Touch activated Switches

[killivolt]

So, an RC and if I Play with some resistors I could also speed or slow. A higher rise maybe un-acceptable for design. However will be be fun to Play with

Thanks, Roff

 

[Roff]

Yeah, the 10k and the 680pF form a 6.8usec time constant. You can change the R over a reasonable range (10k - 100k?) so long as you keep the product RC close to the original timeconstant.

 

[Space Varmint]

So you are going to use the oscillator? Still not sure why. But think of it in "voltage" and time constant. What happens is the capacitor charges up by the RC time constant. Once it reaches the Schmidt trigger threshold, the inverter gate will change state. So now the input to the RC combination is zero volts and the capacitor will discharge by the RC time constant until it again it reaches threshold and the positive output is applied to the input of the first gate and will again charge through the RC time constant.

 

[Roff]

So you are going to use the oscillator? Still not sure why. But think of it in "voltage" and time constant. What happens is the capacitor charges up by the RC time constant. Once it reaches the Schmidt trigger threshold, the inverter gate will change state. So now the input to the RC combination is zero volts and the capacitor will discharge by the RC time constant until it again it reaches threshold and the positive output is applied to the input of the first gate and will again charge through the RC time constant.

There are no Schmitt triggers in his schematic.

 

[Space Varmint]

There are no Schmitt triggers in his schematic.

Well then "inverter gates". I haven't looked recently. It's one or the other.

 

[Roff]

Well then "inverter gates". I haven't looked recently. It's one or the other.

Yes, but a Schmitt trigger oscillator works on a different principle than an inverter oscillator. Also, a Schmitt oscillator is made with a single Schmitt inverter, while an inverter oscillator requires at least two inverters. The R and C that we were discussing are not part of the oscillator, but you may not have been referring to that discussion.

 

[Space Varmint]

You can use two gates with a Schmidt Trigger. What are you talking about? It works the same way by the RC time constant determining the frequency of the oscillator. I'm not gonna argue with you....Bye.

 

[Roff]

You can use two gates with a Schmidt Trigger. What are you talking about? It works the same way by the RC time constant determining the frequency of the oscillator. I'm not gonna argue with you....Bye.

You're right, of course. You just don't need 2 gates. I was thinking of the single gate Schmitt oscillator. Sorry.

 

[Space Varmint]

Way too cool. The smartest guys on here are the ones who know how to humble themselves. Apology accepted. I have used them for single gate too.

 

[Roff]

Way too cool. The smartest guys on here are the ones who know how to humble themselves. Apology accepted. I have used them for single gate too.

Yeah, you may have noticed that there are some on here who just disappear from a thread when they are proven wrong. Either that, or they continue to insist that 2=3. It irritates me, so I try not to be like them.

 

[Space Varmint]

Well, you weren't wrong. You were half right

 

[killivolt]

If work doesn't stop me I should be able to put this on the scope. Then I'll work on the Touch Button.


Glad to see your seeing I to I


Edit: I just got back from the parts supplier.

 

[Space Varmint]

We are waiting on you, pins and needles!

 

[killivolt]

I have the Exciter Circuit Built. I need to know if the rest of the circuit has to be built and connected in order for me to see if is Oscillating at 20khz.

It's a tektronixs 453 Ocilliscope I have no manual and I inherited it. The only thing I've measured with it is a Video Signal seemed to work.

The probe is a Zenith pkw-105 the settings on the probe are (1x ref 10x)

 

[Roff]

The exciter should stand alone. It doesn't need the sensors or receiver.

 

[Space Varmint]

I have the Exciter Circuit Built. I need to know if the rest of the circuit has to be built and connected in order for me to see if is Oscillating at 20khz.

It's a tektronixs 453 Ocilliscope I have no manual and I inherited it. The only thing I've measured with it is a Video Signal seemed to work.

The probe is a Zenith pkw-105 the settings on the probe are (1x ref 10x)

OK, what you do is look at the selector position on the "times division" knob. It usually has a grouping painted around the knob where it says "mS and uS" Of course this is milliseconds and microseconds. So look at the number it is on within the groups like 50, 10, 1 or .1 or .2 or .5 etc. This refers to "per division" which is the vertical lines going through the hash marks on the glass over the screen of your scope. So, adjust the signal so that you have one complete cycle within two lines of the major grid on the glass. Usually there are about 8 to 10 vertical lines. Set a full cycle between two verticle lines. That's division. Now look at the setting on the frequency division knob. Now whatever it is set on (should be 50uS), you take the reciprocal of that number. So 50 times the uS is 50us per one division and the reciprocal of that is 20KHz. It gets you very close to actual frequency.

 

[killivolt]

Ok, I'm at work right now and had to stay to late last night. I'll read and post my findings tomorrow.

I'm a stickler about my boards and usually will go over all my connections at least 4 time during and after.


Thanks for the feedback.

Miller Time

 

[killivolt]

One last one before I go to the house, I wanted to know how far would be suggested to extend the Touch Button without messing things up ? I'd like to keep everything on one board in my Technical Operations Room if possible. so I want to run that line back to it, about 60 ft or so.

Second is I want to parallel Touch buttons at 6 locations.

Edit: I'm heading for the house and will pickup on this question there.

 

[Roff]

One last one before I go to the house, I wanted to know how far would be suggested to extend the Touch Button without messing things up ? I'd like to keep everything on one board in my Technical Operations Room if possible. so I want to run that line back to it, about 60 ft or so.

Second is I want to parallel Touch buttons at 6 locations.

Edit: I'm heading for the house and will pickup on this question there.

Can you try it out? It should work, but I wouldn't want to make any predictions.

 

[Space Varmint]

I would suggest you put some capacitance from the wire to ground on both sides. Maybe about 1000pf or so to remove any noise picked up by the wire if it's going to be that long. The actual signal should make the trip. I think your major concern will be noise.