I’ve been quiet for some time again becaus I became a member of the vieHAB Project. It was started about 4 years ago by Erwin (OE1FEA) but remained dorment for the most of this time. We met at the monthly Metafunk amateur radio meeting where I attended a course to get my ham radio license.
Basically I wanted to do such a project for a long time but never got around doing it. So I jumped the opportunity and became hardware guy. The whole project will be published as OSHW. For our first start vieHAB-1 we will use ready to use modules like an arduino and ublox gps on breakout boards with a backplane.
It is planned to have 2 cams, 2 temperature and preassure sensors, 2m and 70cm radio, GPS and SD-card on board for the first start. I will keep you posted on progress every now and then.
I was trying to repair my tek 2236 and was in need of measuring a -2kV line, only problem: my best Multimeter can only do 1000 V so I had to yank up 30 3k3 Ohm resistors in series to make a 100M Ohm Resistor. All put into some trash plastic tube makes a usable series resistor for the MM.
Be sure to watch the safety advice and keep your hands off the circuit under test!
Good ideas not always turn out for the best but have some value anyway.
The two trafos you see are way to “soft” and at 200 mA the output will drop from 220 VAC to 210 already.
Nevertheless it works fine until that and I will just have to wait and see if some better trafos find me.
I just made up some working test setup for the homebrew oscilloscope project and the screen came to life for the first time:
Here is my setup:
By the way is the 3KP1 / DG 7-113 with the green p1 phosphor. If you ever come across the white phosphor (3kp4) you found some nice piece of rareness. The P4 version was used in the Pilot TV-37, one of the first portable TV-sets. Check out David and Marlene McClellans blog about restoring one! Also check out some video of it here.
While I was working on my Oscilloscope project I discovered, that breadboards are only semi-useful for Bigger things. Everything seems not to add to your project but to just pile up on it. After you added some probes and things that need a bus you will sit on a fragile, unforgiving crapstack, that just waits for you to stick a jumper-wire in the wrong hole. So I decided to make myself some room on the board and push connectors, displays and meters away from the center. Just take a look what came out:
check out the vid to get a walkthrough
So here is a little list what it includes:
* 2 max 232 Level converters
* An arduino NG
* 3 BNC connectors
* 8 banana Plugs
* A 50 V voltmeter
* Tiny tiny breadboard for displays and button stuff
* 4×7-segment display with driving transistors
* Datavision DV-20208 HD44780 compatible LC-display
* 2x lm3914 bar-graph displays with jumper selectable voltage range
* Avr-Net-IO for some Ethernet
* A -10V -5V GND +5V +10V earth 0V 35V Power supply
* and of course a humongous breadboarding area
This is of course just a source of ideas so if you make one of your own please let me know and if you don’t publish yourself, I’d be delighted to show off pictures of yours here!
Some words on construction:
The base is made from a piece of structured plastic (45 x 30 cm) on top of that are some pieces of wood with some plastic veneer that form the body. This makes up the wedge form in the back. On top once again I used some sign plastic covered with red spraypaint, why red? because its shiny 🙂
Ground and Earth are normally separated and can be connected on demand.
While exploring the different methods of generating some waveform I stumbeled on an old project of mine that has been shelved for almost a year because it would not work no matter what I tried. So I got out, redesigned the pcb, soldered new components and wasted 4 hours tracking down some trace issues. But in the end I had a working DDS function generator based on this simple but effective design: http://www.scienceprog.com/avr-dds-signal-generator-v20/
Hi, I just started a dream project: Building an oscilloscope from scratch. Originally I wanted to use a russian 13LO37I but it turend out to be too bulky so I went and scored a waaay smaller 3KP1 / DG 7-113 from ebay.
I’ll put up a high res Photo of the tubes weiring system at my website.