Unified Video System

Owned by Daniel Puratich
Last updated: 2024-11-12 by Tom Chiu
5 min read

Intro

Block Diagram

Links to components are embedded in the block diagram.

To-Do List

I created this for myself to keep track of things, but feel free to comment and I will add/correct the list.

Start compiling the headers/housings needed for these connections between the boards.

I have them below, please review at your convenience!

VTX has built in filter, just remember to add caps at the voltage input to the board.

Will keep in mind during schematic phase.

Compile the total current required on the 5V and 12V rails.

Max of 269mA on board, will opt for linear regulator over switching

Source 5V linear regulator based on current requirement
Figure out whether or not the board 3 way camera switch board can use the common CAN circuit so we don’t have to use PWM pin.

Correct me if I am wrong, but since the 3-way switchboard does not have built-in CAN pins, I would need an external CAN controller and a unique identifier to use the CAN bus. Also, I don’t think the CAN bus can even output a PWM signal, and I don’t see any converters online aside from this one: CAN2PWM Adapter | Currawong Engineering. For this reason, I don’t think the CAN bus would be ideal to use to control the lumenier switch board.

 

On a side note, the lumenier switchboard also sites the following PWM values for selecting each channel:

CH1: PWM value of 1250 or below

CH2: PWM value between 1350-1750 (recommend 1500)

CH3: PWM value of 1750 and above

I am not too familiar with this representation of PWM values, but assuming that these indicate the range of values in bits that are recommended for selecting each channel, this seems to suggest that it would need 12-bits of resolution. How else would we interpret these values?

Headers/Housings

FPX Camera

image-20240613-064042.png

Lumenier Camera Board

 

image-20240613-064451.png

The first and second options make it easier to plug and play, but it has added weight. Soldering option is more prone to error but has less weight. A quick Google search showed that similar solutions have similar 2.5mm pitch pins instead of jst headers.

OSD

VTX

5V Linear Regulator Selection

Two promising ones found on digikey with the following filters: linear regulator, current output: >1A, input voltage max: >15V, in-stock

AZ1117IH-5.0TRG1: AZ1117IH-5.0TRG1 Diodes Incorporated | Integrated Circuits (ICs) | DigiKey

LDL1117S50R: LDL1117S50R STMicroelectronics | Integrated Circuits (ICs) | DigiKey

I am opting for the LDL1117S50R as it provides better line and load regulation based on its graphs with honest 5V output and from 6-18V inputs, while AZ1117IH-5.0TRG1 shows similar behaviour in both categories but only with Vin of 4.5V for its 2.5V output variation and no graphs for line or load regulation for the 5V output component.

Both show very similar behaviour in terms of line and load transient behaviour, with:

AZ1117IH-5.0TRG1: ~60mV max for the line transient and 130mV max for the load transient

LDL1117S50R: ~60mV max for the line transient and 120mV max for the load transient

A bonus is that the LDL1117S50R shows better PRSS of 87dB @120Hz compared to the AZ1117IH-5.0TRG1 with a PRSS of 70dB @120Hz.

Ferrite Bead Selection

Search criteria on digikey: Imax > 500mA given the 224mA max on the board, R @120Hz > 100R, R @DC < 30mR, 0603 package

Final part selected: BLM18SG121TZ1D Murata Electronics | Filters | DigiKey