Saturday, September 28, 2013

Experimenting with a HDMI to VGA converter....

Recently I bought an HDMI to VGA converter in an attempt to feed the output from a laptop to an older LCD projector. When trying to test this converter with a Thinkpad T510 laptop and 25" HP monitor, I noticed that there was no video signal detected.   I tried another Toshiba laptop but could get no signal from the monitor.  At first I thought that this device was defective and need to be returned.

However, after feeding the HDMI signal from the laptop to an HDMI splitter and connecting one of the HDMI outputs with this converter, I could start to see a video signal.    Apparently the HDMI to VGA converter draws power from pin 18 of the HDMI connector, which provides the 5 volt power supply.  The HDMI specs specify that source devices should provide a minimum of 55 mA, but the chipset used by the HDMI to VGA converter must be drawing much more than current than what can be provided by the laptop.

Even more interesting, the video signal could be detected with a 25 foot MediaBridge cable but not with a 25 foot Aurum cable.  The major difference?  The former uses 28 AWG gauge wiring, while the latter uses 30 AWG gauge wiring.

Why does the gauge of the wiring matter?   With the lower gauge wiring, the diameter is usually larger, so the resistance is lower and therefore the current is higher.   Even when using the HDMI splitter that will provide additional power, this current can be reduced by the longer cabling.

The solution seems to be to use an active HDMI to VGA converter, since sufficient current draw is mentioned as a possible issue by the active converter devices sold on Amazon.   However, after this finding, you may also need to consider what HDMI cabling you're using too!

1 comment:

  1. yeah faced a similar situation, then i bough this HDMI to VGA Converter Adapter which has solved the problems.

    HDMI to VGA Converter Adapter Connect HDMI Top Quality