Reducing motor current requirement?

[JerryB123]

Hello,

I have been lurking for a little while as the bug for CNC has been growing. I have finally taken a couple of steps in that direction, but have come across a stumbling block with stepper motors and drives.

I have purchased some LIN 5718L-01P stepper motors (294oz-in, 2.8A, 1.1Ohm, 3.8mH) and some stepper driver boards based on the Toshiba TA8435H. Unfortunately, in my first test the magic smoke was released from the TA8435H. Some investigation revealed that these chips are rated at 1.5A (2.5A peak), which is a little less than the motors will draw. I was thinking that the chopper part would kick in and although I would not get the max available from the motors, it would still work. Unfortunately I got the magic smoke instead, so I am trying to find out how to make this combination work as well as practical.

I have gotten the motors and drivers to play together by adding enough power resistors in series with the motor windings keeping the current below the nominal chip threshold, but this would work even if it was not a chopper driver. I am trying to find out how small a resistance I can put in line and not burn up the driver chip. Is there an 'equivalent voltage' that I can use for the output of the chopper part of the driver to calculate how much resistance I need to add in line with the motor windings to keep the effective chopped current below the max for the driver chip?

The driver based on a TA8435H and seems to be configured like the application circuit in the chip's data sheet (even down to the 0.8 Ohm resistors used for Rnf).

I woud like to use a 24V supply for the motor voltage, since I have recently bought that also.

Thank you for any assistance you can supply.
Jerry

[pminmo]

The chopper should have limited current. You may have damaged the chip because of back emf generated by the motor taking the supply voltage over the maximum.

[JerryB123]

Phil,

Thank you for the reply. Do you have any suggestions about what I could do with this combination to make it work?

I currently am using a 12 Volt power supply and have ~16 Ohms in series with each motor winding, keeping the max current down to ~0.7A, which allows the motors to operate (slowly) without burning up the drivers. But this is just using the drivers for their H-bridge and step capabilities without getting the benefits of the chopper part of the driver.

Before I start reducing the extra resistance in experimental mode, I was hoping someone would be able to shed more light about how this type of configuration should be configured. (Well, I now know that it SHOULD be configured using different drivers, but this is what I have for now and need to use what I have, if possible.)

Thank you.
Jerry