Electronics > Beginners
my analog switch doesn't work as intended
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mheruian:

--- Quote from: T3sl4co1l on November 20, 2018, 08:59:33 pm ---
--- Quote from: mheruian on November 20, 2018, 07:19:28 pm ---Ohh??  :o i never thought of that?? You're right i have overhead lamp over the circuit, psu, laptop and phone are nearby. I even find myself sometimes that whenever i move a certain way close to my circuit is that these noises responds. And then there goes Ms. Sarah's 4316 setup where it fixed out everything but not the way i wanted to use to. Why is that?? But if Ms. Sarah's setup can fixed such noise, then i guess there are still few ways how to have same results having different setup on hers, right?

--- End quote ---

Mind, it's not obvious which one is the culprit, but it's likely something you have running in the same room, or nearby.

That it's high impedance (in other words, that Sarah's shorting-mode switch maintains a low impedance that is more resistant to ambient noise) does suggest it's something nearby with a lot of switching voltage on it, like a completely unshielded, unfiltered lamp of some sort.

Tim

--- End quote ---

thanks for the reply :D i already solved it before checking here again, first, i was able to solve the unclean and instability output of the 4316 when it's 1st switch is on. You're right about switching voltage sort of because what I did was applied what i learned in basic digital electronics (from arduino stuffs because every knowledge i had comes from diy from this) and it was about tri-states, etc. so what I did was connect the 3 switches' triggers (their input and output are still left unconnected) to ground and no additional components, removing the addition components (filter, etc.) and follow again the original diagram posted here. Then turning 1st switch on outputs the input signal all clean and didn't affect the original signal at all. Problem left was when the said switch is "off", it goes again to a state of noisiness as shown below.


then I started deciding putting voltage follower after to meet stable, clean and low voltage off state as images below but failed to.



then after thinking out Ms. Sarah's 4316 setup, it came to my mind to use mosfets to meet shorting of output signal to ground when off as shown below removing the voltage follower.


then it works but the clean and stable off state voltage is still around 7-8mV which is still big and i wanted to at least make it less than 3mV to 1mV


--- Quote from: sarahMCML on November 21, 2018, 12:06:59 am ---Hi again,

I think your best bet is to do away with all the different circuit boards and long wires and rebuild the setup on the large board to the right, using the shortest wiring that you can to minimize stray pickup.
Also have you got enough decoupling capacitors near each IC at the moment?
I've done a partial circuit giving a modification allowing you to use 4 channels at once: you keep your 4316 for signal switching and use a 74HCT4066 to short the outputs to ground when the 4316 outputs are open.
The 4066 has the added advantage of being typically just 15 ohms impedance when on, better than the 4316? You could use a spare 4316, but it's overkill for this job!
I've put a logic gate symbol in for the inverter, but you could of course use a common emitter transistor stage.

Sarah.

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Hi Ms. Sarah :D thank you so much for all the help, you've been a great help, I really appreciate it. Ohh? I guess that would work also, i would buy a 4066 then cause i don't have one, i used 2n7000 n-mosfets instead but i definitely want to try that :D

I hope this post would serve great help to other beginners also. What's left is that i don't know how can i lower the 8mV off state voltage of the switch's output and i plan to input these signals to a PMIC like CS5480's voltage and current inputs. Am I right that the output signals from the switches that will be an input on PMIC CS5480 (CS5480 would be the load of the signals) won't change because its a cmos IC?
mheruian:

--- Quote from: WallyGator on November 21, 2018, 04:17:36 am ---
--- Quote from: sarahMCML on November 21, 2018, 12:06:59 am ---I think your best bet is to do away with all the different circuit boards and long wires and rebuild the setup on the large board to the right, using the shortest wiring that you can to minimize stray pickup.
--- End quote ---

That would be my first step - all those long jumper wires work as antennas to pick up whatever noise is floating around.  That combined with inherently noisy connections in many spring-connector breadboards after being used for awhile makes for problems.  Check for other sources of noise, such as cheap wall-wart power supplies nearby, compact fluorescent lamps, LED lamps etc.

If you get the circuit rebuilt with clean wiring you can establish a new baseline and then work on getting it lower.

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Hi WallyGator :D

thanks for all the advice also, I am now currently preparing on soldering these setup on perfboard so that i would avoid this inconsistencies on breadboard as you said, i hope everything will be fine and would post the result here :)
sarahMCML:
Hi again,

Your 2N7000 idea is probably just as good as using my 4066 method, so if you already have them I'd go with them.
Given the rather small maximum input levels that the CS5480 can deal with, is it likely that you may have to attenuate your signals anyway before you feed them to it? If so, that will likely reduce some noise anyway given the lower impedances that it is seeing.

Sarah.
mheruian:

--- Quote from: sarahMCML on November 21, 2018, 10:38:33 am ---Hi again,

Your 2N7000 idea is probably just as good as using my 4066 method, so if you already have them I'd go with them.
Given the rather small maximum input levels that the CS5480 can deal with, is it likely that you may have to attenuate your signals anyway before you feed them to it? If so, that will likely reduce some noise anyway given the lower impedances that it is seeing.

Sarah.

--- End quote ---

Hi Ms. Sarah, again, thanks for all the help, i really appreciate it and learned a lot :D yup, the voltage divider from the beginning was for it coz it needs mV only.
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