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Resistor Over Heating

amirabbas1234

Aug 24, 2017
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hi all
im trying to get a stepper motor working with an arduino and a a4988 driver, and my circuit is EXACTLY like the image uploaded. well every thing is OK but the resistor at the top of the (brown green brown gold) picture over heats and starts to smell, now i found out that its because my resistors wattage is low (its 0.25 watts)(GOD bless google!!!) now i have ordered 5 and 10 watts resistors and i will use them instead of current one
now i have 2 questins:
1) is there a way so i could prevent this over heating with 1/4 watt resistors that i currently have?(like putting multiple resistors in series or parallel)
2) as u see in the pic there are no resistors connected to any other pins except "VMOT". now should i put some resistors in series with every pin to limit the current and prevent damaging the driver or the arduino?(if YES with what value)
THANKS IN ADVANCE
A4988-Wiring-Diagddram (1).png
 

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Minder

Apr 24, 2015
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Modern stepper drives have done away with the old resistor dropping method, usually you use one or the other, a drive that can maintain the rated current regardless of rpm, or the old resistor method that requires a high wattage resistor,
M.
 

amirabbas1234

Aug 24, 2017
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Modern stepper drives have done away with the old resistor dropping method, usually you use one or the other, a drive that can maintain the rated current regardless of rpm, or the old resistor method that requires a high wattage resistor,
M.
i cant understand what u mean
 

dorke

Jun 20, 2015
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Do you understand why you have the resistor in the first place?
And yes there are many ways...
 

Harald Kapp

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What driver chip do you use? Check the datasheet to see whether the current limiting resistor is required. The chip may or may not have an internal current limiting function.
 

dorke

Jun 20, 2015
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yes, for limiting the current so driver wont burn out
can u please name some ways????

NO,wrong answer!
You have an R-C filter at the Vmot input pin.

Actually the best way would be eliminate the resistor completely (R=0) look here.
 

dorke

Jun 20, 2015
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Read the datasheet.

Why in the first place ,do you think it will burn?
 

dorke

Jun 20, 2015
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And what does a LED have to do with this case?
Read the datasheet!
 

hevans1944

Hop - AC8NS
Jun 21, 2012
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@amirabbas1234: Is your driver board, based on the Allegro A4988 DMOS motor-driver integrated circuit chip, this board from Pololu? Have you read and understood BOTH the datasheets for the chip and for it's carrier board? Do you see anywhere on these datasheets where it is recommended that you insert a resistor in series with the motor supply voltage, VMOT? The chip is designed to source up to two amperes of current to the motor windings. What value of resistor would you select to carry this current without excessive voltage drop from the motor power supply?

Do you have any training or experience in electronics, or is this an Instructables-like "monkey see, monkey do" application? We don't mind helping with that here, but it helps to know your level of skill and motivation.

Many of us got involved in electronics by building Heathkits, the ultimate "monkey see, monkey do" experience with superb illustrated check-off-as-you-go instructions. Only after the kit was built and operating satisfactorily did we bother to read the "theory of operation" section of the manual. Many of course didn't bother to do that, because their only goal was to obtain a piece of equipment at less cost than a factory-assembled unit. If your only goal is to get a stepper motor working with your Arduino, you have made a good choice for the motor driver. Hopefully you will go on to learn more about how and why PWM replaced series current-limiting resistors for stepper motor drives.

I remember, not too fondly, building a stepper motor driver that used 200 watt current-limiting resistor requiring forced-air fan cooling... this in the late 1960s, just before power FETs became readily available. Superior Electric, a stepper motor manufacturer, even had an application note showing how to drive their motors with bipolar silicon power transistors (2N3055 types) and series current-limiting power resistors (wire-wound on ceramic tubes). A few years later, all the commercial stepper motor drivers were using FET pulse-width modulation to control motor current with nary a power resistor anywhere in sight. There is a lot of fascinating history associated with stepper motors and their driver circuits that you should find and read. Back in the day they were considered somewhat exotic, but now steppers are everywhere and in everything.

Good luck with your project!
 

amirabbas1234

Aug 24, 2017
14
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Aug 24, 2017
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thank
@amirabbas1234: Is your driver board, based on the Allegro A4988 DMOS motor-driver integrated circuit chip, this board from Pololu? Have you read and understood BOTH the datasheets for the chip and for it's carrier board? Do you see anywhere on these datasheets where it is recommended that you insert a resistor in series with the motor supply voltage, VMOT? The chip is designed to source up to two amperes of current to the motor windings. What value of resistor would you select to carry this current without excessive voltage drop from the motor power supply?

Do you have any training or experience in electronics, or is this an Instructables-like "monkey see, monkey do" application? We don't mind helping with that here, but it helps to know your level of skill and motivation.

Many of us got involved in electronics by building Heathkits, the ultimate "monkey see, monkey do" experience with superb illustrated check-off-as-you-go instructions. Only after the kit was built and operating satisfactorily did we bother to read the "theory of operation" section of the manual. Many of course didn't bother to do that, because their only goal was to obtain a piece of equipment at less cost than a factory-assembled unit. If your only goal is to get a stepper motor working with your Arduino, you have made a good choice for the motor driver. Hopefully you will go on to learn more about how and why PWM replaced series current-limiting resistors for stepper motor drives.

I remember, not too fondly, building a stepper motor driver that used 200 watt current-limiting resistor requiring forced-air fan cooling... this in the late 1960s, just before power FETs became readily available. Superior Electric, a stepper motor manufacturer, even had an application note showing how to drive their motors with bipolar silicon power transistors (2N3055 types) and series current-limiting power resistors (wire-wound on ceramic tubes). A few years later, all the commercial stepper motor drivers were using FET pulse-width modulation to control motor current with nary a power resistor anywhere in sight. There is a lot of fascinating history associated with stepper motors and their driver circuits that you should find and read. Back in the day they were considered somewhat exotic, but now steppers are everywhere and in everything.

Good luck with your project!
thank you. as a matter of fact im a mechanical eng and gonna study mechatronics in the future, an now im planing to make a simple 3d printer
so NO, i dont have any experties in electronics.
but thank you for ur answer and advices
 

Minder

Apr 24, 2015
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i cant understand what u mean
I suggest you read up on the history of stepper drives, resistors are no longer needed.
Modern drives should be designed in order that the stepper rated current occurs at all rpm's, even when the power supply to the drive exceeds the motor plate voltage, which should Never be exceeded.
IOW the drive has automatic current control/limiting at all rpm's.
M.
 
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