Ideally you will choose a point in the ADC and DAC modules where the digital meats the analog part, and join them from those points, but at the usb connectors is a good start. If you can Join the signal/power grounds similarly. You need to join the USB shields at the USB connectors with a wide strap (braid,foil). All grounds radiate outwards from that and never loop back.

Star Grounding: You need a single defined ground point.

You should read up about ground loops, it is a major (THE major?) issue building recording studios. There will be 115V available to force it to flow, if the connection happens to be a high impedance and poorly protected IC input.(Goodnight Nurse), or you get incurable hum in audio circuits (ground-loop)

If you connect the laptops ports to anything grounded, 75 microamps will flow through the ground/microphone/usb/data wire. Simulate this circuit – Schematic created using CircuitLab

(They are there so that RF energy can flow back out to the low impedance mains to get rid of it) These are the fat blue disc capacitors when you open up a laptop psu. C1,C2 form a voltage divider that floats the laptop at 115V (when you are in a grounded-neutral mains system). Laptops are a real traps for young players when you hook them up to an analog circuit.Ī slightly simplified schematic of a laptop supply shows the totally counter-intuitive capacitors that are straight across the transformer. between the DAC and the output) but it does not look convenient at first sight.ĭo you have any recommandation or any other solution to avoid ground loops in this kind of setup ? I also had other ideas to perform an isolation at another place (i.e. I haven't found such a component so I'm not sure about this. However, I would prefer a solution that is fully transparent for the user.Īs there is no problem with the USB Y cable when the USB data lines are not isolated, I was wondering if it was possible to use a similar principle used in ADuM4160 ((1:1) transformer) to isolate only the power lines from USB, leaving the data lines untouched. Another solution that works fine is to use a USB Y cable, splitting data lines and power lines. Unfortunately it is too expensive for my application. I first thought about using a USB isolator such as the ADuM4160 which works great. If the laptop runs on battery, there is no issue.Įdit : The ground loop occurs when both devices are connected to the same laptop The problem is that if the laptop connected to Device 1 and Device 2 are connected to a different outlet, it creates a ground loop and its characteristic 'hum'. The new workers are skilled and are qualified by the Construction Industry Development Board … which should reduce the amount of time we spend on outages.I have a device (Device 1) that is bus-powered via Full-Speed USB and that is drawing up to 400 mA from a laptop.ĭevice 1 has a DAC that can output an analog voltage to another device (Device 2) through a jack connector, Device 2 being powered externally. “Some of the previous workers were not credited by industry bodies to do certain work on our network, which was a loophole that needed to be closed.

He said the new contractors were skilled and replaced those who were sometimes responsible for shoddy work. The new team started on and have already hit the ground running'. 'We on boarded new contractors and our residents should know that there is no crisis as predicted by some of the residents and even some of the leaders in the City of Johannesburg. However, City Power's Isaac Mangena said while some contracts came to an end, new contractors began working on Thursday. Residents contacted Eyewitness News, saying they were concerned that with the current outages, repair work would not be done.Ĭity Power outlines plans to reduce impact of power cuts in JHB ahead of winterĬity Power welcomes arrest of one of its own over infrastructure tampering JOHANNESBURG - Johannesburg City Power moved to assure residents that there was no crisis with the end of contracts for some workers, including repair teams.

Power ground isolator