Thank you again for attending our session on Power and Efficiency. Here are the questions that followed the presentation and their answers. If you have additional questions, be sure to reach out.
Sam, you said two things that I want clarification on. One is that you use the term ‘shading’ often. Do you mean literally shading? You know, if there's a shade over the cell?
Yes. Literal shading, or covering, either one.
Sam, you said something about adding a super cap, and you use super cap and low cost in the same sense. Is that valid? I mean, when you add a super cap, isn't that relatively expensive to the system that we're talking about?
It depends on the size and the capacity and the form factor. So when comparing to like a standard lithium battery, it may be comparable, but it's not going to be like 5 cents. I guess that's how I'd answer that question.
Martin, you are my next target here. So let's give you the first question from the audience. How busy is it for a developer to create a battery-powered solution with a Digi SOM?
It is a normal task in the development and in the integration of the SOM to a custom carrier board. We provide full documentation for it in our Digi ConnectCore 6UL documentation and Digi ConnectCore 8X documentation, including schematics, and its absolutely doable. There is even a nice comparison in our documentation portal between how you would develop a mains-powered compared to a battery-powered device, including comparison schematics showing both use cases in detail. To summarize, it is absolutely doable and we provide the documentation for customers as guidance.
Sam, can any photovoltaic cell be used with an off-the-shelf energy harvesting PMC?
A great question. I guess like I was saying in my slide on efficiency, first and foremost, you want to make sure that your cell is optimized for your environment, so if it's an indoor environment, you want an indoor PV cell. And then also you want to make sure that your voltage of your cell is under the max voltage of the PMC, which is often five to six volts. So there are many cells available that if you take them outside, they might be very high voltage and potentially damage your PMC. So there's a couple of considerations when choosing that not all off-the-shelf PV modules are compatible with standard energy harvesting power management ICs.
Sam, would you take that one step further? What's an indoor cell, as opposed to an outdoor cell? Isn't light light and a cell a cell?
Light is light, but when you are reducing light intensity by 1,000 times, technology doesn't work the same way. So if processing and manufacturing steps are not optimized to reduce those material defects, then a cell may have very, very, very low performance even lower than 1,000X. It could be very close to zero when you take it from outdoors to an indoor environment. Also that spectrum change. Some PV cells require certain components of a spectrum, and if those components are missing, that panel will just cease to operate.
Sam, but aren't there applications where you don't know if you're going to be indoors or outdoors?
Yes. So those applications, you’ve got to dance around it a little bit and definitely choose the technology that's right for that. But there's usually some tricks that you can play to get around. You usually would choose an indoor technology and then it also works outdoors, but you’ve got to be careful about it.
Martin, are there any other applications where you think power efficiency is crucial apart from the one you mentioned? I think it was you who mentioned that.
Yes, I mentioned a few earlier, for example demanding industrial applications and medical, but those are just two examples. We see it across our full customer base that power efficiency and power management is a relevant topic. We do have a lot of customers in the solar area as well. In addition, it is relevant for logistics with use cases such as warehouse monitoring, where devices are becoming more and more wireless now. They have to move around and you have robots and other smart mobile devices in warehouses. That is a big market where we see a lot of discussion about power management and power efficiency. One more to mention is transportation and agriculture. In agriculture for example, new harvesting machines and tractors are developed with a lot of modern technology on board, such as GPS and high precision localization, so farmers can move around with a mobile device in their hand and do not have to be in the tractor. We see a huge technology explosion in that area and in this market it is also key to talk about power efficiency. If there is anybody in the audience who has a specific application in mind and wants to talk about it, contact us and we can discuss the use case. For us it is always nice to discuss customer applications, of course.
So here is my application, Martin. I'm here in Florida and it's hot, it's really hot, and everything is out in the sun. How does that play into this? Am I just going to melt my cell? Is that a big issue, that these things get super hot?
Martin - In general, I would say not. I mean, I can speak about our solution. It is fully industrial temperature graded so it can take up to 105° C CPU temperature, typically 85° C ambient temperature. They are pretty tough in that regard. And, we have customers with very demanding applications where you need to have some kind of airflow in the system. We actually have only just very few customers who use fans or other active cooling devices on our solutions. Our SOMs are based on NXP’s ARM application processors, which are quite heat-efficient. Typically there is not so much heat generation in those solutions. Which means it is very rare to see customers using fans, typically only passive heat dissipation devices, heat sinks, and similar solutions work fine. I wouldn't see a problem in your application.
Sam - Yeah, I mean, it's very application-dependent and that's part of what we do here at PowerFilm is customize the PV cell to meet the environmental requirements. I mean, applications that come to my head are semi-trailers where the panel might be mounted behind the exhaust of a reefer unit. So you might be seeing those 85 or 100 degrees C temperatures and we need to customize the panel to be able to handle that. I mean, a lot of times, the indoor environments are a lot more generous. Don't need that 85 C. So maybe you can get by with some lower costs laminates and encapsulants that can save you some money, but yeah, it's very application-dependent.
I think you just answered this, Martin, but just to be totally clear, somebody in the audience asked this question, can my own app monitor the temperature and then command the CPU frequency?
Yes, absolutely. It is possible if you have low level access to the system, but it is more convenient on the Digi solution using the APIX programming interface that we provide as an additional component of the system, which allows application developers to utilize the hardware interfaces and power management features of the SOM in a very easy way. This means it is possible to do that directly from your application in actual application code without requiring to go to the system level.
And then along those same lines, Martin what do I need to do to go to the low-power mode in the ConnectCore modules?
That is a very good question. Sending an embedded device into a low power mode such as standby is not trivial, in many cases, because you have to take care that all the components of the system are shut down properly. For example with the wireless interface, you want to handle the connection properly after coming back from a low power state to be able to reconnect. Another example is access to the file system. You don't want to cut power when you are writing data into a file, obviously. You have to handle all these tasks. Normally this is done in a manual process. However, in the Digi ConnectCore solution, we have several scripts to support customers with these challenges. To hande the interfaces and file system access properly just requires calling a script called “standby” and all the components that have to be taken care of to smoothly go into standby are handled by this script added by Digi. It is quite convenient in our solution.