Author Topic: $50 Robot Resistors  (Read 1132 times)

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Offline RS232Topic starter

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$50 Robot Resistors
« on: July 06, 2010, 08:06:00 AM »
Hi, I am trying to make my first robot. I am trying to order parts but it seems that the 1.62K ohm resistor is on back-order on digi-key until mid August. It is also out of stock at mouser and everywhere else for some reason. Is there some other resistor or series combination I can use to make this work? Thanks!

Offline SmAsH

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Re: $50 Robot Resistors
« Reply #1 on: July 06, 2010, 08:59:11 AM »
The resistors don't have to be spot on, so something around 1.62 would do fine, or a combination of two resistors to make something close to 1.62 would work too.
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Offline Selenaut-14

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Re: $50 Robot Resistors
« Reply #2 on: July 06, 2010, 09:17:10 AM »
So do resistors in a series act like batteries in a series?
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Offline SmAsH

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Re: $50 Robot Resistors
« Reply #3 on: July 06, 2010, 09:31:53 AM »
Put resistors in series and you can pretty much + the resistances to get the desired resistance.
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Offline Selenaut-14

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Re: $50 Robot Resistors
« Reply #4 on: July 06, 2010, 09:35:04 AM »
Okay... It seems a bit counterintuitive though. :s
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Offline SmAsH

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Re: $50 Robot Resistors
« Reply #5 on: July 06, 2010, 09:59:52 AM »
Yeah, but if you cant get that exact resistor... Sometimes this can work as a good fix...
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Offline Selenaut-14

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Re: $50 Robot Resistors
« Reply #6 on: July 06, 2010, 10:10:59 AM »
I'll keep this in mind... Thx
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Offline RS232Topic starter

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Re: $50 Robot Resistors
« Reply #7 on: July 06, 2010, 10:31:47 AM »
Okay... It seems a bit counterintuitive though. :s
How is it counter-intuitive? The current travels through one resistor and then the other.

Offline Selenaut-14

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Re: $50 Robot Resistors
« Reply #8 on: July 06, 2010, 10:44:50 AM »
Because I thought that two resistors of different amounts would just resist as much as the larger one... See what I'm getting at? Like say there was a 100 ohm and a 50 ohm resistor. I thought it'd just have a combined power of 100 ohms, not 150.
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Offline RS232Topic starter

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Re: $50 Robot Resistors
« Reply #9 on: July 06, 2010, 10:50:11 AM »
^But as the current passes through each resistor it loses energy. So, it loses energy in the 100 ohm and ten again in the 50 ohm so same as 150 - as long as in series... In parallel its different: 1/R1 + 1/R2.


I was wondering if anyone could point me to another possible combination cause I'm not used to purchasing these things and the different ratings for them - I don't want to pick the wrong thing. I found a 1.65K ohm... But why specify 1.62 if a range will work? I'm not yet sure how to calculate all the stuff out to make sure its OK, since I've never put together a complex circuit. I have had an EE circuit analysis class in college, but I haven't mastered that stuff.
« Last Edit: July 06, 2010, 10:53:27 AM by RS232 »

Offline random robots

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Re: $50 Robot Resistors
« Reply #10 on: July 06, 2010, 11:10:38 AM »
a good combo is 1k and 620 ohm. if you have a radioshack that has electronic components, you can buy that large reel of 1/4 watt resistors which has both resistors.

hope this helps,
Patrick
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Offline RS232Topic starter

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Re: $50 Robot Resistors
« Reply #11 on: July 06, 2010, 11:15:50 AM »
a good combo is 1k and 620 ohm. if you have a radioshack that has electronic components, you can buy that large reel of 1/4 watt resistors which has both resistors.

hope this helps,
Patrick
Thanks, those are both on back-order as well. Radio shack has a reel of assorted resistors of all ohm ratings for 1/4? If so, I may try that as I am going to take some stuff back to RS that I found much less pricey on digi-key.

Offline random robots

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Re: $50 Robot Resistors
« Reply #12 on: July 06, 2010, 11:26:21 AM »
actually, no. radioshack only has about 30 common resistors in the reel. but i have been able to use them in different combos for circuits, and i haven't bought any other resistors ever. buy the reel!!!!!!!!!!!!!!!!! it's a great buy.
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Offline GearMotion

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Re: $50 Robot Resistors
« Reply #13 on: July 06, 2010, 06:34:02 PM »

Offline RS232Topic starter

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Re: $50 Robot Resistors
« Reply #14 on: July 06, 2010, 08:45:13 PM »

 


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