DIY 1 Gig resistor / High value resistors

Hi,
i just look at my 5 1G resistors that i bought some time ago and remember how expensive they were...(~3 Euros for one!)

I already know high value resistors can be made with graphite (pencil), ink etc.

But has anyone around here actually used an improvised / DIY high value resistor? i just played around with a pencil and was able to get a 1gig 1% resistance in a few minutes as a line on the paper...
But this is a carbon resistor and i wonder if it would be usable for audio (noise?) are there home brewn metal film / oxide resistor recipe one might have here around?

And...how would someone apply leads to this, i had to press copper (5 Eurocents) really hard to the paper to measure the resistance... :?
I know this has been done before (WW II improvisation method to fix equipment, but my grandpa's died before i had that DIY obsession...)...


Any opinions, or even better - *experiences* with this topic around here?
:grin:

Thank you and kind regards,

Martin :thumb:

EDIT: Done: Leaded DIY High Value Carbon Resistor, see below.

IIRC I believe I read at a forum in the past (Maybe Klaus's forum some years ago) that some microphone input resistors were made with china ink.

I would try a low leakage PCB with two copper pads solder leads to the pads and draw a resistor.

Drawing a line on paper would be extremely unstable mechanically. There is no real cohesion between the carbon particles, but rather adhesion to the the paper. The resistance is likely to change with humidity (as previously mentioned), but also with temperature, handling, and time. Gus's suggestion of ink is good. Many black inks contain carbon of some form as a pigment, and are therefore inherently conductive to some small degree. Try different inks. Not all carbon fillers are well suited for a conductive matrix.

If you want to make up a resistive ink yourself, grind up some pencil leads into a fine powder and mix it with Elmers glue (polyvinyl alcohol/polyvinyl acetate blend). Good mixing is essential here. Try to really smear the two together, like in a mortar/pestle type arrangement. A spoon and bowl may work as a substitute. If you do this well, your resistive ink won't be too different from the resistive inks that are currently on the market for printed electronics. Try different carbon/glue ratios until you find one that works for the 1G resistor. If your graphite loading isn't high enough, no percolation will occur and the ink will not conduct. Don't use paper for a substrate. Use roughened polyester. Lightly sand the surface with high grit sandpaper, or try ink jet transparency paper.

BTW: I buy my 1G resistors :green: .

-Chris

I can't remember where I got my first batch from. They were less than ideal though, since they were very large and flat. I might have even ordered from directly from the UK when I got my OEPs for my G9. My latest batch came from when Al K offered a group buy here about a year ago. I bought about 10, which will last me some time. I can't remember where he ordered them from.

Regarding how to connect to a home made resistor, I like Gus's suggestion about a little pc board. I can also see using small wire leads glued to the polyester with the same resistive adhesive. Putting a small loop in the end would help keep the wire from pulling away from the adhesive when it's cured. There is the problem with melting the plastic with too much heat from a soldering iron, but it will work if you solder quickly. If you want to get fancy, Kapton (polyimide) would be a good heat resistant substrate. Copper shielding tape with a conductive adhesive is also an option for leads.

I once made an LED flashlight as a demo for work (I'm an R&D scientist for a conductive ink company). The conductor was a silver-nano ink that couldn't be soldered and couldn't be used as an adhesive itself. I wound up using some conductive epoxy from Mcmaster to attach the LED's to the printed traces. The circuits were painted with a paintbrush. I just snapped a pic with my camera phone for an example:


-Chris

:grin: Yes, i bought mine, too! :grin:
Nevertheless i'm a little bit pi*ed about the prices for these ones... and they are definately very bad in availibility (as well as other multiple hundred M resistors - i guess gyraf used 1 gig because it was available and would have used 400MOhm like in u67 if possible!)

And last but not least...DIY is fun. (as we all know)

conductive glue / mix is a nice thing i thought about already. I should try to calculate a bit with specific resistance values before experimenting
:grin:

I just researched a bit on nichrome powder, it's ~200 bucks (USD) for 100g (!)... you know - 'metal film' on ceramics...

BTW, is there something like an 'infinite dummy resistor' / isolator part with leads that can be used for experimenting with ink, pencil or similar? ceramic would be perfect i guess as it can be raw suface...

You are right about paper as a non-usable material, it was just a fast shot and proof of concept for getting a 1gig line of pencil to a usable part dimension (~1 cm) with near to no effort and a cheap DMM.

Thanks for your comments so far and
kind regards,

Martin
:thumb:

Well a few minutes later - and i have a leaded diy 500 M carbon resistor...
Thanks Gus!
I should have come to this from the overclocking pencil trick by myself!!!

I took an epoxy gold plated veroboard piece i got spare for a few cent.
(in fact it's double sided through hole plated thingie...)

I scraped off a small trace between a 2 hole distance in the FR4, i used a knife for that...

Now - pencil, blow graphite, pencil, blow graphite, measure...
...and again... until you get your value.
(you may experiment with the trace width...)
Too high? wipe some of it away...and again...

Hey it's 500M now, nice!
Now i just have to put a second small piece of that veroboard on top of it.
Cut it to shape (both pieces hold together so no graphite blows away).
soldering leads from an old resistor cutoff...

glue it together all around the pcbs - hermetically closed now, i guess...


That's it!
Fairly easy.

i guess 10-20 min alltogether.


:grin: :green:

Bedtime! :sam: :green: :thumb:

Good night,
Martin

FYI

I recently found these at Allied.

Dale / Vishay
Resistor, Metal Film; 2000 Mohm; 0.72 W; +/-10%; 1.5 kV; Axial; -55 to +155 degC
Mfr Part#: RNX-3/8 2G0 K M
Allied Stk#: 895-2158
Availability: 70 In Stock
Discounted item, price applies to in-stock purchases only.
=> $1.16 <=

Good price!
These are probably discounted because they are not RoHS compliant.

if you really need some 1G resistors and the price is too expensive, why not just hammer in 2 nails to a popsicle stick and then solder to the nails :green: you will find the resistance about the same

if you really need some 1G resistors and the price is too expensive, why not just hammer in 2 nails to a popsicle stick and then solder to the nails Mr. Green you will find the resistance about the same

Click to expand...

Another acceptable method for 1G resistor fabrication is to look at the 2 nodes in your circuit and wish (really hard) for current to travel between them. Be advised, however, that if a genie is present whilst wishing the resistor will short.

:shock: Wow yes, it happens the electrons jump over! :shock:

If I take another pill, maybe they begin to dance polka :idea:

I think this is a good question. Where's McGyver when you need him?

I recently saw that Conrad (yeah, I know...) has SMD high ohm resistors for a few cents. The highest value is 120 meg. So you'd have to solder a few in series for usual mic impedances. I haven't tried them yet, though.

here's the link (hope it works)

Digi-key often has the small 1Gohm resistors - MOX200J-100-ME-ND is the part number I use.

Somebody a while back on a different forum suggested trying a small piece of anti-static foam. I never got around to trying it.

they are also several 1G resistors in farnell:
http://uk.farnell.com/jsp/Passive+Components/Metal/VISHAY+DALE/RNX-1/2+1G+F+M/displayProduct.jsp?sku=4669575
and
http://uk.farnell.com/jsp/Passive+Components/Resistors,+Thermistors+&+Potentiometers/OHMITE/SM104031007FE/displayProduct.jsp?sku=1159366

These are the cheapest that I found

g

^ And I think so.
I live in Bulgaria and my farnell's price is 30% higher than the site's price.
That's good for me

:razz: Farnell Europe is feeded by Newark (usa) - so you have to pay 20 Euros for every shipment...below is the single resistor price and the price including shipment and taxes...

Warenwert: 2,71 €
Versandkosten: Unbekannt
Newark Direct Ship: 20,00 €
MwSt.: 4,31 €
Gesamt: 27,02 € :razz:

Not really what you call cheap :wink:

I have used the Allied Dale/Vishay 2 gig parts in two microphones now.
No problems.

I use MXL kits to make mics, they contain as well couple of 1G resistors. The kit is $80 including shipment on ePay.

Nice one, Wayne!
(btw, it was fun doing business with you last time, but i think i overcomplicated things alot :green: - please pardon me - i was too excited about the pico and your kits....)
I just wonder, if a 1 gig resistor in an LD mic may be easily substituted with an approx 2 gig resistor without any negative consequences. (?)
:?:

At this high resistances, maybe only a magnitude change will have a negative effect?

Do i have to dig into this in theory again, or has anybody done this and can share experiences, problems, whatsoever?

I am just trying to source an easier distributor than rs (which you can't use without credit card except being a officially professionalover a committing service here in germany) and even makers of high value resistors in the european market...i will post as soon as i get some positive reply, there is no answer to my emails now...

Kind regards

Martin

BTW: I did some more foam tests, and i can never get a usably high resistance from these (biggest is still approx 20M and i tested quite a lot diff materials).

Here are pics of the dale/vishay 2 gigohm resistor installed in my "FrankenTube" LD vacuum tube microphone.


I have had no problems with using the 2 gigohm resistor.

I compared this microphone to previous versions that used 1 gigohm resistors and I cannot detect any differences.