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Completely newbie planning to build EM theremin

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Posted: 11/8/2012 2:59:49 PM
Hazel
From: Vigo, Spain
Joined: 11/8/2012

threads posts

Hi!

Ii've been reading lots of posts here and i think i have most of the process clear but I still have my doubts about if i'm going to get it. I have never done any electronics but i think i can do it if i follow the pdf replacing the old components, etc..

I can't afford to buy one so i'm going to give it a try. What do you think? am i dreaming?

Posted: 11/8/2012 3:45:23 PM
Chobbs
From: Brooklyn,NY
Joined: 12/1/2009

threads posts

If this is really your first electronics project, like ever?  than...-  Yes, you are dreaming.    The EM is not hard, per se , but definitely not a newbie project.   I'd get acquainted with the tools and materials by doing a couple smaller projects first- start with something real simple like a fuzz box, and gradually work up to more complicated stuff like an Octave or Auto Wah.  Thats what I did.  Youll need to hone those troubleshooting skills!

BTW- th cheapest way to get an etherwave is to just buy one... you'll probably be able to find a used one for a bit less than new.   There is a false economy to DIY.  yes it is cheaper -      (though,   not too much actually when you consider all the other stuff you'll need -like a  cabinet, antennae,  mic stand mount, sanity, and the biggie -time, etc )

-but you definitely have to earn it.  

Posted: 11/8/2012 9:07:58 PM
Hazel
From: Vigo, Spain
Joined: 11/8/2012

threads posts

I guess you are right and i should not try it but... what the hell! it's funny! And what if i succed? Wow, i can't wait :D


Any advise? (besides not to try it?)

Posted: 11/8/2012 9:17:07 PM
dewster
From: Northern NJ, USA
Joined: 2/17/2012

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"Any advise? (besides not to try it?)"

If you don't own them already buy a scope & DMM.  A frequency generator wouldn't hurt either.  Play with it on a breadboard before you commit to soldering.  Pay close attention to subtle but very important issues like sensitivity, linearity, and temperature stability.  Play around with every type of coil you can get your hands on.  Try to remain agnostic when it comes to committing to a particular oscillator topology (guilty).

Posted: 11/8/2012 9:55:39 PM
FredM
From: Eastleigh, Hampshire, U.K.
Joined: 12/7/2007

threads posts

" Any advise? "

The EM theremin does not have a PCB - and I dont think the original prototyping board is available anymore.. So you are really going to need to plan the layout first. My advice here is to get some PCB layout software, something free like DesignSpark, so that you can plot a basic layout for 0.1" PAD BOARD (NOT Strip board or Matrix board).

My advise is also that you split the design over several small boards - You want each oscillator on a seperate board, and the mixer and VCA/Audio stuff on one board IMO.

Read everything you can on both the EM and EW theremins, enter the schematics into the schematic editor of your PCB design software, you are then ready to do the layout.. Lay out for two layers, but make any tracks on the upper layer straight - this way you can wire link these. Keep all your tracks, components etc TIGHTLY on an 0.1" grid - this way you can simply put the components down on the pad board where they are supposed to go, and do point-to-point wiring on the other side, soldering the wire to pads and using the pads to fix the wiring at bends.

Using a schematic + PCB editor, you will be warned if the rule checker sees that you have made a layout error, left tracks unconnected, or have not fitted all the components.

IMO, if you dont do the above and just dive in with a soldering iron trying to copy the EM design, well, you dont have a snowballs hope in hell..

If you use schematic and PCB editor, you should be able to copy the component placements from the EM article as a guide, and the PCB editor will help greatly as you will see "ratsnesting" showing the required connection between components.

My advice would be that this is not a starting project - I would echo Chobbs advice loudly - But hey, luck sometimes favors the foolhardy...

Fred

PS - When you enter your schematic/s, keep the component references the same as the EM if you are copying that, or the EW if you are copying that.. This way you will be able to cross reference against the original parts when you do your layout.

Also - Make all connections to components on the lower (solder side) layer - The PCB layout editor will place "vias" when you go from lower to upper layers - but these will not exist when you build your board - Every connection to the upper layer, and every "track" on the upper layer will need to be hand wired ( - so dont take an upper track to a component pin directly, it MUST go back down to the lower layer before it connects to a pin.. there are no plated-through holes with pad boards)  this is why they need to be straight - if they are not straight, or if they come too close to a component lead, these wires will need to be insulated.

Oh - one last thing.. Use good quality turned pin sockets for all ICs, and as you havent soldered before, I would advise you to buy some socket strips you can cut up to make sockets for your transistors and diodes as well - they dont like getting their legs cooked for too long! - And I would buy a load of cheap components (resistors or whatever) and a spare board, and practice soldering these, and wires, onto this board.. then practice unsoldering them and removing them, and cleaning the board (you will need a solder sucker and some solder wick) then re-mounting them and re-soldering - Do this until the board is a complete wreck!

Also - Use tin lead solder, not the new RoHS lead free rubbish! - The new solder doesnt flow (or wet) as well, is more brittle, has a higher melting temperature, and is quite horrible!

Posted: 11/8/2012 11:38:56 PM
Hazel
From: Vigo, Spain
Joined: 11/8/2012

threads posts

Hi Fred!

First of all, thank you for your help. It is much apreciated.

this is why they need to be straight - if they are not straight, or if they come too close to a component lead, these wires will need to be insulated.

You are talking about the hand wires, don't you? Similar to the wires that you can see here, i guess.

I read somewhere about the distance between some componentes. Some of them should be close and some should be far away. Is that true? Which of them?


PS: I have to mention that i have soldered occasionally.

Thank you all!

Posted: 11/9/2012 1:32:51 AM
Chobbs
From: Brooklyn,NY
Joined: 12/1/2009

threads posts

Hey that flickr image looks familiar! 
(its my first EM!)  

I would just use a  perf board with individual (unconnected) copper dots, and just copy the EM layout and traces -making sure to include all the necessary connections present on the  the original prototyping board. - that's pretty much what I did. 

Posted: 11/9/2012 8:13:31 AM
FredM
From: Eastleigh, Hampshire, U.K.
Joined: 12/7/2007

threads posts

"I would just use a  perf board with individual (unconnected) copper dots, and just copy the EM layout and traces -making sure to include all the necessary connections present on the  the original prototyping board. - that's pretty much what I did." - Chobbs

I agree that this is the quickest and simplest.. But you had built other circuits before. For someone who has never done so, I think that time spent carefully planning the layout is probably time well spent. 

"You are talking about the hand wires, don't you? Similar to the wires that you can see here, i guess."

No - I am talking about wire links from one part of the board to another part of the board - In a perfect layout you wont need any of these, and with careful layout you can sometimes avoid links - but with some circuits it is impossible to route all the connections on one side of the board - one needs to use the other side to carry "jumpers"... This is why multi-layer boards are used - to allow complex routing.. Double sided is minimum one needs for most projects.. With single-sided pad board you need to track any upper layer wiring with jumpers, and for simplicity  tidyness and reliability these should be straight.

Also - making the board is only the start - you will need to debug it. Having a schematic and layout done will greatly assist you in debugging, as you will be able to see instantly what every track is connected to and be able to go point-to-point.. Before you power the board up, you should check that the components are actually interconnected, using an ohm meter - Before you plug the IC's in, you should check the power pins - All eaasy to do if you can trust your layout diagram!

Fred.

Following are some photos showing construction on pad board. This is a quick way to produce fast prototypes - Layout is done on 0.1" grid, with 2 layers - Upper (component side) layer should have minimum tracks, and these should be straight to enable easy wiring.

 

The component overlay was transferred to the component side using toner transfer method. (you dont need to do this - its only "needed" for really complex boards and only worth doing if, like me, you have everything set up to do this easily- as in, modified laminator etc.. And if you have all that, you usually make your own PCB rather than using pad board.. I rarely use pad board anymore - The major advantage to pad board is that you dont have the hassle of etching and drilling a PCB, but this is replaced by the hassle of wiring the track side)

The wire links I am talking about can be clearly seen.

 

 

 

Posted: 11/9/2012 12:17:05 PM
Hazel
From: Vigo, Spain
Joined: 11/8/2012

threads posts

Nice! it's perfectly clear now.

What about the distance between components? Do i have to place some of them close and others far away? (besides the fact they are close in the schematic)

Posted: 11/10/2012 1:36:01 AM
FredM
From: Eastleigh, Hampshire, U.K.
Joined: 12/7/2007

threads posts

"What about the distance between components? Do i have to place some of them close and others far away? (besides the fact they are close in the schematic)"- Hazel

The answer to this is "yes" and its "no" -

Yes: There are better positions for components in any given layout, and there are some components where distance to others can be important.

No: The EM design, APART FROM THE ANTENNA COILS, is not critical.. Keeping components from each "block" together should be enough.

Using the EM layout as a "template" for your layout should be fine.

Fred.

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