of the fancy 'ADF-transfer kits', that people are selling (price of a nullmodem x 10) and in fact these ARE normal nullmodems). So I chose some example file on my DH0, and typed in on the screen to see its content. After that I started the Linux Box and made it to start listening to the serial port (ttyS0):

cat /dev/ttyS0

This wat you will see it on the display, but yoy can redirect it to a file by using the >> {your file}. Then, on Amiga, I have sent the file over a serial:

type {your file} to ser:







As you can see - it works. It works accidentally as I have not done anything to set the serial port parameters, both computers are working in the default settings. I have to install setserial on the Linux Box to be able to configure the serial port, and in order to do that I have to have an internet connection on it up and running, so I guess it's the closest thing that I will be doing.

Some initial evaluation

So today I've received a package from Intersil containing their ISL26134 Evaluation Board. As I have not read the application note earlier I didn't knew what to expect. Surprise was big, just look at the board:

Photo by Intersil.

So we have the full application of the ADC, with all four channels, internal and external reference voltage and all the configuration pins jumper-controlled - nice. But there is more! after a Si8441BB galvanic isolation there is a uC, an AT90USB162 AVR. Let's say that this part I've been expecting (as a maximum) but the uC ISP pins are on a standard 6pin pin-header(!) and there is more - four switches, some LEDs, even an SPI port on a header... hey - is it an ADC or AVR evaluation board?

Tomorrow I plan to do something more than installing the software on my PC. First let's test the board, second let's test the AVR. I hope I can get to it's software (for backup) and then try to reprogram it to use the evaluation board for some future fun.

Amiga Kickstart switcher installation

So let's get starting! First with a Kickswitch installation in my Amiga 500. 

I've recently bought an Kickstart switcher by random chance. Instead of buying a fully tested one I've decided to go for a untested one, that I've found on allegro. It was a set with a A500 rev 6a motherboard in a not-very-mint condition but still everything seemed to be in place, so there I was:

After checking the electrical connections of the switch I delicately pryed the old Kickstar ROM from my Amiga and inserted the connector into the socket. I have insulated everithing with some foamy stuff used for packing electronics (after checking that it is not conductive).

First boot - Kickstart 1.3:

Reboot and switch the kick - Kickstart 2.05 (I somehow expected that one):

 

So... I got a Kickstart switcher up and running for half the price of a regular (fully tested and/or new). Next step - reflash the Kick from 2.05 to 3.1. I hope to get my hands on some eeprom programmer at work.

Let's get started.

Soooo, it seems that I'm starting yet another blog, this time with a plan to keep a strict schedule of uploads and posts ;-).