Reviving the old MOHO thread

[Angel Rodriguez]

HI Brian,

You wrote:

Just wanted to ask if you are willing to share the drawings and schematics for MOHO.  I'd think I'd be interested in building one.  I have two Yuma's operating currently and I'm looking for a new project :)

From the photos it looks like it uses a PCB linear motor coil, instead of a voice-coil type actuator, is that right?

I can probably fabricate all of the mechanical parts myself, but bare PCBs (or the gerbers) would be ideal.  I have some 4 mil and 6 mil 17-7 shim stock and the ability to heat treat to CH900.

Angel writes:

That thread is two years old and MOHO Pro now is all surface mount. See attached photos.  There are no little wires that jump across the hinges and all of the electronics are on the boom.  Between Dave and I we have five of these running and they look great.  Just as good and maybe better than MOHO Star that was thru hole with the electronics on a side board.

The motor is linear.

The attached photo is of all the parts needed,  all printed in one way or aonther.  The little flex circuit jumpers power and signal to and from the the boom.

I am working up a price list for MOHO PRO, one will be the boards and spring and the other a complete kit. I will speed up the making of that list.

Cheers,

Angel

[Brian Kuschak]

Hi Angel,

Thanks.  The Pro version looks great.  I like the 3 point adjustment screws for aligning the position sensor.  Looking forward to hearing more of the details.

Best,

Brian

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[Bob Hammond]

Looking forward to the price list, Angel.

Bob

[Angel Rodriguez]

Hi Brian and Bob and everyone else,

Here is the preliminary price for the MOHO PRO essentials.  

By essentials I mean things that you can not just go to McMasters or Amazon and get on your own. The mainspring is heat treated and will have the needed holes laser cut.  If you have a 24 bit digitizer I can remove it and change the price.  Tomorrow I will try to post the items I call "hardware", that you can just go buy.  Soon after I will post a page called plastic which will have the 3d printed parts and lastly there will be a page I call "optional".

The attached photos is a MOHO pro on the left and a commercial Kinemetrics station on the right.  It shows the 6.7 event south of Africa and the recent 7.1 Indian Ocean event as seen from Panama.

All comments and questions are welcome.

Angel

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[Brian Kuschak]

Hi Angel,

Thank you for taking the time to put together the price list for the essentials.  It sounds reasonable to me, for all these parts.  

Just a few questions:

• I assume the board labeled 10 is actually #9. 
• For the 3D printed parts, will you share the STL files, or only sell them as a kit?  I wouldn't mind printing them myself.
• Do you have an enclosure in mind?
• The helicorder plot seems to be clipping on the largest amplitude events.  Is this the MOHO electronics clipping, or the digitizer?
• One of the things I really liked about the Yuma development was Brett's FBVSolve spreadsheet, for calculating the instrument response.  Are you developing or adapting something similar for MOHO?  
• Out of curiosity, what is the thickness of the spring?

Looking forward to the other lists!

Cheers,

Brian

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[Angel Rodriguez]

Hi Brian,

On Sat, Jul 13, 2024 at 3:18 PM Brian Kuschak <bkus...@gmail.com> wrote:

Hi Angel,

Thank you for taking the time to put together the price list for the essentials.  It sounds reasonable to me, for all these parts.  

Just a few questions:

• I assume the board labeled 10 is actually #9. 

Yes, I will correct that.

• For the 3D printed parts, will you share the STL files, or only sell them as a kit?  I wouldn't mind printing them myself.

Yes, I can provide the STL or 3MF for all of the printed parts along with what print setting I use.

• Do you have an enclosure in mind?

I have several enclosures in mind including one that I will print, the commercial one I use I buy on amazon and will send the URL

https://www.amazon.com/DJC-Supply-Waterproof-Electronics-Mounting/dp/B09324TNT7/ref=sr_1_2?s=industrial&sr=1-2

• The helicorder plot seems to be clipping on the largest amplitude events.  Is this the MOHO electronics clipping, or the digitizer?

The SWARM display software is clipping the display so that it does not swamp the whole screen.  You can disable that.  

• One of the things I really liked about the Yuma development was Brett's FBVSolve spreadsheet, for calculating the instrument response.  Are you developing or adapting something similar for MOHO?  

I think that the same sheet will work, I will check with Dave on that.  BTY, Brett is no longer with us.

• Out of curiosity, what is the thickness of the spring?

0.005  inches and it is treated to the C900 state, we laser cut from shim stock then clean up and heat treat.

 

Looking forward to the other lists!

I have been working on them all day.  I hope to have some of them done by the end of the day.  I would rather that folk buy or make whatever they can.  The step by step assembly manuals are coming along.

Saludos,

Angel

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[Brian Kuschak]

Hi Angel,

Thanks for the follow-up.  Please mark me down for one Essentials kit, and possibly one Magnetics kit.  I'll 3D print the plastic parts and source the mounting hardware myself.  Since it sounds like you're ordering from McMaster, do you have a BOM containing the McMaster PNs?  That would save me some time.  If not, no worries.

• One of the things I really liked about the Yuma development was Brett's FBVSolve spreadsheet, for calculating the instrument response.  Are you developing or adapting something similar for MOHO?  

I think that the same sheet will work, I will check with Dave on that.  BTY, Brett is no longer with us

I was sad to hear that about Brett.  He will be missed.  

I noticed that his bnordgren.org website went down at some point.  Does anyone have a 'final' archive of the website?  The Internet Archive doesn't seem to have captured many of the files.  I have an old mirror from 2018-ish.  It would be great if we could make all the docs and files available to the community again.  There was a wealth of knowledge contained within.  Brett had a great way of communicating complex ideas clearly.  I learned a lot from his writings.  

Best regards,

Brian

[Christopher Chapman]

Hi Brian

Is the Wayback site still in operation ?

Regards,

Chris Chapman

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[Brian Kuschak]

Hi Chris,

The "Internet Archive" link in my previous email is the link to the Wayback Machine for https://bnordgren.org/seismo/FBV/.  

Some files were archived, but sadly many were not.  Or at least, I wasn't able to find them on that site.

Regards,

Brian

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[Angel Rodriguez]

Hi Everyone,

Dave and I have a lot of Brett's work (maybe all) and once I get a chance I will find a way to make it public again.  We will also post all Dave's work and anything I might have and anything anyone else would like to contribute.

Cheers

Angel

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[Angel Rodriguez]

Hi Brian,

I have a  spreadsheet with all of the McMaster numbers and the URLs for everything else, I will get that to the list as soon as I get a minute.  For a retired guy I sure have trouble finding time for little things.  Bug me if I have not posted it in a few days.

Angel

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[Brian Kuschak]

Hi Angel,

No worries, take your time.  I appreciate all your efforts!  

Thanks,

Brian

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[Christopher Chapman]

Hi Angel,

    When I was very young, I quite quickly learned that playing with my toys took very little time. It was putting them away tidily afterwards which took ages ! 

    Could you re-send your last Email, please ? My new computer seems to gobble them up in a most un-help-full way. 

    Regards.

    Chris

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