Variable capacitor

[ecollen]

Collen if we had award categories for the most responsive, polite, appreciative new member I'd bet you would win all three categories hands down! I'd also bet that anyone responding to your topics would vote that way too!

Impressed!
Chris

Hi Chris
Ha, ha. But thanks anyway. My mother would've been glad to hear it!
But that's easy - if only electronics was that easy ...

 

[ecollen]

I've been toying with the idea of making a variable capacitor from single sided PCB (just for the hell of it). PCB has a far higher dissipative loss than air, so the Q of the tuned circuit is far lower.

I also have some brass foil which is more easily cut, and I'm trying to come up with a design for supports that can be laser cut.

If I get further than just thinking about it I'll get back to you. It week be tho later for your project but it may still be interesting.

Hi Steve
It's interesting to hear that, thanks. I haven't thought of using single-sided PCB, but there is a site where our friend Jezan describes how he made one from aluminium sheets
http://www.instructables.com/id/air-variable-capacitor-from-scrap-aluminum-sheets/
and I'm hoping to try that sometime. I have finally managed to find some strips of aluminium - can't quite tell but it seems to be just under 1 mm thick, perhaps 0,8 mm or so - and I will try using that in due course, though I suspect it may not be quite as easy as he makes out. It may still be too thick.
Brass foil sounds a more suitable thickness, but will it be firm enough? Isn't it much like tinfoil, which I'm sure is too thin for this.
I am, however, first of all (!) going to try making Colin's capacitor from tinfoil and sheets of paper. I hope to get time for that soon.

 

[ecollen]

Steve, why not use a double sided PCB? You'd get more capacitance for the square inch. What, no double sided boards in the junk box?

Chris

Double-sided - yes even better. Sounds like that capacitor's gonna get made!

 

[ecollen]

I'm thinking of using the board as the dielectric. Imagine a stack of boards with alternate pieces electrically connected. The alternate pieces can be meshed and unmeshed tho vary the capacitance.

Double sided board (or just foil) with an air gap is the alternative, but if you ever played with a large variable capacitor and damaged any of the vanes you'll appreciate that mechanically maintaining the gap between the plates requires pretty tight tolerances.

Oh, yes, I see. That's right. Sounds like a really good idea.

 

[ecollen]

If you research historic photos and drawings of electronics inventions you will find exquisitely hand made Mahogany platforms adorned with brass and Bakelite terminals. That's what you'll see in museums too! I regret that I lost it but there's a nice fellow that's devoted to crystal radio sets. He has reproduced and created a host of eye popping wood based sets.

Chris

Hi Chris
I've found the site I had in mind. It's the page of our friend Geoff:
http://crystalreceiver.co.uk/radios2.htm
I don't know if that's the one you meant, but in any case he has some superb sets on his pages - some are virtually works of art

 

[CDRIVE]

Hi Chris
I've found the site I had in mind. It's the page of our friend Geoff:
http://crystalreceiver.co.uk/radios2.htm
I don't know if that's the one you meant, but in any case he has some superb sets on his pages - some are virtually works of art

Collen, I don't think that was the website I found a few years ago but it's equally representative of it. What they both have in common is the exquisite workmanship that incorporates electronics with art form.

Chris

 

[ecollen]

Collen, I don't think that was the website I found a few years ago but it's equally representative of it. What they both have in common is the exquisite workmanship that incorporates electronics with art form.

Chris

Hi Chris
Yes, this one has virtually made an art form out of constructing crystal sets and similar equipment. I'm sure there must be several people who can do this, so I'll be looking out for other similar sites. It must be very satisfying making something like that. As for myself, I'm afraid I tend to be a bit too impatient (bit like being a bird photographer, having to sit for hours and hours waiting for the little guy to come and sit on just that perch) and rather finish it so it works and then get on with the next one. But perhaps it's different if you make something that really takes a lot of careful work and effort. I can well imagine that in such a case you would go to some extra trouble to finish it nicely. I'll let you know when one day I make something worthy of that treatment!
Cheers,
Errol
Oh, PS, apologies, this is off topic again and not very important, but I thought I'd just mention you can continue using "Collen" if you like. Many people do (and even more get stuck on "Colin"), but that's actually my surname. First name is "Errol". I think the confusion arose when we first started with e-mail addresses years ago, and I was landed with "ecollen", which also became my username. Some people are now using my first name and some my surname, which naturally is fine, but there could perhaps be a risk of people thinking I have a split personality, or something

 

[CDRIVE]

Hi Errol,
There's a fix for that. You can add your first name under your avatar or you can put it in your signature. Personally I like Errol because I liked Errol Flynn; "Captain Blood", "Crimson Pirate", "Robin Hood". Besides we already have a Colin, though I don't think there's any fear of you being confused with him. He has a keyboard with a governor on it. It only accepts 10 words or less and must be one syllable.

Cheers!
Chris

 

[ecollen]

Hi Errol,
There's a fix for that. You can add your first name under your avatar or you can put it in your signature. Personally I like Errol because I liked Errol Flynn; "Captain Blood", "Crimson Pirate", "Robin Hood". Besides we already have a Colin, though I don't think there's any fear of you being confused with him. He has a keyboard with a governor on it. It only accepts 10 words or less and must be one syllable.

Cheers!
Chris

Hi Chris
Ha, ha! But you mustn't mind Colin's e-mails. Look at that website of his. There's piles and piles of stuff there. That'll keep one going for ages.
Yes, I could change the avatar and all that, thanks. Might do so later.
I think my father liked Errol Flynn too. Family lore has it that it was meant to be "Edwin" (me, that is), one of my grandfather's names, but when my father arrived at the registry office he decided at the last minute to change it. I'm glad he did.
Cheers
Errol (really!)