[Dr.Nos]

Anyone had this problem ? Ive had to replace the Resistors twice now because they get burnt to a crisp (see pic) . Im running Bld60-235 Servos and a 600w Antek An-64115 power supply . I have to set the HV upper limit to 170000 mv or i get Over Voltage flags . Is this related?

Smooth Stepper USB controller
VSD-E Servo drivex3
BL60-235 Servox3
VSDEPI Parallel Port Interface
600 Watt power supply

[john-100]

having downloaded the transformer data sheet
off load the DC supply for the servos will be about 115V x 1.4142 = 162 V plus 3 or 4 %
(depends on the actual mains input ond transformer regulation )

what value are the resistors ?


for example
rounding up the DC voltage to 170V and limiting the LED current to 5 mA
the resistor required will be (170 x 1000) / 5 = 34000 ohms

it could be usefull to measure servo supply to see how high it is when an axis is breaking
and current is being dumped back into the supply


a 33K 1W resistor is close enough and the current will be 5.15 mA and dissapate 170 X 0.00515 A = 0.875 W
if you have the space use a 33K 2W resistor

as another example to make the LED brighter
a 10K resistor would increase the LED current to 16 mA (160V supply / 10000 )
but the resistor runs hotter 160V X 16 mA = 2.56W use a 10K 3W resistor or 10K 5W resistor


if your getteng over voltage alarms you may need to add an extra circuit to dissapate the energy returned during breaking
170000 mV = 170V
whats the maximum supply voltage for the servo drives ?

have a look here :-
http://www.geckodrive.com/support/ap...ergy-dump.html

John

[Dr.Nos]

Hi John thanks for taking the time to explain my issue , this is exactly the answer i was looking for , ... I only replaced the resistors with the same value , which was 1W 10k . So going buy your maths that's way to small .
whats the maximum supply voltage for the servo drives ? 160vdc Max surge 180 Vdc

I will replace resistors in the weekend and let you know how i get on .

many thanks Jason

[neilw20]

With high deceleration programmed, multiple axis can generate overvoltage during rapid braking -- read that as reduce the accel/decel.
If it is a 2/3 axis move the regeneration can be an issue.
The VSD manual states you can use a single braking resistor shared between drives, using the 4th channel if you only use 3 phase motors.
I have not found the information about how to use a shared resistor.
I have been working on a 5 axis machine with six drives for the past 7 weeks.
It has had an auto transformer (4KW) added to reduce the voltage down to about 155v and now has no problems.
The documentation on the Granite drives is rather short, and leaves a lot of guesswork to get it right.
The GDTOOL is rather pedantic about the undocumented reasons for logging on and off, and it is difficult to figure how to get repeatable results.
Rather painful, with 6 big motors to tune, and once the GDtool has had a go the USB, the smoothstepper gets confused -- OMR needed. One More Reboot!
Using to vdepi boards, there is no provision to parallel the estop signals.
This means only one breakout board can use pin 10.
My solution, and a valid one, because the estop is diode orred, is to connect the pin 10's on ports 1 and 2. (with a soldered link - yuk)
I have gone for 100% opto isolation on this rebuild and now reliable, no USB errors is the result.
Back to the original question...
The above led resistor calculations are valid. Use a big value >= 33K and be satisfied with dim leds. 10Ks will cook.

By the way, this machine is 12 x 5 x 2 (XYZ + 2 axis fancy head) and that is meters! You can park 6 fork lifts IN the machine. -- Lots of fun.

[Xerxes]

I have not found the information about how to use a shared resistor.

Resistor sharing works simply hooking up a resistor on one drive which will drain the regenerated from any drive if all drives are connected to the same HV DC supply.

The same works with Argon drives (and there's better documentation for it):
Argon user guide/Wiring - Granite Devices Knowledge Wiki

[neilw20]

Thanks for that.
It makes sense - I will add it to the useless PDF.
I left that machine 6 weeks ago, but will keep it in mind.