Need Help!- Want Gecko Drives for Steppers but Need Help

[wganders]

I'm trying to get my little home-made CNC up and running but need help deciding what Gecko Drives and Power Supply to get. I have 3 Superior Electronics stepper motors with the following ratings:

1.6 Volt
4.6 Amps
200 Steps/Rev
150 Oz-In in Unipolar
8-wire

Anyone have any suggestions???

Thanks in advance.
wganders

[LaserImage]

G540 and a 24v psu - I just got mine to replace a Mechatronics POS and I am very happy with it!

Gary

[dmauch]

The motors if 4.6A unipolar would therefore be 3.2A bipolar series.
I would go with a 8A 24V power supply.
Dan Mauch
Camtronics Inc
www.camtronics-cnc.com

Originally Posted by wganders I'm trying to get my little home-made CNC up and running but need help deciding what Gecko Drives and Power Supply to get. I have 3 Superior Electronics stepper motors with the following ratings: 1.6 Volt 4.6 Amps 200 Steps/Rev 150 Oz-In in Unipolar 8-wire Anyone have any suggestions??? Thanks in advance. wganders

[Mariss Freimanis]

Those sound like round motors. You have two choices:

1) Keep your motors. Pay through the nose for 3 G203V drives, a breakout board and do a lot of wiring to connect everything. Cost: 3($134 / G203V) + $100 for the breakout board = $500 damage, hours and hours of wiring.

2) Get new 'square' motors (Keling KL23H256-21-8B @ $33 a pop) and a G540. The square motors and a G540 will run rings around your existing motors. Cost: 3($33 / motor) +$300 for a G540 = $400 damage, maybe 30 minutes of wiring.

About power supply voltage:

A step motor's speed-torque curve rounds off from the constant torque region to the inverse torque region. This makes the transition speed open to interpretation. To avoid this, I use the -3db torque speed to mark the end of the constant torque region. In other words, the constant torque region ends when torque has fallen to 70.7% of holding torque.

I'm running some tests using a G540 and a KL23H256-21-8B motor because it was handy. The -3db torque speeds at 24VDC, 36VDC and 48VDC are:

24VDC = 456 RPM
36VDC = 720 RPM
48VDC = 1,004 RPM

Temperature Rise: The motor is placed on its side on a 1/2" thick foam plastic slab. A thermocouple is placed between the motor and foam to measure motor case temperature. The foam insulates the thermocouple to read only the motor temperature. The motor phase current is set at 3A and the motor sits idle at a 2.1A automatic standby current. The ambient temperature is 23C.

24VDC = 52C case temperature, 19C temperature rise.
36VDC = 64C case temperature, 41C temperature rise.
48VDC = 79C case temperature, 55C temperature rise.

As you can see, the higher the supply voltage, the hotter the motor even while standing still. That is why it makes good sense to figure out first what maximum speed you need and then pick your supply voltage based on that need.

Mariss

[MrWild]

I followed everything except this, what does the -3db mean?,

Originally Posted by Mariss Freimanis I'm running some tests using a G540 and a KL23H256-21-8B motor because it was handy. The -3db torque speeds...

What would running the windings in series do?

[wganders]

Mariss,

I like your idea of starting fresh and reducing the wiring hassle and you are right about my steppers being round. But, one reason I was trying to save the steppers was the fact that they are NEMA 34 geometry and I wanted to avoid having to make new mounts for my mill for NEMA 23s. What motors can I get in the NEMA 34 style? I looked at some Keling 8-wire motors which ran about $79 each, would they work with the Gecko 540? I think they were about 400 Oz-In motors, KL34H260-42-8A, see attached specs. Also, in case you haven't noticed, I'm clueless when it comes to electronics and really appreciate all the input on this thread!!!

Thanks,
Bill

[Mariss Freimanis]

-3db is when any function (voltage, torque, etc.) falls to 1 / SQRT 2 (.7071) of its original value. For instance, you buy a stereo amplifier and its specs says "20Hz to 20kHz frequency response". That means the output voltage has risen to 70.7% of rated at 20Hz and drops to 70.7% of rated at 20kHz.

Mariss