HDMI Monitor when plugged into laptop causes noise out or speaker and Audio interface to be disabled

naoisesvan
naoisesvan Registered Users, Users Awaiting Email Confirmation Posts: 1 ✭
in Caravan, Recreational Vehicle, and Marine Power Systems #1
Hi, 

I'm not sure if this is the right place, sorry if so. I was wondering if someone could help me guide solve this issue. 

I have a makeshift music studio in my self converted van.

Equipment:
- 2500W inverter/Charger
- Macbook Pro
- 2x AGM Batteries
- Fridge
- Rover Solar Charge Controller
- 460W Solar Panels
- Copper Bus bars positive and negative
- Each connection to the Bus bar has a circuit breaker. 


Anyway.. the issue is as follows:
The Inverter has 2 AC outputs, 1 to the fridge and the other to the Music studio Setup. The Inverter is grounded, the inverter chassis has a ground connection, it's connected to the end of the negative bus bar where all the grounds are joined such as the ground from the solar charge controller, this point on the Bus Bar is then connected to the Chassis, i tested the resistance from the chassis of the inverter and solar charge controller independently between  the chassis of the van, the resistance is ZERO, so I think i have good grounding and only 1 grounding point, so ground loops should be eliminated. 

well I bought a new HDMI monitor recently and the moment I Connect the HDMI plug into the MAC, my Audio Interface (Connected to Mac via USB HUB) Immediately gets disabled as an audio device under the Mac Audio Devices and a loud noise comes out of the speaker. 

I thought this was a grounding issue as the HDMI Monitor is trying to pass to ground via the shortest way and going via the HDMI path instead of the power cable path, i bought a longer HDMI cable, twice the length of the power cable path, but the issue still occurs. 

The Monitor and and MAC are connected to the same socket board extension coming out of one of the two available AC outs from the inverter. 

I tried connecting the monitor directly to the AC out of one of the inverter sockets and even disconnected the power to the laptop, but the issue still occurs! 

So under this situation i am unable to have an active audio interface while the HDMI is connected, if unplug the HDMI cable the Audio interface gets re-enabled.

Now, interestingly, if i disconnect the grounding of the inverter chassis and connect the monitor power directly to the inverter, the issue will not occur, but i hear a slight hum within the chassis due to the chassis ground not being connected, so i don't think it's a good idea to disconnect the inverter grounding, interestingly if i were to connect the monitors power to the socket board which is connected to 1 of the inverter ac outs while the inverter grounding is disconnected the issue will re-appear again! So I'm at a loss of what I should do? it seems to be a grounding electronic interference issue, should I just return the HDMI monitor and try another one, I fear it will be the same circumstance, however with the previous monitor which my friend accidentally put his elbow through, i did not have such an issue , although that was a special monitor for dual 12v 240v camper systems, i only used the 240v on it though.

any ideas? Thanks very much, hope it was clear enough, please ask me any questions to clarify. All the Best. 

Naoise.
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Comments

  • BB.
    BB. Super Moderators, Administrators Posts: 33,626 admin
    #2
    Welcome to the forum Naoise,

    I am guessing you are down in Australia--And accounts for the ~230 VAC @ 50 Hz only power connection.

    HDMI is a digital signal connection... So grounding by itself should not cause any audio noise (unless you are bypassing and use RCA/3.5 mm or other analog audio connection.

    However, system grounding can cause issues with digital signaling. Are you still getting the Video to the monitor in all cases (ground connected/not connected/etc.)? If you are getting Video in both conditions--Then I am really confused about why audio would fail (HDMI being all digital, if video works, so should audio).

    The first issue I can think of... Is the question is your AC inverter a PSW (pure or true sine wave) inverter, or is it a MSW (Modified square/sine wave) inverter?

    PSW inverters generally have a fully isolated AC output. And can either float, or you can ground one lead, typically Blue is used for "Neutral" for Non-USA wiring, and Brown for "Hot". You need to check your AC inverter manual and see how they manage the AC output. In the USA, typically larger inverters have the "Neutral" connected to the AC inverter chassis (and the negative battery bus is grounded to the RV chassis too). Smaller inverters typically have the AC output (Brown "Hot" and Blue "Neutral", or for the USA typically Black "Hot" and White "Neutral" outputs floating. (I don't know Australia's inverter/generator ground bonding rules). Depending on Wattage/Model/etc., larger PWM AC inverters will tie the Blue "Neutral" AC output wire to the AC inverter Chassis. And the installation will tie the inverter chassis to RV chassis (safety grounding).

    MSW Inverters do not have the 230 VAC output electrically isolated from the DC battery input. If you have your Battery Bank Negative Bus grounded, then both AC inverter AC outputs are "Hot" with respect to chassis/battery ground. And if you attempt to "ground bond the AC neutral Blue wire, it will short out the AC inverter--If the battery bank is ground bonded too).

    So--The question of grounding a MSW inverter can cause electrical issues. Generally, most modern AC power appliances do not "care" if the AC input is ground referenced or floating. However, if the ground (green, yellow/green) wiring has been somehow "energized" because of "improper" inverter grounding, it is possible that three wire AC plugs (Hot/Hot/safety ground) could cause problems between a computer and a monitor and the digital circuit/grounding (both the computer and the monitor have to share a common "signal ground reference").

    Another possible issue with MSW Inverters (not directly related with grounding) is their output voltage not being a "sine wave", but a modified square wave--Can cause problems with some AC appliances. It can cause "power bricks" and line cord transformers to overheat (and eventually fail). Also, the peak voltage for MSW waveform is not the same as a sine wave--And some AC appliances operate as if they are running on "low AC line voltage"--Behaving erratically, electric motors can overheat/stall/etc.

    The other issue--Again not related to your grounding issue--Is measure the DC input voltage to your AC inverter. A 2,500  Watt AC inverter can draw a large amount of DC Battery Current (if 12 volts, >200 Amps at full load; if 24 VDC, over 100 Amps). Too small of DC cable diameter, too long of DC wiring to AC inverter, or drawing too much current from a "smallish" DC battery bank--Can all cause low AC output voltage for the inverter... Typically would like to see >11.5 volts or >23.0 volts at the DC inputs to yoru inverter under load. Most inverters will shut down around 10.5 or 21.0 VDC of battery bus voltage.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • softdown
    softdown Solar Expert Posts: 3,925 ✭✭✭✭
    #3
    Less than ideal connection? I had to give up on my HDMI connection after the dogs had accidentally disconnected it too many times. The more injured the connection the more noise there was.

    I'm finding simple old fashioned RCA connections seem to work as well and not nearly as sensitive.
    First Bank:16 180 watt Grape Solar with  FM80 controller and 3648 Inverter....Fullriver 8D AGM solar batteries. Second Bank/MacGyver Special: 10 165(?) watt BP Solar with Renogy MPPT 40A controller/ and Xantrex C-35 PWM controller/ and Morningstar PWM controller...Cotek 24V PSW inverter....forklift and diesel locomotive batteries
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