Sherline Spindle Tachometer & Speed Control

Post technical questions about the Buildbotic Controller here.
Forum rules
No profanity, no gambling, no illegal activity, so sexual or pornographic material.

Posts not related to the Buildbotic CNC Controller are likely to be moved or deleted.
Post Reply
fwarren
Posts: 3
Joined: Tue Jul 26, 2022 10:22 am

Sherline Spindle Tachometer & Speed Control

Post by fwarren » Thu Jul 28, 2022 10:38 pm

The Sherline mill and lathe have a 90v DC spindle motor that uses a KBIC speed controller. I'd like to find a way for my Buildbotics controller to both control the speed and read the RPM. Are there approaches that might work in this application?

User avatar
Doug
Posts: 314
Joined: Fri Feb 02, 2018 4:56 pm

Re: Sherline Spindle Tachometer & Speed Control

Post by Doug » Fri Jul 29, 2022 12:07 pm

Hi Fred,

The Buildbotics Controller has a 0-10 Volt output available on the DB15 connector.

I looked at the datasheet for KBIC speed controllers and it says that you can control the motor speed with a 0-9Volt isolated analog voltage. It says you should connect the 0-9Volt source between P2 and F-. This seems lile it could work, but the 0-10Volt source from the BB Controller is not isolated.

In addition, the BB Controller does not have a way to read the analog signal back from the speed controller and present the actual speed of the motor.

Hope this helps,
Doug

fwarren
Posts: 3
Joined: Tue Jul 26, 2022 10:22 am

Re: Sherline Spindle Tachometer & Speed Control

Post by fwarren » Sun Jul 31, 2022 2:19 pm

Thank you Doug for you help with this. I am still at the bottom of a steep learning curve. I had thought of adding a hall effect or optical speed sensor to the Sherline motor. If I went this way, is there a provision in the Buildbotics controller for a spindle speed input? Also, would there be a way to create an isolated analog voltage given the non-isolated Buildbotics voltage? Perhaps an out-board conversion board?

So far I love the controller you guys have developed. It is elegant and extremely easy to use. The hardest task in engineering is to make things easy and all your hard work has paid off. Thank you!

User avatar
Doug
Posts: 314
Joined: Fri Feb 02, 2018 4:56 pm

Re: Sherline Spindle Tachometer & Speed Control

Post by Doug » Sun Jul 31, 2022 8:50 pm

At present, the BB Controller does not have the ability to read (and make use of an analog input signal). The hardware is in place, but no software to use it.

Systems using a Variable Frequency Drive with a Modbus RTU interface are able to provide speed feedback to the BB Controller. That information is displayed, but the BB Controller does not compensate or take any other action if the speed does not match the requested speed.

I spent some time looking for a Modbus RTU module that might be able to provide the analog output to control to your KBIC and read an analog input from your KBIC. I did find one such module, but could not figure out how to buy it or even how much is costs. I decided that it was not worth pursuing.

I also found the manual for the KBIC control at this link: https://motorsandcontrol.com/media/docu ... s/9433.pdf

On page 22 it says the following: " If the input signal is not isolated, or is a current signal
(4 - 20 mA), the KBSI-240D or SI-5 Barrier Terminal Board Signal Isolator must be used. It will allow
direct connection to process controllers and microprocessors." I found a source for the SI5 Barrier Board here: https://www.kb-controls.com/product.sc? ... anEALw_wcB

If I am reading it correctly, the SI-5 Barrier Board should allow you to connect the 0-10 Volt output from the BB Controller to the KBIC controller so you can at least control the speed. You may want to pick up a cheap tachometer so you can calibrate the speed settings with the actual speed of the spindle. I think you will get 10% or possibly better accuracy doing this. That is usually close enough to make your "speeds and feeds" work out correctly.

Hope this helps,

Doug

fwarren
Posts: 3
Joined: Tue Jul 26, 2022 10:22 am

Re: Sherline Spindle Tachometer & Speed Control

Post by fwarren » Tue Aug 02, 2022 2:33 pm

Hi Doug! Thank you once again for your thoughtful and very helpful information and advice. Such good support makes using the Buildbotics both easier and much more enjoyable.

Post Reply