Electronics > Projects, Designs, and Technical Stuff
Yet another resistance decade box
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ez24:

--- Quote from: Blastcap on August 23, 2016, 07:45:20 am ---Thanks a lot Fortran!
Housing 1,76€
https://www.conrad.de/de/1423193-534346.html
Bannana plug/Binding post 2x 1,72€ (= 3,44€)
https://www.conrad.de/de/sicherungs-steckverbinder-schwarz-10-a-sci-1-st-732314.html

--- End quote ---

I have a couple of switches looking for a home.  Are there any Aliexpress or US Amazon sources for a box like the above (I cannot read German).  If it has been mentioned before and you know where, please list again.  Currently there are over 300 posts on this subject.

What I suggest for Fortran is come up with a list of sources for boxes, switches, plugs, whatever and copy and paste it into EVERY post that he makes under this subject.  That way every time there will be a source of parts.  I think it would be hard for someone new to this to figure out what is going on (because of the large number of posts).  It took me awhile to figure this out (just the resistors and switches, not box)

Or better yet start a new more focused topic.  I think this topic is a poor way to sell these, and since they are "good", this is a pity.

Something like "DIY Resistance Decade Box using SMD resistors - List of sources - $xx to $xx"

Then write a summary and list sources for everything, this topic is getting too long.


bitseeker:
A thread like that could also be a good place for folks to show off their finished versions/variations.
Blastcap:

--- Quote from: Fortran on August 23, 2016, 11:15:14 am ---Well.. if you want 47 ohm then?
or 150?

111 seems to be the best compromise between all ranges but I'm open to suggestions :)

--- End quote ---

I might have expressed myself badly.
Say the first decade is assembled with 8 normal 1 ohm resistors, and the first one in the range is trimmed to be 1 ohm minus contact resistance, so for a total contact resistance of 0,5 ohm the first resistor to contact in the 1 ohm row would be a 0,5 ohm, thus when set to 1 ohm it would just add enough to the contact resistance to reach a total of 1 ohm, and after that its all 1 ohm resistors that are added.

This way 47 wouldn't be a problem (40+0,5+(6*1)), and 111 would end up being 111 even thou you only switch in 110,5 ohm.
150 on the other hand wouldn't have the contact resistance trimmed out, as it doesn't use the 1 ohm range, so it would be 150,5 ohm in reality.
So that is a lack of course.
Fortran:
Yes that's why I figured one third of the total contact resistance on the first three digits would be good.
I hardly ever use the 1R range. But 10 and 100 are more frequently used.
So if total resistance is 0.5 ohm, setting 1000 would give 1000.5 ohm. This is fine since 0.1% of 1K is 1R.

Setting 1 would give you 1.33 ohm.
Setting 150 would give you 150.17 ohm.
Setting 147 would give you 147.0 ohm.


--- Quote from: ez24 on August 23, 2016, 09:59:12 pm ---Something like "DIY Resistance Decade Box using SMD resistors - List of sources - $xx to $xx"

--- End quote ---
Not a bad idea. That way I could keep the first post updated with the most relevant information.
Should I post in the for sale section?
Alex Nikitin:
Here is one of my finished decades.

Cheers

Alex

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