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Old 29th Dec 2020, 9:34 pm   #1
wireless_john
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Default Brachiograph

Has anyone built this simple plotter?

I was hoping to get my grandchildren interested.

https://brachiograph.readthedocs.io/...ted/build.html

John
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Old 30th Dec 2020, 1:35 am   #2
Uncle Bulgaria
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Default Re: Brachiograph

That's very cool, John! Perhaps I could have a line in getting CAD files passed through that...
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Old 30th Dec 2020, 1:46 am   #3
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Default Re: Brachiograph

Hi John,

No, but I did build an alternative pantograph version, similar to the one shown later in your link. ( https://brachiograph.readthedocs.io/...antograph.html )

It was an Arduinio based PlotClock. ( Google that for loads of info. ) My intention was, once I tired of the clock, to re-purpose the kit as a grotty plotter.

I'm not very good with Arduino stuff, and the pantograph design is not tolerant of 'illegal' arm positions. I broke the arms and stripped the servo gears. Not touched it since.

If I had seen the Brachiograph I'd have gone for that instead. It looks much more tolerant of abuse. ( I should have left it as a working PlotClock. That looked cool. )

Cheers,

Buzby
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Old 30th Dec 2020, 8:42 am   #4
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Default Re: Brachiograph

Haven't heard of PlotClock, I'll Google it. My grandsons are 10 and 8 and I thought that if I built it and told them that they could do the same it might be something they would be interested in. In the the same way as when my Father showed me how to make a crystal set in the 1950s/60s. It sparked a lifelong interest in me!

John
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Old 30th Dec 2020, 11:57 am   #5
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Default Re: Brachiograph

Excellent!

Peter
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Old 30th Dec 2020, 1:35 pm   #6
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Default Re: Brachiograph

Those servos are very cheap, I think the last time I bought some it was approximately 30 bob each. Very good too.
 
Old 30th Dec 2020, 2:26 pm   #7
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Default Re: Brachiograph

I've done quite a bit of research into servos and it seems you do need good quality ones like Tower Pro or Futaba.

The usual places seem to be riddled with cheap fakes and the advice is if they're less than $3 or €3 then they're probably fakes.

So I intend to get three Tower Pro ones for £4 each from The Pi Hut. That seems to me to be the best chance of getting ones that'll do the job first time and not have to buy them again.

John.
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Old 30th Dec 2020, 8:10 pm   #8
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Default Re: Brachiograph

Cool project.
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Old 3rd Jan 2021, 12:36 am   #9
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Nice find - keep us updated with if those servos work as a £12 project to have in the bag for a rainy day looks like good value.
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Old 3rd Jan 2021, 9:05 am   #10
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Default Re: Brachiograph

I'm working on it! Servos arrived yesterday. in the middle of making a base for it now.

My wife bought me a Raspberry Pi 4 for Christmas (not the one with the keyboard) so I've got that to set up too. All takes time when you've got plenty of other things to do!!!!

John
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Old 3rd Jan 2021, 3:31 pm   #11
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Default Re: Brachiograph

Quote:
Originally Posted by wireless_john View Post
I'm working on it! Servos arrived yesterday. in the middle of making a base for it now.

My wife bought me a Raspberry Pi 4 for Christmas (not the one with the keyboard) so I've got that to set up too. All takes time when you've got plenty of other things to do!!!!

John
I know the feeling my PI4 is, like the others, hunting for a good project to play with it more... the project queue gets longer but, I tend to favour these sort of mixed physical constructions over just coding these days.
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Old 9th Jan 2021, 1:15 pm   #12
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Default Re: Brachiograph

I've built the plotter now. The instructions advocate glueing the servo motors to the arms but I've tried to avoid doing that. Then when I get fed up with it I can use the servos for something else.

The photograph shows all the bits and I have had it all assembled but now dismantled so that I can see what the servo motors do when I first try anything with it.

I'm having problems getting the program to run. I have written simple things in Python but some of this is a long way over my head!

A question of Googling the errors and experimenting until it works!

John
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Old 9th Jan 2021, 3:05 pm   #13
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Default Re: Brachiograph

Sound like the way I program in Python Following with interest.
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Old 9th Jan 2021, 5:13 pm   #14
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Default Re: Brachiograph

Thanks! I've just solved the first problem I encountered so I'm getting there!
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Old 12th Jan 2021, 9:04 am   #15
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Default Re: Brachiograph

Finally I have it working. The picture is the first thing I drew with it once I had the software side of it working.

Now it has to be calibrated and set up. There were a few little things in the Python side of it that took me a while to sort out so if anyone else tries it, don't hesitate to contact me if you run in to problems with it. I'm no expert on Python but I'll help if I can.

John
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Old 13th Jan 2021, 12:18 am   #16
Colin Ames
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Default Re: Brachiograph

An interesting project. Thanks for sharing it with us.
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Old 17th Jan 2021, 9:25 pm   #17
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Well done John - looks like the pictures I draw
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Old 18th Jan 2021, 9:07 am   #18
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Default Re: Brachiograph

I have it working now but calibrating it is a bit of a mission.

Learning as I go along!

John
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