Author Topic: capacitor  (Read 1852 times)

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Offline MangoBotTopic starter

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capacitor
« on: July 12, 2009, 04:48:12 PM »
What value of capacitor should i use for this gear motor? or should i not add one? Thanks for the help. http://www.pololu.com/catalog/product/1123/specs

Offline Joker94

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Re: capacitor
« Reply #1 on: July 13, 2009, 12:28:32 AM »
i have never added a capacitor to y geared motor, but i don't know if it is good or bad ???

Offline SmAsH

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Re: capacitor
« Reply #2 on: July 13, 2009, 12:33:02 AM »
if its an el-cheapo motor a .1uf ceramic cant hurt, can it?
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Offline Joker94

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Re: capacitor
« Reply #3 on: July 13, 2009, 12:38:34 AM »
i just searched  and found one that had an inbuilt capacitor to guard it from damage

Offline SmAsH

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Re: capacitor
« Reply #4 on: July 13, 2009, 12:41:40 AM »
i just searched  and found one that had an inbuilt capacitor to guard it from damage
and thats just why.
with the cheaper motors it helps to have a small capacitor to absorb any spikes that could damage it.
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Offline MangoBotTopic starter

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Re: capacitor
« Reply #5 on: July 13, 2009, 10:35:05 AM »
ill use a 0.1uf

Offline benji

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Re: capacitor
« Reply #6 on: July 15, 2009, 10:11:39 AM »
if you are going to use a battery then you dont need any capacitor, spikes wont exist in batteries

if you are using a rectifier circuit then include a bigger capacitor, in my opinion you dont need any cap.
good ol' BeNNy

Offline chelmi

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Re: capacitor
« Reply #7 on: July 15, 2009, 10:45:15 AM »
if you are going to use a battery then you dont need any capacitor, spikes wont exist in batteries

if you are using a rectifier circuit then include a bigger capacitor, in my opinion you dont need any cap.

Correct me if I'm wrong, but the spikes we are talking about here are not coming from the power source, but created by the brushes of the motor. The cap is recommended in this case to prevent the spikes to interfere with the rest of the circuit (especially digital parts).

Chelmi.

Offline GearMotion

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Re: capacitor
« Reply #8 on: July 15, 2009, 10:47:40 AM »
if you are going to use a battery then you dont need any capacitor, spikes wont exist in batteries

if you are using a rectifier circuit then include a bigger capacitor, in my opinion you dont need any cap.

Correct me if I'm wrong, but the spikes we are talking about here are not coming from the power source, but created by the brushes of the motor. The cap is recommended in this case to prevent the spikes to interfere with the rest of the circuit (especially digital parts).

Chelmi.

You are correct.

Offline benji

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Re: capacitor
« Reply #9 on: July 15, 2009, 03:46:39 PM »
so you are saying a dc motor can cause spikes? a spike mean a sudden drop of voltage.....
anyways i saw operation of big dc motors without needing any cap at the source
I dont think its needed anyways
good ol' BeNNy

Offline SmAsH

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Re: capacitor
« Reply #10 on: July 15, 2009, 04:16:54 PM »
so you are saying a dc motor can cause spikes?
yeap, sure can! the capacitor is just there to help smooth them out so they don't interfere with anything else in the circuit that may be sensitive to spikes, ie. sensors.
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Offline sonictj

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Re: capacitor
« Reply #11 on: July 15, 2009, 05:00:42 PM »
Its also common practice to use optical isolators to prevent noise from motors and such.  I don't know a ton about them, but my professors recommend them.  I know some guys that built an avr board that they sold to students in my robotics class.  Their board would reset if you had too many servos connected.  I think this is because their power supply did not have big enough capacitors to take the surges of current.

Offline chelmi

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Re: capacitor
« Reply #12 on: July 16, 2009, 10:00:59 AM »
so you are saying a dc motor can cause spikes? a spike mean a sudden drop of voltage.....
anyways i saw operation of big dc motors without needing any cap at the source
I dont think its needed anyways
The cap is not at the source! it's right next to the motors! Apparently some motors have built in caps, maybe that's why you never saw any.

Offline MangoBotTopic starter

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Re: capacitor
« Reply #13 on: July 16, 2009, 01:21:58 PM »
how should i solder it together, attach one lead to each terminal or hook up one capacitor to each terminal.

Offline SmAsH

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Re: capacitor
« Reply #14 on: July 16, 2009, 04:49:23 PM »
yes, one lead of the capacitor to each lead on the motor.
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Offline MangoBotTopic starter

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Re: capacitor
« Reply #15 on: July 19, 2009, 07:29:27 PM »
so then should i put the power and ground closer to the disc and the ends to each terminal?

Offline SmAsH

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Re: capacitor
« Reply #16 on: July 19, 2009, 07:39:59 PM »
what? if you are asking about placement of the capacitor, you have two leads of the cap, two leads of the motor... one lead from the capacitor goes to each motor terminal...
imagine it like wiring it in parallel...
Howdy

 


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