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Author Topic: Couple of basic questions about resistors, parts in general  (Read 1977 times)

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Offline arseniusTopic starter

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Couple of basic questions about resistors, parts in general
« on: February 14, 2008, 03:12:53 PM »
I'm planning on building the $50 robot or a sandwich bot, but I have some questions about parts.

First, I should start off explaining that I am living in South Korea.  So, my options for parts are somewhat limited.  Not because they don't exist here (I'm sure they do considering all the electronics leaving this country), but because I don't speak Korean well enough to find everything.  I spent some time trying to find stuff on websites with only Korean, and it was stressful, to say the least.  Of course I could have stuff shipped from overseas, but I'd like that to be last resort.  I've found a site that has most of its parts listed in English, which is great.  However, they seem to be lacking the resistors listed in the $50 robot.

According to the parts list, you should have 340 ohm and 1.62K ohm resistors.  The site I have found (ic114.com) doesn't have either.  Near fits they have are 330, 390 and 1.8K ohm in both 1/4 and 1/2 watts, and 1.6K ohm in 1/2 watts.  Would 330/1.6K ohm or 390/1.8K ohm be acceptable substitutes?  I think they would be looking at the schematic, but want to be sure.  They're just for the LED and photo resistors, right?

The 220uF+ electrolytic capacitor.  This could be an aluminum capacitor, is that correct?

I could get photo resistors that are .5, 1.0 or 1.5 cm.  What is the difference besides price?

What are the dimensions  of the atmega 8?  I saw two possible sizes for 28 pin DIP sockets, wide and narrow, but didn't know which to pick.  For the future, does anyone know of a roundup or comparison of all or most of the atmega micro controllers?

And finally, if I add capacitors to my motors, exactly what value and type of capacitor would be appropriate?  If I build a sandwich, I'll probably use tamiya gearboxes since they're so cheap.

Thanks everybody!  I hope this isn't too many questions at once!

Offline Admin

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Re: Couple of basic questions about resistors, parts in general
« Reply #1 on: February 17, 2008, 12:18:46 PM »
For the resistor and capacitor values, they don't need to be exact. Anything close to the values I listed will work.

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The 220uF+ electrolytic capacitor.  This could be an aluminum capacitor, is that correct?

electrolytic

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I could get photo resistors that are .5, 1.0 or 1.5 cm.  What is the difference besides price?

check the datasheets ;)
sensitivity, response time, size, etc . . .

Quote
What are the dimensions  of the atmega 8?  I saw two possible sizes for 28 pin DIP sockets, wide and narrow, but didn't know which to pick.  For the future, does anyone know of a roundup or comparison of all or most of the atmega micro controllers?

on the atmel site there are comparison charts
http://www.atmel.com/dyn/products/devices.asp?family_id=607
dimensions are in the datasheets

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if I add capacitors to my motors, exactly what value and type of capacitor would be appropriate?

for DC motors, .1uF will be fine typically

Offline arseniusTopic starter

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Re: Couple of basic questions about resistors, parts in general
« Reply #2 on: February 18, 2008, 04:17:57 AM »
Thanks Admin,

Unfortunately the photo resistors didn't have any data sheets, and no vendor information.  However, it turns out they don't have any of the larger ones in stock, so I have no choice in what to buy.:)

I got the impression from Wikipedia that all aluminum capacitors were electrolytic, but after your reply I reread it and it doesn't say that.

Is there another designation for electrolytic?  I'm asking because when I thought all aluminum caps were electrolytic, I added one to a shopping cart and the product page said nothing about it being electrolytic.  But then when I went back and looked at the data sheet (pdf linked off the part's page) after your reply, the data sheet says that it is electrolytic.  It seems like you shouldn't have to go to the data sheet to find out such basic information, but maybe I'm wrong.

Thanks again for your help.

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Re: Couple of basic questions about resistors, parts in general
« Reply #3 on: February 18, 2008, 09:29:35 AM »
hmmmm I'm too lazy to see if any other capacitors are made with aluminum . . . but according to wikipedia an electrolytic can be made with either aluminum for tantalum . . . but anyway, if it says electrolytic it will be fine . . . you can usually tell if its electrolytic by the cylinder shape, the very high capacitance, and a polarity marking.

For the $50 robot, any photoresistor will work (two of the same type).

Offline arseniusTopic starter

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Re: Couple of basic questions about resistors, parts in general
« Reply #4 on: February 19, 2008, 12:51:57 AM »
Thanks for the tip Admin!

 


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