Switchmode Power

Combining the power of the ATmega2560 MCU with onboard Ethernet, a microSD card slot, an efficient switchmode power supply, and a small prototyping area. [Product page]
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sky
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Switchmode Power

Post by sky » Thu Jun 04, 2015 12:40 pm

I am not completely understanding what this is, and prior to finding out the hard way, I want to first ask. My project will soon incorporate passive POE injectors and I want to know if there is anything I need to have in order prior to sending power to the barrel jack. Is it as simple as shifting the jumpers position? Do I also need to build a voltage regulator or does the EM have that taken care of on board?

andrew
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Re: Switchmode Power

Post by andrew » Thu Jun 04, 2015 10:30 pm

Yes, if you're going to power the EtherMega via the DC socket, change the jumpers. You can use power between 7 and 28V DC - the onboard regulator will convert it down to 5V.

sky
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Re: Switchmode Power

Post by sky » Fri Jun 05, 2015 1:05 am

Thanks for that answer. My followup question is will I still be able to use the USB for uploading new sketches while the unit is powered by the DC socket? My project is in an enclosure, and I only planned for passive POE and USB type B, but I got a B to A adapter inside to accommodate the EM.

TYIA

andrew
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Re: Switchmode Power

Post by andrew » Fri Jun 05, 2015 5:40 am

You will need to switch it over to upload a sketch via USB.

sky
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Re: Switchmode Power

Post by sky » Fri Jun 05, 2015 10:15 am

That will be a problem for my project. Perhaps I could put together a selector switch on the exterior of the box like I have for the RST-EN function that would allow me to switch back and forth as needed.

sky
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Re: Switchmode Power

Post by sky » Fri Jun 12, 2015 8:13 pm

I got some switches in the mail today and updated my project box. The switches connect to RST-EN and the header pins for Switch Mode. Initially, the switches both were in the false position and were first tested that way. Upon toggling the switches and closing the correct loops, power flowed through the USB and the sketch uploaded when the switch is toggled so all is well in my project. Here's some pics;

Image

Image

sky
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Re: Switchmode Power

Post by sky » Sun Jun 21, 2015 2:07 am

johnb wrote:You will need to switch it over to upload a sketch via USB.
I am tweaking my code and frequently uploading new sketches so I tried to leave the switch in the DC Socket position while I upload a new sketch and it uploaded. Can you please test uploading a sketch via the USB while the EM is powered via the DC Socket to verify if I have a glitch? I did need to close the RST-EN bridge of course.

angusgr
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Re: Switchmode Power

Post by angusgr » Mon Jun 29, 2015 4:53 am

sky wrote: I am tweaking my code and frequently uploading new sketches so I tried to leave the switch in the DC Socket position while I upload a new sketch and it uploaded. Can you please test uploading a sketch via the USB while the EM is powered via the DC Socket to verify if I have a glitch? I did need to close the RST-EN bridge of course.
Hi sky,

I'm sorry, I think John misunderstood the question. You can power the EtherMega via DC In or PoE (with the power jumper set to DC In) and simultaneously connect it for programming or Serial Monitor via USB, it just won't draw any power from the USB bus (the power all comes via the DC or PoE link.)

Bear in mind that when you connect the EtherMega in this way, all the grounds are joined together (computer ground via USB to the EtherMega, and then whatever ground comes via the EtherMega's power source.) This can have unexpected consequences so it's worth keeping in mind. However the grounds remain connected even if the Power Source jumper is moved, so in your case it sounds like the situation is fine.

Angus

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