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LAN_403

Avalanche

Tue Sept 04 2007, 06:10PM

Registered Member #103 Joined: Thu Feb 09 2006, 08:16PM
Location: Derby, UK
Posts: 845

I have a new temporary work bench! In the kitchen

Making slow progress with the theremin... the scope is showing the result of filtering the carrier frequency out of the beat of the 2 oscillators in the theremin (1 fixed, 1 variable) and rectifying it. This is the audio frequency you hear, at the moment it is being generated entirely by component tolerences between the two oscillators. Anyway I've written too much...

Coronafix

Tue Sept 04 2007, 10:17PM

Registered Member #160 Joined: Mon Feb 13 2006, 02:07AM
Location: Melbourne, Australia
Posts: 938

Tricky thing the Theremin, never got mine going properly. I had it at one stage then, then my nephew knocked
the antenna off, and I never had the patience to get it right again. I'll give it another go one day, and box it properly too so the antenna can't be knocked off again.

Ragnarok

Tue Sept 04 2007, 10:22PM

Registered Member #659 Joined: Fri Apr 20 2007, 09:14AM
Location: SW Hertfordshire, UK
Posts: 75

TeslaCoilBuilder wrote ...
80 of my 260 6000ÂµF 385V caps

I am deeply envious. A single cap in that size would cost a lot here, and 260 of them would be the equivalent of a mortgage on a small flat.

Reaching

Tue Sept 04 2007, 10:42PM

Registered Member #76 Joined: Thu Feb 09 2006, 10:04AM
Location: Hemer, Germany
Posts: 458

hrhr, you dont want to know, what tcb payed for his 260 caps

that would make you cry and make you angry :)

ok, he payed around 1,30$ for one cap though. he got his caps from an ebay auction which was very popular and discussed in my forum.

Sulaiman

Wed Sept 05 2007, 09:04AM

Registered Member #162 Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3141

TeslaCoilBuilder, That's a scary capacitor bank.

I didn't notice any discharge resistors in the setup.
I would put a resistor across each row of capacitors
or you will have problems servicing the bank,
you'd have to wait a very long time before the bank would be safe to touch.

Steve Conner

Wed Sept 05 2007, 09:14AM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

Ragnarok, you live in the UK right? You make it sound like deepest Elbonia.

I think those guys got their capacitors surplus, from some huge industrial inverter drive that was scrapped in Germany. I've seen photos of guys dismantling it with cordless drills and stuffing the back of an estate car full of capacitors, but I can't remember where I saw them.

Marko

Wed Sept 05 2007, 09:49AM

Registered Member #89 Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145

I think those guys got their capacitors surplus, from some huge industrial inverter drive that was scrapped in Germany. I've seen photos of guys dismantling it with cordless drills and stuffing the back of an estate car full of capacitors, but I can't remember where I saw them.

At RS, 6000uF 350V caps cost 681 dollar each here. So it's 177 060 $ worth of new caps.

Steve Conner

Wed Sept 05 2007, 12:32PM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

Well, you have to understand that RS sell to the maintenance market. Their target market is troubleshooting guys in factories trying to fix an inverter with just one blown capacitor that's holding up production. They will accept a large markup for the convenience of being able to get the part they want quickly. RS have branches in most industrial areas where you can just nip over and get the part (my local RS is about 500 yards away) and if they don't have it, they will get it for you overnight.

I do sometimes buy parts from RS for hobby projects, though, because they have some crazy stuff that's really hard to get elsewhere.

If I wanted 260 brand new large capacitors for a commercial project, I think I would just contact the capacitor manufacturer directly. I don't imagine you would have to pay more than 50-100 bucks per cap if you were buying such a large quantity.

Otherwise I'd wait till some appeared surplus on Ebay. I've often waited years to get the right part at the right price for some hobby thing that I might get around to building some day... :P It doesn't really matter if you get around to it or not though: if you got a good deal on something desirable, you can resell it any time without losing money.

Ragnarok

Wed Sept 05 2007, 01:24PM

Registered Member #659 Joined: Fri Apr 20 2007, 09:14AM
Location: SW Hertfordshire, UK
Posts: 75

Steve Conner wrote ...
Ragnarok, you live in the UK right? You make it sound like deepest Elbonia.

Yes, but I'm also new to electronics, so I'm still having to learn what sort of prices I should expect to pay - and where I should get things.

I am not happy about using eBay, having seen the number of swindles that my brother has nearly fallen into when trying to buy mountain bike parts.
Combined with the fact I can't yet drive, my access to parts is limited to internet stores and local shops. Not great for finding the best deals on components.

Steve Conner

Wed Sept 05 2007, 02:21PM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

Hmm, well I haven't had much experience of buying MTB parts on Ebay, but it has been interesting. I bought a used Orange Sub-5 frame from an Ebay seller a couple of months ago, and the swingarm just recently cracked on me. The seller might have abused it, but then again, it might just have been my own fondness for drop-offs and pies that did it in.

I have bought a lot of electronic components and parts on Ebay, though, and only been burned once. Even then I managed to get some of my money back by threatening the seller with bad feedback. Sure, there is a risk, but IMO, the amount of cool stuff you can get on "Fleabay" outweighs the risk. That Sub-5 was far and away the coolest bike I've ever ridden until it started to crack :|

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