CD4066 switch resistance.

kubeek

Joined Sep 20, 2005
5,765
any ohm will power up the device, that why i need it will not have any ohm
This doesn´t make any sense. Find out if the switch is connected to ground or to +V. Then it will be easy to put a simple transistor instead of a complicated circuit.
 

Audioguru

Joined Dec 20, 2007
11,249
The datasheet for the CD4066 shows:
With a 5V supply its on-resistance is a maximum of 1050 ohms.
With a 10V supply its on-resistance is a maximum of 400 ohms.
With a 15V supply its on-resistance is a maximum of 240 ohms.

It is made to pass a high impedance signal that has very low current.

How much current will flow in the switch contacts?
Why can't you use a transistor or a Mosfet to short the two pins?
 

PaulEE

Joined Dec 23, 2011
423
its powered from 3.7v
If you are doing what I think you're doing, you're using the CD4066 to switch on and off power to a bluetooth module. They pull between a few mA to 100mA, depending upon what mode it is in. These are estimates.

The CD4066, by itself, has a set, spec'd ON resistance (for a given set of operating conditions). The only way to make this on resistance lower is to use a single '4066 with all the switches in parallel. As an example, suppose the on resistance of ONE switch is 100 ohms.

two in parallel: 50 ohms
three in parallel: 33 1/3
four in parallel (one 4066): 25 ohms

These switches are used in situations where their residual (and somewhat variable) resistances are not a concern.

If you want to switch power on and off to a device, there are better ways to do this.

A MOSFET is the first that comes to mind. A good MOSFET has a near-zero on resistance if the gate is driven correctly.

You can also use a good old BJT, as well as an array of other '4066 flavors of electronic switches.

Solid state or classic electromechanical relays might match your needs.

But, if you HAVE TO use a '4066, parallel the switches together and use a supply voltage at which the specified residual switch resistance is lowest.
 

Audioguru

Joined Dec 20, 2007
11,249
Is there a teacher in this crowd?

This kid from Mars (?) who says, "sorry for my bad english" and who says, "dont understand of electronic" cannot be understood and should not be here.
I think we speeky zee English here and we talk electronics geek talk here.

I know people who learned English then got a university degree in electronics and now they are wealthy and fine.
 

Thread Starter

TheDag

Joined Jan 1, 2010
94
Hi,
Near to zero ohm is also not good enough in this case...
If im shorting this two pins with wire its will power up, so any ohm will be a problem.
I need it to be 0 ohm idle, and boost for 5 seconds (for power up) and return to idle....
Thanks in advance....
 

PaulEE

Joined Dec 23, 2011
423
Hi,
Near to zero ohm is also not good enough in this case...
If im shorting this two pins with wire its will power up, so any ohm will be a problem.
I need it to be 0 ohm idle, and boost for 5 seconds (for power up) and return to idle....
Thanks in advance....
Zero ohms is unattainable, unless you plan on pumping liquid helium into your circuit.

Do you want other options, or was the question regarding the '4066 all you wanted an answer to?
 

kubeek

Joined Sep 20, 2005
5,765
I suppose the internal circuit of the bluetooth looks like this:

then this should work:



But be sure to check if the wiring of the switch is really same as i posted before. If it is not it will not work.
Note the first transistor is NPN and the second PNP. Any type will probably work if the rest of the circuit is just a microcontroller or something like that.
 

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Thread Starter

TheDag

Joined Jan 1, 2010
94
Hi,
Ok, I Think with the following picture you will be more understand the problem...
I need to short this 2 pads(Red circle) for 4 seconds, the device will power up...
Even if im shorting this 2 pads with wire for 4 seconds it will power up....
Now i think its more clear...
Thanks in advance...
 

Attachments

PaulEE

Joined Dec 23, 2011
423
Hi,
Ok, I Think with the following picture you will be more understand the problem...
I need to short this 2 pads(Red circle) for 4 seconds, the device will power up...
Even if im shorting this 2 pads with wire for 4 seconds it will power up....
Now i think its more clear...
Thanks in advance...
If that button is hooked up to a microcontroller, a CD4066 WILL WORK.
 

Thread Starter

TheDag

Joined Jan 1, 2010
94
I Think its hooked to microcontroller, but im not sure.
As i said, CD4066 not working well because its permanently shorting this 2 pads...
 

PaulEE

Joined Dec 23, 2011
423
I Think its hooked to microcontroller, but im not sure.
As i said, CD4066 not working well because its permanently shorting this 2 pads...
In order to give a meaningful suggestion to solve your problem, we need to know what that switch is doing. Obviously, it's either completing or breaking a circuit when you press it.

With the battery connected, measure the voltage between those two pins. It'll either be zero (approximately) or some voltage near either +1.2, +2, +3.3, or +5v.

Tell us that information, and then I can tell you how to properly hook up the '4066. It is a good chip.
 

Thread Starter

TheDag

Joined Jan 1, 2010
94
Hi,
The device now is dead (i think) because the 2 pads is over heated and disconnected from the PCB, now i dont know which trace match....
But anyway, I Will ordering new device..
And im still trying to build the "Automatic clicker"
Thanks in advance
 
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