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Perejil
Joined: Jan 15, 2009
Posts: 10
Location: London, UK
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 Posted: Sat Jan 17, 2009 6:58 pm Post subject:
Certain components unobtainable - any suggestions? |
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I was wondering if anyone knows where I can buy a slide potentiometer that is quite long (ideally about 30cm, but a little more or less would be ok). All i can find are 60mm, which is no good for my purposes.
Also, nowhere seems to have a 0.002uF capacitor - any ideas?
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DrJustice
Joined: Sep 13, 2004
Posts: 2114
Location: Morokulien
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| Posted: Sat Jan 17, 2009 8:02 pm Post subject:
Re: Certain components unobtainable - any suggestions? |
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| Perejil wrote: | I was wondering if anyone knows where I can buy a slide potentiometer that is quite long (ideally about 30cm, but a little more or less would be ok). All i can find are 60mm, which is no good for my purposes.
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You can get various 'Linear Positioning Sensors' of that size and larger. At those sizes they're usually not called potentiometers anymore, even though the function is the same. You can also get them in the form of ribbon-type variable resistors, cylinder/pistons, slides (almost like normal slide pots) , cable reels etc.. in lengths up to several meters. However, we're moving into the relam of industrial hardware here, so they are not cheap.
Here is a discussion right here on EM on using the ribbon-type variable resistors. Here are some from Sparkfun that you can buy quite cheaply. You would need to make the sliding knob and associated mechanics yourself. That thread may have other sources, and maybe some of our members know of more(?)
Edit: at some point 'Photoelectric Distance Sensors' may be more economical or practical, if the application allows it. Just mention that to let the imagination run... 
| Quote: | Also, nowhere seems to have a 0.002uF capacitor - any ideas?
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Use 0.0022uF (that's 2.2nF). That's a standard value and close enough for most purposes. My guess is that the given value 0.002uF is a typo, as you will not normally find them anywhere. Standard capacitors have 10, 15, 22, 33, 47 or 68 as the most significant digits of the value.
DJ
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Last edited by DrJustice on Fri Feb 06, 2009 2:58 pm; edited 1 time in total |
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opg
Joined: Mar 29, 2004
Posts: 954
Location: Berkeley, CA, US
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| Posted: Fri Feb 06, 2009 7:19 am Post subject:
0.0033uF capacitor |
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I just placed an order for some components but just now realized that they did in fact have 0.0033uF capacitors. What's a safe substitution for this - closest value or some in parallel?
Thanks!
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DrJustice
Joined: Sep 13, 2004
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| Posted: Fri Feb 06, 2009 2:56 pm Post subject:
Re: 0.0033uF capacitor |
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| opg wrote: | I just placed an order for some components but just now realized that they did in fact have 0.0033uF capacitors. What's a safe substitution for this - closest value or some in parallel?
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You're right 33 is also one of the common values. I missed that one out of the list above, I'm sorry if that caused any confusion. I better mention that there are other values in between the ones listed, but they're not used nearly as much.
As for the correctness of the value, it depends on what the capacitor is used for. If it's power supply decoupling then its not so critical, but elsewhere you may want to try 0.0022+0.0010 uF in parallel.
DJ
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opg
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cthulu
Joined: Feb 07, 2009
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opg
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