Submitted by Bertl on Fri, 06/20/2014 - 16:59
While it may seem like AXIOM development is currently
on summer break - it is true that the planned crowd
funding got delayed - there is a lot going on behind
the scenes. So I thought I'd give a short update on
what is currently cooking on the technical side.
We made an initial design for the AXIOM Beta power supply for testing, which basically consists of a two
stage regulator, where the first stage is a switching
regulator to accommodate a wide range of input voltages,
and the second stage is a low noise LDO which ensures
that we reach and keep the desired target voltages
with as little loss and noise as possible.
In April we were offered some space on a larger PCB panel, so we got the chance to get some PCBs made without having to pay for them - Big thanks to Gabriel! We decided to get two of those preliminary switcher boards made for testing. When the PCBs were ready, we populated half a board and ran some basic tests, which were promising but not perfect for several reasons: For one, the chosen parts are not optimal and will probably get replaced in the next version. Second, the design still needs some minor improvements to make it easier for DIY assembly. We are currently preparing some kind of systematic testing to further improve the design.
While we waited for the power supply PCBs, we found some time to finish the first test version of the dual micro SD PMOD module planned for AXIOM Beta and also managed to add a FAN controller, again for testing. The PCBs have been ordered from OSHpark and should arrive in the next week, so that will probably become the next module to work on. In the gaps between, we did a lot of planning and component identification for the Beta board, which included going through a number of different crystals to satisfy the various clock requirements of the planned devices. This made me think about adding a dedicated clock chip to the mix to reduce the area and improve configurability. We found a number of interesting potential candidates and decided to do some testing on them, which resulted in two more side products in the form of PMOD clock module I and PMOD clock module II.
The layout is simple and kept generic, so it allows to try out different crystals and various chips from the same family without having to change the design. And of course, they can be reused for other projects as well. PCBs and components have been ordered and should arrive in the next few weeks. This reminds me that we are - mostly due to the delay with the crowd funding campaign - on low budget and every donation, regardless how small, is very welcome, because it will allow us to continue all those Beta preparations instead of sitting around and waiting for the campaign to finish. We will give some more updates when the PCBs arrive and we finished assembling and testing them.
9 Comments
For previous donors, will
For previous donors, will their amounts go towards qualifying in anyway towards the kickstarter deal?
no
no
I suggest to add a rectifier
I suggest to add a rectifier to the power input. It happens so often, that your cables are wrong and it only adds a few cents and a little voltage drop...
The plug we plan to use is
The plug we plan to use is keyed so it shouldn't be too easy to get the cables wrong, and a rectifier is quite large or rather expensive and as you said, it adds a voltage drop, but I got the message and we will consider adding at least a protection diode to prevent damage to the power supply if somebody manages to get the cables wrong.
Sorry to hear the crowd
Sorry to hear the crowd funding was delayed. Thanks for the update on the design process. I hope the crowd funding comes together soon (the money is burning a hole in my pocket!) LOL.
We are doing our best, but we
We are doing our best, but we want to make sure we do it properly :)
Hi: Why don't you use some
Hi: Why don't you use some switched power supply integrated like Murata's modules?. Thanks. Jesus
No particular reason. Do you
No particular reason. Do you have any suggestions for modules which would fit our requirements?
Input 5-40V, Output 1x5V/3A, 1x3.3V/3-5A, Size <= 20x25x6mm without barrel jack.
The Murata product selection tool (http://dcdc.murata.com/) seems to be offline.
there is also the possability
there is also the possability to use the selector at farnell.com for a dc-dc module. i have looked quickly but i haven't found a solution with this requirements. maybe the MAX16931 will do the job but i'm not sure.
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