Re: [CAD_CAM_EDM_DRO] Re: Major encoder trouble, need advice.

On Thu, Sep 25, 2008 at 5:00 PM, William Newell <woodwelder@...> wrote:
> Hello Henrik,
>
> Perhaps it's time to borrow an oscilloscope and check to see what all your
> signals look like. A picture of what is happening would help a lot. Many
> x-electronic techs keeps scopes around for such purposes.
>
> Good luck,
>
> Bill N
>
> _____
>
> From: CAD_CAM_EDM_DRO@yahoogroups.com
> [mailto:CAD_CAM_EDM_DRO@yahoogroups.com] On Behalf Of Henrik Olsson
> Sent: Thursday, September 25, 2008 10:57 AM
> To: CAD_CAM_EDM_DRO@yahoogroups.com
> Subject: Re: [CAD_CAM_EDM_DRO] Re: Major encoder trouble, need advice.
>
> Hello again,
>
> I've now tried powering the encoder with a separate 5VDC power supply, a
> 1000uF capacitor across the powersupply terminals and a 1uF MKT cap right on
> the encoder. That didn't help....
>
> I checked the encoder and there is NO termination across the signal-pairs on
> the encoder, perhaps that's why it seems to work "better" (but still not
> working) when I add "my" termination in // with the SN75115's internal.
>
> Is it possible that the lack of termination at the "encoder end" of the
> cable is causing this even if I add the resistor-cap termination 300mm away
> from the encoder? If so, why the heck isn't it inside the encoder where it
> should be...(?)
>
> Moving on, I rearanged my wiring so that I now have a 'true' star-point.
> I'll try with words to describe how it's setup:
>
> * Heatskink of UHU connected to GROUND/EARTH/PE - one single screw serves as
> my start point here.
> * Motor supply (130VDC) negative connected to starpoint.
> * Motor housing connected to starpoint.
> * Motor cable shield connected to starpoint and *only there*.
> * Logic supply for UHU (15VDC) -ve connected to starpoint.
> * Encoder supply (5VDC) -ve connected to startpoint.
> * UHU motor supply input -ve connected to starpoint
> * UHU logic supply input -ve connected to starpoint
> * Separate +5V feeds the encoder, it does no longer get its power from the
> UHU.
> * Encoder -ive connected to starpoint
> * Encoder cable shield connected to starpoint.
>
> At first I didn't have the encoder GND and shield connected to star-point
> but instead to GND in the connector on the drive, it didn't work. So I moved
> both of them to the star-point but that actually made it worse - many more
> invalid transitions in a short time.
>
> Now, as I see it the ONLY ground-loop that may exist is the onboard GND-link
> between logic level GND and motor supply GND.
>
> I've ordered a couple of 26C32's but they'll probably won't arrive untill
> after the weekend.
>
> Best regards,
> /Henrik.
>
> [Non-text portions of this message have been removed]
>
>