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Step motor H-Bridge help

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Zwilorg

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Hello,

I have a 4A,20V power supply to run a bipolar step motor.

I know that i can´t use a simple one like L293 because of the limit on the input current.

Which H-bridge would be most suitable for this motor?
i could also use two L6202 i think.

Ideas would be much apreciated!

Best regards,
Zwi
 

Zwilorg

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It holds up to 2A per phase right?

In the datasheet pag8 of the L298:

"This circuit drives bipolar stepper motors with winding currents up to 2 A. The diodes are fast 2 A types."

But as mencioned on the link you posted the connections are made in parallel made this is why he got it working at 4A.

Thank you for the input
 

Zwilorg

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technical data NEMA23 motor

max voltage [VDC] 60
nominal voltage [VDC] 24-48
nominal current [A] 4,2
holding torque [Nm] 2,0


This are the specs of the bipolar motor i have, can´t i get it working with the L298 or the L293?

I tried with the L293 and the Pic i have got wrecked (16f877)

If not can someone help me out on this?
 

Zwilorg

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the link you sent ckshivaram, "Schematic: 4A H bridge using the L298 IC"

can i use two L298N and give the 4A to each winding? i think this is my main problem, only giving 2A per winding!
 

Zwilorg

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i can´t find those at the stores over here or on the stores in the internet like farnell...

I tried to make it work with the L293 and the motor does a low noise like it is trying to start... but nothing happens...

What could be the problem? the coding works fine on the simulator and i am read alot about it so i think it is okey.

the problem must be either on the current intensity being to much low or the voltage is not high enough...


(the l293 after 2min starts getting really hot)

can i use bridge it 2 outputs only but that old up to 6amp and join them? one for each winding?
 

Zwilorg

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Just fried a L298N... that didn´t even started the motor... i don´t understand why :S

the power suply i am trygin right now only goes to 20V and 3.6A.

maybe that is the problem?
 

FvM

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Basically, you operate the motor at reduced current with reduced torque. In any case, the current sense resistors and Vref most be dimensioned for the intended output current. It's constant current PWM mode.

P.S.: I just realized, that the above linked L298 H-bridge circuit simply shorts the sense terminals to ground. In other words, it's operating the stepper motor in constant voltage rathe than constant current mode. This can only work with a stepper motor with sufficient phase winding resistance. No fast stepper motor will have it.
 

Zwilorg

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Basically, you operate the motor at reduced current with reduced torque. In any case, the current sense resistors and Vref most be dimensioned for the intended output current. It's constant current PWM mode.

P.S.: I just realized, that the above linked L298 H-bridge circuit simply shorts the sense terminals to ground. In other words, it's operating the stepper motor in constant voltage rathe than constant current mode. This can only work with a stepper motor with sufficient phase winding resistance. No fast stepper motor will have it.

the SensA and SensB are grounded yes but with a resistor of 1k between the l298 and the ground.

maybe that is what you are talking about?

(why can i move the motor with the l293 that has a lower current and not with the l298 that has a higher current? 1,2A to 2A if am not mistaken)
 

FvM

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The current sense and control point is fairly presented in the L297 and L298 datasheets. I see, that the example circuit uses 0.5 ohm sense resistors for 2 A output current. 1K is surely not a reasonable value. But besides connecting a suitable sense resistor, the current sense input of the L297 must be connected, too. I assume, that your circuit doesn't utilize constant current.

In this case, the phase current is only limited by the supply voltage and the windings resistance.
 

Zwilorg

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i never thought about that. So i do need the l297, gotta buy it then,

So:

1- buy l297
2- buy resistors of 0.5ohm
3- build it all again

right?

-> i always have enable A and enable B at high from the microcontroller is this correct?

-> and to get the 4A the datasheet refers too should i do the combination of PIC-l297-L298N for each winding?
 

FvM

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I understand from your post, that you're driving the L298 from µP directly. Than you're in fact missing a means of PWM current control. If you intend to operate the motor only at low speed, you don't necessarily need constant current operation. But you have to reduce the current by some other means, e.g. lowering the supply voltage. Or apply a fixed PWM from the µP. But you should know how to calculate and control motor currents before designing your circuit.

P.S.:
and to get the 4A the datasheet refers too should i do the combination of PIC-l297-L298N for each winding?
It's not clear to me, if you actually need 4A? If so, you would need one L297 and two L298, or any other circuit that can generate phase signals with PWM current control in place of the L297.
 

Zwilorg

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if i get this working i will be forever in debt to you and ckshivaram!

i am going to buy the parts and see if i can get it working i hope so!
 

alexan_e

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technical data NEMA23 motor

max voltage [VDC] 60
nominal voltage [VDC] 24-48
nominal current [A] 4,2
holding torque [Nm] 2,0
In the first post you said that you have a 20v/4A source (which will probably not be enough for two phase drive but you can use one phase) and if I understand the data you have provided correctly you have a motor that works well within the current range with 20v supply (nominal voltage [VDC] 24-48).

If this is the case then you don't need to use the PWM because the current will be limited anyway from the coil resistance so you can just use a discrete circuit like A simple H-Bridge design « PocketMagic and just provide the correct steps.

For bipolar operation modes check Stepperworld Bipolar Tutorial

Can you verify that the resistance of your motor is more than 5-6 ohms?

Alex
 

Zwilorg

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In the first post you said that you have a 20v/4A source (which will probably not be enough for two phase drive but you can use one phase) and if I understand the data you have provided correctly you have a motor that works well within the current range with 20v supply (nominal voltage [VDC] 24-48).

If this is the case then you don't need to use the PWM because the current will be limited anyway from the coil resistance so you can just use a discrete circuit like A simple H-Bridge design « PocketMagic and just provide the correct steps.

For bipolar operation modes check Stepperworld Bipolar Tutorial

Can you verify that the resistance of your motor is more than 5-6 ohms?

Alex
i am providing the correct steps to the motor because i tested it on the Simulator and i have been on the site you sent already ;)

i can´t check resistance right now because i don´t have any multimeter at my house.

the problem is really on the circuit because has i said before the motor works (slowly and akwardly) with the l293 for a while and with the 298 it doesnt work and after a while the l298 just blows...

i have been searching about the L297, the program on the PIC needs to be different right? i can´t control the motor the same way i did while connecting directly to the 298.

i need to control the Clock pulse (the delay between steps) and the Cw/CCW,

i don´t understande the pin CONTROL:

"Control input that defines action of chopper.When low chopper acts on INH1 and INH2; when high chopper acts on phase lines ABCD."

is this the ON/OFF of the motor? or the Enable A/B of the L298?

----
Edit: Solved the L297 programming part... i got stuck on a stupid thing lol
 
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