UltraSound 2.0 After upgrade..

[Novastar]

Just for N00bs, I am *NOT* the same dude as "Nova conceptions". I have absolutely nothing to do with the Ultrasound, so... please... keep that in mind.

Novastar [~is NOT equal to~] Nova conceptions



I know you veterans know what's up... but... seriously--after getting a very small handful of messages, I want to nip that in the bud.

[grayven]

So does that mean you wont be fixing the mom switch issue Nova?

[Strydur]

Yup..send all complaints to Novastar!!

[damian]

Hi All,

I work as an electrionic engineer and I think a simple RC debouncer is alls thats needed. I think it will solve all your switch wow's. I'm new to the custom saber scene but I'm going to put in an order for the 2.1 "MHS sound/speaker/battery combo" and "DPDT Momentary green illuminated switch". as soon as there in stock. Hopefully soon and when I get them I'll try a few things and post the solution assuming I can find it. i googled an RC debouncer diagran for ye and found a good one here http://embedded.com/showarticle.jhtm?articleid=18902552 its figure two. If some one can try it out and play around with the resister and cap values then it should be prob solved. I think 95% of people will find this fairly easy. If this doesn't work then there are a few other more complicated circuits that I can think of that might do the trick but I think this is the best place to start. When the parts are in I'll put in my order and when my order comes I'll post pics of the final solution. As for the future I think that a software solution is best or maybe better quality switches. After all the help I got on the forum I hope this helps and I can give a little back,
Damian

[Ri-on Ozryel]

I ran into the bounce problem on the first batch but was able to get around it by de-bouncing the switch with a capacitor. The capacitor I used was monolithic ceramic capacitor (either 50 WVDC or 100 WVDC) with a value of 0.1 uF.





I used it on 2 different switches with no problems on either one.

[Darth Leximus]

Now that seems like a simple solution

[Strydur]

Ok..I have some of these on the way to try out..thanks.

[Eandori]

No, just a capacitor is not a good solution. What you will likely find is that if your circuit worked without a cap, it will work with. If it failed without a cap, it will fail with. If you use a capacitor, you must also use a resistor. Because Capacitors help by 2 ways...
1. Shorting out high frequency transitions
2. Making voltage rails slowing increase or decrease

Without a biasing resistor your capacitor will charge based on the amount of power in that voltage spike. Too fast or too slow and you didn't fix the issue. So to make a capacitor work, you use a resistor. For the values, you make sure that 2.2RC = S the rise/fall time you want. Where R = resistor value, and C = capacitor value and S is time in seconds if I remember right.

The equation will give you how long it takes for that RC circuit to go from 0% to 90% of the next value (ex: from 0v to 9v when the peak is 10v). Biasing your RC circuit makes the rise time you want it to make. Now that you have that, you also need to KNOW WHAT KIND OF RISE TIME YOU NEEDED. Do the inputs on Alex's US2.0 board need to switch at 1ms? 1ns? How slow is too slow? How fast will will be limited by not removing the actual switch debounce because it was a lower frequency then your 2.2RC circuit.

Now that you can finally have a working RC Circuit... you still need an inverter or comparator. Because digital logic does not often like rounded curves as input. You need hard 0 to 1 transitions. An inverter or comparator gives you exactly that. Takes a rounded RC circuit output, and makes it into a hard (fast) transition for the actual digital chip.

or...

You could bypass all of that and just use the NAND circuit I suggested on page 11 of that document.

You don't need to understand it, just build it how it's wired in the diagram. If you really want to understand it, you need to understand NAND logic gates and the speed at which input to switched output happens. Then trace that signal through the circuit and see how it works. Effectively, signals travel slow enough that the to AND gates end up latching the input from the first trigger. By the time the NAND circuit has latched the first input, the switch has stopped ringing.

[LordCyric]

No, just a capacitor is not a good solution. What you will likely find is that if your circuit worked without a cap, it will work with. If it failed without a cap, it will fail with. If you use a capacitor, you must also use a resistor. Because Capacitors help by 2 ways...
1. Shorting out high frequency transitions
2. Making voltage rails slowing increase or decrease

Without a biasing resistor your capacitor will charge based on the amount of power in that voltage spike. Too fast or too slow and you didn't fix the issue. So to make a capacitor work, you use a resistor. For the values, you make sure that 2.2RC = S the rise/fall time you want. Where R = resistor value, and C = capacitor value and S is time in seconds if I remember right.

The equation will give you how long it takes for that RC circuit to go from 0% to 90% of the next value (ex: from 0v to 9v when the peak is 10v). Biasing your RC circuit makes the rise time you want it to make. Now that you have that, you also need to KNOW WHAT KIND OF RISE TIME YOU NEEDED. Do the inputs on Alex's US2.0 board need to switch at 1ms? 1ns? How slow is too slow? How fast will will be limited by not removing the actual switch debounce because it was a lower frequency then your 2.2RC circuit.

Now that you can finally have a working RC Circuit... you still need an inverter or comparator. Because digital logic does not often like rounded curves as input. You need hard 0 to 1 transitions. An inverter or comparator gives you exactly that. Takes a rounded RC circuit output, and makes it into a hard (fast) transition for the actual digital chip.

or...

You could bypass all of that and just use the NAND circuit I suggested on page 11 of that document.

You don't need to understand it, just build it how it's wired in the diagram. If you really want to understand it, you need to understand NAND logic gates and the speed at which input to switched output happens. Then trace that signal through the circuit and see how it works. Effectively, signals travel slow enough that the to AND gates end up latching the input from the first trigger. By the time the NAND circuit has latched the first input, the switch has stopped ringing.

Yeah, What he said!

[Eandori]

Here you go guys... I drew up exactly how to wire the exact NAND chip I referred you to sold by Digikey. I took a screenshot of the chip description in the spec document, then drew on wires to help explain. Do exactly this and it will work, plus this will let you debounce 2 different inputs!

NOTE: The switch used in this setup is a double throw switch. Not a single throw switch. You will need to buy a double throw switch as well as your NAND chip.



Cheers,