Encoder signal sharing

[staffshome]

Hello all,
i need some help with sharing quad encoder output to my dro display & controller encoder inputs.
I have looked at some opto isolator chip datasheets but my electronic knowledge is poor.can anyone help with chip spec & circuit detail.
5v encoders
dro 5v
Controller 5v ( seperate power supplies )

Thanks Adrian

[Al_The_Man]

Having both DRO and controller connected to the encoder should normally be OK, it depends somewhat on the nature of the encoder output, you need to specify if it is standard RS422 differential or push/pull or open collector.
If the DRO is suppling power the second input just needs the signals and the common, no 5v.
Al.

[frankee]

Hi,

If the encoder has TTL or open collector outputs there's a good chance you won't need any kind of interface circuit, and you can wire the encoder outputs (channels A,B and the pulse index if used) directly to the inputs of both your controller and the DRO ... provided that you also wire the signal grounds together.

Frank

[staffshome]

the encoders are TTL output.the 0v (grounds) come from 2 different power supplies will it be ok to interconnect the 0v.
i would prefer some isolation between the circuits if it is practical.
my limited skills are ok for assembly work but not design.

Thanks again adrian

[frankee]

Of course, we don't know what type of your controller you have, but I wouldn't worry about connecting the grounds together. The only application that I have worked on where isolating encoder inputs is absolutely necessary is with CNC plasma cutters. In that case, the EMI created by the jumping arc starter, and picked up in the encoder cable, is pretty well guaranteed to damage any TTL inputs, but in your case, because you have a DRO, I'm assuming you're converting a mill to CNC.

Do you have access to Digikey or some other electronic component supplier, can you solder up a small circuit board, and do you mind spending a couple of hours and say about $50 to make up a small isolating interface?

[staffshome]

hello Frankee,
thanks for the help / info,as my previous post,i would prefer isolation.
building a small circuit / soldering no problem.I can work from a circuit drawing / sketch,just don't have much electronics knowledge.
RS components / maplins / Farnell here in uk we do have digikey but i have not used them.
4 axis mill conversion using m641 controller (www.eaziform.co.uk)
So any help much appreciated

Thanks adrian

[frankee]

Hi Adrian,

I can post a schematic here for you, but it will have to be the day after tomorrow (Wednesday) since I'm out of the office tomorrow ... unless someone else could/would do it sooner.

Frank

[Al_The_Man]

As a matter of interest, I make it a point to make all my power supplies and systems common and make this common to earth/service ground.
I find less problems with noise this way.
There is a 99.9% chance that your DRO has a floating common anyway, but even if it is referenced to chassis, it should not matter.
Al.

[staffshome]

Thanks to Frank & Al,
Frank, if you can post me a schematic that would be great.
Al, Thanks for info reower supply common 0v,I have already done that on my mill LV power supply +5,+12,+24 vdc seperate regulated outputs,0vdc common for all.I may have been misinformed by a n other as not to common up the seperate psu 0v from DRO as it may cause a problem with overworking/heating of 5vdc regulator on Controller card ??? (shows i know very little about electronics!!!
Thanks again Adrian

[Al_The_Man]

I may have been misinformed by a n other as not to common up the seperate psu 0v from DRO as it may cause a problem with overworking/heating of 5vdc regulator on Controller card ??? (shows i know very little about electronics!!!

Or the person giving you the advice!
Al.

[H.O]

Hi,
Attached is a schematic for an isolated "encoder splitter" that I've designed. It converts differential encoder signals to single ended, isolates them and finally buffers them.

I use it with my HP-UHU drives and the Smoothstepper and it seems to work fine, I did have some noise problems but adding 1k in series between the isolator and the Smoothstepper inputs fixed it.

Works for me, YMMV.
/Henrik.

[staffshome]

Hi Henrik,
Thanks for the schematic,just a couple of questions.
Did you assemble on custom pcb or veroboard ?
will this work ok for me- I need original encoder to dro & isolated encoder to controller,your circuit is perfect as controller connection is +5v,Chan A,Chan B,0v.
Will it be ok to piggyback encoder inputs to dro & your circuit.
Thanks & regards Adrian