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POT Selection

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POT Selection

Postby MrPresident » Mon May 16, 2016 2:01 am

I am working on a circuit for a LT3080 using a Lab Power supply circuit from the Datasheet. It has a POT to adjust both the current and the voltage. The POT for the current specs 100k 0A to 1A. The POT for the voltage specs 1MEG. Neither mentions voltage which is common for most circuits. However when I order from Digikey I have to select a POT with a voltage rating. How do I know what voltage to use? My PSU will have a 19.5 volt 3.5 amp input power supply (a laptop brick). Can someone give me a little enlightenment on selection of these POTS please?

Thanks.
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Re: POT Selection

Postby KMoffett » Mon May 16, 2016 3:47 pm

The four important parameters for most pots are resistance, wattage, taper, and mechanical design. Unless you are dealing with a high voltage circuit, the voltage rating is generally not important. Since this circuit is low voltage, you can select almost any linear, 100k and 1M pots that suit your layout. When you pick the ones you think will work, post links here.

Ken
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Re: POT Selection

Postby MrPresident » Mon May 16, 2016 4:26 pm

Thanks. I'll post up my picks later today.
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Re: POT Selection

Postby MrPresident » Mon May 16, 2016 4:37 pm

Not sure why this one is 4 times more expensive. Makes me think I'm missing something.
Current control
http://www.digikey.com/product-detail/e ... -ND/468347

Power control
http://www.digikey.com/product-detail/e ... ND/3780751

Thanks for your help.
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Re: POT Selection

Postby KMoffett » Mon May 16, 2016 8:14 pm

That Current pot has a screwdriver adjustment shaft. Is that OK?
That Power pot is not stocked by Digikey, and is only available in 1000 unit quantities. Thus the low unit price.

Ken
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Re: POT Selection

Postby MrPresident » Mon May 16, 2016 8:33 pm

MrPresident
 
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Re: POT Selection

Postby KMoffett » Mon May 16, 2016 8:57 pm

The Current pot in the link is 100Ω. I thought you needed a 100KΩ.

Ken
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Re: POT Selection

Postby MrPresident » Tue May 17, 2016 11:26 pm

I am really sorry. Your newbie tolerance quota must be really high. I can't even get the easy part that I know right. That is what I get for trying to browse Digikey when I should be working.

I think this is better.

http://www.digikey.com/product-detail/e ... ND/4733099
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Re: POT Selection

Postby KMoffett » Wed May 18, 2016 12:21 am

Unless you need the switch this should work too: [urlhttp://www.digikey.com/product-detail/en/cts-electrocomponents/450T328F104A1A1/CT3064-ND/4733114][/url]
I've been at this since I was 12, and it still amazes me what I still get to learn. And, in how many areas I'm the newbie. :)

Ken
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Re: POT Selection

Postby MrPresident » Wed May 18, 2016 11:08 am

Thanks. Did not notice the switch. I think I am about ready to proto this up and see what explodes. I appreciate your help and patience.

For anyone listening from Denver, I went to the Microcenter last night and they have organized and stocked their DIY electronics section 1000% since last time I was there. It was poorly stocked and you could not find anything. It looked like Toys R Us on Christmas Eve. It is really top notch now. Tons of Adruino stuff as well as caps and resistors etc. Singles as well as nice assortments pack for reasonable. And well stocked.

Thanks again Ken.
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Re: POT Selection

Postby MrPresident » Wed May 18, 2016 11:18 am

If you could indulge me one last question.
Carbon vs Plastic resistive material. Is carbon worth the extra money to a DIY hack? The plastic is much cheaper.
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Re: POT Selection

Postby KMoffett » Wed May 18, 2016 1:23 pm

I've never researched the subject. So, here is and answer to your question: http://www.potentiometers.com/potcomFAQ.cfm?FAQID=19

Ken
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