Sunday, May 16, 2010

This isn't metalizing I know, but I did it today...

Mini Neon Driver
From Disposable Camera Flash

This is a high voltage DC circuit made from an old disposable camera flash. Its similar to the popular Joule thief I believe. Here is the diagram:
This is exactly as it is in the flash except I've removed the rest of the circuit, like the high voltage capacitor. Ouch! Also the switch in the doodle is closed permanently.
In its place I put a mini neon bulb. I like freeform circuits.

Below its running at 1.5v. I don't know whats the voltage across the neon. (over 100v but less than 400v)

Here's the power supply. Its reading .5 amps at 1.5v it goes up quickly when the voltage rises any more. As this is a DC circuit only one side of the neon glows.Would it be possible to do AC by using two of the above circuits at 1.5-o-1.5v?

The neon in the power switch is more impressive...
The Guts of the Thermistor Gauge.

I refer you to the link on my earlier post of the circuit by Roy Schmaus. Its based on an LM324 Op Amp. I'm just trying to get my head around these devices now. They seem to be used for everything under the sun. Here is my circuit nearly finished.

I've included a 7815 voltage regulator on the board too. You can see that on the right. The three components behind the black croc clip. There is a 7 watt resistor on there which is waaaay too big for the thermistor I used but it was 470 ohm, just what I needed, so I went for it!

At this stage I've yet to put two trimmers on. One to be part of the LM324 divider circuit. And the other to drop the output voltage/current to be used in a moving coil metre.

I got this cheapo multimeter from a Chinese Shop in Barcelona. I don't always go so far to buy components! I took the board out, cut the battery holder and screw posts. This gave me a flush back which fit neatly on to a project box.

So I put in a DC socket and an old mobile phone charger cable out for the thermistor connection.
I managed to squash the circuit in.
Here it is, with thermistor soldered on for testing.

The circuit is amazingly sensitive to air movements around the thermistor. A couple of tips if your building this are:
-There will be a delay after you power up before things get to the levels/temperatures/voltages they are supposed to be at. So give your circuit a few seconds before you take a hammer to it.
-Try putting the thermistor in a little cardboard tube to protect from drafts and your breath which may cause weird readings.

Friday, May 14, 2010

Zero and Beyond!
Thermistor Vacuum Gauge Construction.

I had been thinking for a long time about getting a gauge for very low pressures. I came across this little project a year or two ago but it was beyond my understanding and abilities at the time.

It came from

Even with this nice circuit to work from I still had the problem of electrical feed-throughs. Then one day not too long ago the solution pop into my head.

Strip fluorescent lights!

I had a T4 size fluorescent tube which is just under 16mm dia. Now that's just larger the the external measurement of a 1/2” copper pipe. So the brass fitting could be adapted to fit. Using an O–ring to keep it air tight.
Strip lights have two electrodes nicely sealed in to each end! Perfect! So I cut the tube on the lath and with a hot wire. I then washed out the fluorescent powder. I believe these lamps have may have mercury vapor in them so I didn't breath while I was doing it...

Then I covered the electrodes with a bit of Al. foil to protect them as I rounded the cut end with a flame to de-stress it a bit.

I popped it all in some safety pickle and got the Dumet wires back to nice clean copper. I could then , with a bit of flux, solder the thermistor to the inside.

Once I fitted this to my home-made ‘QF16 from plumbing pipe fitting’ my feed through was complete!

This is turned from a 1/2" tank fitting. I'll go into this in another post.

I'm just waiting for my Viton o-rings to arrive and I'll hook it up.

Wednesday, May 5, 2010

The filament power supply

The power for my filament comes from a rewound microwave oven transformer
(MOT). There is loads of info' online about doing this so I won't go into it here. I'm getting about 6v tops out of this one.

There is also a 'dimmer' suitable for use with inductive loads. It came from a company called 'Brocott'. I got it through You can see the little VR going through the lid of the box to vary the power. (Its a really crappy VR wobbling all over the place. I may have to replace it with something a bit more substantial. Saying that, it doesn't matter at all for the brute force output.)

I'm going to put an illuminated power switch and a 50 amp ammeter to keep an eye on the power without burning my eyes out watching the filament!

Anyone know if you can convert a DC ammeter with external shunt to AC? I've gone and bought the wrong one!

This is my roughing pump(or at least it will be).
Its an Edwards Speedivac ES150. An antique I know!
Anyway, this is what started me in the way of vacuum. I pulled this out of a skip in The National College of Art and Design, Dublin.
I got it home and cleaned it up a bit. It looked terrible. I suspect it had been used for degassing of plaster and resin.
I began to read about rotary vane pumps and got it moving again.
With the help and advice from a generous man named Eoghan Murphy from Vacuum Spares in Cork, I tried light grade motor oil to see if it was completely fuckt of not.

Well, a lot of brown gunge came out when I emptied the old oil. I replaced it with new oil, spun the pulley a few times and switched it on. And off it went!!

My salad bowl sits on top of a silicone ring. I cut it from a silicone baking dish that had a flat bottom. It seems to work OK for now. I'm using silicone vacuum grease between ring and salad dish and the base.

The base is 6mm thick Al. plate. I just had it in the workshop so I used it.

For my high current feed throughs I tried two different options here. I'll go into them later.

There are also two signal feed throughs. 5 in total 3 in one and 2 the other.

And in the middle there is a 1" copper pipe to the vacuum pump.

I had great success today! I got a much better Al. coat in my belljar ( salad bowl).

This is a 140mm dia. pyrex salad bowl. I wet ground the rim flat on a sheet of glass with some carbide powder. 80/200/400 grits I think. They are the ones I have, and it was a few months ago now.

This was the best I got before I made a few changes. But even this help me keep the faith!

Saturday, May 1, 2010

Vacuum Metalizing

I'm going to try a blog with details of vacuum experiments.
Now, I haven't any formal vacuum technology. So most of the info that I'll put up will probably be wrong/dangerous/fun.

Saying that there are some amazing starting points on the web for this subject.
I plan to do vacuum metalizing. Now if your still reading this you probably have some idea of whats involved.
But still I'll give my quick description anyway-

1-You get a space and make it as empty as you can.
2-You get some Aluminium foil and heat it up till it disappears.
3-You admire the shiny surface of everything.

Not much to it you say. Well I found that there is. And I'm having a fascinating time trying!

I'm starting this blog a bit late in the project so I'll be craming lots in at the start to get it up to date and then it will crawl at the pace of any good no budget project.