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03-05-2014 07:59 AM
Hi,
i have this circuit to control the direction of brushless dc motor
to remove the brake the brake should connected to Black and this happen after i give D0 and D3 high and this one work fine
to move back same we have to connect brake + back + black then D0+D1+D3+D4should high and this one work fine
when i want to move Forward should BRAKE+BACK +FRW+BLACK then the 6 pins should be high , but in this situation all the pins is low
any suggestion ?
the module i have 9403 and cdaq 9188
03-05-2014 09:50 AM
How much current do you need for those optocouplers? If any more than 10mA, then this actually makes sense.
The 9403 has an overcurrent protection in it. When you reach a certain total output current (spec claims 64mA), then the OCP kicks in an turns all of the outputs to high impedance. I would recommend finding some digital buffers that can supply more current for you optocouplers. I frequency use the 74ACT245SC.
03-05-2014 09:52 AM
03-05-2014 10:09 AM
so 64ma is per channal ?
03-05-2014 10:26 AM
@Eng.Tareq wrote:
so 64ma is per channal ?
No, 64mA total. Yeah, you definately need to find a buffer that can handle some current. That optocoupler could need 50mA for the control.
03-05-2014 10:27 AM
But how can i run until 4 PHOTOCOUPLER ? if i put 5 or 6 it go to over current state ?
03-05-2014 11:09 AM
@Eng.Tareq wrote:
But how can i run until 4 PHOTOCOUPLER ? if i put 5 or 6 it go to over current state ?
That 50mA is a maximum. From the data sheet, it looked like 20mA was a typical. It didn't have a spec for minimum current. But running 4 might just be doable (assuming no more than 16mA per optocoupler) and then a fifth causes the OCP in the DIO module.
Again, put in a digital buffer that can handle the current to control those optocouplers.