Resisitors--Resistors--Resisitors

[SVEN1]

What in your opinion should i buy to make the Golden Sabre?

Should I use the carbon film or metal film that are being sold on ebay from China at low prices? Or buy a brand name resistor that costs more?

Any advise would be appreciated.

[Götz von Berlichingen]

I would use 1% Metal Film.
Reason: low noise, low temp. drift, quite exact, reasonable Price.

[mario]

I have used metal film resistors. If used in audio components, the audio may sound a little un-natural. I would use both, depending on application.

[pelanj]

The key is low tolerance - for a metal detector, I would really use metal film resistors with 5% tolerance or better. Carbon resistors tend to be more temperature dependent which is not what you want.

[SVEN1]

I am assuming the resistors you can purchase from overseas are OK to use?
I have bought some metal film and starting checking them. They all vary somewhat in value, maybe two out of 8 are the same value. But, fall in the 1% tolerance.

http://shop.ebay.ca/i.html?_nkw=resi....c0.m270.l1313


I have read that China etc. sells off rejects or inferior resistors, is that true, should I stay away from them and look for brand name resistors like Vishay?

Thanks

[Carl-NC]

In most cases it doesn't matter. Carbon film is usually 5%, which is usually plenty good. If you think you need 1% matching, then better pay attention to cap matching as well. Ferinstance, you usually want tight matching between all-metal and disc channel filter taus, which includes both R's and C's.

Metal film has lower thermal noise and so is a better choice in the preamp circuitry, but otherwise not necessary. Temp coefficient in a metal detector doesn't matter... even at 500ppm/C that's only +/- 1% for a +/-20C temp swing.

As for Chinese resistors, I don't know.

- Carl

[SVEN1]

Thanks!!!

[kt315]

SVEN, I have huge amount of garbage PCB's from TV sets, SVGA monitors, old PC's, power supplies. why you do not want to go at your neighbour garage sale, TV', PC', mobile phones workshops, and to find out all these?
in trash technology resistors capacitors etc. are not problem. only go and get them. no need to pay for chinese.

http://www.geotech1.com/forums/showt...ight=recycling

truly yours

[SVEN1]

SVEN, I have huge amount of garbage PCB's from TV sets, SVGA monitors, old PC's, power supplies. why you do not want to go at your neighbour garage sale, TV', PC', mobile phones workshops, and to find out all these?
in trash technology resistors capacitors etc. are not problem. only go and get them. no need to pay for chinese.

http://www.geotech1.com/forums/showt...ight=recycling

truly yours

Still cheaper to order from overseas, garage sales and recyclers want to charge you for the stuff. Plus takes too much time for me to try and locate exact parts and in quantity in good shape and remove them from the PCB. The city I live in is just a small town which has a lack of anything electronic. Closest city is 4 hours away that actually sells component parts but, still the Chinese stuff.

[der_fisherman]

For anyone who wants to build a detector, maybe one from the pages of this forum, check out SilverDog's website here:-
http://www.silverdog.co.uk/
He sells PCBs and kits for some of the metal detectors discussed on this forum. If you buy a kit, you don't need to shop around for many parts, most are in the kit for very good cheap prices. You can order many other parts at the same time.

I am waiting for a new VLF kit to be organized by him before buying my first kit from him, but many others are very happy already.

He will probably send anywhere, but check up with him first.....I have no connection at all to either him or his business by the way.

He is in the UK, but that should not bother most people.

I always go for the 1% metal film as I like to be exact, there is enough tolerance in some caps to throw things off without adding inexact or noisy carbon resistors....
Its always a good idea to measure all resistors before soldering them in as occasionally a wrongly marked resistor gets passed on.....

I do the same with caps as well, so its a good idea to have a way of measuring capacitance. Most are more, seldom is the measured value less than the marked value.
Best regards
Andy

[SVEN1]

I ordered parts from an ebay seller, he always seems to have good stuff.
I don't mind having more on hand for any other projects I might build.
http://stores.ebay.ca/viodol

[der_fisherman]

I ordered parts from an ebay seller, he always seems to have good stuff.
I don't mind having more on hand for any other projects I might build.
http://stores.ebay.ca/viodol

Well put. I buy in lots of 100 for less than $3 - metal film 1%.

I like having some stock!!

Regards

Andy