Theremin components

Great! I'm finding the pieces i need and learning about electronics in the process.
The last piece(s?) i need is the Connector set with at least ten conductors for connections between the main circuit board and front panel, but i have no clue what to look for
I'd like to say thanks to all those who responed, cause it really helped

I mostly use Insulation Displacement connectors - the "box headers" (http://www.rapidonline.com/Cables-Connectors/Connectors-Multipole/IDC-Connectors/Straight-boxed-headers/28899) are mounted on the PCB, and the connector into it takes ribbon cable..

One needs to squeeze the ribbon cable into the (flying) Socket connector (http://www.rapidonline.com/Cables-Connectors/Connectors-Multipole/IDC-Connectors/Cable-mounting-socket/63686) in a way that causes the insulation on the ribbon cable to be cut and displaced.. The tool to do this is quite expensive if one only needs a few connectors made - but one can easily make the connection by carefully aligning the parts (they clip together and hold the ribbon in place, so its quite easy) and then tightening the connection in a small vice.

The page for IDC connectors from Rapid Electronics (http://www.rapidonline.com/Cables-Connectors/Connectors-Multipole/IDC-Connectors) shows a range of options - There is also a page showing general PCB Interconnect (http://www.rapidonline.com/Cables-Connectors/Connectors-Multipole/PCB-Interconnect) parts.

All these parts are available from many suppliers (Rapid does seem to have some of the best prices though) and there are a lot of non-RoHS parts being sold cheap.

The big advantage of the IDC system is time - Hand crimped / soldered individual connectors are a real pain.. The possible disadvantage of IDC is that, if not assembled well, the connection can be unreliable. Sometimes I use a 20W connector to carry 10 critical signals, and double-up each signal.

The other useful thing with the 2 row box headers, is that one can lay the PCB out so that one edge (all odd or all even numbered pins) is connected to ground - This way, every signal carrying wire on the ribbon has a ground wire next to it..

But this raises one thing you need to be aware of - there is a lot of capacitive coupling between adjacent wires on the ribbon, so you need to take great care with allocation of signals, particularly if there are any high frequencies or anything at high impedence.

Fred.

Theremin builders may be interested in some variable inductors I have found..

These are, in fact, capacitor-less 455kHz IF Transformers which can be wired to provide a good selectable range of variable inductances.

Part is the 421F106-RC available from Mouser http://gb.mouser.com/Search/Refine.aspx?Keyword=42IF106-RC

Inductances obtainable are:

4-6 --------------> 21 uH
2-3 --------------> 72 uH
2-3 + 4-6 --------> 172 uH
1-2 --------------> 308 uH
1-2 + 4-6 --------> 490.7 uH
1-3 --------------> 680 uH
1-3 + 4-6 --------> 940.8 uH

Turns:
1-3 ---> 153
1-2 ---> 103
2-3 ---> 50
4-6 ---> 27

Al(nH) = 29
inductance (nH) = (N*N)*Al

N = Number of turns, (N*N)looks silly, but easiest way I can find to denote N squared. When connecting windings on a common 'former' you cannot just add the inductances - calculate total turns of connected windings, and then calculate inductance using Al.

Given an inductance and number of turns for any winding, one can calculate Al (inductance factor) and apply this to any other windings where number of turns is known, but inductance is unknown.

[b]see my mini-tutorial on these calculations[/b] Here (http://www.thereminworld.com/forum.asp?cmd=p&T=4805&F=3)

Oh, and yes.. connecting the wrong ends of windings together will not add inductance, but will reduce it.

The above are obtained by connecting to pins shown above, and by wiring the secondary and primary together to change effective number of turns.

Above values are calculated - I am waiting for samples of this particular IFT.. But have tested other Xicor IFT's and found actual values close to my calculated ones.

I have used these inductors (IFT's) in several oscillator circuits without problem.

Fred.

[b] THE ABOVE HAS BEEN EDITED AND CORRECTIONS MADE [/b] I muddled number of turns with uH in my last, and it was obvious nonsense! ;-)