Powering the eDrumin externally

[Pim]

Hi,

I have a question about how to power the eDrumin. I know that the eDrumin has a power input and I would like to use a battery to power the unit.

My questions are:

1. What voltage and ampere are needed? I think I read 9V and 0.5A but I rather would like to make sure. Using the wrong voltage over a extended period of time usually damages electronic devices, as far as I know, and I would like to keep the eDrumin intact . So what are the exact specs?

2. Powering the eDrumin externally was initially implemented if people use the MIDI port instead of USB, so the USB provides power for the eDrumin.
Is it possible to transfer only the MIDI data over USB and simultaniously power the eDrumin via a battery? Or will using a USB cable always power the eDrumin? Or worst case, does using a battery while using USB destroy the eDrumin?

Best regards,
Pim

[Rob]

1. What voltage and ampere are needed? I think I read 9V and 0.5A but I rather would like to make sure. Using the wrong voltage over a extended period of time usually damages electronic devices, as far as I know, and I would like to keep the eDrumin intact . So what are the exact specs?

Minimum recommended power requirements are 6V and 100 mA

2. Powering the eDrumin externally was initially implemented if people use the MIDI port instead of USB, so the USB provides power for the eDrumin.
Is it possible to transfer only the MIDI data over USB and simultaniously power the eDrumin via a battery? Or will using a USB cable always power the eDrumin? Or worst case, does using a battery while using USB destroy the eDrumin?

It's a fairly simple circuit--just a dual diode between USB 5V and the 5V output of a voltage regulator. I can't be sure that plugging in external power will prevent current draw from the USB. If you really want to guarantee that power will not be drawn from the USB port, then you might consider cutting the 5V power line in a USB cable. I will do some tests this weekend.

[Pim]

Hi Rob,

Thank you for the fast reply. And please excuse my (maybe stupid) follow-up questions, I only have a very basic (to none) understanding of how electrics work.

Minimum recommended power requirements are 6V and 100 mA

But isn't power over USB 5V, i.e. lower than the recommended minimum 6V?

And if it is *minimum* 6V, does that also mean I can just use the 230V straight from a wall outlet here in Europe?

It's a fairly simple circuit--just a dual diode between USB 5V and the 5V output of a voltage regulator. I can't be sure that plugging in external power will prevent current draw from the USB. If you really want to guarantee that power will not be drawn from the USB port, then you might consider cutting the 5V power line in a USB cable. I will do some tests this weekend.

Thank you for doing some testing. I wouldn't like to tamper with the USB cable.

In case you were wondering why I have these questions:
I would like to buy another eDrumin but I don't have any USB ports available on my laptop anymore. I use an active (powered) USB hub but I ran into a problem. After a while, my VST host can't find the eDrumin anymore and I have to manually re-select it in the menu again, especially when the drums were idle for some time (i.e. no pad was hit).
Which is a pain when it happens, I wouldn't take the risk of my drums suddenly not working anymore when performing.

I would like to point out that I never have that problem when I plug in the eDrumin straight into the laptop.

So my guess is that the USB hub fails to power the eDrumin after a while for just a split second. Even if the connection is lost only for a fraction of a second and the connection is immediately re-established, my VST host loses that MIDI device and I have to reassign it manually.
(The hub is 5V and provides 2A total. There are 2 other devices plugged in, Akai APC Mini and Novation Launch Control.)

So I thought I would just power the multiple eDrumins via a battery and only use the USB for MIDI data transfer.

I play outside a lot and my whole setup runs on batteries. The weakest link is my laptop (it has the shortest battery life) so I really don't want my laptop to power the eDrumin (that's why I use an active USB hub).
(To clarify: Losing connection to the eDrumin in my VST host when using the USB hub does (also) happen when the hub is plugged into a wall outlet, so the battery is not the cause for this problem.)

If I understood it correctly I could also connect the eDrumin via USB *and* a battery without harming the eDrumin? What is the downside with that? That the eDrumin would sometimes draw current from the USB hub and sometimes from the battery?

Best regards,
Pim

[Rob]

External Power
6V because there is a 0.7V drop across the reverse polarity protection diode. As stated in the manual and in the FAQ, 12V is maximum recommended voltage. Powering from USB and DC jack should be okay, but I didn't test this extensively.

Connection Issue
There are so many variables at play here that diagnosing your connection issue could be quite the hassle. For a sanity check, I'll do some tests on my own Windows machine as well, although I seem to remember doing this before and had no problems.

Mac users never have this issue because Core MIDI is so well designed. If you want stable MIDI in Windows, use Ableton Live. It's the only DAW I know of at this time that allows you disconnect and reconnecct MIDI devices on the fly without needing to restart the software or reactivate the MIDI device. How come all DAW aren't coded this way?

[Pim]

Hi,

Connection Issue
There are so many variables at play here that diagnosing your connection issue could be quite the hassle. For a sanity check, I'll do some tests on my own Windows machine as well, although I seem to remember doing this before and had no problems.

I think that the problem is most likely caused by my specific USB hub.

Mac users never have this issue because Core MIDI is so well designed.

I prefer Windows (or Linux). I know that almost everybody uses Apple when it comes to making/producing music but I haven't had any issues with my Win laptop so far. Everything runs stable, I admit that I was sceptical at first but after over 3 years of running my system without problems, I think the hype for Apple and the aversion for Windows laptops for live use is rather of a psychological nature.

Of course, you could point out that I actually ran into a problem. But connecting the eDrumin directly to a USB port of the laptop works fine without any problems. That's why I think it's the power provided by my specific hub.

If you want stable MIDI in Windows, use Ableton Live. It's the only DAW I know of at this time that allows you disconnect and reconnecct MIDI devices on the fly without needing to restart the software or reactivate the MIDI device. How come all DAW aren't coded this way?

I do like Ableton Live but when I started E-drumming, I only wanted to use VSTs to play live, so I only needed a VST host software; that's why I went with Live Professor 2 and I'm also quite happy with it.
I am sure Ableton is overall the more powerful software, but what prevents me from switching are the learning curve and setting everything up again (all VSTs, EQs, panning, and so on). After all, if it works, why fix it?

To be honest, this is the first time I encountered this problem of a device being "lost", the other MIDI devices never "drop out". And like I said it doesn't happen when the eDrumin is directly connected to the laptop.

From what I read here in the forums, people already plugged in several eDrumins via a (passive?) USB hub and they haven't encountered this issue.

I guess this is a special case that doesn't apply to many people since I would like to save laptop battery energy and power the eDrumin(s) externally. So if using a USB cable and a battery simultaniously won't damage the circuits of the eDrumin that would be my go-to solution. If you do run some testing, I would be happy to hear about your findings.

Best regards,
Pim

[Mylo]

What I experienced the other day...

When playing I plug the eDRUMin into a powered USB hub. But when updating the firmware I follow the instructions and plug the device into the computer. When the update is finished I plug it back into the USB hub. Now when I start SD3 after all this USB switching I have to reset/rescan my MIDI devices in SD3 so SD3 can find the device again. I just assume this has to do with the firmware update causing the loss of USB information and SD3 has to discover it again.

[Rob]

I've had two units hooked up to an unpowered hub into Cubase 8 for the past 12 hours and the connection hasn't dropped. I'll leave it running for another 12.

I also checked the current draw when both USB and external 9V are connected. The device still drew 24 mA from the USB, so I suspect the dual diode is oscillating between the two voltage sources. I would need proper power management IC to turn off the USB power all together.

Regards,
Rob

[Pim]

I've had two units hooked up to an unpowered hub into Cubase 8 for the past 12 hours and the connection hasn't dropped. I'll leave it running for another 12.

I also checked the current draw when both USB and external 9V are connected. The device still drew 24 mA from the USB, so I suspect the dual diode is oscillating between the two voltage sources. I would need proper power management IC to turn off the USB power all together.

Regards,
Rob

Hi,

Thank you for running the test. So I still believe the problem is with my active USB hub (i.e. the specific brand I use...I should get a different active hub to test this).

0.024A is not much. Might there be any drawbacks that the dual diode is oscillating between the two voltage sources? Might that damage the eDrumin device over time?

Best regards,
Pim

[Rob]

I doubt it. From there the current goes though a couple bypass caps and then into a second voltage regulator, so should be pretty stable and well within the specs.

[Pim]

I doubt it. From there the current goes though a couple bypass caps and then into a second voltage regulator, so should be pretty stable and well within the specs.

Hi,

Cool, thanks. Then I will just power the eDrumin externally while still using the USB cable and see if that changes anything. Otherwise I will exchange the USB hub as a next step.
Thank you for the support.

Best regards,
Pim