Centroid Community CNC Support Forum

Until you know there is noise on the analog input from the Acorn, then it could be internal noise in the driver converting the analog signal to digital. When running the driver in test or jog mode, the up/down buttons generate digital signals, not analog ones that route through the analog to digital converter.

How stable is the rpm when running the analog input from a 9V battery? How about a 1.5V battery?

Thanks.... Will do.

Hello Tom,

I performed your suggested battery test by removing the leads from the Acorn analog output and attached 1.5V, 3.0V and a 9-volt battery. The output from the batteries went through the same shielded cable and into the servo driver. Using the analog signal from the batteries, the servo driver performed much better!

I set the driver to monitor the analog voltage. The voltage was displayed with very little fluctuations. +/- one tenth of a volt. When using the Acorn analog signal there was as much as a .5 volt fluctuation.

Furthermore, the rpms displayed by the spindle encoder also had minimal bounce. Again, just small fluctuations of the tenths place.

One other observation is that when the servo driver was connected to Acorn, and the spindle is turned off, the servo driver's voltage monitor continues to fluctuate. When I disconnect the wires from the Acorn analog out, the voltage displays a steady zero volts. In other words, even with Acorn outputting zero volts, the servo sees a bouncing signal, but when I disconnect it from Acorn, it shows a steady "0". This means that the servo displays a steady zero volts, with the shielded cable attached, AS LONG AS THE CABLE IS NOT CONNECTED TO ACORN.

I am lost on this one. Is the impedance of the cable + noise filter not playing well with Acorn? This is the exact same JMC JASD series servo driver and noise filter that Uwe used on a similar build. One possibility, the servo driver is in a different enclosure than Acorn. I am going to try using a heavy wire to connect the grounds of both enclosures together. I'm thinking there might be a ground loop effect between the two enclosures.

One other question; I have attached images of a 50 pin connector that is used to connect the i/o to the servo. Does anyone know what this connector is called. I would like to buy one so I can experiment with other cables etc. without destroying the one I already built. The servo came with one that has solder type connectors and was a bit fidley.

I think this is it: It is printed with SM-50L https://www.ebay.com/itm/196047590849?i ... R47g6IvNYw


Thanks... Richard

I connected the two enclosures with a 10-gauge wire to have a common ground, and 90% of the voltage fluctuations are gone. I'm going to do a bit more testing, but I think I am pretty much there.

Look up 3M "Mini-D Ribbon" (MDR) connectors, including part numbers 10150-3000PE and 10350-52x0-008.

https://www.digikey.com/en/products/det ... PC/2767102

This is what Yaskawa and Delta use. Yours looks like the same thing.

Thanks. I will check that out

I solved the fluctuating voltage problem by connecting the servo driver enclosure and main enclosure with a common ground wire!

One question... The analog out signal measures. .05 volts when I turn the spindle to 0 rpm. Is this acceptable or should it read 0?

I did run the spindle bench calibration routine previously with nothing connected to analog out. All ran fine.