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Author Topic: 3 phase stepper motor (problem with l293)  (Read 551 times)
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Poland
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Hello!

I'm suffering one problem with l293 (quad H bridge). smiley-wink

-Whenever I connect psu arduino pins + power supply my l293 gets hot (only during movement).
-My motor is "sound making", It moves but slowly , not like connected directly to PSU(This is main problem)

What I did:
-Tested the voltage on motor pins (about 1.5)
-All connections are good
-I'm sure that it's not the code

My circuit:
http://elabz.com/wp-content/uploads/2011/11/three_phase_BLDC.png
(I'm using only plain circuit + arduino no other parts)

I have 12V pc PSU 350W.
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Poland
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(Sorry for double post)

I disconnected the motor now voltage goes to 7.2 (in quick cycle)
so I'm pretty sure that the motor.
I'm using:
Japan Servo KZ42FP4-761
-3 phase
-2.4 Ohm
Can't find datasheet so I have no more info.
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Quote
I'm suffering one problem with l293 (quad H bridge).

No, its a quad half-H-bridge...

It cannot drive a 3-phase motor with standard trapezoidal drive waveform as
that requires two outputs to be energised and one to be high-Z at each
step in the cycle.

So what waveform/sequence are you trying to use with it?  Where's the code?

12V supply and 2.4ohm windings plus a L293 = burnt-out L293, it cannot handle
that current level at all.
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Poland
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Oh your right.
Today I burned my ic. It exploded and hurt my finger (nvm that)... smiley-razz

What ic should I use?

I have 2 codes:

-using sin. tested, from elabz (I will probably use this one)
-simple high/low
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You need a way to reduce the voltage, and PWM gives you that, but normally for 3-phase you'd PWM
just the high sides (or just the low sides).

If you PWM both low and high you then use a PWM duty cycle from 50% to 100%, and invert the
drive of low and high-sides (its rather like class-D amplification).  50% duty will feed balanced
AC to that winding which is effectively zero.

Its not clear (can't google the motor) what current levels you actually want - 1A will make the L293 hot,
1.5A is pushing it.  More than that and you'd need a higher current 3-phase bridge (which would have
to be discrete MOSFETs to keep thermal losses under control, DMOS devices are about 0.3 ohms at best,
discrete MOSFETs down to 0.003 ohms are available.

If you want a challenge, look at the datasheets for chips like the FAN7888 and HIP4086 which make a 3-phase
bridge when 6 n-channel MOSFETs are added (plus a few other components).
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Poland
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This is way harder then I expected.  smiley-roll-sweat I think it will be easier to just but and old scanner or printer and get typical 4-5-6 wire motor.
One bad thing about this is that i constructed a device (cnc drawer, I can post pictures later on). Bolts run smoothly and everything is fine except motors. smiley

But thank you for your replay I checked these IC's but as I said I don't think its worth it.

Price of IC = 4 stepper motors  (small ones, or just disassembled ).
(Today I got "car boot" sale so wish me luck)



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