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Topic: Hi Power HBridge, DC Motor (Read 3 times) previous topic - next topic

Anachrocomputer

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It's impossible to fit this L298 on a normal breadboard...


I fitted an L298 to stripboard (Veroboard) by carefully bending the pins outwards, leaving a wider gap in the middle (for ground).  There's a photo here, but it's not very clear:



http://www.flickr.com/photos/anachrocomputer/3104717449/

Not sure if this would work for a solderless breadboard!  But with the currents involved when driving motors, you might be better off making a small soldered board for at least part of the circuit.

agent smith

#16
Feb 24, 2009, 11:37 am Last Edit: Feb 24, 2009, 12:32 pm by agentsmith Reason: 1
Retrolefty: yeah you're right, less is better :)
If I use both outputs for the same motor, is it still possible to link the two sense pins, to use just one arduino pin?

Anachrocomputer: interesting pic! On the datasheet they say to use 1A fast recovery diode (trr <200ns). Is it ok the 1N4001 diode? I found also the 1N4936RLG which is much cheaper.
Can I use diodes to save the enable pin? I mean, the enable pin is high when one of the two inputs are high.

Is there an easy way to override the enable pin when a certain voltage threshold has been exceeded?
Otherwise, what are the risks of having a stalled motor for a few seconds?

Erac


If I have a 24 Volt, 250 Watts, with 15Amp DC motor and I only have L298's as my DC motor driver, Can possible hook 8 L298's in parallel to withstand the high current rating of my motor?  How to do it?

Limit of the L298: 2A 46 V

Help..



P_Wood

According to P = I2R...
Given: I = 6.7A and R = 0.1
You would need a resistor(or a stack of them) that could handle AT LEAST 4.5Watts. Your standard resistors are 1/4Watt. Even if you put 10 1ohm (1/4Watt variety) resistors in parallel--achieving the desired resistance of .1ohm , you could only expect to handle 4Watts.
Just something to consider as a 0.1ohm resistor is not too common.

P_Wood

@retrolefty
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then it would be better to amplify the current voltage drop to utilize more of the full 0-5vdc range.

Wouldn't it be easier to just change the reference voltage for the ADC(AREF)? You could use a voltage divider(trimpot maybe?) to set the 'range' for the ADC by setting AREF to 1.34V. That way you could get the full resolution out of the ADC. Perhaps I'm just being facetious.. Who needs that kind of resolution for current sensing in motor control, anyway? ;)

Pat

felis

LMD18200 from National is a nice motor controller too. It's rated at 3A/6A peak, has internal clamp diodes and supports locked anti-phase PWM so you can use single pin for both speed and direction.
/felis

zoomkat

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If I have a 24 Volt, 250 Watts, with 15Amp DC motor and I only have L298's as my DC motor driver, Can possible hook 8 L298's in parallel to withstand the high current rating of my motor?  How to do it?


As previously mentioned, the L298 chips probably will not parallel very well. You probably need to get an H-bridge with MOSFETs made to handle your large motor.
Consider the daffodil. And while you're doing that, I'll be over here, looking through your stuff.   8)

zoomkat

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I finally found a single easy to use chip I could use to control my Dc motor. I was hoping you guys could help with it. (I am a total Newbie when it comes to electronics, Software guy by trade).  I am using a TLE6209 to control a dc motor. What I would LOVE to do is know when my motor stalls out. I know that my motor will draw 2 about amps during normal operation, and it will draw 6.7 amps stalled. That's what I want to detect - the stall state. Do I need more to detect this? Can I use this chip directly? Any input would help.


The ZXCT1009 chip is made for reading current flow across low resistance points in circuits.
Consider the daffodil. And while you're doing that, I'll be over here, looking through your stuff.   8)

gardner

In my (limited) experience the L298 is an absolutely awful motor controller.  It has a huge (>2 ohms) on resistance and dissipates an astounding amount of heat.  Unless you have a large transit bus for a heat sink, it will go into thermal shutdown and behave very strangely indeed.

Much better to get one based on a VNH2SP30.  Pololu has some.  These guys have an on resistance in the 100 milliohm range and do not dissipate noticeable amounts of heat in operation.  There are many modern MOSFET-based motor controllers to choose from.

Erac

Thanks for the replies!

Finally decided not to use the L298 because of its limitations. I instead bought this motor speed and directional motor controller ( http://secure.oatleyelectronics.com/files/K243notes.pdf ) ,but the problem is: the speed can be controlled by 1-2mS pulse from standard R/C hobby remote controls that control standard servos. ( converts the 1-2ms pulse to analogue voltage).

How can I possibly control its speed and direction using my arduino microcontroller? I've never used a  1-2mS pulse from standard R/C hobby remote controls? Do I have to buy a separate circuit?

Pls help?

Regards


P_Wood

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How can I possibly control its speed and direction using my arduino microcontroller? I've never used a  1-2mS pulse from standard R/C hobby remote controls? Do I have to buy a separate circuit?

The 1-2ms pulse-control method is the same that is used to control hobby servos. There is an existing library for working with servos that would work well with this. However, instead of myServo.write(angle), it would likely be myServo.write(speed). Since the angle usually ranges from 0 to 210 degrees, 105 would likely stop the motor and 210 would be either full-speed forward or reverse (depending on how you wire it) and 0 would be the opposite. The myServo.write() function takes the desired angle(in your case, speed) and outputs the appropriate pulses.

Search for hobby servo signal/control. From there you can find good info on this method of control.

zoomkat

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How can I possibly control its speed and direction using my arduino microcontroller? I've never used a  1-2mS pulse from standard R/C hobby remote controls? Do I have to buy a separate circuit?


It should be very simple. Per the below, you should only have to set a pin up on the arduino to control a servo, then connect the arduino servo pin and ground to the motor control board as described.

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The 1-2mS input should be connected to the terminals marked "GND" and "SIG".

Consider the daffodil. And while you're doing that, I'll be over here, looking through your stuff.   8)

Erac

Thanks for the support P_wood and zoomkat, some questions..

@P_wood:  Are the libraries ( functions) for the direction and speed control included in the Arduino? I will just have to type in the codes you gave and callibrate?


@zoomkat: So I will connect the GND of my motor controller ( K243) to the GND pin of my arduino and the SIG to the desired pin I will be using for the motor control? Is that right? I will just connect it directly?

Hope for your support

Regards

zoomkat

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@zoomkat: So I will connect the GND of my motor controller ( K243) to the GND pin of my arduino and the SIG to the desired pin I will be using for the motor control? Is that right? I will just connect it directly?


That is what I would do. I suggest you get a 10k linear taper pot at Radio Shack to use per the instructions while testing your kit. When it operates as designed with the pot, then remove the pot and connect the controller to the arduino. Testing using a pot will rule out arduino issues if the controller doesn't work when first built.
Consider the daffodil. And while you're doing that, I'll be over here, looking through your stuff.   8)

Erac


Thanks for the support zoomkat.

How do I change the direction of my motor using this motor controller (http://secure.oatleyelectronics.com/files/K243notes.pdf) through my arduino? I can't understand how to go about it?wiring.. etc

Help anyone

Regards,
Erac

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