2 ports with one cable

Jon_101

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Mar 5, 2019
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Hi everyone, is it possible to share ground with 2 ports? please see image attached.
Thanks
F16V3.JPG
 

TerryK

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Should work, at least I do not see any problems. I would like to know the supply cable lengths (the ones fused). P13 is 2 meter but I read that as from the P1/P13 'Y' to the P13 string connector. The 3 core 18 AWG length cable may have a bit of voltage drop across the 7 meter length but as minimal current will be in that, a data reference only, I do not suspect that to be a problem.

Voltage drops from either 12 Volt supply to the Falcon and/or the 5 Volt supply to the P11/P13 'Y' may un-reference the data signal enough to cause a problem. The reason I mention why I would like to know those cable lengths.

A couple side-notes. V- (GND) of the supplies are made common through the Falcon and the 3 core 18 AWG cable (and the supply cables). The data signal logical 'High' to the 5 Volt strings is derived from the one 12 Volt supply (the one on the right as shown) and of course the Falcon electronics.
 
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Jon_101

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Mar 5, 2019
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Should work, at least I do not see any problems. I would like to know the supply cable lengths (the ones fused). P13 is 2 meter but I read that as from the P1/P13 'Y' to the P13 string connector. The 3 core 18 AWG length cable may have a bit of voltage drop across the 7 meter length but as minimal current will be in that, a data reference only, I do not suspect that to be a problem.

Voltage drops from either 12 Volt supply to the Falcon and/or the 5 Volt supply to the P11/P13 'Y' may un-reference the data signal enough to cause a problem. The reason I mention why I would like to know those cable lengths.

A couple side-notes. V- (GND) of the supplies are made common through the Falcon and the 3 core 18 AWG cable (and the supply cables). The data signal logical 'High' to the 5 Volt strings is derived from the one 12 Volt supply (the one of the right as shown) and of course the Falcon electronics.
Thanks Terry for your comments, power supplies wires are about 20cm each, 3 core wire will carry no voltage at all, just data. Sorry I didn't understand the last paragraph.
 

TerryK

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To help explain: For your design, the V- (GND) of the supplies need connected, a common as I called it. This forms a V- reference for the data signal for all of the pixels, both the 12 Volt and the 5 Volt pixels. The V- of the Falcon's V1 and V2 connectors are tied together on the Falcon's PC Board. The V+ of the Falcon's V1 connector only route to Ports 1 to 8 which are separate from the V+ of the Falcon V2 connector and Ports 9 to 16. So P1, P2, and P3 strings and the left hand supply are OK, a good V- reference, V+connection, and such.

The data signal reference (V- or GND) for the 5 volt pixels must route back to the Falcon to properly be able to drive those pixels. So the 5 Volt supply V- needs to route to the Falcon which you have incorporated. Thus you have satisfied the requirement that the V- of all the supplies are tied together. The Falcon's internal V1 to V2 GND connection is indirectly doing that for you.

Regarding the data signal logical 'High', for the pixels I am currently aware of, all pixels require a 5 Volt signal where the logical 'Low' or '0' is at or very near 0 volts, that is the V- or GND. A logical 'High' or '1' will be near 5 Volts. Even 12 Volt pixels need the 5 Volt data signal. I'm not sure about the 24 Volt pixels but I suspect a 5 Volt data signal for those as well.
From a practical point there is a high and low threshold for the data signal 'High' and 'Low'. So as long as the low is below and the high is above their individual thresholds, the pixel takes the data signal and runs with it.
With your design, the 5 Volt supply V+ powers the pixels and obviously must not route back to the Falcon as doing so would cause it to fight the 12 Volt supply on the Falcon's V2 Power Connector. Therefore the 5 Volt 'High' that the 5 Volt pixels need has to be synthesized by the Falcon's electronics. In this case, derived from the right hand 12 Volt supply.

A bit long-winded. I wasn't sure how much detail was wanted or needed. Cheers.
 
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Mark_M

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Looks perfectly fine.
There's a display around the corner from me that has the exact same scenario for 5 data lines from their F16v3. They run up to 10m.
They had no problems with <9m, but said beyond that there was flickering issues. Answer they found was a null pixel.
 

Jon_101

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Mar 5, 2019
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Looks perfectly fine.
There's a display around the corner from me that has the exact same scenario for 5 data lines from their F16v3. They run up to 10m.
They had no problems with <9m, but said beyond that there was flickering issues. Answer they found was a null pixel.
Thanks Mark, as you said I need to keep the wire less than 9m, and that is why I used f-amp for the (7+4m) branch.
 

Jon_101

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To help explain: For your design, the V- (GND) of the supplies need connected, a common as I called it. This forms a V- reference for the data signal for all of the pixels, both the 12 Volt and the 5 Volt pixels. The V- of the Falcon's V1 and V2 connectors are tied together on the Falcon's PC Board. The V+ of the Falcon's V1 connector only route to Ports 1 to 8 which are separate from the V+ of the Falcon V2 connector and Ports 9 to 16. So P1, P2, and P3 strings and the left hand supply are OK, a good V- reference, V+connection, and such.

The data signal reference (V- or GND) for the 5 volt pixels must route back to the Falcon to properly be able to drive those pixels. So the 5 Volt supply V- needs to route to the Falcon which you have incorporated. Thus you have satisfied the requirement that the V- of all the supplies are tied together. The Falcon's internal V1 to V2 GND connection is indirectly doing that for you.

Regarding the data signal logical 'High', for the pixels I am currently aware of, all pixels require a 5 Volt signal where the logical 'Low' or '0' is at or very near 0 volts, that is the V- or GND. A logical 'High' or '1' will be near 5 Volts. Even 12 Volt pixels need the 5 Volt data signal. I'm not sure about the 24 Volt pixels but I suspect a 5 Volt data signal for those as well.
From a practical point there is a high and low threshold for the data signal 'High' and 'Low'. So as long as the low is below and the high is above their individual thresholds, the pixel takes the data signal and runs with it.
With your design, the 5 Volt supply V+ powers the pixels and obviously must not route back to the Falcon as doing so would cause it to fight the 12 Volt supply on the Falcon's V2 Power Connector. Therefore the 5 Volt 'High' that the 5 Volt pixels need has to be synthesized by the Falcon's electronics. In this case, derived form the right hand 12 Volt supply.

A bit long-winded. I wasn't sure how much detail was wanted or needed. Cheers.
Thanks Terry, definitely my +5v line is not connected to +12v line.
For data threshold (I guess it's supposed to be 3.5v), and it shouldn't be a problem for under (7-9m) wire length, and I'm using f-amp for the longest branch (7+4m).
For the common, should I connect to the v2 ground instead port's ground? or it won't make a difference since they all are connected?
 
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TerryK

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It will not make any difference as all of the Falcon's 16 ports GND connections are tied to the V- of both the V1 and V2 power connectors.

The Falcon's port driver IC is I think a SN74HC157 (or similar). The output driver will attempt to keep the logical 'Low' below approximately 1.8 Volt and the 'High' above 3.2 Volt, sort off. Sort of because the output thresholds of the 74HC157 vary a bit depending upon what it is driving and where its supply is between the valid 4.5 to 5.5 Volt. Assuming of course there are no electrical problems on a port output. Texas Instruments makes the driver IC's specifications readily available.
Hopefully the pixel ICs input thresholds align nicely but it is difficult to determine due to the Chinese datasheets being vague and in some instances incomplete.
 

darrenr

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I have done this and it works fine. I'm about to do it again this year for two more channels to drive my new mega tree. In the remote box I have 12v and 5v power supplies and share the V- across the lot.
 
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