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Old 23rd August 2009, 09:22 PM   #1
kaushik is offline kaushik  India
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Default diy stepped attenuator under 10$

i started the building of DIY attenuator ,mechanism with
available parts at home
i always knew that the attenuator can be made with some
rotary arrangement.

But the roadblocks were ,

1) how to ensure durable contacts
2)how to make the rotary slider stay at a position
3) protecting from dust /impurities
4)how to exactly give contacts to moving rotary contact
5)keeping costs very low and avoiding machinery

i after a little thinking i have done little progress
adding plans and then pics


Click the image to open in full size.

Click the image to open in full size.
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Old 24th August 2009, 10:54 AM   #2
kaushik is offline kaushik  India
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first pic depicts the back side of the assembly, here i have
added 23 IC socket pins taken out by breaking the socket.

each pin has 2 sides
1)sharp pin side
2)flat contact side

How to build the circular contacts:


Put pin side thru holes ,and solder on the other side,contact side is bent .
The pads (socket pins)are laid on a circular fashion to so that slider touches 1 contact at each stable position.



second pic shows the rotary click mechanism
although it looks complicated ,it is NOT.
click mechanism works with a sprocket wheel designed from a toothpaste cap(i am sure there are many cheap robotics wheels,tape mechanism wheels that can be used).

spring + piston
Here I house 1 tiny spring taken from DPDT switch,piston is a tiny plastic cube,outer shell is a piece of refill.All attached with super glue.

I will add picture to make it clear .
piston is
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Old 26th August 2009, 07:03 AM   #3
suds is offline suds  India
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When it comes to stepped attenuators, when changing volume, the contact breaks from one point and makes at another point during this break and make there will be "Glitch" or switching noise. how to avoid this and make a smooth transition.
One method would be using make before break mechanism, but these kind of switches are difficult to find, besides cost.

Any other ideas ?
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Old 27th August 2009, 10:04 AM   #4
MaxS is offline MaxS  France
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Hello Sirs,



I do not know if this kind of device will respect your $10-budget but I want to show you some ideas :
http://www.novotone.be/index.php?opt...jets&Itemid=34

But for sure, mechanical parts and PCB may not be so cheap. I hope it will help you !


Have a nice day !
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Old 27th August 2009, 10:14 AM   #5
suds is offline suds  India
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Thanks for the info.. ! its not about $10 , I posted here cause I did feel like creating another thread.

I have some idea about stepped Attenuators, But the issue is,
when there one changes volume, there will be disconnection and re-connection when switch contacts move from one point to another point, during this transition, there will be unwanted response in form of distortion, glitch, undesired effects .. what ever one may call..
It is possible to prevent this ???
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Old 27th August 2009, 10:32 AM   #6
kaushik is offline kaushik  India
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MaxS
thank you , it is very helpful . The PCB in india is very cheap approx 2$, including all the whole device will be
near 10$.

suds read the translated page

http://translate.google.com/translat...istory_state0=

the resistor pattern is cleverly laid to avoid that "glitch"

so floating contact while shifting is totally avoided .
I am poor at mechanical design, my tested sproket is
not durable enough.

Please suggest some reliable locking mechanism(mechanical part)
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Old 22nd October 2009, 09:07 AM   #7
kaushik is offline kaushik  India
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Default found a mechanical part for steps

Ok after searcing and even building one teethed wheel
I decided to go with some already available spares,
I have found the 'mouse encoder'..see the small blue spare...will cost just 10 cents max, can be had from damaged mouse for free!

http://www.eehomepage.com/reports/20...insitu_mid.jpg

to be a suitable device , highly reliable and smooth.However the encoder is just a stepping device..its electrical operation will not be used.

more pics: Click the image to open in full size.

attaching an wiper pcb contact will do i hope..
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Old 22nd October 2009, 06:10 PM   #8
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Here's an interesting implementation -

DACT Type 21 Stepped Attenuator Potentiometer 100K 2A3 - eBay (item 120474000457 end time Oct-26-09 11:06:39 PDT)
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Old 22nd October 2009, 06:12 PM   #9
Glowbug is offline Glowbug  United States
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I'd be a little wary of the reliability of something like that, unless a bunch of people had good results with it for a while.
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Old 22nd October 2009, 08:21 PM   #10
kaushik is offline kaushik  India
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Quote:
Originally Posted by quadtech View Post
I have seen that before also i have seen light speed attenuator ,
i will use smd resistors and finally try to make a low cost.
In many countries ebay + shipping+ customs =2x price
Glowbug,
the encoder is a mechanical part,well tested for very reliable mouse scrolling,so steps are very reliable,
main cream of this DIY is... the rotary contact arrangement

2 PCBS one with slider,and one with static contacts,both wil be spring loaded to remain rock steady in contact..
I need ideas for this..
early stages may give some problems but i hope finally
will do well...
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