PDA

View Full Version : variable resistor tool







superswill
22-01-2011, 09:22 PM
members,

I recently worked with a fella who produced out of a bag a variable resistor tool

in short it was used for replacing/tricking thermistors on AC systems.

he said after he found it in my pocket they were available on line, OK please give a clue where................................................................................

I have looked at making one as parts could be sourced from maplin RS ect but this box of tricks was just right for the job, croc clips/prongs and a twist selector for ohms

any clues on where to get one?

chilliwilly
22-01-2011, 10:28 PM
Variable resisitor tool?... is that the same as a 10k pot? If so they're available at RS, Farnells, and Maplins as you've seen. Does your mate sustitute the thermistors with a pot then trim the resisitance to match the thermistors design parameters, then measure the the setting value of the pot?

Grizzly
22-01-2011, 11:45 PM
Hisuperswill.
I may have the wrong idea, but what I have is old fashioned by todays standards.
It is known as a decade box.
A search under that title may clarify?
Grizzly

superswill
23-01-2011, 12:06 AM
Variable resisitor tool?... is that the same as a 10k pot? If so they're available at RS, Farnells, and Maplins as you've seen. Does your mate sustitute the thermistors with a pot then trim the resisitance to match the thermistors design parameters, then measure the the setting value of the pot?

thats the toy

superswill
23-01-2011, 12:08 AM
Hisuperswill.
I may have the wrong idea, but what I have is old fashioned by todays standards.
It is known as a decade box.
A search under that title may clarify?
Grizzly

Grizzly,

I will look into this

Tesla
23-01-2011, 12:28 AM
Hi superswill
the resistances I have come across are 10K, 8K, 5K, 3K and 2K for space temps and something like 180ohms on an oil temp. So best bet is to get one with a trim pot similar to what chilliwilly has suggested. That way with any sensor you can have control over the dead band of the switching too.

marc5180
23-01-2011, 10:18 AM
Hi Paul,

Is is something like these.

http://cpc.farnell.com/cebek/edu-005/educational-kit-resistor-box/dp/HK01092


http://cpc.farnell.com/tenma/72-7270/resistance-decade-box/dp/IN04175

charlie patt
23-01-2011, 10:27 AM
i made one from cpc catalogue if you need any help they have a good technical line

superswill
23-01-2011, 10:27 AM
Hi Paul,

Is is something like these.

http://cpc.farnell.com/cebek/edu-005/educational-kit-resistor-box/dp/HK01092


http://cpc.farnell.com/tenma/72-7270/resistance-decade-box/dp/IN04175

just the ticket, ordered two, thank you marc

marc5180
23-01-2011, 10:30 AM
Let me know if they work will you?

I was thinking of ordering one of them a few weeks back.

superswill
23-01-2011, 10:38 AM
Let me know if they work will you?

I was thinking of ordering one of them a few weeks back.

the Guinea pig will test and update

mbreward
23-01-2011, 12:25 PM
Go for a 10 turn pot as a single turn pot will not give you the accuracy

superswill
23-01-2011, 02:33 PM
Go for a 10 turn pot as a single turn pot will not give you the accuracy

Thank for for the info

Gingerair
23-01-2011, 08:22 PM
http://uk.rs-online.com/web/search/searchBrowseAction.html?method=retrieveTfg&Nty=1&Ntx=mode%2bmatchallpartial&Ntk=I18NAll&Ns=stockPolicy_uk%7c1%7c%7cnew_uk%7c1&Ne=4294922322&Nr=AND%28avl%3auk%2csearchDiscon_uk%3aN%29&N=4294956388+4294919203&Ntt=decade+box&multiselectParam=&selectSubRange=Decade Boxes#breadCrumb

Not got one myself but got a mate who swears by his..

Ginge :)

superswill
05-02-2011, 08:34 PM
Let me know if they work will you?

I was thinking of ordering one of them a few weeks back.


Marc,

is working well, i went for the CPC one

a few extra "mods" later mind

see link:

https://www.yousendit.com/download/MzZGTXRkNmMyWGMwTVE9PQ