logic gate and dinx

[monokinetic]

Hi all,

Im just in the process of laying out a circuit for this schematic:

http://www.electronics-lab.com/projects/sensors/024/index.html

Its a touch switch, which is when you have 2 metal sensors and when they are bridged by  human skin (electrocution hopefully avoided!) they send a logic on signal, this will go to a DINX4. I roughly understand how this works but I want to run it past some gurus :)

My question is, this circuit is setup to send a 1 second logic high signal and the page name mentions you can increase the length of this by increasingt he capacitor value. What Im trying to do is set it up so that its logic on when then bridge is made and logic off when the bridge is released. This is to try and simulate note on/off behaviour.  Any suggestions how to implement such a behaviour?

Also from memory its possible to invert the DINX behaviour so it registers a trigger  when it receives a logic on rather than being pulled to ground, which is the default. Does this mean I have to connect the resistors to ground instead of  +5v ?

Looking forward to the help!! Kind Regards in advance

Dave mK

[airmailed]

hi Dave,

i'm not much of an expert but i think some kind of inverter circuit would do you for inverting the signal from your gadget before it gets to the dinx, a not gate or something...  not sure about the on/off bit

[TK.]

Hi Dave,

such a touch sensor feature is already provided by MIOS, you don't need additional digital logic.

More informations can be found here http://69.56.171.55/~midibox/forum/index.php?topic=1544.0

Best Regards, Thorsten.

[monokinetic]

Hi TK,

thanks as ever for such quick responses, I think you will always be faster than me :)

I read through the messages from Willba and you and I think it looks like he is doing something very similar to me, ie using simple metal connectors hooked up to a DINX and using skin resistance to trigger a switch response from a MIDIBOX app. However please forgive me because I still have some questions:

Your post mentions that no further digital logic is required with the DIN being used as a touch sensor. I have already tried using the DINX and the MIDIO128 app to see if the simplest touch switch (ie making the switch contact with my finger to link the VS and D1 pins) but it didnt seem to trigger any signal. You mentioned to Wilba the "MIOS_SRIO_TS_Sensitivity value", which I presume is in "midio_presets.inc" but I cant see any exact variable with that name though, could you point me to where to change this value? (EDIT: or is this the value in the MIOS_VECTORS.inc file in the MIDI128 fodler before recompiling?)

If I understand your mails to Wilba then just adjusting this value to increase sensitivity should let me use this MIDIO128 app and a normal DINX4 to read my touch switches. But do I need the 10Mohm resistors shown in the schematic I linked in my first mail or can I just connect the appropriate DINX pins to my touchsensors (with very short cable!)?

I look forward to your replies, If I can get all this working soon then it will be used for my 1st Midibox powered installation for a free exhibition here in sunny prague ;)

regards

D

[TK.]

Hi,

within the MIDIO128 application the Sensitivity is part of the data dump, this means that you don't need to add additional code, you can select the value in your midio128.ini file (see mk_midio128_syx.zip package), or you can predefine it in main.asm (search for DEFAULT_TS_SENSITIVITY)

The default value is 3, and this is a very good value which normaly works perfectly.

But - of course - you need to modify your DINX4 module like shown in this schematic:

http://www.ucapps.de/mbhp/mbhp_din_touchsensors.pdf

otherwise it cannot work

Greetings from the rainy Munich (however, more time for tinkering ;-)

Best Regards, Thorsten.