i thought i'd make myself a general thread for asking various questions...


DECOUPLING?



i just add those two caps to every power unit of my schematic, yes?
and on a PCB i'd place them close to the chip, no?



DPDT or SPDT?


i use two NAND gates to drive my counters and multiplexers.
there is the option of giving a trigger signal by push-button or toggle, or toggling a switch to make it oscillate.

first i drew it with a SPDT which means that both units are always on and i just switch between the output signal.

it would be more correct to use a DPDT to also switch off the unit that is not in use or does it not matter much? benefits would be drawing less current, generating less heat and such, so i guess i should.. but...

edit: in my schematic i can now see that i'd have to use a 3PDT, actually



GENERAL QUESTION

• how do i connect several IC's together on the same power rail, the right way? I just had an idea to make a simple step sequencer, now i got 20 or so chips to connect. all designed to run on a 9v battery.... i'm probably also need to how and where to use buffers.

 

Your trigger button will not make a pulse because the switch should cause the capacitor to go to ground, not to +9V.

Your oscillator wrongly has its pin 5 disconnected and the switch shorts the +9V to ground.
The pot for the oscillator should have a series resistor to set the highest oscillator frequency.

You do not need to switch off the unit not being used.

Calculate the supply current to find out if a 9V battery will power 20 chips for a few seconds or a few hours.

 

DECOUPLING?
View attachment 223964
i just add those two caps to every power unit of my schematic, yes?
and on a PCB i'd place them close to the chip, no?

No and yes. It depends.

It depends on:

• type of circuit and application
• analog or digital
• semiconductor fabrication, BJT, FET, CMOS
• current and power consumption
• frequency of operation
• rise-time and fall-time
• PCB layout

The general rule of thump is to put one 100nF ceramic capacitor as close as possible to power and ground pin of every IC.

For a digital circuit, put one 10-100μF electrolytic capacitor where power enters the board. The value will depend on how much current is required by the board. For CMOS digital ICs drawing less that 20mA, 10μF should be enough.

Analog or mix signal application is a different story.

 

The general problem with having a multiple open ended set of questions is that inevitably one question will receive the lion share of attention leaving the others largely untouched. It would be better (my opinion) if you posted a thread concerning one part of the many questions you may have. When you have sufficient information on that thread it may just answer some of the questions you may have in other areas. AND those who answer your question are answering just the one question with all the focus it deserves.

 

Your trigger button will not make a pulse because the switch should cause the capacitor to go to ground, not to +9V.

but.. but.. it works just fine.. the signal goes on to the clock in on the 4017 and it counts, step by step when pressing the button.

Your oscillator wrongly has its pin 5 disconnected and the switch shorts the +9V to ground.

oh yeah,.. i see that now.. i cancelled the DPDT thought altogether now..

The pot for the oscillator should have a series resistor to set the highest oscillator frequency.

you mean something like this?

You do not need to switch off the unit not being used.

gotcha... seems like quite a lot of work anyway, increasing the BOM and such..

Calculate the supply current to find out if a 9V battery will power 20 chips for a few seconds or a few hours.

hehehehehe...

No and yes. It depends.

(...)

The general rule of thump is to put one 100nF ceramic capacitor as close as possible to power and ground pin of every IC.

For a digital circuit, put one 10-100μF electrolytic capacitor where power enters the board. The value will depend on how much current is required by the board. For CMOS digital ICs drawing less that 20mA, 10μF should be enough.

alright,,, the circuit is mostly digital.. it's CMOS-based squarewave oscillations mashed up and chopped in all sorts of ways.
i will put 100nF caps to every single IC and then a 10µF to where the power to the board goes in..

Analog or mix signal application is a different story.

the 1's and 0's will be mixed and treated as audio in the end, so i guess that's what you'd call a mixed signal application..

The general problem with having a multiple open ended set of questions is that inevitably one question will receive the lion share of attention leaving the others largely untouched. It would be better (my opinion) if you posted a thread concerning one part of the many questions you may have. When you have sufficient information on that thread it may just answer some of the questions you may have in other areas. AND those who answer your question are answering just the one question with all the focus it deserves.

good point. i think i will follow your suggestion.. yeah.

i have a question about SR latches, but i will read this first


thanks everyone

 

but.. but.. it works just fine.. the signal goes on to the clock in on the 4017 and it counts, step by step when pressing the button.

Sorry, I see now that the capacitor prevents extra pulses caused by the switch contacts bouncing.

you mean something like this?

Yes, the extra resistor is in series with the pot. Try 10k ohms for the maximum beats of about 10 per second.