Tony Bullard (Customer) asked a question.
DSG7 0-10 volt PWM analog control
I'm using 0-10 volt PWM at 20,000 Hz input and can't set minimum speed to 0 with input 0 volts. It needs about 3 PWM volts just to start rotation. Maximum speed can be set with 10 volts. Do I need analog input or will the PWM frequency change the start voltage? Thanks for any help.
Tony
I searched for part number DSG7 on Automationdirect.com website and doesn't show that we sell this part?
Please try this: https://www.automationdirect.com/adc/search/search?fctype=adc.falcon.search.SearchFormCtrl&cmd=Search&searchquery=IRONHORSE+gsd7&categoryId=0&TxnNumber=-1&searchqty=10
Thanks you.
I'm sorry It's GSD7 not DSG7.
I don't see anywhere in the GSD7 specs or manual that PWM is an acceptable control, and they do emphasis that a DC control voltage must be isolated. On the other hand 20kHz is fairly fast, it probably wouldn't take too much capacitance to smooth it out to close to DC, there may or may not be enough stray capacitance already, though if I was having problems I'd try a simple RC filter.
At 20khz, assuming 100% duty cycle = 10V, then 1V would be 10% of (1second / 20,000) or 5 microseconds, maybe a rather short pulse for something expecting "DC"?
The manual is somewhat lacking in detail, while they do show the possibility of using a nominal 0-10VDC (isolated) control signal, they don't specifically say how voltage maps to speed, there could be a dead band and maybe not starting until the voltage is 3 could be normal? I would test it with an adjustable DC power supply.
Thank you Tinker. You have brought up some good points. Is the output of the drive even linear to the input. If not I will have to setup a closed loop feedback to control the drive. The application is a CNC lathe with a DC spindle drive controlled by Mack4 with a Pokeys57CNC motion controller at my son in laws 200 mile away. I'll try to get him to plot the voltage / speed of the three types of input and go from there. The inputs are supplied "speedpot", PWM signal and an adjustable DC power supply. This may take some time and I hope to get back with an answer for those who may be interested.
You have given me something to work with. Thank you again.
Tony
I am guessing that this system has the add on GSDA-DP-S https://www.automationdirect.com/adc/shopping/catalog/drives_-a-_soft_starters/dc_drives/accessories/gsda-dp-s
While the Automation Direct Reference mentions PWM as an input/output type for the conditioner I don't see it mentioned in the manual.
Thank you but my system doesn't have the add on. It uses an isolated Pokeys57CNC motion controller for the PWM.
Then give up on PWM. The dc controller doesn't work with it.
Bcarlton if you are referring to the GSD7 controller I respectfully disagree with you.
I have the GSD7 working very well with PWM @ 20Khz. As Tinker suggested there is a dead band of 1.924 volts in my case to start. I mapped the PWM to speed in the working band and added the dead band to get 100% and the output is very linear. I’m very pleased with the device. Thank you Tinker for giving me ideas to work with.
The only spec sheet on the GSD7 series I can find shows potentiometer as the only supported input type:
https://cdn.automationdirect.com/static/specs/gsd7dcdrives.pdf
Can you give a link to a manual or spec sheet that talks about a PWM input?
With PWM you may be able to emulate a potentiometer's voltage divider input in a way, by getting a sort of averaged speed from the "on time" and "off time" of the voltage pulses, but it seems like that is much more trouble than simply using the correct input type the drive is designed for.