No response when connected more than 2 boards, 25 Sep. 2014 20:14

Hallo!

I have a problem with controlling 3 ANNAX boards (front, side, back).
I controll them by PC with IBIS-Utility. It‘s ok when I connect 2 boards, but when I connect 3rd, all displays no response.

Firstly I thought that the current is too low, but now I bought power supply with 3,5A and the problem still exist.

I realized PC<->IBIS by this manual:
//487481.forumromanum.com/member/forum/entry_ubb.user_487481.1341209229.1114728707.1114728707.1.schnittstellenwandler-ibis_world.html?onsearch=1

Please help me.

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RE: No response when connected more than 2 boards, 26 Sep. 2014 17:53

What type of transistor are you using?
Make a picture of your circuit.

Best regards
Raiko

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Solaris2001

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RE: No response when connected more than 2 boards, 26 Sep. 2014 20:55

I‘m using NPN transistor BD139 (http://www.datasheetarchive.com/dl/Datasheet-0103/DSA0010362.pdf).
Here‘s scheme:

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RE: No response when connected more than 2 boards, 27 Sep. 2014 09:29

The schematic and the BD139 are correct.
What is the voltage between WBSD and WBSM while no sending data and all three are connected?

Depending on the input impedance of the device and the resistance of R1, the voltage could collapse.
Unfortunately, the input impedances are not always equal in IBIS systems.

Best regards
Raiko

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RE: No response when connected more than 2 boards, 27 Sep. 2014 13:24

When 2 displays are connected, the voltage between WBSD - WBSM is 14,2V.
With 3 connected voltage is 12,6V.

So I should change R1 to smaller resistance?

Regards,
Leszek

Geändert von Solaris2001 am 27.Sep.2014 13:25

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RE: No response when connected more than 2 boards, 27 Sep. 2014 13:56

12,6 V is close to the limit. You should use 330 Ohm for R1. I think the voltage between WBSD and WBSM will be around 16 V.

Best regards
Raiko

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Solaris2001

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RE: No response when connected more than 2 boards, 27 Sep. 2014 14:37

It works fine! :)

Thank you!!

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RE: No response when connected more than 2 boards, 27 Sep. 2014 15:16

my pleasure

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